Right Sizing a New Boiler... the easy way

[@avipharmd7646]

great video. that steam radiator is beautiful.

[@williamclaypool764]

Thanks and good day !

[@lancerudy9934]

I need more of sizing boilers. Thanks

[@TECTubefilms]

We did not want to "oversize" this video. LOL

[@bricknboxer]

I saw the Slant Fin display and thought for sure you were going to talk about the Slant Fin app for calculating heat loss. It's easier than a manual J heat loss calculation. There seems to be a 20% fudge factor built in so be aware of that and don't add any to it "just to be safe". I did a fuel usage calculation on my own house also and found it to be 80% of the Slant Fin app number. You need an honest heat loss figure AND the emitter radiation to determine if a modcon is going to run in the condensing range.

[@TECTubefilms]

Our only issue with the Slant/Fin load calc app is that you need to enter all the info (floor area, room heights, etc.) that you would need to enter with any load calc software. If we are going to go that route, we will use a software tool that also gives us the cooling load too. We tend to use EDS for simple boiler/furnace replacements with A/C and we use Wrightsoft for more complex projects that involve ductwork such as new construction or gut-rehabs. Plus the Slant/Fin app does not really scale well for commercial projects. No offense to our friends at Slant/Fin... we still like you.

[@JessicaBriarmoon]

I would love some input. We are building a house & business space with workshops and garages under one roof. Our total radiant heat area is about 12,000 square feet. It's a diy project so requiring a lot of researching. We are trying to figure out what boiler to get to handle the radiant heat, which will be in concrete on all floors. We will want to zone them (12 manifolds with their own zones) since many spaces won't require much heat on a regular basis. We don't have natural gas so we would need to do propane. We are doing ICF so luckily, we will already have a very efficient building to begin with. And to be able to run the domestic water in the house (less than 5 occupants full time so it isn't a huge domestic water load required). I would love to hear your input on which systems would be the right ones and if you have any videos on how to set up those systems.

[@dw3403]

What did you find out? Did you need 2 systems for that amount of flour space?

[@robsemprini1511]

Slant fin makes that heat loss software , it works well. Doing a work up on an older house ( "r" and other values ) can be quite tedious.

[@richiewilde1621]

If I have in floor heat in my garage (in the concrete floor) and I take square footage x(times) 40btu and I come up with 55,680 btu total with 14.5’ high ceiling and in mid Michigan. Walls are 4.5”-5” blown in isolation. I am debating between 90,000 and 120,000btu modulating/condensing boiler , is the 120k over kill? I keep garage at 70 degrees

[@TECTubefilms]

4 car garage? 40btu is the max. Most systems are 25-35. So the 40 already has a large safety factory in it. So you likely need a boiler with 35,000 to 56,000 output. So yes, both 90 and 120 input sound like overkill. We should also reiterate that this method is for resizing a boiler to be smaller than what you already have. What size do you have now and how much does it cycle?

[@richiewilde1621]

@@TECTubefilms they(previous home owners)have a 40,000 btu 80gallon hot water tank. When we get under 0 degrees outside it will only get to 66 degrees inside when set to 69-70 degrees. During that time the hot water tank is running all day and night with the water circulating around 80-90 degrees. Water is set to 130 at the tank

[@TECTubefilms]

@@richiewilde1621 Is this hot water tank an "indirect tank" for domestic hot water OR is this hot water tank a "buffer tank" for hydronic heating?

[@richiewilde1621]

@@TECTubefilms it’s just used to heat the water for the infloor heat, closed system with circulator, it’s only job is heating water for the floor.

[@TECTubefilms]

@@richiewilde1621 Wait... are you saying it is neither an indirect tank nor a buffer tank, but rather a standard water heater???

[@roadkingjp]

Great videos! Ho do you calculate the BTU output of a Sunrad. Thank you.

[@TECTubefilms]

This is the book you want to get - heatinghelp.com/store/detail/e-d-r-ratings-for-every-darn-radiator-and-convector-youll-probably-ever-see

[@MichaelValencia]

How can I hire YOU as my plumber? YOU are literally the only person I see. Doing this. Every other plumber coming in just “eyes” out the estimates and then somehow derives what boiler is appropriate... when I ask them to do this estimate they look at me like I’m growing a second head.

[@ChadAmI80]

Glad to see its not just me. I felt like I had a neon sign that only "pros" could see above my head. Its not just plumbers. I feel like the past 3 people I've hired did not appear to be very knowledgeable about stuff that I picked up on by watching a few videos.

[@ChadAmI80]

Thanks for such an informative, straight to the point video. Side question...I have a 1940 brick house with a boiler installed in 1997. We are looking to finish the basement. I've had a 2 local HVAC guys tell me No, but I want more opinions...we want to remove the steel supply and return lines in the basement and replace with PEX AL PEX to clear up some head room. Steel riser pipes would continue up through walls to feed cast iron radiators. I've been told that we shouldn't do it because it would cause short cycling issues. I understand a loss of mass will result in faster water temp drop, but clearly there must be a way to mitigate the loss of mass in the system to prevent short cycling the boiler isn't there?

[@ross1116]

Boilers dont short cycle so, your working with morons. I own a heating business, I have an engineering degree, I run an HVAC/R college program and scored over 145IQ. Trust me, run your pex, you will be fine.

[@thomasbroking7943]

Bill on the raiant would raising the temp from 90. Say to 110 change the btus of the concrete floor??

[@TECTubefilms]

Radiant floor water temps often range from 85 to 110 degrees. Yes, the hotter the water, the more BTUs can transfer. Additionally, the cooler the room temp, the more BTUs can transfer. The quantity of heat transferred (BTUs) is a function of the delta T across the heat exchanger, which in this case is a floor. With that said, we seldom see anything toward the 110 range since it is generally too hot to stand on. Below is what our friends at REHAU recommend for water temps of a floor and the associated maximum output based on those water temps in a 65 to 72 degree room. Floor Area Type Temperature Limit Heat Output (Max.) Perimeter 95ºF (35°C) 54 BTU/hr(ft2) Occupied 85ºF (29°C) 34 BTU/hr(ft2) Bathroom 91ºF (33°C) 46 BTU/hr(ft2) Distribution 95ºF (35°C) 54 BTU/hr(ft2)

[@cooper8318]

So I'm building a house with radiant heat concrete floors and the SF X 40 = 93K. I would like to use a combi boiler to heat the domestic water as well. Is this 93K calculation including the domestic water as well? Or do you have an equation to add to this number? Forgive my ignorance, I'm still learning

[@17johnnyfreedom76]

Is the 550 - 600 BTU output of the typical residential fin you referenced per foot of fin?

[@TECTubefilms]

Yes, per linear foot of the section of pipe that has the fins (not the entire baseboard itself)

[@Madethisaccttonight]

He’s saying 30 inches but the 3 column measures 5 sq ft at 38 inches on the chart. Did he mean to say 38?

[@TECTubefilms]

Yes this is an error. Either he measured 38 and verbally said 30 OR he measured 30 and looked at the wrong row on the chart. (Bill wears his classes more now 6 years later LOL)

[@ranger178]

my house came with Delco boiler 1 size fits every house it was like 3/4 of a refrigerator up to 250 thousand btu even after new burner and smaller tip it was a ridiculous monster i replaced it with smallest boiler i could get 3 sections around 80,000 and it was still plenty big enough my rule of thumb is you want boiler to just be able to keep up on coldest possible day of the year running constantly

[@TECTubefilms]

Love it!

[@ejswbradshaw1]

Thanks your video its very helpful. My mother has a boiler that runs on propane. She has to fill the propane tank every 2 months for $800. Only the boiler uses the propane tank. The boiler is about 20 years old and according to the calculation it is double oversized. Would replacing the boiler to the correct BTU's lower the propane cost a lot? I thought about high efficiency wall hung boilers, but read they aren't good because the water plugs them up. Would you recommend those? She's on a well.

[@TECTubefilms]

A correctly sized boiler will save energy. A high efficiency boiler will save energy. Improved air sealing of the envelope will save energy. Outside air reset control on a boiler will save energy. Lots of ways to cut that fuel bill down but someone has to first determine why the bill is high.

[@TECTubefilms]

We are not sure what you mean by water plugging up a boiler.

[@diegohernandez8609]

the boiler should be on a closed loop and therefore if filled with clean water, should not be getting “plugged up” by the well water, unless there is a leak and the system has an autofill bringing well water into the system. Perhaps your mother has a water heater, rather than a boiler?

[@mike7gerald]

My gas meter for the coldest month recorded 1430 cubic meters in 30 days, (I'm in Canada and it gets to -40 degrees). And since gas gives 35300 BTU/cubic meter, my usage was 140209 BTU/hr. That is the most accurate way. It shows that in the coldest month my boiler must put out 140209/hr so that I won't freeze. (Please correct me if my logic is wrong since I'm shopping for a new boiler to replace my ancient 60-year-old model).

[@TECTubefilms]

Here is a video to calculate heating loads by gas consumption - kzbin.info/www/bejne/ipDHpn6KeLWKhKc

[@cardo1111]

I have a Beacon Morris kick panel heater that supposedly puts out up to 12500 BTU’s on high would I add the 12500 BTU on top of my Fin tube calculation. Any advice as always is much appreciated. Thanks for the great vids.

[@TECTubefilms]

Yes, you would sum up the outputs of all terminal units (fin tube, radiators, kick space heaters, air handlers, etc) that are fed from that boiler. Great question!

[@cardo1111]

Tec Tube Thanks you have been a huge help, contractors seem to just want to swap out the same size that was there. I really appreciate your time, great vids and expertise. This is where I am at: I am trying to size a replacement boiler for my house it is in the lower Hudson Valley in NY. (20 miles outside NYC) It’s a bi level with 2518 heated square feet I have a 114.5’ of heated fin tube and a Beacon Morris kick panel blower heater that supposedly puts out 12500 BTU on high based on this my demand is about 81,200 BTU. I imagine I would base my sizing on the DOE output number posted by the manufacturer factoring in efficiency of the unit. My current leaking Utica is 150000 BTU input, 124,000 DOE output it lasted about 35 years. Sounds too big, house was built in 1963, vinyl sided double insulated windows now. Boiler is in lower level heated space in a closet. I am going to replace based on my demand using DOE output as the gauge of power, I don’t want to go way over based on the calculation. Thanks again!

[@TECTubefilms]

@@cardo1111 Based on the info you are telling us, your current boiler cycles itself on/off a lot (even on cold days) and only sends a maximum of 81,200 BTUs out to the house anyway. May as well just get a smaller boiler that puts out only 81,200. And that is assuming none of your fine tube is oversized (which it always is). If you install a modern 95 to 97% AFUE condensing boiler (and you should), you need to look for one that is 85,000 input. Or round up to the next whole size. We might suggest a HTP Pioneer 100, HTP UFT 100, IBC HC 23-84, IBC SL 10-85, Carrier BWM 100, or Bryant BWM 100. There are lots of choices at that size range. Some make more sense depending on the application and the type of individual zone control.

[@TECTubefilms]

@@cardo1111 With the jump from 73 to 95% efficiency combined with a correctly sized boiler... and an OA reset schedule, we would not be surprised to see your gas heating bill cut almost in half. Once you get that first bill, let us know!

[@cardo1111]

Tec Tube Thanks again! Those HTP’s look like really nice efficient units, however the budget will only allow for the standard 83-84 efficiency units.

[@MrSprintcat]

Would it be possible for you to show a video on how to put an outdoor reset on a standard efficiency boiler? With an indirect tank in the system and baseboard thank you

[@TECTubefilms]

That process would be specific to the brand of outside air reset controller you are installing... Honeywell, Tekmar, etc. We can give you this tip, though: always install it on the North side of the structure to avoid direct sunlight.

[@MrSprintcat]

I actually called the manufacturer of the boiler it's a New Yorker and the model number is a CG30D. They advised me that boiler cannot be used with an outdoor reset. I'm not sure why the guy wouldn't explain

[@TECTubefilms]

@@MrSprintcat He was either incorrect or overly cautious. You can put an OA reset on all boilers. In fact for boilers under 300,000 BTUh, it is required by the DOE. And for all sizes, it is required by IECC. With that said, if it is a non-condensing boiler, you cannot have an aggressive OA reset schedule. You have to keep the return water temp high enough to avoid accidental condensation.

[@MrSprintcat]

Thanks for getting back to me .its to funny I called NEW YORKER. BOILER back and talked to the same guy and he had his coworker with him , they told me my boiler wouldn't work with an OA . because my boiler has an on board boiler reset.??? They said to understand what they were talking about I would have to look in the manual. 😂😂😁😁.. I know the return line temp should be around 137 degrees.

[@1974jrod]

Tec Tube I think you were off on your concrete floor calculations. 24 x 40 is 960 not 9600.

[@chrisE815]

Thank you. I'm doing some research on replacing a 30 year old unit in a home I have an offer on. Is there a boiler type you would recommend if I purposefully decided to over size? Obviously the system should be designed to avoid cycling. In the future, if I decide to put an addition on with baseboard heat and radiant flooring in the basement/shop space, can adding an extra 500-700 sf of living space be easily accommodated? Just wondering how I should go about planning for future additional demand.

[@TECTubefilms]

We would recommend you size the system for the heat loss of the current structure. You will likely still have plenty of extra safety factor to handle and addition because almost no one every actually sizes it small enough (even when they try hard) for the correct size. Plus you can always add in a 2nd small boiler in parallel with the other boiler if needed.

[@cyoungso]

Better off with 2 smaller boilers if you feel you need the boost capacity. Let one run 90%of the time

[@cardo1111]

Maybe a silly question when measuring fin tube length are we just measuring the length of the fin assembly in the baseboard not including the copper pipe? I have 2518 s.f. Of finished heated space in a Bi-level. I have a 150,000 BTU water rating input with 107,800 BTU 1983 Utica boiler I will be having replaced. I am concerned whether or not this is the right size unit, as you said the contractors seem to just want to swap what is in there based on the previous unit’s label without even thinking about calculating what the correct size for my home is.

[@TECTubefilms]

Correct, just the part that has fins on it. Do not include the bare copper tube.

[@ryanhoger1]

150,000 sounds like a lot. I have 2,800 ft2 and heat the whole house with a 60,000 BTUh unit that has never fired above 83%.

[@cardo1111]

Tec Tube I appreciate the response. Another question if you would . I live in the N.Y. metro area suburbs (southern N.Y.) My boiler is in the heated lower level of a bi-level home. Based on this I am assuming the spec of the boiler I should use for sizing my unit is the DOE heating capacity?

[@cardo1111]

ryanhoger Thanks for the input. My current unit is operating at 72% efficiency based on the specs is from 1983. But 150,000 Input BTU does seem high, (also has :124000 DOE capacity and IBR number is 107,800 BTU) the house was built in 1963 but has some updates including low e double insulated windows. The boiler is also located within the heated space in a closet. I am going to measure my Baseboard fin tube. I live in the NY metro area as well winters here are relatively cold.

[@robsemprini1511]

Back in the day , Plumbers used the "finger method. They would stand across the street and hold their fingers up - how many fingers covered the house would be how many sections. True story. So many guys still put WAY too much baseboard in houses…I love sun-rads (semi-recessed ) myself, they are variable and don't take up wall space. No mention of them in this vid , but they work well also.

[@TECTubefilms]

We remember the days of the old finger method... well at lest Bill remembers... we are too young. LOL

[@thomasbroking7943]

I heard that also but hope its hearsay

[@TECTubefilms]

@@thomasbroking7943 It was fairly common. It "worked" for two reasons: 1) houses were all built about the same in terms of insulation, leakiness, and windows and 2) no one cared if stuff was oversized because fuel efficiency and comfort were not large concerns... people just wanted to stop having to put wood in the fireplace so a boiler was a very comfortable choice.

[@jamescecil4629]

Can you adapt a boiler buddy to a outdoor wood boiler to control the lower needed heat for radiant floor pex

[@TECTubefilms]

You can put a boiler buddy on any type of boiler. It does not care what is heating the water. However, a buffer tank is not likely what you need. The boiler buddy does not cool the water down. What you likely need is a 4-way mixing valve. We used to use them a lot back in 90s before condensing boilers were popular but we have not seen one in a long time. But then again our entire market is natural gas and propane (both of which work very well with low temp condensing boilers) so we don't deal with wood or oil boilers around here.

[@bobbymele9057]

On the residential Baseboard calculation how do you calculate Sq. Ft. Of Steam ? Also, do you measure only the finned section of copper length of pipe or entire run?

[@TECTubefilms]

Don't measure the length of copper pipe or the whole baseboard. Just measure the length of fin.

[@TECTubefilms]

We don't do much with steam baseboard, but take a look at the Slant/Fin website and look at the catalogue data for output per foot.

[@bobbymele9057]

@@TECTubefilms thank you for response

[@rupe53]

I did a few rough calculations on modest size homes of under 2,000 sq ft. and found if you have 8 rooms with 12 ft of baseboard each, you wind up with a boiler size of 52,800 BTUs. Good luck finding a decent boiler that small... and it still might be oversized as we upgrade windows, doors, and add insulation. You could down fire the boiler to a point, but the easier solution would be to lower the boiler limits and hold the water to say 140 / 160 degrees. Yes, the burner(s) will short cycle in moderate weather but what else can you do? BTW, with the advent of indirect fired domestic water this lower temp will not be a problem.

[@TECTubefilms]

Why wouldn't you install a smaller boiler AND lower the water temp setpoint below the traditional 180?

[@TECTubefilms]

Here are a few smaller boilers that we use frequently in our office: Carrier BWM50 outputs 9,200 to 46,000 BTU/h IBC HC1350 ouytputs 12,400 to 45,400 BTU/h Carrier BWM75 outputs 13,800 to 69,000 BTU/h HTP Elite EP80 outputs 7,680 to 76,800 BTU/h IBC SL1085G3 outputs 10,100 o 79,000 BTU/h IBC HC1350 ouytputs 14,500 to 85,900 BTU/h

[@rupe53]

@@TECTubefilms ... in my own home the radiation is figured for 140 - 160 degree setting. Since I worked in the oil heating business for years my focus was on oil fired boilers that were available 30 years ago. When I did the job, I got the smallest boiler I could find and down-fired it... and that still has excess capacity to do hot water nonstop. My place is probably the cheapest to heat on the block. At this point gas is available but I likely still have another 10+ years to go before the boiler needs replacement again.

[@MegaGeorge1948]

What about steam boiler heating systems in older homes?

[@TECTubefilms]

The same method works with steam radiators, but instead of 170 BTU/h for 180F water, you would use 240 BTU/h for 215F steam

[@MegaGeorge1948]

@@TECTubefilms Thanks for the info.

[@robsemprini1511]

Also , steam is measured not by btu per hr. , but Cubic feet per hour. You need room in the "steam chest" to make steam.

[@TECTubefilms]

@@robsemprini1511 All of the steam boilers that we stock are rated/listed by BTU/h input and that is what is also listed on the nameplate tags. This includes Burnham, Carrier, Bryant, and Utica.

[@robsemprini1511]

Then they are NOT rated for steam. Steam is measured by volumn. Not btus. Like nat, gas...And it matters. If you don't have room to make the steam - you can't make it.Look at steam baseboard (for single pipe)..or better yet I will make a post expelling this. It IS becoming a "lost art" like Holohan said. Take a better look at that plate ; a lot of times they are marked for both water and steam.

[@mohassan7050]

I have a MAC 150 Utica combi boiler and it has been nothing but a nightmare. I can not find a technician who can fix it in Massachusetts. Any tips? The error code now is E110. It keeps running and stopping. It also never gives hot water fir more than a few seconds. Anyone who could fix it on Massachusetts?? Please

[@TECTubefilms]

Sorry, we only have contractor relationships here in the Midwest where we are based. Massachusetts is a big boiler market so we would think there would be more contractor options there to service hydronic systems than we have here. Guess not.

[@sultaanjatt9013]

What about if there’s no radiators and using boiler with hot water coil and air handler (heating house thru duct) so do I need same size of boiler what I need fo radiator system?

[@TECTubefilms]

You do a load calculation on the building with software to be the most accurate. Less accurate (and still slightly oversized) would be to add up the BTUh capacity ratings of all of the hot water coils.

[@kirill_gusev]

My old house has a 1 zone with baseboards and 2 zones with radiators. Do I need to include a length of pipes (cast iron for 2 zones, copper for for 1 zone ) for estimating BTUs? The oil-fired boiler is on the way out (seepage between sections). Everyone says convert to gas. But some says new high efficient oil boilers is better option? Is this true? We planning stay long in this house and we are in MA, so heating season is long. Thanks!

[@TECTubefilms]

No, do not increase boiler size to cover the heat loss of pipes. That is already built-in to the safety factors of this method.

[@TECTubefilms]

In regards to the natural gas vs. oil discussion, there are a lot of factors involved there. One major part will be how much you pay for oil (supply and delivery) and how much you will pay for gas (supply and delivery) in your local community. Then you have to adjust for the efficiency since even a high efficient oil boiler (typically 83-88%) won't be as efficient as a high efficient gas boiler (typically 92-96%) Natural gas also burns cleaner so if you care about the environmental pollution there is that to consider. Lastly, depending on your community there could be challenges for how your oil is provided (do you have to schedule it, pay for it upfront to get a good deal, etc?) that would go away with gas, but also possible installation costs for a gas meter.

[@TECTubefilms]

Who is suggesting you convert to gas? And who is saying keeping oil is the better option? If either of those are the local gas or oil company, just remember that they are biased. A HVAC contractor that services both may be a better resource to consult with.

[@kirill_gusev]

@@TECTubefilms Thank you for taking time to reply. Lot of good info. One more question. There is a possibility I would need to add 2 more zones. Both radiant floors. DO I need to include these in boiler sizing calculations and how to estimate it? Thanks again!

[@TECTubefilms]

@@kirill_gusev If you are not adding square footage to the heated area of the building, then you do not increase the boiler size by adding more terminals (baseboard, radiators, radiant floor, etc.) because you are not heating a larger structure... you are just heating it differently. However, if this is a new area that was not previously heated by this boiler, then yes you need to add the new building addition to the boiler size. This would be determined by a process we call the "load calculation" or "heat loss calculation." Do not use the radiation count method described in this video for anything other than existing hydronic heated areas.

[@elia2441]

How do you do the calculation for the fin tube base boards

[@TECTubefilms]

Watch the video starting at 2:09. For most residential baseboard, it is just 550 multiplied by the length of baseboard that has fins.

[@elia2441]

Tec Tube I have multiple base boards do I add up all the lengths then multiply that number by 550?

[@TECTubefilms]

Yes, if all the baseboards are served by the same boiler, then you need to sum them all up to see what size boiler you need. You can either sum all the "active lengths" and multiple by 550 or you can multiply each baseboard by 550 and then sum all the baseboards up. The same answer will result.

[@RalphsHeating]

Is the piping and pick up factor that is built into the boiler specs based only in the IBR and nothing extra in the DOE rating? Thanks in advance.

[@TECTubefilms]

The "DOE rating" for a residential boiler would be AFUE. This test includes boiler cycling. For a commercial boiler, the rating is Thermal Efficiency (TE) and this is a steady state test (warm it up, get it operating the way they want, and then take the measurements). Does that answer what you are asking? And then to add one more layer, when a tech in the field tests the efficiency with his/her analyzer, that is a Combustion Efficiency test, which is also steady state, but different than TE.

[@RalphsHeating]

Tec Tube No I am asking about the built in extra sqft of radiation in the boiler ratings. See page 2 , item 2 of the installation instructions of the Carrier BWBB water boiler. The AHRI rating. I am assuming the AHRI rating listed is the same as the IBR output? www.utcccs-cdn.com/hvac/docs/1009/Public/0C/IM-BWBB-01.pdf. Is this extra 1.15 not in the DOE rating and that is why it is lower?

[@TECTubefilms]

We downloaded the manual you are talking about. Yes you are correct in that Carrier is using the term "Net AHRI" the same as the Utica boiler tag in the video is using "Net IBR." When ARI merged with GAMA in 2008, it changed its name to AHRI (to add the word heat) and we presume this is why sometimes you see Net IBR or Net AHRI. Anything older than 2008 would never say AHRI on it. Here is the definition of "net" by the AHRI standard: 3.10.2 Determination of Net Ratings. AHRI Net Ratings are determined by dividing the Heating Capacity by the piping and pickup factors of 1.333 and 1.15 respectively as Steam Factor and Water Factor, and rounding to the nearest MBH. Steam square feet shall be determined by dividing the rounded Net Steam Rating by 240. It may be cataloged to the nearest square foot or the nearest 5 square feet. The DOE output on the Utica tag is what Carrier's document is calling "heating capacity." This is sometimes called gross capacity and this is the number related to the AFUE (also an AHRI term). So no matter what they call it, there is gross capacity and net capacity. Gross is the larger of the two. Unless your boiler and the majority of your piping is in a completely unconditioned basement (like it was in the 1930s), our suggestion is to ignore these "net" numbers and only focus on the gross output (aka DOE output). And even at that... the DOE output is the largest replacement boiler you will need. If you do the measurements that Bill is describing in the video, you will end up buying an even smaller boiler.

[@RalphsHeating]

Tec Tube Thanks! Great info!

[@tommurphy8428]

Enjoyed the video, but your calculations of the output of the radiant system are off by a factor of ten. 24sf X 40 Btuh is 960, not 9600. Similarly for the commercial calculation. 1200, not 12000.

[@TECTubefilms]

You are correct. We didn't catch it until after it was shot and published... actually we didn't catch it at all but saw a comment from another viewer. The 40 BTUh per square foot formula is correct, but Bill's math was wrong. And we keep reminding him about it each week. LOL

[@mahmudaliza4079]

Is it wrong to go by the sq footage of the house instead of this method?

[@TECTubefilms]

Square footage alone? Yes. However, a proper heat loss calculation uses square footage along with ceiling height, window size and type, air tightness, insulation, climate, and other factors to calculate the heating size needed. That is the best way to calculate the heat loss... and the one required by energy codes. The method we showed in this video is easier than a proper heat loss calculation, but not as good. The square footage alone would be a horrible way to do it.

[@deysanimations1949]

I have a house with 3 units each floor is 35785 btu plus an extra radiator of 8925 in the hallway by the stairs with a total of 116280...I purchased an slan fint with a total of 150000 btu just to be save , the exaust from the boiler which is gas by the way is connected to a mansory brick chinney that STARTS ON THE BASEMANT AND end up on the roof WHICH IS ABOVE THE THIRTH FLOOR . but the thirth floor is not heating as it supposed to..cast iron radiator here...circulator pump is working fine and the water on the pipes of the radiators is circulating what could be the problem..i believe I have enough btus to heat up the house but always have the problem..anyone knows what is happening..thanks

[@TECTubefilms]

Lots of possibilities of what could be the issue, but it is unlikely a boiler sizing issue or even a boiler problem. It is likely a distribution problem, such as incorrect piping, an air bound radiator, a valve issue, etc.

[@TECTubefilms]

@Sam S Vertical rise is not a factor in circulator pump sizing since it is a closed loop system. What ever we push verticially against gravity in one pipe is offset by gravity pulling downward on the return pipe. Circulator pumps are sized for GPM (which is based on required BTUs) and static pressure resistance. We will also add that is is EXTREMELY RARE to have an undersized circulator.

[@ballymohan9716]

you probably need more baseboards in each room i have the same amd i have to lower my temperratur because it gets too hot

[@farmerjon5532]

I need to replace a 1974 gas hot water boiler that HAS to be oversized. It's 270,000 btu. The gas meter needle looks like its moving in time lapse. My problem is I am concerned about my old iron pipe sizes, and how that works with a modern boiler? Some of the pipes are quite large in diameter. For reference, the house is a 2800 sq ft ALL brick house, yes, including interior walls. It has updated windows and insulation in the attic. I'm sure part of the reason it was so many btus was efficiency, as the internal boiler heat exchanger is cast iron. I understand that this unit was more intended for commercial buildings when it was made. Can a new boiler interface with existing large circulating pipes? Some of it is like 1 1/2- 2", closer to the boiler. It would be unrealistic to change much else besides the boiler itself, as it is all cast iron radiators and black pipe.

[@TECTubefilms]

Yes, you can still retro-fit. Larger pipe size is always more favorable than smaller, as it yields less head loss.

[@darrinmc]

I had a modulating condensing boiler installed a few years ago and the max output is much larger than the house needs for its heating load. The contractor said they needed the extra capacity to support the indirect DHW tank. Is that a valid reason to put in a boiler that is larger than necessary?

[@TECTubefilms]

No, it is not. The boiler should be sized for the larger of the two loads... either space heating or hot water. For a house in most climates, space heating is larger. The boiler will not be doing both at the exact same time. It will switch back and forth.

[@bricknboxer]

You can get away with a some oversizing of a modcon boiler if the minimum fire rating is low enough to prevent short cycling. Having lots of small zones makes that tough. An old single zone system of big pipes and cast iron radiators is much more tolerant of oversizing. @@TECTubefilms

[@TECTubefilms]

@@bricknboxer Your statement is true... you can round up on the sizing if you also pay attention to the mod con boiler's turndown rate as related to your smallest zones. However, why oversize it all? Let's just "Right-size it."

[@anastassiakarouta4325]

I had a new boiler installed and I beleive they oversized it and it cycles 3-5 minutes and doesn't heat my house when it's really cold out. They can't figure out why but they tell me it's not shortcycling and not oversized. I have 134 ft of fin 3 zones and tankless hot water They installed 11,000 btus. They say they have to add extra btus for the water. Is it oversized? The contractor agreed to put a new one in but I'm afraid he will oversize again. Please help.

[@TECTubefilms]

It would be hard, and probably unethical, for us to assume we can size your system without having ALL the details. Plus that is the role of the HVAC contractor. With that said, 11,000 BTUh would be a really small boiler. For 134 ft of baseboard, we would be expecting an 80,000 BTUh boiler based on the re-sizing method laid out in this video. How does that compare to your old boiler's size?

[@TECTubefilms]

Do you actually have a boiler or are you trying to heat your house with a tankless hot water heater? Normally, we would use a boiler and add an indirect tank water heater to that. When we do that, we do not increase the size to account for the domestic water load. But that is another discussion for another video.

[@TECTubefilms]

If you are in the midwest and your contractor purchased the boiler from us, we can assist them with troubleshooting the issues you are having.

[@anastassiakarouta4325]

I meant to say it's 110,000 btus, my old boiler was 99,000. I'm in Ct ant they did bring the manufacture rep along with other techs. They measured house at 2,700 SQ ft and heat load calc is 64,000, house was built 1990. Still no one has a clue. It's a peerless wbv series. I know that it runs 3 min on 3 min off when it's cold and trying to raise temps.

[@TECTubefilms]

@@anastassiakarouta4325 If the load calc was 64,000 BTUh, then you would select a boiler with that output. So if it was a 95% AFUE boiler, you would need a 67,500 boiler to handle the heat load on a cold design day. If they make a 60k and an 75k, you would select an 75k but go no higher. If you want an 80% AFUE boiler, then you need a 80k boiler. The load calc needs to match the boiler output, but the boilers are sold by the input.

[@MrMkapusta]

Is 50 x sqft(of home) adequate in calculating boiler size? Came across this calculation while researching. If it’s any concern the home uses the fin baseboard system

[@TECTubefilms]

Adequate? Sure. But in most weather regions it is going to result in a boiler or furnace that is MORE THAN DOUBLE OVERSIZED. If you are in northern Canada with very poor insulation, this might work. For example, my house is 2,860 ft2 so that would come to a 143,000 BTUh system. I only have a 60,000 BTUh system and it was fine on a negative 26 degree day two years ago.

[@suzyfueshko9593]

You only said the the baseboard must be measured, I didn't see where you tell us how to calculate what sized boiler for the baseboard heat.

[@TECTubefilms]

Bill mentioned it at 3:06, stating 550-600 BTU per linear foot of residential fin tube. We probably should have done a sample calculation in the video like we do with our in-person training classes for contractors.

[@ATeamAdam]

I agree this is useful for steam boilers. But I think this method can still contribute to over sizing. Who cares what the output of the emitters are. They use to size cast iron radiators to heat the house with bedroom windows open. Perform a manual J and or look at gas usage to nail the sizing of a boiler. A BTU is a btu. If your heat loss is 40,000 btus and your emitters are 120,000 - I dont know about you but I would rather install the 40,000. My back is getting old.

[@TECTubefilms]

We agree... the radiation count method will still yield an oversized boiler (but not as oversized as the one it is replacing). The problem with load calcs... which are code required by most energy codes now... is that stubborn contractors are refusing to believe that the old boiler was double sized so they keep adjusting the calculation inputs until it yields the boiler size they were expecting based on their old rules of thumb. The radiation count method gives them another option, similar to gas meter calcs, to see how badly the old one is oversized and believe their load calcs (if they bothered to do one).

[@bernadettesherwood6442]

Prices

[@Evan-lx9lw]

Why not do a heat loss calculation, then you KNOW the heating NEED? THEN you determine if there are too few or too many emitters, etc. Size the boiler for the NEED, not the installed emitter.

[@TECTubefilms]

Agreed! We would love for there to be an accurate load calc done on every project we get asked to bid a replacement boiler for. However, the vast majority of contractors just re-size the new boiler based on the old boiler's tag. When we ask them why not do a load calc, the reasons are often 1) it takes too long and 2) I don't know the details of the building like wall insulation, etc. Bill started using this "radiator measurement" method decades ago to help get contractors closer to the proper sizing you might get with a load calc but without the effort. It is a compromise of doing a load calc (which they refuse to do) and just replacing like for like.

[@ajalbrecht9956]

You have to measure the radiators because without the radiators you're just going to oversize the boiler in the house

[@blackpine6693]

How many installers except in new construction which most likely the are specified by engineers of som sort....go through all that figuring....on boiler replacement. The plumbers I have dealt with looked at the name plate on the old furnace and take it from there....if the footage of already installed baseboard will only put out so much Btu per hour no matter what the rating of the furnace....too big the furnace will cycle on and off .....to small and the furnace will run continuously.......I believe installers continue to put in the larger rated furnace so when the weather really drops on those few occasions they do not get nasty calls from the home owner...when they hear the boiler running all the time....

[@TECTubefilms]

Correct, most contractors replace like for like. Our point is that you can do a radiation count (i.e., "all that figuring") in 10 minutes, provide a smaller boiler that will run more efficiently, with less wear and tear, and a lower first cost AND still avoid the possibility of a nasty homeowner call for a boiler can't keep. Even with the radiation count method we described, you will still be a little oversized. Plenty of safety factor.

[@TECTubefilms]

Side notes: a furnace and a boiler are different things... one heats air and the other heats water

[@TECTubefilms]

It is also best if plumbers stick to plumbing and not get involved in HVAC :)

[@LRBennettInc]

I find in so many cases that people don't mention that the SlantFin's performance is at 200 degrees. We always find 90% of them set at 170 and after we leave they always tell us how much more comfortable it is. Also be careful mixing the cast Iron with the SlantFin you will be in big trouble trying to make that comfortable. Just don't do it.

[@TECTubefilms]

We do mix cast iron radiators with baseboard on the same boiler, but we put them on separate circuits with their own tstat and circulator.

[@TECTubefilms]

SlantFin catalog does list output for water temps from 110 to 220 in 10 degree increments.

[@daviddishan]

Great information for pro n navis

[@vicpinto1970]

An Off An Off?

[@hightekinc723]

24x40=960

[@TECTubefilms]

Correct. :)

[@dpm3758]

Thank you!

[@dennistreacy3595]

Let's now add onto this wild guess of the boiler size method above; If the house was designed as a gravity flow system the target water temperature was originally 140 degree target water temperature. Look up each cast radiator at 140 target temperature. However sizing the boiler based on a lower water temperature will require a condensing boiler to be installed.

[@TECTubefilms]

The old gravity systems by us were all designed for 180F supply. But if you have one designed for 140, then use about 110 BTU/h for the EDR calc.

[@TECTubefilms]

Yes, if you design systems that have supply water temps below about 155 (and hence return temps below about 135), you will condense the flue gases and hence should only use a condensing boiler.

[@dennistreacy3595]

@@TECTubefilms Flue gases will not condense when the boiler was originally designed to fire with coal. Once the boiler came up to temperature the boiler never was allowed to cool. There was no slug of cold water coming back to the boiler.

[@TECTubefilms]

@@dennistreacy3595 We don't know much about coal boilers. If the old boiler was running hotter exhaust temps natural gas boilers, then that would prevent the flue gases from condensing with 140 degree return water temps. In either case, the old boiler's fuel type won't affect the re-sizing of the new boiler. As mentioned use 110 BTU/h in your EDR calc for 140 degree supply system.

[@ross1116]

Boilers dont short cycle so steady state is immaterial in this discussion.

[@TECTubefilms]

Boilers short cycle ALL THE TIME…

[@edwardjanowiak]

You never actually said anything about sizing the boiler. You did a nice job explaining how to figure out how much heat comes out of the radiation but you never actually spoke to actually measuring the heat loss on the structure and if we’re dealing with hot water that’s with the heat load should be based on. If were talking about steam I get the importance of how many BTUs it takes to fill the radiators with steam, but on a hot water system the boiler should be size to the heat loss of the structure. Length times width times height times eight was an old-school way to size a heating system in a home with no insulation and single pane windows. If the boiler and the connected radiation was sized based off rule of thumb such as that, then as the years go on the house gets updates like insulation and double pane windows we could easily reduce the boiler size by half. If one sizes a boiler based off the connected radiation in a hot water application in a situation like I just described, we’re going to end up with an oversize boiler, or furnace for that matter. Am I missing something or is there an additional video that points out how to do a proper heat loss calculation on a structure?

[@TECTubefilms]

You are correct! The radiators should be sized for the heat loss of the room and the boiler should be sized for heat loss of the structure. For residential systems, the best way to do this is with an ACCA Manual J calculation. A Manual J is generally done with software these days, but you could also do it manually if you wanted. With that said, we have pretty much given up on getting contractors to do a Manual J calc on a boiler change out. Most just want to swap like for like because it is easy and fast. The don't want to spend an hour or two doing a load calc. So that is why Bill advocates to at least do a radiation count as described in this video. It is not perfect, but at least it allows a smaller boiler to be used. Maybe they have a 150,000 BTUh boiler now, a perfect load calc might yield that they only need 73,540 and Bill's method might show a 100,000 would cover all of their existing radiation. This particular video is not for the purpose of doing a heat loss calculation. As stated in the video title and in the description section, the purpose of this video is to give a simple alternative sizing method.

[@thomasbroking7943]

Won't u come home Bill Bailey won't u come home.. Had to .❤❤

[@TECTubefilms]

We had to Google that Patsy Cline song...

[@richardcranium5839]

@@TECTubefilms lol

[@blackmanops3749]

Misleading title. A basic overview on Joules vs volume of house would be great for those of us who can't afford the "ACCA Manual J calculation" software and are confused by the on-line guides that conflate square footage with cubic volume(!) and factor in variables that change un-knowably over time (number of people, window sizes/types, etc). Apparently oversizing is a good approach given it's continued success in the "real-world". So far I am seeing 50 to 60 BTU's per square foot for Northeast locations. So if I use 64 (i.e. 2^6) I should be good for a drafty house with a cat door in Northern NH.

[@TECTubefilms]

Why is the title misleading? Are you implying that a Manual J calc is easier than a radiation count? We have no problem with a Manual J load calc if you can get the correct info on the home construction.

[@TECTubefilms]

We have seen a lot of premature boiler failures... especially with low mass condensing... because of oversizing. It causes short cycling.

[@TECTubefilms]

50 to 60 BTUh per square foot?!?!?! Maybe for a 100 year old house with single pane windows. But for newer homes (1990s construction), that can be double the size needed in say Boston.

[@blackmanops3749]

@@TECTubefilms I'll walk back my claim a little. I was looking for something a little different I guess. While it's true you gave a good general overview of sizing, I was looking for specifics on calculating BTUs for a volume of space. What is online is confusing and sometimes contradictory. The Manual J Calc approach I have come across online cost money and seems way too involved for what some others boil down to a simple "50-60 BTU per square foot" rule of thumb. I was hoping for something that was a little better than the over-simplified rule of thumb, but not so minutia-laden as to get lost in the weeds (like maybe a manageable overall volume calc times an opening loss factor, plus a hot water option to arrive at a reasonable range). As far as short cycling, I hear you on that point. But which is preferred, short cycling or struggling to keep up (always-on)? I would think having extra capacity would be overall a better trade-off. But I don't have the experience to know what the typical cost/benefit tradeoff is. Getting that insight is why I watch and appreciate video's like yours.

[@blackmanops3749]

@@TECTubefilms Yes. Exactly. But with leaky window upgrades. There are a lot of old stock housing like this in NH where I am.

[@Bob.W.]

I have 3 100 square feet steam rads on my 3rd floor. Wanna help me lift them? :)

[@Elkmonger]

When they right sized the company I worked for my position was eliminated :-(

[@TECTubefilms]

You are saying that by your company installing a correctly sized piece of equipment, they no longer needed you to work there? What was your job? Did you go back to problem jobs caused by your co-workers due to over-sizing and band-aid them?

[@Elkmonger]

@@TECTubefilmsNah "right sizing" was buzz word 10 years ago for "look out we're going to be eliminating positions". I took the severance package and started a Consulting Engineering Business and never looked back. I should have done that 10 years prior. That company I had worked for has since hired as many or more people than they eliminated. Lots more red tape and politics. I consult to them on a regular basis now. It's really been good. I get to just be an engineer and solve problems. In and out here's your invoice.

[@Elkmonger]

@@TECTubefilms I found your video because I recently replaced a Weil-McClain CGI-5 with a Weil-McClain Aguabalance 155 Combi unit. It's for Radiant floor heat. I can tell you I was VERY skeptical as I carried this new unit into my utility room like a suitcase that it was going to replace the CGI boiler (that on a good day I could lift maybe an inch off the ground). However, I am TOTALLY SHOCKED at the performance. I can't wait until the next propane delivery to see what the difference is. The CGI either cracked or rusted out one day after my last propane delivery (yup she broke early hours Xmas Eve. Woke up the house was 58 degrees F).

[@TECTubefilms]

@@Elkmonger Ok... you were talking about a completely different type of right-sizing than this video was speaking to. Got it.

[@terencemeehan8237]

Sorry, but this is wrong. You are sizing a boiler to the radiation installed in the building, so your relying on the guy who originally installed it? He got the boiler size wrong, too big but got the radiation right? He probably sized both by IBR calculations which are antiquated and and are a mistake we are continuing according to you. The ONLY time you size to radiation is with steam, anything else is a heat loss calculation of the structure, which is done by IBR.

[@TECTubefilms]

We agree! And in our full length webinars and in-person hydronic classes, we advise that a Manual J load calc (residential) or ASHRAE load calc (commercial) should be done. However, most contractors will either not do those calcs or they do not trust the answers. We have found the "radiation count" method to be something we can get them to do. Yes, it will still be oversized... because the radiators were originally oversized. However, historically the contractors oversized the boilers more than the radiators or baseboard... a lot more, in fact. So the radiation count gets them much closer to the correct size than if they just replace it with the same size boiler the old system had.

[@TECTubefilms]

1 hour webinar - check out minutes 13 thru 30 - tecstorage.com/controls/Webinars/2014-10-27%20Boiler%20Replacement.wmv

[@TECTubefilms]

Live in-person class coming up on Dec.4 - tec.coursestorm.com/course/hydronic-system-fundamentals-pdhs-for-pes-melrose-park