EXPANSION VESSELS, sizing, installing and how they work. all trainees need to know about ex vessels.

Derek tells us in the video all about heating and potable water expansion vessels. He cuts open the vessels to show us inside, explains how they work and how they should be serviced and installed everything a trainee gas engineer needs to know about expansion vessels.

[@coldscug]

Thank you for the detailed video. One thing i wanted to add here is that there are more than one reason for the expansion vessel to go to the return side. The first is obviously to save it from high temperature and the second is to gain the positive pressure of the circulating pump. In a small house it may not be an issue but not for a commercial or industrial setting.

[@zahurzaman4865]

Thanks Derek well explained about the system design for sizing an expansion and it’s purpose.

[@johnward5006]

Great video, as always. Glad to see you use minimal physical energy to charge vessels. In the early days I used a bicycle pump! Only ever use battery power now!!!

[@addaplaster4976]

Cheers, Derek. Another great video.

[@vladimirstafasani4630]

As always top video love it. Thank you Derek

[@richardharris5858]

Another great video Derek. Thanks

[@monikanader9454]

Great video, well explained. Thank you👍👍👍

[@AhmedAhmed-zj4zd]

Well done Derek very useful vedeo I learned alots from ur vedeos Thanks very much for all ur effort

[@rivkiroyde4362]

Thanks Derek great video 🙏👍🙏

[@manjsingh6500]

I can’t stop watching 👍😊

[@anarchyr32]

Finally a informational video from someone who isn't Indian

[@michaelbeard5508]

Michael Beard Thanks Derek very helpful video well explained.

[@mohammednadeem7274]

That was an awesome video & very well explained Derek, how did you manage to do all the calculations too much maths in there, 🤣🤣😂😂, it was brilliant and enjoyed watching it, a very useful video on expansion vessels. It was cool what we got to see inside the big beasts. 👍👍😀😀

[@seamusfitzgerald5917]

Very good and informative video.

[@secondchance4498]

Chris Taylor Thanks Derek.

[@tobyfletcher6803]

quality advise good videos

[@raul835]

Very thorough

[@hussaingonoo8408]

Another excellent video Derek, any chance of making a video on how to test flow switches on a boiler?

[@tomkatgastraining]

I could put that on the to do list 👍🏻

[@robi4387]

Always set the work piece solid and have two hands on any angle grinder preferably using the side handle. The ligaments in your fingers will take 18 months to heal if damaged and an operation under general if snapped.

[@mj0n4id36]

Interesting. Was never to sure about expansion vessels but now I feel a little bit better. I’ll definitely be watching this one a few times though. *Especially the maths* on sizing them up. Once the expansion vessel takes up the expansion of the central heating water, what then happens with that water? Does it always stay inside the expansion vessel or does it make its way back into the central heating system again? Also, what does this pressure in the vessel actually do? What’s it’s purpose? Sorry if the questions are silly and don’t make sense. I had to ask. Thanks Derek. Much appreciated 👍🏻 Asian Jon. Training.

[@tomkatgastraining]

Yes the water stays in the vessel and the air in the vessel keeps the pressure behind the diaphragm so when the water cools the air pushes the diaphragm down again

[@jaganadenmauri8706]

Hi Derek nice explanation as always, Could you let me know where can I get one of these coefficient chart please Thanks

[@valentinmirauta7059]

Hi Derek On the calculation when you get to the maximum pressure of 3 bar where the 1 comes from so it makes 4 ? Where can I find all the formulas used and the chart ? Thanks

[@umar_azam]

Hey! Great video, insightful for both the tradesman and civilian (like me!). One thing I’m getting a bit confused on is whether a 300L megaflo and a 30kw system boiler would need a separate expansion vessel for 10 radiator system? I held off on buying one as the merchant included it but my builder suggests that a megaflo has one in. The merchant explained that the megaflo one is only for the hot water and not for the central heating, again not sure. Key for me if it’s needed or not which is something I’d hope you can help explain :)

[@tomkatgastraining]

The megaflo has a built in expansion vessel for the hot water and a system boiler has a built in expansion vessel for the primary water to heat the cylinder and radiators. They are separate waters so need the 2 vessels

[@imaginehomes3871]

II don't see how multiplying by 1.3 is 3%. x 1.03 is 3% more. 1.3 is 30% more. Can you explain this, thanks. I asked Altecnic and they said that the pressure vessel size is correct if from cold to hot the pressure rises by no more than 0.5 bar so if you calculate it and then it rises by more than that you need a larger one.

[@tomkatgastraining]

If I could I would lol it’s the factor that they use for the water volume it made no sense to me either but that’s what is used.

[@tonysmith7028]

@@tomkatgastraining Also 0.5x0.2=0.1 not 0.7.

[@tomkatgastraining]

@@tonysmith7028 if you watch the video you will see I put the mistake on the screen that you add it not times it and I even say later in the video about the mistake

[@willlomas2725]

Excellent video Derek.Just wondering what are your thoughts on flushing expansion vessels to prevent Legionella building up inside.I have recently been pulled on a Legionella risk assessment and have be asked to have all vessels/pipe work modified enabling them to be weekly flushed....seems over kill to me.

[@tomkatgastraining]

I think that if you install the vessel higher than the cylinder a use copper pipe and not flex’s there is not much chance of getting legionella.

[@brianstanbridge4271]

Brilliant video and explanation. My boiler expansion tank within the boiler has gone. Can I leave it in place and put an external tank on the return

[@TONE11111]

yes..

[@freezefoot]

Great tutorial.Loved all the detail and the practical aspect in the workshop at the end.An adult learner question please:@19:30 you gave us a figure of 1.3 for expansion .not quite sure how you came to this figure or how that is linked to 3%(0.03?).Is it a generic figure for expansion or one you came up with by calculation.Thank you again.Look forward to your next video.

[@tomkatgastraining]

It’s a figure the manufacture came up with for the expansion of the water so 3%

[@freezefoot]

@@tomkatgastraining Thanks for the clarification

[@jamesabdilla]

@@tomkatgastraining 3% is 1.03 not 1.3. 1.3 would be adding 30 percent not 3 percent.

[@atlantisfirstaid]

@@jamesabdilla is correct. The calc should be 1.03 not 1.3. 1.3 is 30% expansion

[@hengamehalibakhshi3423]

Dear sir thank you. I have a question about L/D ratio for expansion vessels in oil industry?

[@samchappell233]

👍👍

[@aryehelectricalltd7247]

rule of thumb 1 litre per kw or you boiler plus one size up when is fare from each other

[@manjsingh6500]

😊👍

[@chriscooper5875]

Surely it was .5+.2 gives you .7 if you multiply it it gives u .1

[@brightlylightly2097]

If my electric water heater is 100 litres what size expansion vessel do I need pls?

[@SuperWayneyb]

🤘🤓🤘

[@davidb2464]

Hi Derek, For those of us over in Belfast, with no water meters, is there a rule of thumb calculation as to how much water there is in a system, (for instance, a normal 3 bed semi with 10 rads would have about ?????? litres), and does the amount of water ish have to be very accurate?

[@tomkatgastraining]

It has to be as accurate as you can get it or the vessel could be to small and you get more than a 0.5 bar increase. I don’t know of any rule of thumb for the volume but most combis are set up for about 130 to 140 litres

[@davidb2464]

@@tomkatgastraining Hi Derek, thanks for the video and this snippit of info.

[@cerealkiller4248]

I had to work out expansion on a system using something similar to this on a large commercial heating system a few years ago. They’d had new boilers, and someone had noted they had no expansion vessels. He was correct, they didn’t, but what they had was a buffer tank of water filled by a float valve. When the system heated up the expansion was controlled by a pressure switch opening a solenoid valve dumping the increased water volume into the buffer tank. I explained this to the engineer reporting no vessels, but he was adamant about there being no vessels. I left him to run with it ( he was my supervisor), and he put in 2 small vessels prob less than 100L total. He ditched the buffer tank, so, when the system expanded from cold the system kept shutting down due to high pressure. I was asked to look at it. I’d not done anything like that for decades, and after a lot of googling came up with a figure of ( roughly from memory) 420L. When I submitted it to the customer ( the local authority ) their engineer just said “we operate on 1 litre of expansion required for every 1 KW of output of the heating systems boiler/s” to which they ordered up 2 x 300L expansion vessels. They went in and there’s been no further issues since. Talking to other commercial engineers since, the 1L for 1KW seems to be an accepted way of calculating vessel sizes on large unknown heating systems.

[@jayseabie215]

33:53 Tut tut, water from the schrader valve doesn't always mean the diaphragm has gone, most times it's probably just condensation. Shoulda mentioned that methinks. (Of course average Joe plumber will just go for a straight replacement rather than double checking!)

[@tomkatgastraining]

Tut tut that would only happen it the Schrader valve is at the bottom of the vessel as the water is heavier than air so sinks to the bottom of the vessel. Should have mentioned that me thinks but average comment makers only go for the negative.

[@mali2132]

@@tomkatgastraining Yea we also need to know the difference between Negative Remarks and Good Constructive Criticism

[@Handymandavid]

Hi, how can a 3 per cent comes to 1.3? it must be 1.03

[@dm4728]

Just about to make same comment, 1.3 is 30% expansion

[@robi4387]

I thought I would see if anyone else had spotted that and I'm glad someone did. I know the general rule is to size CH expansion tanks at 10% of the system volume and most people say that that is conservative. It also seems that most heating engineers oversize both radiators and boilers, but that's another topic.

[@Handymandavid]

@@robi4387 thank you for your very great videos and Chanel. Can I suggest a topic for video? Basically, I came across this situation that I have been asked to do a cp12 for an office and they asked me if I am commercial engineer and I explained that what commercial mean in gas industry, had another situation that it was a commercial property and I doubt it that is the gas pipework needs to be labeled or not, another situation was they joined two offices together and they had two meters but the total kw was more than 70 but pipework was 22mm because they fed from different meters and I didn't know if I can do it and raised it with gas safe and they said I can do it. I am sure you will find other situations related to the commercial and can make another great video about it.

[@steve250276]

steve ward

[@b21playa]

You allowed 30% expansion in your formula, not 3%. Excellent explanation though :)

[@timdawson15]

Yes, should have been 1.03 not 1.3!!!!

[@mohammadabohasan9737]

Why you make it complicated when it’s easy 150x3%=4.5 L

[@mali2132]

When you do the calculation it works out at 6.18 Lts (Not 7.8) Which is 4.12% not 3%

[@user-tenbellies]

1.3 is 30%… 1.03 is 3%

[@joaovittoria2533]

👍👍