How Combi Boilers Work - Plumbing Tips

[@plumberparts]

*Links to the tools I use everyday here:* www.amazon.co.uk/shop/plumberparts Plus, follow my *Vlog “TimesWithJames”:* kzbin.info

[@SapphireKnightofWhiteLotusCity]

The first video I saw where I actually understood... Thanks mate...

[@AliciaSykes]

Really helpful video! I've always been worried that my hot tap water wasn't "clean", as I know radiator water is recycled and can get quite grimy. But your video, showing that they're two separate systems which don't mix, transferring heat through a heat sync, has put my mind to ease - thank you!

[@JohnJKelly-of4dc]

There's no issues with them, they're great

[@ElBee92]

Fantastic walkthrough. With it getting very cold in the UK at the moment, I did wonder how the combi worked!

[@Rom-ju5tf]

Dude you are great teacher.

[@jellyboy123]

just had a Worcester Bosch Combi installed come to this video to know how it all works its amazing coming from a old fashion tank boilers

[@jonanthony7709]

Very useful and well explained. So far I have had only systems which required loft header tanks and have always had water softners. We are now moving to a new home which has a combi-boiler. Can we have a water softner or will it damage the heat exchanger?

[@justmakingcomments1]

Great video, very good that you mentioned the heat store that most gas boilers wouldn't have unless they are some sort of hybrid type a bit like the Worcester Highflow!

[@glennproctor4178]

Very useful video, I've had combi boilers for years but only now understand how they work!

[@palanivisu1344]

This was brilliant outline of how heat exchange works and idea of how combi boilers works, many thanks for this video

[@plumberparts]

+Palani Visu No worries mate!

[@tommurphy457]

Hi pal. Very well explained. Tell me do I still need to keep my copper cyclinder

[@jessestrum]

hi the hot water supply to the taps, does it also supply a mixer on the shower, cheers love your videos

[@markbusby9709]

Hi plumberparts, thanks for the very usefull videos, great help, I live in the UK just finishing my house refurb, nearing the installation of a new boiler, I live in a bungalow with converted loft space (two rooms) so no room for tank, Im faced with the decision of a combi boiler or un vented system, my brief research so far, and one very expensive quote for the unvented boiler system are very expensive, compared to the simpler combi system, I realise that there is no "stored hot water in the combi" just turn and go!.... So my question is what is the benefit of choosing unvented over combi, or visa vera, cheers Mark

[@adriano9586]

This is a very good and simple explanation!

[@DrBroncanuus]

I want to ditch my open vent heat only boiler for a combi system...but i have 3 shower rooms and 3 loos n my house ..can a combi cope ?...should i consider a storage combi boiler ? and will my power showers still work without the shower pump and just the combi pumping the water ?

[@ninjapixiequeen]

if you have a 4 bed house operating as a household a combi boiler would not be the best choice, as the water is heating through a heat exchanger as opposed to being heated in a tank it is best for smaller properties, they are cheap and easy to install but you're better off with a higher capacity in a larger home. i'm in training at the mo but i recently did a theory exam on hot water systems and this was our instruction. hope that helps

[@nixonsmateruby1]

I want to know if I can heat a combi boiler by ceramic heat plate rather than gas? Will the Combi boiler detect it's warm and pump it around the heating system for radiator?

[@dharmadoc]

Great video! 👍 I have a dumb question... With a combi-boiler, do I need to turn on the house heating to heat up the water for a shower?

[@grahamhamley6446]

Excellent explanation of the pressure paddle .......

[@kevinski7927]

We do live in a hard water area.I will look into it.Thanks very much.

[@narcsurvivors2445]

My gf has an oil fuelled combi like this , my question is , does she keep the hot water "on ' via the select switch indoors , or only put it to on when needed ? She says to run a bath it goes cold towards the end , she usually has the switch to off , and only switches it to 'on' for a bath . as she's worried about wasting the oil fuel. It's a Worcester greenstar danesmoor external 18/25 ErP Many thanks.

[@Jay-cx1er]

Thanks this really helps with my training. Great explanation 😊

[@Ilovetosingem]

Hello there. Nice video as always. Q. So the water heater is acting just like the copper tank in my cupboard, the coil heating the water, correct? Also, do the combi boilers need the pressure topped up, like the other systems. Thanks again for you expertise. Stay safe you and yours.

[@jamesturnerphotograp]

Is it possible to shut off the heating feed to the central heating system to drain down the central heating and work on it, whilst maintaining a hot water supply to the taps?

[@bradbartlett2663]

Can you help at all? I currently have an oil boiler and am considering switching to a gas tank boiler. What should I do? I need a new boiler as my oil one is quite old now and we’re renovating. I think gas is cleaner.

[@paul1962uk]

brilliant idea having the boiler outside

[@TomaszRykala]

I can't believe this video is 12 years old. I'm feeling old, but also educated!

[@1972piledriver]

I have a boiler very similar to this but inside the house, since yesterday I have no hot water radiators are heating up ok, any idea what's happening

[@germanshepherdforty3]

I have a combi boiler for my water and a boiler for my central heating system. My central heating boiler needs to be replaced, can my combi boiler be used for my central heating.

[@herdwick3]

Excellent , mate . Keep at it . I'm an amateur , but want to plumb in my stove , using 28mm pipe . End feed fittings much cheaper than solder ring , but are they more tricky to use for an amateur ?

[@nedarichards1947]

I have a combi boiler and at the moment is in the bedroom (on the outside wall facing the garden). I would like to move the boiler in the garden, so I want to keep the boiler outside of the house. Is this possible? I have seen someone else do it. Is it a good idea? How much is the approx cost that im looking at?

[@firefighterno1]

As always an excellent video - well explained - thanks for posting geezer

[@richbutler718]

Hello , can you give me some advice , I need to replace my stop cock in the kitchen , the combi boiler is in the old airing cupboard upstairs above the kitchen, I have a direct replacement stop cock , I can turn the mains water off in the street. After I have replaced the stop cock , will I have to do anything to bring the system back to normal, ie if the water comes down from the boiler above , do I just go through the, “topping the pressure up process “ Any advice would be gratefully appreciated. Thanks

[@johnbewley9166]

Got a firebird combination boiler , it’s runs for a few hrs then locks out and you have to press reset button on on digital control box to start again , pressure does vary a bit , got any ideas been doing it for a couple of weeks now and seems to be happening more frequently

[@KAWAWA23]

HEY PP,WHAT IS BAR MEANS WITH THE COMBI HEATING SYSTEM?AND IS THE VALVE OF COLD WATER GOING TO THE BOILER NEEDS TO BE ON ALWAYS?HOW DOES THIS WORK?IM JUST WONDERING IF THE WATER INSIDE THE HEATING RADIATORS WILL EVAPORATES WHILE HEATING IS ALWAYS ON?HOPE TO HEAR FROM YOU SOON.TY

[@magna59]

Keep up the good work . Knowledge is power ........ yell out the safety issues please , for those who think they can take the lid of a combi & be safe..... there are potential problems lurking !

[@PROXIMASTARMAN]

@plumberparts i was told by a number of people on the net that it sounds like the diverter valve could be stuck and it was.i little jiggle and bingo the heating is back on and still running after 2 hrs so if it happens again i know what to do. thanks for the imput.

[@sidstam]

Fast vid for my slow brain, but got the general principle of it, so many thanks.

[@MrNelson52]

This is a bit of a long one for you but here goes. I have a grant 26e vortex combi outdoor boiler 3 years old. It started producing black smoke / sooty fumes so totally cleaned all the burner box and tabulators, new rope seal nes burner nozzle of the correct type 0.75/80 EH etc. Fired the boiler up and still the same problem would run for a couple of Hrs then the flame eye would carbon up. Got an engineer out and he set the oil pressure to 8 bar but could not get the CO2 down to 12% the nearest he could get was 14.7% this with the air fully open, when he closed the air down the CO2 just shot up. Luckily he had another burner RDB1 and put this on but this had exactly the same problem. The engineer has no answer as to why. Any help would be much appreciated. Colin

[@jonanthony6078]

My friends warm flow combo isn't firing up the relay is rattling ,could it be water damage on relay circuit

[@ipod1978]

I’m sub’d to your channel pal and this was the first video to pop up when searching for combi boilers. Quick and easy split (2 parter lol) question if you don’t mind…. We don’t have gas where we live. We have an old F&E header system which is a pain in the ass. Although this video is a few years old would you still recommend an oil combi system if gas is unavailable? Secondly am I correct in assuming if I had an oil combi boiler installed, I could have a combi boiler fitted in the shed where my current boiler is located and simply have the old boiler removed, remove the hot water cylinder upstairs and completely do away with both the header and expansion tanks in my loft? This is just slightly more expensive than a gas set up … but… we unfortunately simply don’t have the option of gas and won’t for a few years yet. Any help would be welcomed. Nice job on the tiling in your bathroom btw. Pissed myself laughing when you broke a tile but made for a great finish.

[@Hevva67]

Can you or anyone else tell me why the heating only works, when the central heating is on? I have a Oil Combi boiler, think it’s a Grant one. It only heats the water, if I put the heating on! I just tried it again, first time in years, and I left it on for like ten minutes, the pilot light ignites at first and starts “heating”? But the hot water never gets hot.... ran it for at least two minutes... Do you have to run the cold water tap first? Anyway, back to putting the heating on at the same time..........

[@TheSpyder53]

Hi I’ve got a grant boiler installed in February this year, problem is it seems to have a lot of air within the boiler how do I solve this apart from calling out the installer

[@LabRat6619]

Grant are good boilers, have installed hundreds of them.

[@falacomleo]

hi, i am having a little problem.. my combi boiler is not getting 1 bar pressure is only at zero. There is one flexi hose that connects from main to the return pipes but when i disconnect the main there is no water also coming to the flexi, also there is no valve to open or close from the main only the one underneith the boiler... if you like i can send a video or pictures thanks

[@deanneedle6776]

My shower goes hot and cold at regular intervals. Diverter seems OK as the micro switch isn't tripping as the temperature changes, and all other taps provide constant temperatures. I was going to change the shower thermostat, but noticed the temperature regulates correctly when another tap is running as well as the shower. Any ideas? Thanks

[@laddie6686]

MY COMBI KEPT SWITCHING OFF (RED LIGHT) PLUMBER CAME TOOK FRONT PANEL OFF, WENT UP TO THE TOP AND USED A VERY SMALL PIECE OF SANDPAPER, HE CLEANED SOMETHING. MACHINE WORKS FINE BUT INTERESTED TO KNOW WHAT HE DID. ANY IDEAS?

[@darrenfreeman4936]

great video, i found the hanging rad video helpful cuz i installed 3 yesterday and used your method, all level. i would like to see a video on tap maintenance, from changing washers to why jumpers come liise and get stuck etc :)

[@indiawest2025]

What are the benfits of the one that you crouching next to?

[@James-sc1lz]

Is it okay to have cold water come in using the valve when the boiler is on? If so, why? My combi might be playing up. Water hot and cold

[@PROXIMASTARMAN]

hi james, weve had a brand new Ideal Isar HE30 boiler for about 4 yrs and its been trouble free till now. the hot water is still coming thru the taps but the central heating has stopped working. on the screen it has status = C and the blue burner light is blinking constantly. any advice on what the problem could be and if a diy fix is possible would much appreciated ? thanks

[@mattmartin3086]

Hi plumberparts. Gr8 video btw. I have a volkera compact he. It fires up for 2 or so seconds then tries to drop gas and turns off to solid red. Fires ok but goes off to red seconds later. I have numerous posts on the net with the same problem but because they obviously sorted their problem I never get to see what "sorted" their problem. Could you please help with what the problem could be as I can't afford to be messing with dummy engineers that charge the earth for still left with same problem

[@vikinj]

Doesn't these boilers freez when it gets really cold,like below 0 degree C ?Or is the system filled with antifreez?

[@DarioVolaric]

So if you have central heating, the heater water is pumped through the radiators if you turn on the heating, and otherwise it cycles through the tank?

[@plumberparts]

+ᴅᴀᴚᴉᴏ ᴠᴏᴌᴀᴚᴉᴄ Kinda!

[@chinclow65]

I have a combi ravenheat HE 120(T), the old model with 3 way valve working without any issues for the last 8 years, However now to have hot water (ie unit registering hot water flow at the tap) you would need to open the hot tap at relatively high flow which is wasteful and impractical as you would be splashing and messing the place, specially in the kitchen with small hot water bore. PS: This phenomena is shown in the video "hot water with combi boiler" on youTube which has no narration or written real solution to the fault. You thoughts on the root cause of this fault is very much appreciated Thank you

[@davidpatrick8770]

We have just had a new Worcester Bosh Greenstar highflow installed. Big problem with hot water . Open hot water tap warm water then hot in a few seconds, a few seconds later water turns cold for few more second. Then water starts to gets to temperature in 5 more secs. Lot of water and gas wasted. Is this normal. Two Worcester Bosh engineers say boiler is working to spec

[@AK_DRONEVIEW]

hello mate .. no hot water from my oil boiler, how do I do it please?

[@PROXIMASTARMAN]

@plumberparts im pretty shure its the combi boiler the model is ideal isar HE30. theres a few of them on here but not with this fault.

[@spartt4360]

Hi All new heating system was replaced in my house with combi worcester boiler. Can I ask is it nessesary to install a stat or put a timer on electric supply to save energy? I mean if I turn my radiator valves down to 1-2 at night just to keep them slightly warm, will boiler use alot of gas for that? Does combi boiler work in 1 efficiency mode- like heating water / not heating, or if I only running tap slooowly with not much of hot water it uses small amount of gas to do it? Sorry for stupid question but I am new to them. not sure if 1 stat in 2 bedroom house would help to save much energy.. For example if my stat is in living room and radiator valve is turned to (1), but other rooms radiators turned on (4)- Stat will tell boiler to crack on to reach 21C and boiler will be running full capacity when my other 2 rooms will be roasting. Thanks

[@foppo100]

You sound confusing .If you open your tap slooowly you are still using gas.If I run my hot water tap slowly the water gets very hot with my combi boiler.

[@armarnigray]

Great explanation video... please may you do a video explaining how a combi boiler heats portable water and radiators without cross contamination... I understand there's a 2/3 port valve that controls the water flow but can you explain it please

[@sozzerz]

if we keep the CH on and let the rads get hot then it now bangs too. no air in rads. do we need a new DHW thermostat and the boiler bleeding and charging? is the heat exchanger damaged? inside the heat exchanger tank, is it a tank filled with separate, isolated water with two pipes running through it (DHW, CH) or is it tank with CH water passing through it with one DHW pipe passing through it? does the pump over run work on DHW or just CH? sorry for all the q's I'm on a small phone and in pain

[@plumberparts]

Seddon bleed the boiler but only after it's been off for an hour to avoid scalding. PP!

[@barringtonbond4234]

Such as Potterton, Worcester, Valliant Baxi Biasi, etc etc You do know your stuff and don't think im criticising, just thinking of the thousands that would like to know about there own combi boilers

[@justineahononga]

Thank you so much for your video it's was a great help.

[@plumberparts]

+justineahononga Thanks for your comments, glad you've got a better idea about how these boilers work now!

[@TheDerek47]

What would be the term for a combi boiler in North America & does it require a 200 Amp breaker panel?

[@bashirabdullazade6474]

hi how can i isolate the water going to boiler. I want to flash the system, but do not want to flash the inside boiler. so I want isolate the boiler when flashing . thanks

[@andrewdonaldson6334]

the plumer who came out on Saturday said not all of them do its a baxi 105e I think should I get a second appinion?

[@plumberparts]

Do what?

[@650GSF]

Hi ya, figure this one out if you can, I have a valiant combi boiler, when the heating is off my rads still get warm, to stop it happening I have to turn the hot water control on the boiler right down so the hot water is only look warm, if I turn it up to the point I get hot water the boiler seams to keep running on and of all the time and the rads get warm to the touch, running up my gas bill :( is their a valve or something that is sticking letting the hot tap water go into the rads ?

[@mataicakau237]

I got a combi 30HE boiler and it has no power showing on it. Turned on the main switch but no power lights coming from the boiler..No sign of life! what should I do?

[@handymandaz]

If you drained a combi system down how would you fill it without causing the pressure to rise dramatically

[@MrTheCoolMonkey]

how much are combi boilers? for say 4 bedroom house? and do they cost more to run

[@saywhatiwantidontcare]

I have one of those boilers oil fed . But why does the hole house stink of oil when it working

[@paulcarrick6870]

Hi hope you can help we've had a heating engineer service our worcester combi boiler he then replaced the pressure relief valve and fitted a new expansion tank but when we used our shower it started tripping the boiler so he turned the pressure down saying the boiler was getting to hot from the water pressure used for the shower, now we're struggling to get the hot water taps to fire the boiler is there anything we can adjust ourselves to improve this. if we turn 2 taps on it fires the boiler up?

[@plumberparts]

+Paul Carrick Get a different engineer in! Sounds like an air lock or something. PP!

[@paulcarrick6870]

+plumberparts thanks for the reply yeah will have to try something like that were moving house in 3 weeks so dontvwant to spend a fortune but want it right. Hope it's nothing major though

[@deborahdoherty6729]

can I turn off the electric to get a light fitted would the gas boiler just reset itself

[@lastpostbugler]

I have the BAXI Combi 105e boiler. I would like to know how to RE START the pilot lite. The plumber ( sorry heating engineer) has quoted me 175 call out fee. I told him he could go forth & multiply for that price. ( & thats prior to carrying out any work) Perhaps you could do a vid on the subject

[@plumberparts]

+Belfastchild Hi mate, we're not allowed to make vids on Gas stuff, otherwise GasSafe will kill us! PP!

[@GeorgeMadeThis]

So when its heating water the central heating is on?? I've just had a MASSIVE bill from my gas provider and the manual for my boiler only shows hot water controls. So I'm trying to understand this whole thing haha. any help would be appreciated!!!

[@plumberparts]

***** Which boiler have you got?

[@chinclow65]

***** HI Good work and advice. I have a combi ravenheat HE 120(T), old model with 3 way valve, to have hot water (unit registering hot water tap flow at the tap) you would need to open the hot tap at relatively high flow which is wasteful and impractical as you would be splashing and messing the place which is not the way the unit is designed to operate. I would appreciate any thoughts that you could have on the root cause of this fault. Thank you in advance.

[@robwood1983]

Brilliant video and well expained

[@barringtonbond4234]

adding to that Valliant could be a bit too complexed so therefore you could describe the workings of a potterton or Ideal which are fairly straight forward to look at and then say this applies similar to most domestic Combi boilers in the average family home especially those of you in more built up areas and not a house in the middle of a farmers field with a Combi boiler outside looking as big as a Oil Boiler Thankyou

[@reconnaisancesapper]

Great video there mate.

[@sammyslimm]

wicked video, always wondered how my combi worked! cheers

[@sozzerz]

our greenstar 28i jnr DHW was very hot, then after starting to fill a bath for the first time in years the water went cold and the boiler started banging (think sledgehammer on the boiler). did this one more time the next day then no more hot water. when we open the tap water comes out of the pressure valve outside. CH was okay but now the pump overrun does not work 90% of the time. I'm thinking its overheating and the banging is steam?

[@plumberparts]

Yep. Needs a full drain down. Power flush and also the heat exchanger checked. Good luck dude! PP!

[@sozzerz]

+plumberparts hi thanks for the info. sry for all the Q's. okay got a update for you.. CH okay pump overrun runs now. but this is strange CH at 1.5 bar rads hot at top and bottom and have no air in them. but the DHW is cold with no ignition and when the hot tap is open water comes out of the small curled pipe outside, the overflow pressure relief valve pipe I guess. how can this be if the CH has the right bar? this started after the last big bang (boiler not universe) also if thermal cut out kicks in does that stop everything, pump overrun and so on?

[@sozzerz]

+plumberparts is it safe to run the CH for a few times a day if its got water at the right bar but the DHW part of the system is empty?

[@eleet2299]

I have a grant Vortex combi 26 boiler. the hot water pressure is low do you have any ideas cheers T

[@plumberparts]

+EL EET Furred up heat exchanger.

[@PhilipGeorgeOnline]

well, Now I know how a combi boiler works, but will still be calling in a plumber, My success rate with anything bathroom related is no good. You put out some good plumbing tutorials, thanks

[@thomaspotter604]

Thanks for the knowledge 👍🏻

[@THEPINKFLOYDIANS]

I ran out of boiler juice, filled the tank, do I need to bleed the system........... oh I have a big bubble on the outside which is half full is this a sign of it needing bled??

[@THEPINKFLOYDIANS]

my unit looks exactly the same as the one in the video.

[@dennispratt3344]

we are oap our valliant combi has a weeping leak on the dhw chamber! can it be repaired ? or does it have to be replaced with a new one ! as i see it it just has two gaskets one top & bottom bolted & thats were it is weeping thanks den.

[@plumberparts]

Hi Den, is it not leaking on the nuts that the pipes go in and out of? James, at PP!

[@dennispratt3344]

+plumberparts thanks for the reply mate love your video's i think it's leaking on the top & bottom gaskets of the black chamber & just wondered if the gaskets could be replaced rather than a new replacement @ about £140 for the part the boiler i think is about 25yrs old or would you suggest putting the repair cost towards a new boiler id'e give you the job been in the trade all my life but now retired on pension & allways done my own repairs thanks den

[@plumberparts]

I'd go and change the chamber, although a new Valliant combi is £900 and it's probably be miles more efficient now. It's your call! best, James at PP!

[@dennispratt3344]

+plumberparts thanks James any best place for parts please? den

[@razzi3E]

How do you increase the water pressure inside the unit?

[@fasttofuryos]

I have a comby boiler , name is grant comby boiler 70 mk2 .i am not a plamer but i think is the wather valve bypass because I lose hot wather outside . so , can someone what is the problem if I lose presure and hot wather come outside

[@jacquelinemcaneney3409]

Need boiler for shepards hut what do u recommend

[@armorhelix]

Great video. Very informative. Thanks.

[@kevinski7927]

Our hot water turns cold and then back to hot.Any suggestions as to what could be causing this?Thanks

[@simonetobie1000]

I have exactly the same problem and have to wait with the hot tap running for at least 2-3 minutes before the water gets hot again.

[@WolfoxMaty]

Still feel lost, can you tell me please how to increase pressure on this one?

[@jacobcolombe9561]

I assume you're referring to pressure loss in your central heating system? Try filling the system and take note of what the pressure is standing at. If the pressure starts to drop it could mean you have a small leak in your central heating system... I'm still learning about this kind of stuff myself so it's just a suggestion. 😊

[@suunnyykhan8111]

can you explain how heat exchanger work please

[@mcfly10146]

looking at some of these questions I think pp may regret saying he;d answer any questions..!

[@educatedrock]

Bar means 14.1 PSI, Cold water must always be on because it does evaporate. Plate ex changer has hot water from the boiler and cold water from city water and mixes through the plant and heats up cold water, very efficient but has its limits. Pending on your house or apt. Apt is ideal, larger homes in North American will battle to keep up because Americans waste water for more then Europeans. Most tradesman in North America recommend hot water tanks because its easier for them and they're dumb

[@ed209robocop]

how do you setup a gas valve on a ravenheat combi RSF 84E. Ed

[@kevtaylor9379]

how do you release the clip on a baxi 3-way diverter valve actuator (243341)?

[@plumberparts]

+Kev Taylor I'll have to have a look!

[@one-off3264]

Anybody have any experience of reliability Grant Vortex Vs Worcester Bosch heatslave oil combi?

[@macukay764]

Very good thanks

[@lukepowell2576]

Great video, Thankyou

[@adilelhajji9514]

a great each is which video thanks