boiler and cylinder to combi conversion

[TerryWaite]

hi, when doing a boiler and cylinder to combi conversion, do you have to re-pipe all hot water outlets from the boiler or just remove some of the 22mm as much as is reasonably practicable?

Also, if the customer has a thermostatic mixer shower fed off tank and cylinder, if you put mains pressure hot water off a combi to this, surely it will be higher than the tank cold pressure on the cold side of the mixer, override it and not mix properly?

Would you also have to re-pipe the cold to the shower? Or even rip the cold water storage tank out and convert all the cold to mains? Theres probably a number of ways but I just wanted to know the general consensus.

 

[diamondgas]

What are you planning/quoting to do TerryWaite? Sounds like you're kind of new to this kind of work yeh?

 

[stevetheplumber]

we always price to disconnect the tank and connect mains to down service and we remove as much 22 from the hot services as we can usual scenario is hot from boiler is connected to the hot supply under kitchen sink and capped at base of old airing cupboard if possible we remove under bath but often this is inaccesable

 

[TerryWaite]

I am fitting a combi in a house with no heating in at all, just an electric immersion heater doing the hot water. Customer wants heating but wants the immersion heater taking out and a combi in. I have been doing commercial heating for years but not massively experienced at domestic.

Is it better to take the tank out and connect the mains to down service? That way you would have equal pressure to the shower wouldnt you? Is that the way most people do it steve or do some people leave the tank down service in? Where do you usually connect the new main to this? In the loft or somewhere on the top floor?

Many Thanks

 

[Js58gas]

First it depends where you are fitting the boiler, also you need to make sure u have enough mains pressure to run a combi. If you are fitting say in the kitchen you pick up the mains and hot supply there to the boiler, in the airing cupboard cap the draw off as low as you can and normally in the loft I take the mains from the tank and connect it to the cold supply pipe from cold storage tank to make everything on mains. The only thing with this if the pipes are old it has been known to cause leaks .

 

[TerryWaite]

First it depends where you are fitting the boiler, also you need to make sure u have enough mains pressure to run a combi. If you are fitting say in the kitchen you pick up the mains and hot supply there to the boiler, in the airing cupboard cap the draw off as low as you can and normally in the loft I take the mains from the tank and connect it to the cold supply pipe from cold storage tank to make everything on mains. The only thing with this if the pipes are old it has been known to cause leaks .

Thanks, just what I was looking for. When you check the mains pressure initially have you just got one of them pressure gauges that clamp onto the end of a tap? And when you say cap the draw off as low as pass. in the airing cupboard i assume you mean the old hot draw-off from the immersion heater? Is it aceptable to do this, there could be a long dead leg under the floor couldnt there which you wouldnt know unless yuou took the floor up?

 

[sparra1100]

no you need a mia cup to check the flow rate sound like ye getting in a bit deep here mate ,to hard to explain on here wats needed but make sure youve syphoned the emersion tank thro the hot not just the taps before you cut anything

 

[TerryWaite]

you shouldnt have told me, just let me get wet! thank you.

 

[Halesowen1]

Beware if you are doing this and not up for the job, as you are converting from a gravity system ( low pressure) to a Combi system (high pressure). Firstly the heating pipework may well have numerous leaks as it is put under high pressure and the hot water pipe work could also leave you with a few water features. Just be careful, its not always the plumbing part thats hard, but the problems you may have to get yourself out of when these problems arise.

 

[GQuigley67]

i am doing this at least once a week sometimes more, done 2 this week, 2 back boilers out and combis in, we always remove tanks and change to mains so the house has equal pressures at outlets.

When I finish pipiing up the boiler I turn the mains on to the boiler, check all the cold pipework then open the service valve to the hot water pipe and then check all exposed pipework for leaks, once satisfied I slowly pressurise the heating system while checking for leaks, I pressurise it up to 2 bar as this is what the pressure would be when hot and leave it for a while while I continue with the cross bonding/wiring or anything else on the job. This will generally show up any leaks on the heating system, but one we done the other week the tap connector to the hot tap on the basin blew off while we werent on the job though, a day or 2 after we had finished. so these things can happen and its best to have a disclaimer made up that you cant be held responsible for existing pipework.

 

[marleyco]

One of the main factors will be boiler siting. Minimum runs and disruption. Flue, gas route, And water connections all to be considered for quote etc. Scenario of boiler in kitchen, hot and cold taken from sink along with condensate. FLow return and gas might be a problem. BOIler where hot tank was will be good for all water connections But gas and condensate might be problem.

 

[GQuigley67]

best place for boilers these days is the kitchen with condensate pipes.

 

[marleyco]

i am doing this at least once a week sometimes more, done 2 this week, 2 back boilers out and combis in, we always remove tanks and change to mains so the house has equal pressures at outlets.

When I finish pipiing up the boiler I turn the mains on to the boiler, check all the cold pipework then open the service valve to the hot water pipe and then check all exposed pipework for leaks, once satisfied I slowly pressurise the heating system while checking for leaks, I pressurise it up to 2 bar as this is what the pressure would be when hot and leave it for a while while I continue with the cross bonding/wiring or anything else on the job. This will generally show up any leaks on the heating system, but one we done the other week the tap connector to the hot tap on the basin blew off while we werent on the job though, a day or 2 after we had finished. so these things can happen and its best to have a disclaimer made up that you cant be held responsible for existing pipework.

This happened to someone I know. Only he went home and got the call that made him virtually sick. Wasn't his fault, was bad connection on a hot tap, still it flooded out his boiler which was below bathroom. He got lucky and no real damage done

 

[AWheating]

i am doing this at least once a week sometimes more, done 2 this week, 2 back boilers out and combis in, we always remove tanks and change to mains so the house has equal pressures at outlets.

When I finish pipiing up the boiler I turn the mains on to the boiler, check all the cold pipework then open the service valve to the hot water pipe and then check all exposed pipework for leaks, once satisfied I slowly pressurise the heating system while checking for leaks, I pressurise it up to 2 bar as this is what the pressure would be when hot and leave it for a while while I continue with the cross bonding/wiring or anything else on the job. This will generally show up any leaks on the heating system, but one we done the other week the tap connector to the hot tap on the basin blew off while we werent on the job though, a day or 2 after we had finished. so these things can happen and its best to have a disclaimer made up that you cant be held responsible for existing pipework.

had a simular thing happen to me many years ago, fitted combi to exsisting open vented system and 2 days later the flexi pipe on the bathroom basin split open. Lucky for me i had got a date with the tennants daughter and was in the living room on the sette trying to get some when it went and no damage was caused. Made me look good saving the day

 

[TerryWaite]

hows about i put a pressure reducing valve on the main just after the stopcock down to say 1.5-2.0 bar? i will convert down service to mains in the loft so there are equal pressures, also, the pipework supplying the rads on the ground floor, would you run all the pipework upstairs in the floor and drop to low level for the radiators? it is a suspended wooden floor downstairs is it better to just run pipes underneath the ground floor too to the radiators? It would look alot neater that way, now pipe drops down the walls, but im thinking ill have to take all the downstairs floor up too to do it that way, but I dont mind if thats the better job.

If ran underneath the ground floor, would all the boards in the area where the pipes were being ran need to be taken up? Or do people just take a few up and use speedfit/ hep20 or something?

 

[TerryWaite]

had a simular thing happen to me many years ago, fitted combi to exsisting open vented system and 2 days later the flexi pipe on the bathroom basin split open. Lucky for me i had got a date with the tennants daughter and was in the living room on the sette trying to get some when it went and no damage was caused. Made me look good saving the day

hahaha thats a belter!

 

[GQuigley67]

i am doing this at least once a week sometimes more, done 2 this week, 2 back boilers out and combis in, we always remove tanks and change to mains so the house has equal pressures at outlets.

When I finish pipiing up the boiler I turn the mains on to the boiler, check all the cold pipework then open the service valve to the hot water pipe and then check all exposed pipework for leaks, once satisfied I slowly pressurise the heating system while checking for leaks, I pressurise it up to 2 bar as this is what the pressure would be when hot and leave it for a while while I continue with the cross bonding/wiring or anything else on the job. This will generally show up any leaks on the heating system, but one we done the other week the tap connector to the hot tap on the basin blew off while we werent on the job though, a day or 2 after we had finished. so these things can happen and its best to have a disclaimer made up that you cant be held responsible for existing pipework.

would like to add a wee bit to this, the one i finished on saturday and had it pressurised at 2 bar for a while and seemed OK, need to go back as the pressure is dropping , almost certainly not my pipe lol

 

[TerryWaite]

there is no heating in at the minute, completely new installation

 

[GQuigley67]

so its a boiler feeding a cylinder only ??

 

[TerryWaite]

no at the minute there is no boiler, just an electric only immersion heater

 

[GQuigley67]

i went to an emergency call out the other day, tank connector was leaking, anyway noticed the F&E tank was dry, so questioned this with customer found out she had a combi, turned out easier for me and better for her to just convert to mains, when i do conversions i remove all pipework and tanks if i can, if i cant just leave them there but all pipework is removed, much neater and imho its lazy if you do a conversion and leave the cold still gravity and leave the old F&E tank in all piped up as if its still in use

 

[TerryWaite]

yeah i agree with you there, if its not in use, dont leave it in all piped up, atleast disconnect and remove the pipes, and preferably remove the tank

 

[SafeGasInstall]

it is a criminal offence to leave any copper or brass behind you !!!

 

[TerryWaite]

it is a criminal offence to leave any copper or brass behind you !!!

i second that

 

[GQuigley67]

thank god for scrap lol £170 i got the other day, payed for my mates wages and some diesel lol