combi boiler plumbed as a system boiler advice please

[fraz63]

I,ve just had a gas safety inspection done and the engineer pointed out that while the boiler was a combi type it has been plumbed to heat a water tank, what he called a system boiler, should I have the boiler re-plumbed to operate as a combi.???:thinking:

 

[erpkid]

Not that unusual. I installed a combi at home as a quick fix during the building work we carried out here. Now it functions as a system boiler with just the kitchen hot tap being fed from the combi element.

 

[lame plumber]

combis are cheaper than system equivalents to buy, so a no brainer really

 

[Howsie]

combis are cheaper than system equivalents to by so a no brainer really

Makes no sense to me I'm afraid.

 

[850Rick]

If you dont no then im definatly puddled lol

 

[mountainman]

I've fitted many combi's as system boilers over the years, always works a treat.
And as already mentioned, still the combi option for a nearby draw off or two.

 

[buckley plumb]

why not done them in larger houses - had combi hw side feeding kitchen taps for instant hw and then fit an s plan to feed htg and unvented cyl nothing wrong with that .also seen combis used as water heaters only where the htg is just a 22mm pipe looped under floor and back

 

[fraz63]

Is the combi set up cheaper to run? I mean, and forgive any plumbing ignorance, but as I understand it the boiler will be keeping a large tank in the attic heated to a constant temp ready for use,( all hot water taps are supplied by this tank ) whereas the combi set up only heats what you use.yes??,no?? ergo, not burning gas when not in use.

 

[lame plumber]

Makes no sense to me I'm afraid.

why pay more for a system boiler when you can set up a combi as a system boiler on a cyl for less as combis sell more they are cheaper than a system boiler in the first place.hence no brainer for those with a brain:rolleyes2:

 

[leethegasman]

I,ve just had a gas safety inspection done and the engineer pointed out that while the boiler was a combi type it has been plumbed to heat a water tank, what he called a system boiler, should I have the boiler re-plumbed to operate as a combi.???:thinking:

You may have a system boiler with a diverter kit that fits to the boiler. I some times use this set up depending on existing pipe layout and condition of existing cylinder.
Or as said in previous posts could be a combi feeding some out let's and cylinder feeding others which in some cases is a good set up.
A way to tell which system you have is run hot tap nearest to your boiler and if boiler fires up then goes off when you turn hot tap off odds are its a combi.
You will have to have your heating and cylinder time switch off if you try this.or post some pictures.

 

[AWheating]

Is the combi set up cheaper to run? I mean, and forgive any plumbing ignorance, but as I understand it the boiler will be keeping a large tank in the attic heated to a constant temp ready for use,( all hot water taps are supplied by this tank ) whereas the combi set up only heats what you use.yes??,no?? ergo, not burning gas when not in use.

a combi will only give you a limited supply flow rate of hot water. This is why they are sized on hot water output.

 

[Howsie]

why pay more for a system boiler when you can set up a combi as a system boiler on a cyl for less as combis sell more they are cheaper than a system boiler in the first place.hence no brainer for those with a brain:rolleyes2:

Well if you would have put that in the first place we might have had an idea what you were wittering on about.

 

[lame plumber]

Well if you would have put that in the first place we might have had an idea what you were wittering on about.

i did,with less words, as I hate wittering

 

[kozak1968]

I moved a combi to a new position and the customer wanted an unvented cylinder fitted. The boiler was sitting around for a while till it could be fitted.By the time i got new flue, condense trap, front panel etc because things were lost and damaged it would of been cheaper to by a new system boiler. Some customers think they will save money.

 

[Howsie]

i did,with less words, as I hate wittering

Sure.

 

[stevetheplumber]

we often used a combi as a system boiler as they are often cheaper as the price wars ttend to focus on combis we would put the kitchen on the combi hot water side so always hot water there

 

[fraz63]

we often used a combi as a system boiler as they are often cheaper as the price wars ttend to focus on combis we would put the kitchen on the combi hot water side so always hot water there

I have no problem with the combi being used in this way, its just that with the set up I,ve got, I have to wait till the tank/cylinder in the loft has warmed up before I get any hot water, I was trying to get an Idea of how a combi hot water supply compares with a system supply, its a two room, kitchen and bathroom, tenement property and I havent got into the loft yet to see how well the tank/cylinder is insulated, Is it possible to have the system checked for performance.

 

[leethegasman]

I have no problem with the combi being used in this way, its just that with the set up I,ve got, I have to wait till the tank/cylinder in the loft has warmed up before I get any hot water, I was trying to get an Idea of how a combi hot water supply compares with a system supply, its a two room, kitchen and bathroom, tenement property and I havent got into the loft yet to see how well the tank/cylinder is insulated, Is it possible to have the system checked for performance.

If you have no instant hot water and have to wait for your cylinder to warm up. then it looks like you have a system boiler which is not a combi boiler.

 

[erpkid]

If you have no instant hot water and have to wait for your cylinder to warm up. then it looks like you have a system boiler which is not a combi boiler.

Or it could be that you have a combi with no instant water draw off. Neither case is anything to worry about unless later on you have a persistent demand for short term hot water when a combi would help. This might require a small amount of re-plumbing if your boiler is a combi.

 

[theanalyst]

What if the boiler is in the loft and you cant hook the DHW up to the kitchen (sensible option)
Does anyone just leave the DHW isolated under the boiler and let it just heat the cylinder?

 

[leethegasman]

What if the boiler is in the loft and you cant hook the DHW up to the kitchen (sensible option)
Does anyone just leave the DHW isolated under the boiler and let it just heat the cylinder?

I personally would not

 

[buckley plumb]

I personally would not

leave cold live but isolate hot outto be safe or go into boiler parameters and disable hw function or remove flow sw

 

[leethegasman]

leave cold live but isolate hot outto be safe or go into boiler parameters and disable hw function or remove flow sw

I did not mean this could not be done I was saying I personally would not.but do install in the way I said in my previous posts.

 

[buckley plumb]

I did not mean this could not be done I was saying I personally would not.but do install in the way I said in my previous posts.

Sorry too much brandy too early

 

[Reg Man]

No problem using a combi as a system boiler providing the DHW side of the combi is a water to water plate heat exchanger not a gas to water heat exchanger on a few dual heat exchanger models.