combi boiler used in central heating mode only as system boiler

[iainfrancis]

The customer wants a multi fuel system using thermal store...wood, lpg, solar. He does not have the cash right away for all the investment but needs to move into the house soon. He wants mains pressure hot water which the house is already plumbed for so one way forward is to to plumb in a combi for use in the meantime and use the same boiler to feed the thermal store as and when he goes ahead with this....central heating mode pipe work only. What problems could there be in doing this or will be it be problem free. The question is specific to the use of the combi in this way...other aspects can be dealt with...warm thanks in advance for any advice.....

 

[Ray Stafford]

There is no theoretical problem with using a combi boiler as a system boiler. It used to be quite common when it was by far the cheapest way to get an 80,000 btu boiler.

 

[SimonG]

Just take a feed from the combi to one hot tap in the house.

 

[Ray Stafford]

Just take a feed from the combi to one hot tap in the house.

Hi Simon. That's certainly the way I have usually seen it done, but is there any actual need to do that?

 

[Killy Bing]

No great need, we install intergas combis above unventeds and put a bypass to the hot incass the cylinder goes pop 🙂 also usefull if only one persons in a larger house for long periods.

 

[SimonG]

Hi Simon. That's certainly the way I have usually seen it done, but is there any actual need to do that?

Can do it with an oil Worcester combi (I've done it), I know from the forum that the intergas ones don't need it but not a clue about any of the other gas boilers.

 

[Killy Bing]

Oil worcester combi really 😛 i laaavvvv servicing them!
Are you talking about the heatslave style?
thats slightly different as its a storage combi and as such it has separate circuits much like the intergas.

I'm guessing the diverter valve in the others would just degrade as they normally do without use on the dhw after a while?

intergas would be your best bet to use as the ch and dhw are on completely different circuits.
you can even set it as a system boiler and completely forget about the combi side.

the others still need to be piped.

 

[SimonG]

Oil worcester combi really 😛 i laaavvvv servicing them!
Are you talking about the heatslave style?
thats slightly different as its a storage combi and as such it has separate circuits much like the intergas.

I'm guessing the diverter valve in the others would just degrade as they normally do without use on the dhw after a while?

intergas would be your best bet to use as the ch and dhw are on completely different circuits.
you can even set it as a system boiler and completely forget about the combi side.

the others still need to be piped.

Aye the old heatslave, one of the lads took an angle grinder to one to convert it to a system boiler.

 

[Ermintrude]

Just take a feed from the combi to one hot tap in the house.

If boiler near kitchen run separate supply from boiler to hot on kitchen sink and one to rest of house. When u install unvented just cap the leg going to rest of house, leave combi on kitchen sink.

 

[stevetheplumber]

we always used to put the shower on the combi that way you often dont need to heat the cylinder so often
probably got it wrong but isnt there a way you can feed the hot from a heat store through a combi for mixed systems

 

[Ermintrude]

we always used to put the shower on the combi that way you often dont need to heat the cylinder so often
probably got it wrong but isnt there a way you can feed the hot from a heat store through a combi for mixed systems

Yeh valliant is best system ( mix and match is a can of worms)