indirect cylinders versus thermal store efficiency query

[Worcester]

How does a unvented thermal store pass building regs?

Sorry my mistake in explanation, they do need to, and thanks for questioning it There are special clauses in Part G for both vented and unvented thermal stores, the difference is that for various reasons, the installers (though we do anyway ...) don't have to hold a G3 unvented certificate.

It's because the stores don't have a way of automatically replenishing the water (fluid) in them - they are a sealed system, as such they are considered a part of the central heating system. (They do tend to have large expansion vessels attached ) and also inherently they don't have temperature relief valves for the same reason. (pressure release yes, temperature or combined temperature and pressure - no )

Note: In johnnymc's particular instance because he has an uncontrolled heating source - the wood stove, then some part of his system will need to be vented, the easiest way may be to connect it directly and use an vented thermal store (he still gets 'mains pressure' hot water of course) and of course (already presumed this was 'understood') - he'd need to fit a tmv on the ho****er outlet - there are other ways though to still be compliant and of course in Ireland the regs may be different anyway.

With biomass, heat pumps, solar thermal, gas and oil boilers (condensing and not in some cases) et al in a multi fuel environment, there are only a very few people out there that fully understand how to design an effective system with all the correct requirements on flow and return temperatures, then add in the metering requirements for the RHI and you've lost >99% of the boiler fitting companies out there.

 

[Gray0689]

Sorry my mistake in explanation, they do need to, and thanks for questioning it There are special clauses in Part G for both vented and unvented thermal stores, the difference is that for various reasons, the installers (though we do anyway ...) don't have to hold a G3 unvented certificate.

It's because the stores don't have a way of automatically replenishing the water (fluid) in them - they are a sealed system, as such they are considered a part of the central heating system. (They do tend to have large expansion vessels attached ) and also inherently they don't have temperature relief valves for the same reason. (pressure release yes, temperature or combined temperature and pressure - no )

Note: In johnnymc's particular instance because he has an uncontrolled heating source - the wood stove, then some part of his system will need to be vented, the easiest way may be to connect it directly and use an unvented thermal store (he still gets 'mains pressure' hot water of course) and of course (already presumed this was 'understood') - he'd need to fit a tmv on the ho****er outlet - there are other ways though to still be compliant and of course in Ireland the regs may be different anyway.

With biomass, heat pumps, solar thermal, gas and oil boilers (condensing and not in some cases) et al in a multi fuel environment, there are only a very few people out there that fully understand how to design an effective system with all the correct requirements on flow and return temperatures, then add in the metering requirements for the RHI and you've lost >99% of the boiler fitting companies out there.

That's what had us confused we was taking about a stove from the outset uncontrolled heat source that's why we was saying vented

 

[SimonG]

It makes sense now. Cheers.

 

[bennygas]

Hello there, sorry to interrupt - haven't been on here for ages, but nice to be back. Couldn't help but find this business about part g and thermal stores etc interesting - it was something that bothered me in work going back a while so I ended up looking into it a bit. This kind of summarises what I ended up thinking on the matter....


Building Regulations requirements G3 (2) and (3) apply to all stored hot water - including primary vessels, thermal stores, accumulators/buffers in all buildings, irrespective of how they're heated - and that goes for sealed systems and mains fed systems (the only difference is in the prescribed nature of the energy cut out serving the vessel and the use or not of a tprv). The only exception is where the hot water storage is part of an industrial process.


it could well be a bit of a problem for the renewables sector if it did but realise it - my perception is that many seem unaware of the implications of part g (everyone I speak to seems to think its all just about megaflos etc - but it really is quite far reaching). I dare say the building regs will be updated at some point to take into account the changes that have occurred in the technologies being plumbed in to big tanks, but until then, strictly speaking, a lot of biomass stuff for example, doesn't comply with part g.