Two zone valves on a combi boiler

[Inverness]

i never seen this done until I saw it yesterday. There is two room stats on each level. But the rooms that ave the room stats the radiators aren't locksheilds Ey have trvs? I've always learned that this would conflict with each other and the house would never reach the temperature set on the room stat as the trv would always stop the flow to radiator before the room stat is satisfied. It is a twin channel programmer I don't understand if you have two zones on wen one is satisfied how does the other zone get chance when this would switch off boiler?

 

[Darren Jackson]

Building regs say we zone all floors now and the TRV's are not fitted to the rad in the same room as the room stat to eliminate the conflit you mention. They are wired to a wiring centre and individually controll the boiler regardless of what either zone is doing at the time.

 

[Darren Jackson]

Just to clarify if one zone is satisfied it simply closes the 2 port to that zone & the boiler still has power to heat the remaining zone.

 

[steadyon]

Boiler gets fired from either zone, or both.
If the TRV in the room with the room thermostat is left on maximum, there should be no conflict.

 

[Inverness]

Surely the temperature set on max with the trv located nearer the floor level will cut the flow before it has time to satisfiy the room stat. the temperature set at 30 on the room stat and the trv set on five it will still conflict with each other surely?

I'm I correct that the room stat only closes the zone valve not the boiler? So what happens about the boiler interlock? Cheers

 

[Inverness]

Thanks for all your fed back. I'm only learning so I'm asking questions so I can learn.

 

[Darren Jackson]

As stated earlier there should not be a TRV located in the same room as the room thermostat as one will cancel the other out. It will not affect interlock if wired up correctly. Infact will help interlock.

 

[Inverness]

Ok well the house that I saw this two zones a 2 storey building had trv in the same room with the radiator.

 

[Chuck]

i never seen this done until I saw it yesterday.

Deleted my original answer because it overlooked the 'zone valves' mentioned in the title but not in the question.

What type of thermostats are they? Do they predate the combi?

The system described could work okay as long as the TRVs had higher setpoints than the thermostat in the same room. It wouldn't comply with current regulations, however. Might have been okay in the distant past when systems could be timeswitch controlled, have TRVs everywhere and a bypass.

Better to convert to something more conventional IMO.

 

[Darren Jackson]

Yes I come across it a lot, however it is not correct and you should point it out to the customer. Explian the conflict between TRV & room stat. Then offer a price to swap it to lockshield to comply with regs.

 

[Baz]

if not draining down just remove trv top but would need to keep trv top or cap to be able to switch valve off if required