separate zones in heating system

[Smimsie]

Hi, hope this is in the right place to ask:
I've recently had a garden building constructed to house my piano. It is heated by a radiator powered by the household combi boiler. The plumber has put a valve underneath the boiler so I can turn it to either heat just the garden room or to heat both the garden room and the house. Wiring has been put in place from the house to the garden room for a wall thermostat, but no thermostat has been installed. I would like to have a thermostat installed to turn the heating on and off (to both house and garden room as a single zone) as at the moment, I have to do this manually at the boiler. My question is that the plumber has told me that if I have a thermostat installed, he is required to set up two separate zones within the heating system as I am heating two separate buildings (which seems plausible) but if I don't have a thermostat installed, I don't need two zones, which seems unlikely. I'm now concerned that I don't currently comply with building regs as I can't see why having a thermostat would change the zone requirement. I have tried googling but would really appreciate some insight from those more familiar with boilers and regs! Many thanks for any advice.

 

[John D v2.0]

Does the garden Room meet building regs? Extending the main heating system to an outbuilding does not meet regs full stop unless the garden Room has been designed to habitable room building regs for insulation etc. Insulating the pipe run outside sufficiently would be tricky but i guess that's done already.
Regarding the zoning I'm not familiar with that but my concern would be with a trv throttled down at the other end, most of the heat would be lost on the pipe run before it got to the outbuilding!

 

[Smimsie]

As far as I'm aware, the garden room does meet building regs - its is basically a one room house, built of brick with proper foundations (pilings) and insulated properly throughout. Building Inspectors were here multiple times to check things during construction. The heating pipes are buried underground and insulated. What is a trv? thank you!

 

[Mottie]

Thermostatic Radiator Valve.

 

[Smimsie]

ah, that makes sense. I've had to turn the boiler temperature right down as it was overheating, with only providing low heat to one radiator most of the time.

 

[oldbutnotdead]

There is somewhere in the Approved Documents some requirements about zoning (usual zones would be upstairs, downstairs, hot water if applicable). Each zone would have its own thermostat, there would be a motorised valve in the pipework for each zone. The more modern route to compliance seems to be 1 thermostat in the house (in an area heated by a radiator without a TRV) and TRVs on all the other (appropriately sized) radiators. So your plumber is probably correct when he tells you he'd have to zone the system if you put a thermostat in the piano room.

Your big problem will be the inefficiency of firing up the boiler to drive a zone with a single radiator on it (what's the heat loss on the piano room), added to the nuisance value of the boiler firing up overnight (when the piano room calls for heat and the rest of the house is asleep). Plus (I'm assuming we're talking a valuable piano here) you're not addressing humidity issues by just heating the room.

Long term you'd be much better off with a local heating and humidity control system for the piano room

 

[Nakajo]

Each zone would have its own thermostat

This might be the case, but not necessarily.

 

[Smimsie]

Inefficiency is what I am really worried about - at the moment, the boiler is running full time for 1 radiator :/ There is no thermostat in the house, just a manual temperature setting on the boiler, which is turned down to stop the boiler overheating when it is just running one radiator. I have a dehumidifier in the piano house which comes on as required but I think you are right about a local heating and humidity system. Please could you recommend somewhere I can find out more about them? I'm really lost on all this. Thank you

 

[cdbe]

Try the plumbing and heating forum on..........www.diynot.com

 

[lt8480]

I assume the temperature control on the boiler is just setting the water temperature for the radiators (say set at 50-70 C?).

A TRV in the garden room is not correct in isolation.

The plumber sounds to have installed the necessary parts for a logical system including thermostat wiring, but then no thermostat? Was this requested?

If you have just a house usually 1 zone is sufficient and then TRVs on the radiators. But with a garden room things get a bit more complex. If very close to your house then 1 zone may be sufficient but if its say at the end of a garden then 2 zones should be used.

Assuming the latter...

You should have a thermostat in both the house and the garden room, the garden room pipework from the boiler should then have a valve near the boiler to turn the heating flow on/off to the garden room as a required.

This probably sounds familiar as basically what your plumber has done but with a manual valve and no thermostats. The good news is he has done the wiring by the sounds of things. So basically the manual valve that has already been installed near the boiler should be changed to an electronic motorised zone valve and connected to a thermostat installed in the garden room. Then when the garden room is sufficiently hot the water stops flowing to the garden room.

If you just leave your current valve open all the time and have just one heating zone (whether on a house thermostat or not), and then put a simple TRV on the radiator it will result in hot water circulating to the garden room and back to the house even when no hot water is needed in the garden room. The TRV just stops the water flowing into the actual radiator but water will still go to the garden room and back). Due to the distance from the house (and being outside) the water flowing there and back may drop quite a bit in temperature and therefore your boiler would just run continuously even if you fitted TRVs and they were all turned off.

 

[^woody^]

The Building Regs may require that that this type of building have its own independently controlled heating and not be connected to the main house system if it is to be exempt from requiring permission.

With regards to zoning or just having better control, if this is something you are thinking about then consider a smart heating system with independently controlled radiator valves - this will effectively place the garden room in its own zone. Look at Drayton Wiser or Tado or Honeywell. This may not be a remedy for any Buiding Regs issue, but it would be a lot cheaper than running pipes and controls for a traditional zoned system.

 

[lt8480]

I was thinking similar ^woody^ and putting a Tado smart valve on the radiator, but then discarded the idea as it will still result in water circulating to the garden room and back which will cause the heating to over work surely?

 

[John D v2.0]

Only if you have a bypass at the garden Room end which would be unusual and unnecessary

 

[^woody^]

I was thinking similar ^woody^ and putting a Tado smart valve on the radiator, but then discarded the idea as it will still result in water circulating to the garden room and back which will cause the heating to over work surely?

No, if the valve closes in the garden room then no water will circulate on the section of flow/return pipework leading to it. Likewise, if the garden room radiator calls for heat, then only that section of pipework will have water circulating if all the other radiator valves are closed.

 

[lt8480]

No, if the valve closes in the garden room then no water will circulate on the section of flow/return pipework leading to it. Likewise, if the garden room radiator calls for heat, then only that section of pipework will have water circulating if all the other radiator valves are closed.

Hmm yes thinking about it more that radiator sounds like it is already effectively zoned off rather thank being on a circuit with other radiators. In which case a smart TRV would work.

Tado is pretty good value, a base control thermostat in the main house and 1 smart TRV for the garden room would be about £200 and very simple to install.