curiosity question - heating zone valves

[Steve]

Lets say I had a heating system with a zone valve on every radiator - each room has its own electronic programmable thermostat.

I don't want the boiler to fire up for just one radiator. So how would I take the outputs from the zone valves so that it would take 2+ zone valves to fire the boiler? Is this possible?

 

[EFLImpudence]

LOTS of wiring or radio fittings, LOTS of money and little gain unless, I suppose, the house is very large.


Why would you only want the boiler to fire for two rooms if you were cold in one?

 

[RF Lighting]

I think you'd need some sort of programmable logic controller to run all the inputs into.

Would it not be easier to fit programmable thermostatic radiator valves in each room?

 

[Steve]

efl the point is its wasteful to just fire the boiler for one room and many boilers will not modulate down to this power level thus might cycle. so waiting for two zones to require heat would lead to better use of the power of the boiler. unless you had a radiator that is not on a zone for example a hallway or bathroom.

 

[Steve]

Rob I have never liked trvs of any description. They are to low to get an accurate reading of temperature as well as being next to a big heat source! And there's the issue that when the house is hot enough the boiler will still cycle to heat the bypass radiator in the hallway or bathroom.

 

[Newboy]

It's very strange logic to suggest that's it's more efficient to let more of the house get cold before heating it up again!

The simplest solution is to use TRV's/programmable stats to control the temperature in each room or zone.

The reason for still fitting a room stat is to ensure that the room with no TRV provides the feedback to shut down the boiler

 

[EFLImpudence]

efl the point is its wasteful to just fire the boiler for one room

All central heating could be said to be wasteful. It's purpose is to warm you.

Having to go to a second room to adjust the thermostat there because you are cold in another is silly.

 

[efficiencyman]

Rob I have never liked trvs of any description. They are to low to get an accurate reading of temperature as well as being next to a big heat source! And there's the issue that when the house is hot enough the boiler will still cycle to heat the bypass radiator in the hallway or bathroom.

Yes Steve I have had similar views for over 30 years so I wired multiple Honeywell 4043`s controlled from properly sited room stats, fed from my programmer. All the zone stat "call" SL`s are wired via the brown to open the relevant zone valve x 6. All 6 grey micro switches are fed from the 3A / 5A fused isolator spur. The x 6 orange micro sw. "call" wires are linked together to bring "on" the boiler/Pump. Including the orange for DHW.
To over come any cycling of the boiler I have fitted an ECO pump (better not mention the brand) but there many on the market now that monitor the pressure when multiple valves close, this then electronically shuts the power consumption down from 44watts to 4w or as appropriate. I also have bypasses via bathroom and some under floor in conservatory which dissipates heat during the winter or in summer via pressure relief valve during boiler run on. I have not had any problems with cycling of boiler or no lack of heat to any rooms to the temp as set for each room/zone. If you really wish to spend more with prog stats for each zone that's your option for a very comfortable fully zoned system that`s eco in the long term but the initial outlay a bit high when compared with TRV`s. When compared with the short life of sticking TRV`s my 4043 Honeywell valves have been fantastic for over 30 years.

 

[SimonH2]

It could be done fairly simply.
Arrange for each zone valve switch to connect a supply to the signal wire via a resistor - you will probably want to use low voltage. At the boiler, you sense the current flowing - the move zone valves that are open, the higher the current. Adjusting the level at which the boiler comes on is a matter of adjusting the setpoint on the current sensor.
Also, if you use different resistors for different valves, you can have it so that a single large rad can bring the boiler on, but it needs two small ones.

But TBH, if I were going to those lengths these days I'd be looking at some of the electronic TRV options, a modulating pump, and a buffer tank with thermostats to control the boiler. Modulating pump, TRVs, and buffer tank (thermal store) works quite well and gives a beautifully quiet system.