Economical heating without a thermostat

BikingBud

Qyburn said:

BikingBud said:

Not being flippant but what are the advantages of a stat that manages all of the heating?

Logically, if the rads have TRVs and the boiler is set to an efficient setting on return temp then what added value does a room stat give?

A thermostat would switch off the whole system once the setpoint is reached. Otherwise boiler and pump are running pointlessly even if all TRVs are satisfied and closed.

It needs to be sited in a sensible place, not such that a nearby TRV would mean the temperature never reaches the thermostat's setpoint. Or, the issue we have, not in a room with some other heat source unrelated to the CH. You don’t ant lighting the stove to switch off heating everywhere.

Which set point and where? Seems like a compromise and as we see on here it confuses many.

Boiler running pointlessly? What about modulation and return temp monitoring?

glennevis said:

BikingBud said:

Not being flippant but what are the advantages of a stat that manages all of the heating?

Logically, if the rads have TRVs and the boiler is set to an efficient setting on return temp then what added value does a room stat give?

We know room stats and TRV are often in conflict so why not remove it and let the TRVs do the work.

I see the value in a timer, temp set back during the working day and overnight, but not supplementary stats that might be in conflict.

When I moved in to my current house there was no thermostat on the combi boiler though there are TRVs on all but one rad.

Without a room stat the boiler would fire up and continue running until the boiler's internal thermal cutout kicked in. Initially this could be for 2-3 hours. After a while when it had cooled down a bit it would fire up again, repeating until switched off at the mains. I was never very confortable with that situation which felt like I was thrashing the boiler.

So for a tenner I fitted a manual dial thermostat. Money well spent. Now the bolier operates as it should, firing up once or twice an hour, performing well within its operating parameters. And yes, it does use less gas.

Why would the boiler be running all the time? Not sure thrashing itself to death is a realistic assessment, the boiler would only continue to burn if the return temp was below threshold. The internal thermal cut out would kick in once the demand has dropped off, characterised by the limited drop off in return temp.

If it was cold and the TRVs were allowing flow through the rads that was then heating the room and transferring energy out of the system then yes. The boiler controls would kick in and demand energy via return temp monitoring, maximising condensing effect and applying hysteresis curves to avoid quick cycling. If the rads are not emitting, the return flow is above the boiler ignition temp and nothing happens.

And in the same manner the boiler can moderate the burn rate, the pump should also be able to moderate and run at low flow to operate as the sensing line. If it comes back too cold then add energy. If it comes back at the same temp then only monitor. 

I think we have such a legacy of old systems that are not about effective and efficient control but rather accommodation of different poor systems that were set up with little concern for efficient and therefore lower cost running.

On the flip side take out all the TRVs and set up the system, correctly balanced, to ensure the energy goes into the correct rooms at the correct ratio.

squirrelpie

Might also be worth contacting your local Citizens Advice Bureau