Understanding my Central Heating System

[Graham Carpenter]

Hello

I have recently moved into a new house where the hot water and central heating is supplied by a Logic Combi ESP! 35 boiler. There is no hot water cylinder, which is something I have not met before.

There is a wall thermostat in the downstairs hall, and also in the master bedroom upstairs.. The radiators in these two rooms do not have a thermostat valve, but all other radiators do. I have a number of questions concerning this system:

1. If, for example, the upstairs wall thermostat is set at, say, 20 degrees, but all the radiators upstairs are set on the highest setting No 5, will the radiators override the wall thermostat and heat the radiators when the radiator in the bedroom with the wall thermostat is not hot?

2. Are upstairs and downstairs completely separate, or if the downstairs wall thermostat is set higher than the upstairs one, will that govern?

3. If I go away in the winter and as a precaution against freezing leave the wall thermostats set at say, 10 degrees, and the radiator thermostat valves set at the lowest setting No 2, can I turn the water off at the mains to comply with house insurance, or must the water be left on to allow to top up the radiators due to evaporation?

 

[stem]

The boiler will heat the domestic hot water instantaneously, so when a hot tap is opened cold water flows into the boiler is heated and goes directly to the tap.

Building regulations now require systems to have separate 'zone control' for living and sleeping areas. they work totally separately, hence the two room thermostats. Each room thermostat will turn off all of the radiators in its respective zone (using an electrically operated motorised valve) when the temperature set on the room thermostat is reached, regardless of the settings on the TRV's. The radiators in the rooms that have the room thermostats in should not have TRV's fitted as they could interfere with the correct operation of the room thermostat.

Your heating system will be sealed, so evaporation isn't a problem. It would only be filled up by manually opening a valve when the pressure has dropped, so is not permanently topped up by the mains water supply. [ie no cold water storage tanks in the loft]

For frost protection leave the TRV's as they would normally be and set both room thermostats low, the room stats will turn off all of the radiators when their set temperature is reached.

 

[ianmcd]

1. If, for example, the upstairs wall thermostat is set at, say, 20 degrees, but all the radiators upstairs are set on the highest setting No 5, will the radiators override the wall thermostat and heat the radiators when the radiator in the bedroom with the wall thermostat is not hot?

No the opposite, the room thermostat (boiler interlock) will over ride the radiators thermostats

2. Are upstairs and downstairs completely separate, or if the downstairs wall thermostat is set higher than the upstairs one, will that govern?

Both circuits are separately controlled by their own thermostats

3. If I go away in the winter and as a precaution against freezing leave the wall thermostats set at say, 10 degrees, and the radiator thermostat valves set at the lowest setting No 2, can I turn the water off at the mains to comply with house insurance, or must the water be left on to allow to top up the radiators due to evaporation?

You can turn the water off if you want , it wont affect the radiators

 

[stem]

Here's a simplified sketch I made earlier for someone else that asked a similar question. It might help your understanding.

 

[Graham Carpenter]

Sorry for the delay in acknowledging your replies to my post. They were both very much appreciated.