Oil Heating with TRV's Help

[jchannon]

I have a oil powered boiler out in the garage. I have a timer control inside for the water and heating.

On all the radiators in the house they have TRV's each with a green circle around number 3. What does that do because when I set it to just under 3 by a few millimeters the radiator virtually goes cold. Put it past number 3 and the rad is red hot.

I have read it is more efficient to get rid of the TRV's and have a room thermostat if the boiler supports it. How much of an effort and cost would that be to get someone to do it?

Cheers

 

[Boilerman2]

If the particular number is circled (i.e.3) this is the manufacturers recommended comfort set point (usually 20-21;c), in reality you have to set the valve to suit your particular requirements, you need to understand that the TRV is measuring the Room temperature, so if you adjust the valve, you will have to wait at least ONE HOUR to asses the result

 

[jchannon]

Does that mean when on 3 and its not 21C then the radiator is goes full pelt until it registers its 21C. When I set it to 2 and it goes cold is that because the room is at the temperature that 2 relates to?

 

[D_Hailsham]

Does that mean when on 3 and its not 21C then the radiator is goes full pelt until it registers its 21C. When I set it to 2 and it goes cold is that because the room is at the temperature that 2 relates to?

Essentially, yes.

But a TRV is not like a switch, ON or OFF. It's more like the throttle in a car. When the speed is below that required the throttle will be wide open. As the required speed is approached, the throttle will be closed, a bit at a time, until the engine is producing just enough power to maintain the required speed.

Problems with TRVs are frequently due to faulty balancing of the system.
See How to balance a CH System

 

[jchannon]

Thanks!

I think they must be working properly however our house is always cold no matter what. I have always cranked the TRV up to 6 (MAX) and kept it on that. The TRV may be the right temperature at the RAD but the room is nowhere near that temp.

I wonder if I need double/larger radiators.

 

[D_Hailsham]

I think they must be working properly however our house is always cold no matter what.

I wonder if I need double/larger radiators.

OK Let's start at the beginning!

1. Find out how much heat is needed for your house. To do that use the Boiler Sizing Wizard

2. Find out how much heat is produced by your radiators. Unless they are designer types or very old cast iron ones, you can get a good idea by using the Stelrad Elite Catalogue

The boiler wizard result assumes a regular boiler (not a combi) with a hot water cylinder. So you need to deduct 2kW from the result to find the heating requirement. Compare this with the total radiator output to see if where the problem lies. Remember that you cannot have 20kW of rads being fed from a 10kW boiler. So, provided the boiler is already adequate, you can add more rads. But if the boiler is under-sized you will have to install a larger rad - or live with a cold house.

If you have a combi, it will probably be large enough as combis need a much higher output to heat the tap water to an acceptable temperature.

 

[jchannon]

Does it matter that I have an oil fired boiler before I run the wizard?

 

[D_Hailsham]

Does it matter that I have an oil fired boiler before I run the wizard?

No. The wizard just tells you how many kilowatts of heat you need. How you produce it is irrelevant. Just remember to deduct 2kW from the final answer.