Radiators only getting luke warm

[stevewilson1]

Hi,

I have an Alpha CB24 boiler that has been regularly serviced. I recently switched the heating on and to my surprise the radiators only got luke warm!! The pipes going into the radiators..... one is hot and the other is only luke warm. Has anyone else come across this? Is it a case of flushing the system? Any help would be really appreciated.

Steve.

 

[kevplumb]

might be the pins on the trvs sticking

 

[picasso]

Got the thermostat on the front of the boiler turned up?

 

[kevplumb]

Got the thermostat on the front of the boiler turned up?

ahh youve had that one as well

 

[picasso]

oh yes, they dont like to pay for their own mistakes, get all annoyed with themselves they do

 

[Kain]

lockshield fully opened?

 

[stevewilson1]

might be the pins on the trvs sticking

Thanks for the reply, I initially thought this so removed the top section of the TRV and made sure the pin could be pushed in and out, and they all can. Steve

 

[stevewilson1]

Got the thermostat on the front of the boiler turned up?

Thanks for the reply. Now that is a school boy error!! Yes it's turned up fully.

 

[stevewilson1]

lockshield fully opened?

Thanks for the reply, I'm not quite sure I know what you mean by the 'lockshield' Could you tell me what that is and what it does please, Thx

 

[Kain]

Hi,

The lockshield valve (outlet) which regulates the amount of water leaving the radiator, if is not open enough to let the water circulate the radiator will be stuck with a bunch of cold water.

 

[kevplumb]

lockshield fully opened?

what about the system balance

if you open the lockshields fully

 

[stevewilson1]

Hi,

The lockshield valve (outlet) which regulates the amount of water leaving the radiator, if is not open enough to let the water circulate the radiator will be stuck with a bunch of cold water.

Yes they are fully open, It seems as if the hot water takes a long time to get through. If i leave them on for a couple of hours they do get a little warmer but I dont know whether this is just heat transfer or not. One thing I have noticed which I forgot to mention is a rusty stain outside the house below the overflow/vent I dont know if this is any help! Thx

 

[kevplumb]

whats the system pressure (cold) should be 1 / 1.2 bar

and check it with the system hot and post findings
chances are the prv is passing

possibly duff expansion vessel

 

[D_Hailsham]

Hi,

The lockshield valve (outlet) which regulates the amount of water leaving the radiator, if is not open enough to let the water circulate the radiator will be stuck with a bunch of cold water.

Yes they are fully open.

This could be part of the problem. The lockshield valve controls the flow rate through the radiator, which depends on the size of rad and the required temperature drop between inlet and outlet. Leaving all LS valves fully open means that the rads are not getting the correct flow rate.

The design of most LS valves means that they are fully open when only half open. The normal range of adjustment when balancing a system is usually anywhere from 1/8 turn open to a max of 1½ turns open.

See How to balance a CH system

Was the heating working OK last year?

 

[stevewilson1]

Thx for the replies guy's sorry i have been away for a while!!
The pressure when cold is 1 bar and rises to approx 1.5 when the system has been on for a while. The heating was ok last year although it may not have been as efficient as we had a really bad/cold winter and I think I put the lack of heat output down to that! But it wasn't as poor as it is now.