Cold line of radiators.

[dwaviation]

I have three radiators downstairs that are fitted from the same line and none of them are that interested in warming up. The flow and return run in parallel for about seven metres with a small radiator at the end, using four ‘T’ pieces the other two radiators are ‘T’ pieced off of the flow and return, the length of their pipwork on each ‘T’ is about six inches as it passes through a wall into another room, Each radiator has a TRV which I am assuming is pretty pointless for the last two in the line but they are set to max anyway. All the radiators have been bled but apart from the first in the line which gets a six out of ten for heat the others remain stubbornly at around two out of ten, lukewarm at best. The flow, as it enters the room from the ceiling is actually very hot…. The rest of the system works brilliantly, just having a problem with this line

 

[Biguns]

Have they ever worked, If so what intervention has caused this condition

 

[Bahco]

Your answer will be in no 2 here

 

[dwaviation]

Plenty of reading there... That should keep me busy for a few days, Thanks

 

[dwaviation]

Tried turning all the rads off, switched pump to highest setting (3) and opened the three rads in question up full. Worked a treat BUT when all the other rads are back on and the pump is back to two I can feel the flow pipe into the rads is absolutely boiling hot but on the the other side of the TRV it's lukewarm (TRVs are on max) same with TRVs removed (pin does work) - I'm guessing the TRVs?

 

[Biguns]

Have these radiators always had this problem, if so I would suspect balancing (see faq5) If this condition has just started the problem lies elseware

 

[D_Hailsham]

Tried turning all the rads off, switched pump to highest setting (3) and opened the three rads in question up full. Worked a treat BUT when all the other rads are back on and the pump is back to two I can feel the flow pipe into the rads is absolutely boiling hot but on the the other side of the TRV it's lukewarm (TRVs are on max) same with TRVs removed (pin does work) - I'm guessing the TRVs?

if it's the same with TRV heads on and off, then the problem is not dur to the TRVs. The clue is that the rads heat up on their own but not when the other dads are turned on. It's a balancing problem.

See How to balance a CH system. Although it suggests using thermometers, it is possible to get reasonable results by feeling the pipes. At least, they should be better than you are getting now.

 

[dwaviation]

Thanks all - It is a balancing problem... Does anyone know what the temperature differential should be between the flow and return pipes on a Baxi Solo 2 80pf ? It's not mentioned in any of my literature.

 

[D_Hailsham]

Does anyone know what the temperature differential should be between the flow and return pipes on a Baxi Solo 2 80pf ?

11°C - it's in the installation manual.

 

[dwaviation]

Well my little Maplins IR thermometer told a story..! Have managed to balance all the rads around the house and my cold line is now lovely and warm, as is the whole house. However I can't seem to get the boiler differential below 25 degrees. My pump setting is on two at the moment but three makes too much noise (the pump is right above the living room ceiling) and the wife complains.... Are there any other options available? and will I damage the boiler? Do I change the wife?

 

[D_Hailsham]

I can't seem to get the boiler differential below 25 degrees. My pump setting is on two at the moment but three makes too much noise (the pump is right above the living room ceiling) and the wife complains.... Are there any other options available? and will I damage the boiler? Do I change the wife?

Normally pumps are inaudible, even on max speed. Are you hearing the actual pump or the sound of the water circulating? Provided all rads are getting equally hot there should not be any need to increase the pump speed.

Do you have a bypass?

Changing the wife is probably the most expensive solution; and there's no guarantee that it will solve the problem!

 

[dwaviation]

No bypass fitted and the noise comes from a junction of pipes next to the pump - All radiators are equally hot with the exception of a large one in the living room which I allowed to run a little warmer.

 

[D_Hailsham]

No bypass fitted and the noise comes from a junction of pipes next to the pump - All radiators are equally hot with the exception of a large one in the living room which I allowed to run a little warmer.

Is the junction on the inlet or outlet side of the pump? There is an arrow showing direction of flow on the body.

You should have a bypass. The boiler manufacturer recommends one if you have TRVs, even if you have a Y-plan.

You mention that the differential is about 25C. Is this with all TRVs fully open? What differential do you have across the rads?

 

[dwaviation]

The noisy junction is on the outlet side of the pump in the area of the motorised valve. I am not aware of any bypass being fitted, there certainly isn't anything around the boiler- simple pipe in, pipe out of the HE, nothing else in sight.

Temps across the rads are in the region of 12 degrees with TRVs removed, temp across the boiler is 18 degrees.

What is a Y plan?