Radiators hot on one side

[LeonR]

Hi,

I was hoping somebody could help me understand the behavior of our radiators.

information:

Ideal Mexico boiler
Open vented gravity fed
No electronic switch valve that I can see.
4 pipes go in to the boiler, 2 smaller which seem to go to the pump/radiators
2 larger pipes which I assume go to the coil in the hot water cylinder.
Downstairs is 10mm microbore
Upstairs is 8mm microbore, new radiators, lock shields and TRVs
Pump set to top speed (level 3)

situation:

I bought a laser thermometer (or whatever it's called) to check the system and I noticed that two of the upstairs radiators are about 20c hotter on the input side.
It's almost perfectly half way when the temperature starts to drop.

60c Input, maybe 40c on the output side.

I tried bleeding the radiators on both sides, just to be sure and there is no air in them.

Is this to be expected?
My theory is that the radiators are doing their job and radiating the heat in the first 50%? Or the flow rate is too low.

I don't want to spend too much time diagnosing if this is what generally happens anyway.

Cheers!

 

[PrenticeBoyofDerry]

What side is hotter, Locksheild or TRV side?

Try turning all over rads off and see if you get full heat.
You would expect a temp drop across the flow and return of about 10 degrees.

 

[LeonR]

The lock shield side is the hottest but to be honest the TRVs are bidirectional so I did not put the lock shield on the input/return pipe on purpose (just placed based on ease of access.).

I tried turning off the upstairs rads apart from one (and left the lockshield fully open) and two of the downstairs to 1/2 turn on the valve and it warmed up about 2c more, but one side stays noticeably cooler.
The downstairs rads are partially seized so I don't dare turn them off fully at the moment (that's why I am slowly replacing the radiators).

Cheers,
Leon

 

[JohnD]

are they tall, column radiators?

 

[LeonR]

Upstairs I have 3 radiators, dimensions below

1 is 40cm x 120cm single panel - this has no temp loss

2 are 50cm x 140cm (these are the ones that seem to be 20c cooler at one end, I can easily keep my hand on one end, but not the other)

Strange!

 

[LeonR]

I think it might be a faulty TRV, thanks for the ideas