What *are* cold spots? Rad sludge?

[Safety First]

Hi all and thanks for taking the time,

I have an infra-red (pistol type) thermometer. Can anyone tell me what percentage temperature range across top and bottom of a radiator shows that sludge is an issue?

For instance 72.2c at top and 31.5 c is this accountable by convection only ?

A number of heating engineers have asked about our radiators in discussing our system; its possible need for flush etc. They ask if there are any cold spots etc

There's a definite lag in speed of heating (from switch on), i.e., lowest centre of rad warms up a lot slower than at top, but then convection would mean this is normal, no?

Surely also conduction would mean that all parts end up something like hot eventually. I am not sure that when others report 'cold spots' (i have been reading others posts!), they are in fact a bit cooler???? or...??

TIA.

 

[Dan Robinson]

Either sludge or poor circulation.

Which tend to go hand in hand anyway.


A thermal camera is required really. Those pistol things are shyte.

 

[Safety First]

Either sludge or poor circulation.

Which tend to go hand in hand anyway.


A thermal camera is required really. Those pistol things are shyte.

Thanks for the reply, though when I am asked if there are cold spots, I am not expected to have a thermal camera, am I?

Other people talk of 'finding' cold spots (with their hands).

I know that sludge and poor circulation go hand in hand.

I would expect someone in the know, to be able to refer to specific differential that is indicative of poor circulation.

For example, 70c at the top, 15 at the bottom. This would look bad if i had another house to refer to in which the greatest differential was much less.

 

[Dan Robinson]

You're welcome.

 

[D_Hailsham]

For instance 72.2c at top and 31.5 c is this accountable by convection only?

No.

Use you "useless" IR thermostat to measure the temperature of the two pipes connected to the rad; there should be approx 10C difference. If the surface temperature at any point on the rad is lower than the reurn temperature (the lower of the two pipe temps) then there is sludge at that point. Sludge tends to collect in the centre at the bottom.

 

[Safety First]

For instance 72.2c at top and 31.5 c is this accountable by convection only?

No.

Use you "useless" IR thermostat to measure the temperature of the two pipes connected to the rad; there should be approx 10C difference. If the surface temperature at any point on the rad is lower than the reurn temperature (the lower of the two pipe temps) then there is sludge at that point. Sludge tends to collect in the centre at the bottom.

That is what I was looking for...
Knowledge and methodology.

Thank you.