Best method to measure boiler flow and return ? ? ?

[hosburger]

Hi,

It states in my boiler manual that the ideal boiler flow temp is 55c. But I can't seem to find a reliable way to measure this. I have a digital laser thermometer. When I point this at the 22mm copper pipes under the boiler ( the flow and return ) they never read more than 35c yet if I measure the surface temp on the radiator closest to the boiler it reads 66c.
Please , has someone got areliable way to measure flow temp ?

Cheers

 

[D_Hailsham]

It states in my boiler manual that the ideal boiler flow temp is 55c.

I would like to see where it says that. Which make/model boiler do you have?

I have a digital laser thermometer. When I point this at the 22mm copper pipes under the boiler ( the flow and return ) they never read more than 35c yet if I measure the surface temp on the radiator closest to the boiler it reads 66c.

It's because the thermometer averages the temperature over a larger area than just the spot of the laser. How big will depend on the Distance:Spot ratio. If this is 8:1 it means that at 8cm distance the spot will 1cm diameter. If you want to measure the pipe temperature accurately, get the thermometer right against the pipe. But note that, at that distance the laser may not be shining on the pipe. It depends on whether you are in line with the pipe or at right angles to the pipe.

 

[barryauid]

I think this has something to do with it.

The radiation heat transfer emissivity coefficient

http://www.engineeringtoolbox.com/emissivity-coefficients-d_447.html

 

[hosburger]

Sorry it's a Baxi 100 he plus condenser.

I have been playing around with the thermometer a bit and I am convinced the copper surface mucks up the readings too. The hottest spot on the closest rad ( which is painted white ) is up to 76c but the hottest reading the copper flow pipe reads is 32c ( about a foot under boiler and measuring at various distances from the pipe ).

 

[D_Hailsham]

I think this has something to do with it.

The radiation heat transfer emissivity coefficient

http://www.engineeringtoolbox.com/emissivity-coefficients-d_447.html[/QUOTE]
The effect will be negligible. A painted pipe or radiator will have a coefficient of about 0.96 and heated copper pipe about 0.78.

If you want to eliminate this factor, the solution is to wrap your pipe in black insulating tape and measure the temperature from the tape. You could also do apply a strip to your radiator and measure that.

 

[Agile]

IR thermometers are fine for checking the temperature of walls etc, but pretty useless for heating tasks.

A contact thermometer does the job and gives quite repeatable results.

Tony