Infrared thermometer giving duff readings!

[Chameleonclaude]

I just bought a rolson infrared thermometer to measure my Primary flow and return as well as both ends of the rads to optimise my system.

Problem is it is giving me duff readings. The instructions say that this can happen if the surfaces are either transluscend or shiny. The remedy is apparently to place masking tape ipon the surface of say the chrome 15mm copper and read again once masking tape has reached temperature.

I tried this but i firstly don't think a piece of masking tape will ever get as hot as the copper and therefor i'm a bit lost with this thing.

Anyone out there got one. If so what do i do?

 

[45yearsagasman]

IR thermometers are not suitable to use on pipework, as you have found out. Clamp on surface sensors are by far the most accurate

 

[Agile]

If only you had read a little about them on this forum then you would have understood their limitations.

The reality is that they do have some applications but central heating measurements are not one of them!

A contact thermocouple is the only way to obtain accurate measurements.

Tony

 

[Chameleonclaude]

I've realised that 😞

Can you recomend a cheap but accurate one?

 

[45yearsagasman]

Google K type thermocouples. Ebay may be your best bet, or try Maplin.

 

[Chameleonclaude]

What about the dial thermometer that are held ipon with a spring. There £12 so could buy two and leave them on the flow and return permanently?

Thanks btw

 

[Agile]

They are of little use as well!

Maplin do sell some cheaper meters with a type K socket. Then they sell the sensors seperately. I like the simple wire ones which can be held against any pipe.

Tony

 

[D_Hailsham]

Problem is it is giving me duff readings.

In what way are they "duff"?

The instructions say that this can happen if the surfaces are either translucent or shiny. The remedy is apparently to place masking tape upon the surface of say the chrome 15mm copper and read again once masking tape has reached temperature.

Black insulating tape is better.

I don't think a piece of masking tape will ever get as hot as the copper

The thermal insulating properties of a piece of masking or insulating tape about 0.2mm thick is negligible. In any case the thermometer is not measuring the amount of heat given off by the pipe/tape but the amount of infra red radiation.

One thing many users of IR thermometers do not seem to realize is that they collect over a fairly wide area, like a torch beam and just average the information collected. So the closer you get to the pipe, the more accurate the measurement. When you are very close the red laser beam is useless, just make sure the collection area is in line with the tape.

 

[MJN]

D_Hailsham has made all the pertinent points so I shalln't repeat them. However I can echo the fact that an IR thermometer is perfectly adequate for this task but, like any tools in the hands of a bad workman, will not function to any reasonable level if you don't learn how to use them properly. It beggars belief why you would wilfully ignore the instructions provided.

Go with the insulation tape, focus right in and you'll be fine.

Mathew

 

[Chameleonclaude]

So i followed your guidance and the highest temperature reading i've managed to get from the primary flow is 65 degrees. This reding was taken with the boiler on maximum. Its a worcester bosch 24ri and it's about three years old.

I know that boilers modulate the gas flow based on temperature but am fairly sure they should maintain a stable temperature on the primary flow. Obviously the primary flow wuld cool down if the room maintained temperature for a half hour or so.

I'm not convinced! The readings i get from the white radiators look much more accurate. I think i will be looking for a strap on (thermometer that is!) as the maximum boiler setting is prbably actually producing flow temperatures of about 85.

Thanks for your input though.

 

[D_Hailsham]

the highest temperature reading i've managed to get from the primary flow is 65 degrees.

... the maximum boiler setting is probably actually producing flow temperatures of about 85.

So you are making the assumption that the IR thermometer is inaccurate because you think the flow temperature should be 85C.

The boiler stat may be set to 85C, but the water will only reach that temperature if the boiler runs long enough to do so, which will depend on how cold it is. If it was -1C outside and the house was stone cold when you put the heating on, then the boiler would probably get up to 85C while the house was heating up to 21C.

But if the house has only cooled down a few degrees overnight (mine dropped 6C max in the recent cold spell) and the outside temperature is higher, then the house will heat up quicker and the flow temperature may not reach 85C before the room stat turns the boiler off.

The readings i get from the white radiators look much more accurate.

What temperature are you getting from the rads, according to the IR thermometer?

 

[Chameleonclaude]

When the flow was measureing 65. The inlet of the closest rad to the pump was 50 degrees when though all rads where fully open and unbalanced.

This question is probably got too many variables to answer but i'll ask it anyway. If all the rads are fully open as they are, and the room thermotat was increased to unreacheable temperature, how long roughly would it take for the boiler to reach full heat?

 

[D_Hailsham]

When the flow was measuring 65. The inlet of the closest rad to the pump was 50 degrees when though all rads where fully open and unbalanced.

That's a 15C drop from boiler to first rad. If the flow was actually 85C, as you seem to think, the drop would be 35C. Both are much too high - unless the boiler is in a shed at the bottom of the garden and connected to the house by uninsulated pipes. You need to find out why you are getting such a large drop; it could be due to a wrongly adjusted bypass valve.

What boiler do you have?

This question is probably got too many variables to answer but i'll ask it anyway. If all the rads are fully open as they are, and the room thermostat was increased to unreachable temperature, how long roughly would it take for the boiler to reach full heat?

Try Ebay for crystal balls!

 

[Agile]

it does depend on the power output of the boiler.

Most systems reach the set flow temp in about 20 min. but by 30 min there would be something wrong if it had not reached it.

Tony

 

[Chameleonclaude]

I'll do a more thorough test tonight but i know the bypass is allowing 4 litres per minute when CH motorised valve is open, and 5 litres per minute when closed. 5 lpm is the boilers stated requirement for over run.