Central Heating Temperatures and Diagnosis

rwiddowson · 27 Dec 2015

Hi

I need to replace a couple of radiators. I have a separate thread for that.

I read that to balance radiators, as a novice, you measure flow and return temps on the rads so I bought myself a digital infrared thermometer. A point and shoot thingymabob!

Just been playing around with it. You have to get close to the pipes to get an accurate reading because of the distance to spot ratio.

I've found the instructions for the old Potterton Netaheat MkIIF, located the flow and return pipes and measured the temps.

As the flow exits the boiler the temp of the pipe is just over 100 degrees but literally 3 inches along it drops to around 47 degrees?

This cannot be normal, can it?

Dan Robinson · 27 Dec 2015

Those ir things are useless.

rwiddowson · 27 Dec 2015

Wish I have asked that the other day as you cannot return to Toolstation if opened. £30 down the drain. What do you recommend for measuring pipe temperatures?

Kev F · 27 Dec 2015

Wouldn't it be cheaper just to get a professional in.

rwiddowson · 27 Dec 2015

My time is free so it couldn't possibly be cheaper!

jeff the gasman · 27 Dec 2015

Don't try to use it on shiny pipe. Use it on the radiator panel where the flow enters, top, centre and then wher the return exits.

Dan Robinson · 27 Dec 2015

rwiddowson said:
Wish I have asked that the other day as you cannot return to Toolstation if opened. £30 down the drain. What do you recommend for measuring pipe temperatures?

A contact thermometer and/or your hand.

I have a £2k thermal camera but still balance systems by hand.

The camera is brought out to show off or prove a point.

rwiddowson · 27 Dec 2015

OK. Jeff the Gasman. Thanks for that.

It does say in the instructions not to use it in shiny/polished surfaces but the copper coming out of the back of thboiler is very dull.

What would you expect water temperature to be coming out of the boiler? Surely 70-80 Celsius is nearer the mark?

Dan Robinson · 27 Dec 2015

Depends on the boiler settings.

Also you could be reading the back of the combustion box.

Like I said, these things are useless.

Google emissivity.

D_Hailsham · 27 Dec 2015

Dan_Robinson said:
Google emissivity.

Shiny copper = 0.05
Oxidized copper = 0.65
Paint = 0.94

Most IR devices are calibrated for an emissivity of 0.95

Wrap some black insulating tape round the pipe and measure off it.

75pete · 27 Dec 2015

Google, magnetic temperature gauge, you can also get them with a spring connection for pipe use. Get two then you move from rad to rad.

D_Hailsham · 27 Dec 2015

75pete said:
Google, magnetic temperature gauge, you can also get them with a spring connection for pipe use. Get two then you move from rad to rad.

When I first tried to balance my system - over 25 years ago - I purchased a Brannan round thermometer with a spring to hold it against the pipe. The biggest problem was that it was so slow reacting to changes in temperature, so you had to wait ages after adjusting the LS valve. It took hours to balance the 15 rads in my house, and I wasn't satisfied that it was right. 10 years ago, when I moved, I purchased a second Brannan thermometer, hoping it would make life easier. It didn't, as they were not giving consistent readings. Put them next to one another on the same pipe and there could be a five degree, or more, difference in the readings. Not much good if you are balancing to a 10 degree differential. I later found that, above 40C, the thermometers are only accurate to within +- 4C. So an 8C difference between two thermometer is perfectly possible.

rwiddowson · 27 Dec 2015

Wow! Some really good advice here from a few posters.

I am looking at the system overall and trying to ascertain in which order the rads are heating up. Quite interesting because it is not in the order I thought and I am still unsure to be exact order.

The IR thermometer proved useful for this at least because in one room (with 3 rads) the rads were cooler by 2 degs approx each as system was firing up.

I'll ask this question also whilst I remember.

Someone said it would be a good idea to change all valves to TRV's and new Lockshields. Question is though surely it makes NO SENSE to have 3 TRV's in one room?

The house has 16 radiators.

I also have a thermostat to fit. Question there is which room is that best positioned in. The room we use most or a room on the North side?

simond · 27 Dec 2015

I use an IR remote thermometer from Lidl, cost around £29.

As D_H says, use a surface like a white painted rad and it is surprisingly useful and quick. My hands aren't very good at detecting 55C from 65C but the Lidl unit is.

My subbies laughed at it - now they ask to borrow it. As Elton John said, 'don't knock it till you've tried it'.

OK made the last bit up.

Dan Robinson · 27 Dec 2015

rwiddowson said:
NO SENSE to have 3 TRV's in one room?

Makes perfect sense.

Just don't put them where the room stat is.

diynot

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Central Heating Temperatures and Diagnosis

Similar threads