Laser thermometer - radiator balancing ?

Might need to temporarily stick a small strip of insulating tape to let the thermometer "see" consistent emissivity?

Nicer to look at with a thermal camera!

Also consider that the laser will produce a small aiming spot whereas the IR temperature sensor will have a much wider acceptance angle so don't be too far away from the area you are trying to measure.

Personally when balancing radiators in the past I've measured the temperature of the copper input pipe and the copper output pipe and not the surface of the radiator. I haven't used a IR thermometer but a digital meter with thermocouple probes physically attached to the pipes.

If you have Thermostatic Radiator Valves fitted you only need to get the radiators approximately balanced because the TRVs adjust the flow to individual radiators as the temperature of the room approaches the temperature that the TRV is set at.

The behaviour of the first radiator will depend on the function of the pump. If the pump takes the newly heated water from the boiler and pushes it through the heating system, the first radiator gets the full flow from the pump (the subsequent radiators get part flow direct from the pump because part of the full flow was diverted into the first radiator). Thus the flow speed into the first radiator is going to be slightly higher than in the rest of the system. If it comes in on the left, it could be half way across the radiator before the hottest of the water reaches the top of the radiator and on to the right. In time the temperature of the top of the radiator will equalise through conduction along the metal of the radiator, and I don't think your different temperatures is anything to worry about.

If the pump is on the end of the run, sucking water from the system and delivering it back to the boiler for reheating, then it will be the last radiator rather than the first which has the fastest flow rate.

The idea of balancing, is to get all radiators to see a similar flow of heated water through them, a similar drop in temperature across each, by adjusting one of the valves. Each radiator, should show a drop of 20C across it, flow to return pipes.

On my system, I fitted all but one radiator, with a TRV, and all of my radiators get similarly hot, at switch on - maybe due to good design, so I've never bothered to balance them. I did once intend to attempt to balance them, I got as far as buying a couple of cheap digital displays, with sensor on the end of a wire - my idea was to clip them on the pipe, with a bit of pipe insulation.

I paid around £2.50 each for the displays, which run on pair of little coin cells, which didn't last more than a few months. I built the displays into a small bracket, and converted the displays to run on a AAA cell. I now have the display permanently attached to the flow and return pipes, of my boiler, in the boiler cupboard.

I set all the TRVs to be fully on and then used the IR device to look at the radiator temperatures next to the flow and return pipes. Then adjusted the lockshield to make all the temperature differences nominally the same.

The issue is often with small radiators.

TRVs will eventually settle down and the radiator flow and return temperatures should widen, or even go cold.

Thanks for all the replies.

I have 10 rads - 6 with TRVs and 4 without. Two of those I added myself (a cloakroom and the porch). And I've nevre touched the system since apart from to descale and add inhibitor. Maybe balancing isn't needed in light of the TRV comments ?

I am looking at maybe putting "smart" TRV on the rads that have the bodies. These would allow much more fine grained messing with programs such as turning the bedroom rad off during the day. And lowering the flow to the quieter rooms.

If you have a modern condensing boiler then balancing is more efficient - you enable a smooth flow of heat throughout the house which enables condensing and weather compensation to work nicely.

If you are using TRVs alone the heat demand may become jumpy: when the TRVs open you suddenly are demanding much more heat than you were before, when means the return temperature drops and that potentially means the boiler senses it needs to up the flow temperature. That can lead to the boiler cycling as TRVs randomly turn on and off in a way the boiler can't predict.

Can those TRVs proportionately lower the flow, or just turn the flow on and off? ie sense the room v desired temperature, learn the characteristics of the room and know that to get a temp rise of X deg/hour to meet the target within Y minutes you need to open the valve Z much? The only ones I've seen (which is not a lot) were just crude on/off switches.

Theo

I've always used around 11/12C difference however these days the CH system should be DESIGNED for a low flow temperature (50/60C) and a greater drop across the radiator. An older system may/will have been designed for a flow of maybe 70C.

Snap, apart converting the batteries. I bought a job lot of 6 for £10 and found that when the probes were measuring the same reference there was a 3 degree discrepancy between them. I chose the two that were reading around the mean temperature and both displaying near the same temperature. I too have them now measuring the flow and return pipes close to the boiler.

I've found balancing in the past has more to do with making sure that all radiators get the hot flow and all run at near the same temperature will all TRVs fully open. The problem is often that one radiator in the system doesn't get hot and you have to throttle all other radiators back bit.

Although it's debatable if you actually need them, when I replaced all my TVRs* I purchased auto adjusting/balancing TVRs. When installing there is a setting based on the flow rate and KW output of the radiator. The lock-shield valve is left fully open. There is also some debate if they work with proportionally controlled CH pumps. Well, I have both and for me they seem to have balanced the system without further intervention. The problem may be for many people is they don't know flow rates or the KW output of their radiator and for the latter a parameter one changes with the flow temperature of the boiler. Not knowing these means that you have no way of knowing what to pre-set the TVR to. I don't mean the normal user adjust knob on the TVR but a "dial" value that is set during installation.

• My CH heating system was around 25 years old and when I got a new boiler I took the opportunity of replacing all the TVRs and lock-shield values. The old TRVs were getting a bit unreliable with sticking pins etc.

Many modern systems may may incorporate a proportional pressure controlled central heating pump. As TVRs open and close the pump adjusts flow to compensate. Balancing is still mainly making sure that all radiator can output their maximum heat and that is done with all TVRs disabled (or set to a maximum adjustment value.

The TRVs I fitted (quite a while ago) are labelled Danfoss Thermostatic and they gradually reduce the flow as the room approached the target temperature the TRV is set to.

Isn't the gradual reduction just how the "wax motors" work, presumably the battery powered wifi TRVs work differently (worm screw bearing down on the valve maybe?)

Yes, the 'smart' TRVs I had were a motor to screw down the pin on the valve. You could hear them opening and closing. But AFAIK they didn't do proportional control to open the valve just a little bit if you are close to the target temperature. That's something inherent in how the non-smart wax ones operate, and I was wondering if some smart TRVs did it too.

Theo

I have the Honeywell Evohome system with 20+ HR92 rad controllers; they have proportional control. The system works well but I wish I'd spec'd a modulating boiler.

The magic source of smart s*it is the ability to superimpose that feature via something like HomeAssistant, which is capable of creating very complex actions based on inputs.

And if that is too extreme, Google Home has automations available which can be chained to create some quite complex routines.

remote opening curtains may seem like a frippery, until you have a bedbound partner who can control them (and lights and switches) by voice.

source ? sauce :)