Balancing Radiators - can I do it?

ashnojutsu

I've got 2 bay radiators, and 4 new ones fitted - 3 singles and 1 double. These were all tested and worked fine. I've had to unmount them to paint the walls. Now I'll need to re-hang them, and a the plumber mentioned to me I would need to "balance" the radiators. He said it's easy, and I don't need any specialist tools.

Any one care to give me some instructions, or point me in the right direction?

Tom99

You balance them by adjusting the lockshield valve on each rad.
By and large those rads closest to the boiler, by length of pipe run, have the valve partially closed and those furthest away fully open.
If you open all the valves fully, turn the heating on and see which rads heat up 1st. They will be the ones where you partially close the valve.
Your aim is to have all rads heating up at the same rate.

FreeBear

Tom99 wrote: »

If you open all the valves fully, turn the heating on and see which rads heat up 1st. They will be the ones where you partially close the valve.
Your aim is to have all rads heating up at the same rate.

That's the short version. Longer version -

With the heating system cold, go round all the radiators and open up all the thermostatic valves, taps, and lockshield on every radiator. Take the opportunity to bleed the system and then turn on the heating, and make a list of the order the radiators heat up. Turn the heating off and allow the system to cool down.

With a thermometer in hand - Preferably a digital one (or even a pair) such as https://www.lakeland.co.uk/71642/Lakeland-Oven-Probe-Thermometer or https://www.ebay.co.uk/itm/1-2-5X-Digital-LCD-Refrigerator-Thermometer-Aquarium-Fridge-Freezer-Sensor/153422407549, close off the lockshield on the radiator at the top of your list. Crack it open a little bit at a time until you get a 12°C drop in temperature between the feed & return pipes (you'll need to have the boiler running for this). Move on to the next radiator and repeat.



Following day, go round and check the temperature drop across each radiator. Tweak a little if it is way off. Job done.

fezster

Only addition I'd make to the above is that for a condensing boiler, you should be aiming for a 20 degree delta between flow and return. Assuming your radiators have been correctly sized, you'd then aim for the same delta across them.

southcoastrgi

If they are downstairs ones just open up the lock shield end fully & back 1/4 turn

Mutton_Geoff

Tom99 wrote: »

You balance them by adjusting the lockshield valve on each rad.
By and large those rads closest to the boiler, by length of pipe run, have the valve partially closed and those furthest away fully open.
If you open all the valves fully, turn the heating on and see which rads heat up 1st. They will be the ones where you partially close the valve.
Your aim is to have all rads heating up at the same rate.

The aim is to have a drop across each rad of 12 degrees (or whatever the drop required by your boiler is). I've only balanced system boiler heating and that requires 12 degrees.


https://www.diydoctor.org.uk/projects/balancingcentralheatingsystems.htm

bris

You're aiming for 20 degrees or more for an efficient system on a condensing boiler, at those targets the boiler is running at it's cheapest, basically using less gas.


In reality it's pretty hard to achieve.

jaizan

I find one of those infra red thermometers that cost about £7 on ebay to be ideal. Instant readings, which are ideal when you need to rush around comparing several radiators. Just measure closely and at the same positions on every radiator.

paulcam

bris wrote: »

You're aiming for 20 degrees or more for an efficient system on a condensing boiler, at those targets the boiler is running at it's cheapest, basically using less gas.


In reality it's pretty hard to achieve.

As far as I understand this....

The condensing aspect has nothing to do with the drop, it only requires the return water is cool enough to condense the water vapour in the exhaust flu gases. This happens at around 54C. Above that the water vapour will not condense properly in the condenser and you will not 'steal' the latent heat of evaporation from that flu gas which can add close to 10-20% efficiency to the boiler.

A 20* drop would allow you to run the heating at 74*C. However a 12*C drop would allow you to run the boiler at 66*C which is fine for most places, any hotter and you risk children burning themselves on radiators.

On balancing the hardest part seems the simplest. "which radiator heats up first". I have no idea how you people think that is possible. I can't see how it is. You wait until what you think is the first one heats a bit then go the second and think.... "now is that warmer?", of course you can't tell because humans are rubbish at temperature.

fezster

It's not as simple as saying running at 66 degrees will be fine. Most radiator power outputs are quoted at a delta T of 50.

If you run at 66/54, the delta T is 40 at an average room temperature of 20 degrees.

If you run at 75/55, the delta T is 45. This is 15%.more power output.

The conversion factors are:

40 0.748
45 0.872
50 1.000

Depending on the size of your radiators, they may not be sufficient to heat the space running at the lower temperature.