Balancing Radiators...

[Adrian80]

Hi All,

I read the faq about balancing radiators and want to pose a question.

The boiler circulates water to all the radiators and because of the different lengths of pipe work and organisation of radiators some get more than their fair share of hot water. Leaving some luke warm or cold.

So the name of the game is to give the radiators just enough hot water to heat up, and no to much as this wont leave enough hot water for the others.

So if you were to close all the LS on the radiators. Then open the one that heats up the first, just enough so it heats ups, then move around to the second and open the LS until that one heats up..

You continue the process until you completed all the radiators.

Hopefully if there is a bit of spare capacity in pressure, and the pressure hasnt dropped so low that water doesnt circulate through the radiator you first balanced, all the rads should be hot/ balanced.

This wouldnt require you to measure temperature on the flow or return and all you would need to do is listen for the flow of water through the radiator.

I suspect their might be problems in this approach, you might limit the circulation around your heating with all the LS turned as low as possible, and put to much strain on the pump.

Anyway the reason i suggest this is because i got a thermometer to balance my system as suggested in the faq, it was crap and couldnt measure anything quickly or reliably, so had a go just by feel.. and then came to the strategy described above. All seems to be working ok at the moment, and i am interested in your thoughts.

bw
A

 

[MickyP10]

My thoughts as a non plumber? Turn the system on and feel the rads, turning down the hot ones until they all feel similar. Clip-on thermometers are crap. I have an infra-red which is much better. BUT, you can get close without either.

(Awaits the fallout...)

 

[ajrobb]

It is usually said that a LS only restricts flow if open less than 1.5 turns. After balancing, if all your LS are open much less than 1.5 turns, turn the pump speed down a notch and try again. Conversely, if you can't get all the radiators hot, turn the pump speed up...

I run HW at different times to CH, so I made sure HW was off before balancing.

Look to your boiler manual to identify if you should be aiming at 11°C or 20°C drop across the radiators.

Look to your TRV instructions to see if you should be balancing with head open or off completely or manual head open by so much. If you take the heads off, it is always worth checking that the pin moves freely (push it in and it should pop back out again).

 

[Adrian80]

Thanks ajrobb,

my LS seem to be much more graded, you almost have to turn them 3 times to get the water flowing a little bit.

Do all pumps have speed settings. I looked on mine and couldnt see it?

But more than my problems,

Does the approach of listening for running water sound like a bad idea?

A

 

[bengasman]

Unless you have balanced so many systems that you can get pretty close by hearing and feeling, the way to do it is as described in faq. You can't do it by counting turns or otherwise.

The balancing is not done because some get more hot water than others, but to achieve and equal drop of a set value over all the rads.

 

[ianniann]

Listening isn't a good method. A nearly closed off radiator will make more noise than one with a fully open valve.

Make sure by hand they all heat up at about the same rate and you won't be far wrong. Don't spend money on thermometers just to balance your own radiators, but if you have clip-on or infra-red thermometers then use them.

An external pump will almost certainly have a speed control right on the pump. One built in to a newish boiler, espceially a combi, may well be controlled electronically through the boiler control panel.

 

[MJN]

Anyway the reason i suggest this is because i got a thermometer to balance my system as suggested in the faq, it was crap and couldnt measure anything quickly or reliably

You really need an IR thermometer to give you the accuracy, repeatability and speed of measurement required. Otherwise, as you found out, it can take a very long time such that shortcuts are inevitably sought!

I'd recommend the ETI TN1 which can be had for around £15 if you shop around. Also, put a piece of insulation tape on the point of measurement in order to ensure consistency of readings (if you're interested, it is the variations of emissivity that would otherwise cause issue).

Mathew

 

[Adrian80]

Listening isn't a good method. A nearly closed off radiator will make more noise than one with a fully open valve.
.

I completely agree. However if you know the radiator is off, then you begin to open it, the water squeezes through, makes a lot of noise etc. As you carry on turning the flow becomes smoother, less noisy i.e. the radiator is more open.. then it becomes quiet, the valve is nearly fully open or open and a lot less turbulence is being caused.

So as long as you know where you started from their may be utility in the old lug holes...

 

[Adrian80]

that shortcuts are inevitably sought!

Mathew

Indeed a shortcut that i found useful, and the radiators all seem to be hot. Potentially others may find it useful, but... like all things has limitations.
A

 

[Adrian80]

The balancing is not done because some get more hot water than others.

Is balance an ilussion. if you had no TRV is could accept the system may be balanced, but with TRV as one closes the pressure in the system will be increased and may put the others out of balance. I assume the pressure difference caused by the closing TRV will not be equal across the whole system..

 

[ajrobb]

Is balance an ilussion.

Yes, TRVs change the balance. Many systems have an automatic bypass valve (ABV) that opens to compensate (typical factory setting of 0.2 bar). Otherwise the pump produces more pressure with reduced flow, which increases flow noise apart from anything else.

The ideal is to match maximum total radiator flow to the boiler's design flow rate. If the radiator output matches the boiler output then all well and good. What to do when the radiators are too small for the boiler (typical combi boiler in small house/flat) seems to vary with the boiler and pump.

Personally, I'd rather the boiler could protect itself from reduced flow. I think some can (e.g. by limiting the temperature rise across the boiler) but some can't and can damage the heat exchanger if not protected by the installation.

 

[bengasman]

that shortcuts are inevitably sought!

Mathew

Indeed a shortcut that i found useful, and the radiators all seem to be hot. Potentially others may find it useful, but... like all things has limitations.
A

All rads getting hot does by no means prove the system is balanced properly. A car that starts does not necessarily pass the mot

 

[Adrian80]

I agree that the system may not be balanced. but isnt the name of the game to hot radiators?


I suspect the lack of balance, specifically to much pressure may cause problems to the pump, and also may be less efficient than hoped, and probably a noisy system...

A

 

[ajrobb]

I agree that the system may not be balanced. but isnt the name of the game to hot radiators?

Condensing boilers change the game. They are more efficient at lower average temperatures. Depending on the boiler, typical designs want either 11°C or 20°C temperature difference between feed and return.

If the pump is set too high and the radiator lockshields are open too far, the flow rate through the boiler can be too high and the temperature difference is reduced. This increases the average temperature in the boiler and that reduces the condensing efficiency.

An average installation might use an ABV to maintain a flow rate through the boiler. This might be a requirement of the boiler but the efficiency drops when the ABV opens and raises the return temperature. I think a better installation might use an adapting pump, which reduces speed as TRVs close, and a boiler that can cope with reduced flows. That way, the average temperature in the boiler drops as TRVs close and condensing efficiency increases.

 

[MJN]

if you had no TRV is could accept the system may be balanced, but with TRV as one closes the pressure in the system will be increased and may put the others out of balance. I assume the pressure difference caused by the closing TRV will not be equal across the whole system..

Not true.

As a TRV closes the pressure increases equally across the system. The balance, or relative proportion of flow, across the remaining radiators in the system is not affected. Of course, flow through the remaining radiators will increase however they will still be in proportion to each other i.e. they will still be balanced.

Your shortcut method of balancing is flawed, and your resulting theories are based on a false premise about what balancing is, why it is beneficial and how it is achieved.

Mathew