Balancing central heating

[Malcolm Loades]

New property to me with old CH system. I guess the pipework and rads are around 20-25 years old but the boiler is less than 18 months old. A couple of the radiators are not as hot as others so I did a bit of googling and discovered all about balancing. Checked the inlet side of each radiator and they are all fully open (this should not be so). I now understand how to balance the system but where I'm stuck is with the requirement to start with the radiator nearest the boiler first and then work outwards.

I can guess which radiator is first and indeed it is almost red hot. The two cool ones must be near the end but is there anyway of guessing/telling the orders of the others? One cool one is on the ground floor, the other cool one is vertically above it on the second floor. There are no vertical pipes visible anywhere, all pipework is under wooden floors.

 

[45yearsagasman]

Checked the inlet side of each radiator and they are all fully open (this should not be so)

Not correct. The inlet side is normally open and the flow through the rad is controlled by the other valve which is called the lock shield. As to finding the order or rads, that's best done when the system starts.

 

[Doggit]

Now this is an interesting thread to join in. There's a guy I occasionally work with, and he insists that balancing a system, means making sure that there's an 11 degree drop across the rad, whereas to me, it's about making sure that all the rads come up to about the same temperature.

As 45 says, you can find the order the rads heat up when the system first starts, but if you open each lockshield by say half a turn, and then go round opening or closing the lockshield fractionally each time, so that they all come up to a similar temperature. The further rads will need to me more open, and the nearer rads closed off slightly.

And if you don't have thermostatic valves on each rad, you'll then need to do a bit of fine tuning so that after the rads are all about the same temperature, you then let a little more or less water in to make sure that the rooms come up to the same level.

 

[Malcolm Loades]

Not correct. The inlet side is normally open and the flow through the rad is controlled by the other valve which is called the lock shield. As to finding the order or rads, that's best done when the system starts.

Sorry, my inability to explain things properly It's the valves on the left of the radiators which have caps (as opposed to knobs) on them which are all fully open. I'm obviously wrong in thinking this is the inlet side.

 

[muggles]

The inlet (flow) side is the side which gets hot first.

There's an article on balancing radiators in the FAQ on here

 

[Malcolm Loades]

I'm becoming confused! I've looked up lockshield and almost everywhere says something like "..... “lockshield” valve — the one at the opposite end of the radiator to the main on/off wheel valve". Muggles says the inlet side gets hot first, that's the left one on all my rads. 45years seems to say that's wrong and that you balance the system with the one on the other end - the one I thought was fully open when you wanted the rad to work and fully closed when you wanted it off.

 

[muggles]

OK, post a picture of one of your radiators and we'll take it from there

 

[Doggit]

Okay Malcolm, It doesn't matter which way round your valves are, it's just a matter of understanding what they do. Nowadays, you often have a thermostatic valve on one end, and a "lockshield" valve at the other. The older method, is a valve that opens and closes fully, where the other end has a cap on it that you lift off, and then use a spanner to turn it. One end is designed to turn the radiator on and off, and the other end is adjusted to let a certain amount of water into the rad, and then gets left alone - this is the valve that you use to balance the system with, so that less water gets into the nearest rad, and more gets let into the furthest rad, simply because the water has further to travel, and therefore create a greater resistance.

In your case, you open the valve fully on the right side, and then adjust the valves on the left side to control how much water gets in to the rads, and then leave them alone.

How do you other guys start the process, half turn open, 1 turn? or what.

 

[Agile]

To do it extra quick I open each to about a 1/2 turn, bit more on distant rads and bit less on close ones.

If they are set to an 11 C differential then the top will be hot!

But 11 C is only the target for a NON-condensing boiler!

Condensing boilers should be close to 20 C. In practice this is often difficult to obtain so 15 C is a better objective.

Tony

 

[DP]

But 11 C is only the target for a NON-condensing boiler!

Do not agree with that statement

 

[Agile]

You often like to disagree with some of the things that I write.

But without explaining why, I don't see that as very constructive.

 

[Malcolm Loades]

Okay Malcolm, It doesn't matter which way round your valves are, it's just a matter of understanding what they do. Nowadays, you often have a thermostatic valve on one end, and a "lockshield" valve at the other. The older method, is a valve that opens and closes fully, where the other end has a cap on it that you lift off, and then use a spanner to turn it. One end is designed to turn the radiator on and off, and the other end is adjusted to let a certain amount of water into the rad, and then gets left alone - this is the valve that you use to balance the system with, so that less water gets into the nearest rad, and more gets let into the furthest rad, simply because the water has further to travel, and therefore create a greater resistance.

In your case, you open the valve fully on the right side, and then adjust the valves on the left side to control how much water gets in to the rads, and then leave them alone.

Perfect, thank you. That's how I first understood it but other responses made we think I was wrong.

Now to do the job.

 

[Steelmasons]

If they are set to an 11 C differential then the top will be hot!

Eh???...would a 20c deltaT @ 80c flow temp be cooler than that of an 11c deltaT @ 65c flow temp???

 

[Agile]

No the 80 C flow will be hotter.

But for a condensing boiler the flow should be 70 C for better efficiency.

The top of a rad will be close to the flow temperature.

Common misconception that the top will be midway between flow and return temperature.

 

[Steelmasons]

//www.diynot.com/diy/threads/forum-rules-general-info.19448/

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