central heating issue

[willknapo87]

Hopefully someone can shed some light for me.
I have a oil boiler with a pump and a total of 9 rads in my house,
All the rads work particularly well except the 2 in the living room,
They just don't seem to hold any heat.
They have had new valves, been bled, and I've flushed them out.
I've tried to balance the rads throughout the house which has made the rads hold a little heat
Any ideas onwhy they aren't heating up properly?

 

[45yearsagasman]

Firstly, have they ever worked properly?

 

[D_Hailsham]

What do you mean by "hold heat"?

Any rad will cool down once the room stat has reached the set temperature and switched the boiler off. It will start heating up again when the room stat turns the boiler back on. Normally when the room temperature has dropped by on to two degrees.

How far open are the lockshield valves on your rads?

Do you have TRVs on any rads?

 

[willknapo87]

By hold heat I mean every other rad in the house gets hot when the heating is on bar the 2 in the living room, the rads have been balanced and the valves are brand new.

 

[D_Hailsham]

By hold heat I mean every other rad in the house gets hot when the heating is on bar the 2 in the living room, the rads have been balanced and the valves are brand new.

So the two rads in the living room are not getting hot.

Does one connecting pipe feel hot and the other cold?

Also, please answer the other two questions in my earlier post.

 

[willknapo87]

The lockshield is probably a full turn open.
And yes the connecting pipe does get hot.
After I balanced the rads a few weeks ago it worked fine Then I turned the other rads on one by one,
Then as a couple of weeks have passed they seem to get less hotter

 

[D_Hailsham]

After I balanced the rads a few weeks ago it worked fine Then I turned the other rads on one by one,

What procedure did you follow when balancing the system?

PS Do you have any Thermostatic rad valves (TRVs)?

 

[gigz]

Open the lock shields a bit more. Some people make balancing harder than it is, its not rocket science. Turn upstairs rad lock shields down a bit as the heat will naturally rise to these.

 

[willknapo87]

I turned all rads off then one by one fully opened the opposite to the lockshield valves. The lockshield valves were turned once.
And I have no thermostat valves

 

[D_Hailsham]

I turned all rads off then one by one fully opened the opposite to the lockshield valves. The lockshield valves were turned once.

That's not how to balance a system.

Try this method:

1. Close all LS valves; then open them 1/3rd of a turn
2. Set all wheel valves (other end of rad) to fully open
3. Set the boiler temperature to at least 75C
4. Set room stat high (so boiler does not go on and off)
5. Let the system warm up
6. Check (by feeling the pipes) the temperature difference, between flow and return, at the boiler and at each rad.
7.If no noticeable difference, go to step 11
8. Go to the rad with the greatest difference (i.e coldest return) and open the LS valve opened very slightly (1/12th turn or less).
9. Wait 5-10 mins for the system to settle down.
10. Go to step 6
11. Stop
13. Set room stat to usual temperature

If you have something to measure the pipe temperatures, then use that.

 

[Steelmasons]

I disagree Mr Hailsham , that is not the correct way to balance a system.

Don't care where you quoted it from.

Last radiator/s with most resistance would be fully open on lockshields.

When I install a system I balance as I pipe each radiator , experience says it all.

....and if using Drayton TRV's then balancing won't be an issue.

 

[D_Hailsham]

Last radiator/s with most resistance would be fully open on lockshields.

I assume you are talking about the last rad in the index circuit, i.e the circuit with the greatest total resistance. That does not mean the last rad has the greatest resistance. The important thing is the differential pressure across the radiator as this, along with the required flow rate, determines how far the LS valve needs to be open.

When I install a system I balance as I pipe each radiator.

You should patent your method.

if using Drayton TRV's then balancing won't be an issue.

Why is that?