New rads with TRV's are not hot

[mrchristian]

I have recently replaced two old rads with two new column rads (same equiv btu) on the ground floor of my house. At the same time I thought it would be sensible to include TRV's. Even though the previous set up seemed to work perfectly, I now find myself with two warm at best/cold at worst rads (even when I remove the TRV's open the valves fully).

I have a basement where the radiators have never worked since I moved in (I replaced an out of commision boiler and open-vented system with a sealed system). The hot water from the boiler seems to refuse to travel down to basement)

What has upset the balance of the household heating? Is it the TRV's? If I where to update all the rads with TRV's would this help? Why are basement rads cold (one did heat up a tiny bit when I isolated them). Probably about 4 questions in one here - can anyone help?

thanks C

 

[D_Hailsham]

I now find myself with two warm at best/cold at worst rads (even when I remove the TRV's open the valves fully).

System needs balancing

I have a basement where the radiators have never worked since I moved in The hot water from the boiler seems to refuse to travel down to basement

Water is pumped round the system, the location of the rads is immaterial. It's a balancing problem.

What has upset the balance of the household heating? Is it the TRV's?

Possibly. The heat given out by a radiator depends on the flow through the rad. If the TRVs are more restrictive than the previous wheel valves, the flow will be less and consequently the heat. This can be corrected by proper balancing.

If I where to update all the rads with TRV's would this help?

Not really, you will still have to balance the system

Why are basement rads cold (one did heat up a tiny bit when I isolated them).

Not balanced.

Balancing procedure:

You will need either two clip on pipe thermometers (£12 each) or an infrared thermometer (about £25 from Maplin). I have used both and prefer the infrared as it has a faster response, is more accurate and can be used for other things, e.g checking the temperature distribution over the surface of a rad.

1. Turn boiler off and allow to cool
2. Make sure HW is turned off
3. Open all LS valves fully; remove all TRV heads and open all manual rad valves fully.
4. Turn the boiler temp to max and bring system up to temperature.
5. Check, by feel, the order in which the rads warm up and make a list.
6. Adjust the bypass (if fitted) as per mfr instructions
7. Measure the temperature differences between the flow and return pipes at the boiler. What it should be will depend on the boiler -refer to the installation manual. If the temperature is not right, you need to adjust you pump speed (higher speed gives smaller difference and vice versa). Set the speed to give as a difference as close to the mfrs recommendation as possible.
8. Turn the boiler off.
9. Close all lockshield valves. Leave TRV heads off.
10. Restart boiler
11. Go to first rad in list made in step 5
12. Attach the pipe thermometers (if used) to the rad and open the LS valve a quarter turn.
13. Wait until temperature has stabilised on the two thermometers (or use the IR thermometer to measure flow and return temp in the pipes adjacent to the valves). If the difference is smaller than that at the boiler, close the LS valve a fraction, or vice versa. Wait until the temp has stabilised and check again.
14. When you are happy with the first rad, move on to the next on the list.
15. Repeat steps 12, 13 and 14 for each rad on the list.
16. When you have reached the last rad, check the boiler temp difference and adjust pump speed if necessary.
17. Go back to the first rad and test it is still giving the correct difference
18. And so on, going round and checking the temperature difference until they are all as near the required drop as you can make them. Don't expect perfection
19. Replace TRV heads and set to required temperature

A very small change in the amount a LS valve is open can have a considerable effect on the temperature difference. Because of the way LS valve are constructed, it is virtually fully open when it is one and a half turns open. So most adjustment will be within one turn from closed.

If you find that the wall thermostat is turning the boiler off before the TRVs in the other rooms work, you should close the wheel valve slightly, so the rad gives out less heat and the room/hall warms up slower. It's a matter of trial and error.

 

[mrchristian]

Thank you so much - I think I have underestimated the sensitivity of the LSV's. I will follow your advice (let you know tomorrow if it works - if you are interested- i am sure it will).

Again thank you,

Christian

 

[ChrisR]

Quote:
I have a basement where the radiators have never worked since I moved in The hot water from the boiler seems to refuse to travel down to basement

Water is pumped round the system, the location of the rads is immaterial. It's a balancing problem.

SLudge can also stop low radiators working. It's very common.

 

[mrchristian]

Sludge has always concerned me - the rads where put in over twenty years ago. Thing is I have drained the system a couple of times and draincock is at the bottom of the system (of course) - water's a bit black but no sludge - wouldn't the water be blocked from draining if sludge was present in basment rads?

C

 

[gigz]

I agree with both of the above, if it is sludge you need to get this sorted as it will be nearly impossible to balance properly. I would either get it powerflushed or take the offending rads off and manually flush then run some x400 round for a few weeks, drain and re-flush with clean water and add x100 then balance as above. Could also be the pump although it would probably be the upper rads that would be affected.

 

[Slugbabydotcom]

Had one with a very similar scenario last week. Turned out to be a blocked return filter on a Baxi 80e.
Also look out for a blocked manifold if its microbore or basically a blockage anywhere in the circuit to the D/S rads and back through the boiler.
Are the valves fully open under the boiler?
Another case I had once was where both the valves were actually in the open position but the return valve had snapped off inside and was almost closed restricting it to the size of an 8mm pipe. > Not enough for a full system!
Check for an open or otherwise faulty by-pass if there's one fitted.
Try closing off the rads that do work so the the force of the pump can act more directly on those that dont. Closing off a by-pass or tightening an automatic by pass will allow more of this force through to the affected rads.
Take a downstairs rad off and see if you can get water from both valves.

 

[jacobball]

if you have sludge in a radiator, hydrogen will build up as a by-product of it, and the top/middle of the rad will be colder. when you vent the air from it, if you hold a lighter near the air vent, if a small flame appears, it is hydrogen and sudge is your problem.