Shredding money… radiator issues

[Lukewarm123]

Hello

I have a problem with 2 radiators in my house. I have Gas heating (installed within last 7 years).
2 radiators upstairs (in adjacent rooms) are lukewarm at best to touch, I have had numerous plumbers out, power flush done, system flush done, radiators no sludge, radiators are now taken off the wall and a copper pipe between each radiator to see if was a radiator problem but with the heating on full tilt they are still Lukewarm and not hot to put your hand on. When other radiators in the house are all turned down to about level 2 of 5 the pipes become warm. However it is a fairly large house and I want the other rooms to be hot so this isn’t a permanent solution.
The pressure has been checked and everything seems fine, no trades person can tell me what is wrong yet I am out a fortune investigating. Can any one suggest what might be the issue?

Thanks

 

[gmartine]

Has it always been this way? If you're satisfied there's no undo resistance or blockage then it comes down to your boiler's ability to either produce enough heat or circulate it. I'd have the pump looked at or increase it's speed.

 

[Last Plumber]

What size are the radiators?
What size is the pipework?
What are your flow and return temps on the rads and on the system?

 

[MOSSEP]

probably a pump issue, if the rads are quite a way from the boiler it may be struggling to get water them

 

[oz-plumber]

Probably piped up wrong from the beginning.

I would hazard a guess that one radiator is piped to the flow and one radiator is piped to the return.

Basically, both rads are technically pipes as a one pipe system.

Hope you can understand what I mean.

Had exactly the same issue a couple of months ago, changed pipework and system worked perfectly

 

[Knappers]

There is definitely things worth checking but it sounds like you've had it looked at.
I'd put money on it either being piped wrong as above or a pipe blocked with scale or a bit of rubble.
Sounds like a re-pipe job

 

[Bronze_tap]

Probably a long run of 15mm pipe underfloor to those cool radiators... ( Or a blockage)
To fix: replace 15mm underfloor pipework with 22 mm...

 

[Ben-gee]

My money is on Oz, one rad is plumbed flow and flow- other is return /return.
You’ll get a bit of warmth but not much.

This scenario is more common than you might imagine and is often overlooked by plumbers as a cause of your symptoms.

Having said that it could be a weak pump. But on-site it would be easy to determine which of these is going on.

 

[Lukewarm123]

Has it always been this way? If you're satisfied there's no undo resistance or blockage then it comes down to your boiler's ability to either produce enough heat or circulate it. I'd have the pump looked at or increase it's speed.

No it hasn’t always been this way - worked when we first moved in and prior to this (bought house from family). Can you update/upgrade just pump? Apologies I have no plumbing knowledge

 

[Lukewarm123]

Probably piped up wrong from the beginning.

I would hazard a guess that one radiator is piped to the flow and one radiator is piped to the return.

Basically, both rads are technically pipes as a one pipe system.

Hope you can understand what I mean.

Had exactly the same issue a couple of months ago, changed pipework and system worked perfectly

Have recently had wooden floor installed so can’t access pipes in floor underneath - rads worked before when system was first installed, would it be more likely the pump than size of the pipes? (I hope something accessible!)

 

[Timmy D]

Have you turned off all other rads to see if they get hot? I assume you have?

If piped correctly, with all other rads off and all valves fully open on problem rads, they should get hot.

If they do, then it’s a balancing issue. If they don’t, then it’s either a piping issue, or potentially a high spot collecting some air.

If they don’t get hot after the above test, I’d then close one valve and half disconnect the other valve and draw off water until hot.

Time how long it takes.

Then close that valve and open other side and draw off again.

Time how long it takes.

These draw offs might remove air if it’s there and get it circulating.

The timings might help you determine if it’s piped wrong.

You also might find that 1 valve on each road are piped together creating a large ‘radiator’, this joining pipework might be where the air is.

If you fully shut off one rad (both valves) and the further away valve on the other rad, then disconnect the closest valve on this rad and water doesn’t come out, this would prove they’re piped in series.

With a little bit of time, this should be overly difficult to fault find.

What area are you in - someone on here maybe able to help?