2 pumped c/h system All aspects of plumbing questions and answers, help, tips and information

[morris minor]

Hi Dave, just got back from Cardiff and only had a chance to have a quick glance at your reply. I will print it out and have a propper read of it, it sounds as though you might have hit the nail on the head

[morris minor]

Hi Dave got the wiring finally sorted out, and my daughter has just moved into the bungalow over the week end. I have (she really) just come across an other problem this time its withone of the rads not heating up properly or sometimes not at all. The previous owner had converted the garage into an extra room and add a rad in it the feed and return is taken off the pipes befor the pump ( the pumps are in the loft in the house and not in the boiler housing). Any suggestions as to over come this problem, I thought by either reducing the return on the lock-shield valves or by moving the pump on the c/h circuit from the loft to the boiler.

[Dave From Leeds]

Hi Morris,

Glad you've sorted out the wiring. How did you do it? Did my ideas help?

Anyway, onto the latest issue, you mentioned some time back that there were two radiators taken off the pipework before the manifold. Is the problematic rad one of these? Is the other one OK? I suspect from everything that you previously said about the way the system is laid out that these two radiators will still be in the pumped CH circuit so it may simply be an airlock in this radiator. Have you bled them all? I'd try bleeding them all in turn, starting with the highest ones if they're different heights. If they are all the same height start with the one nearest to the pump and work away from it. By the sound of it the one that's not warming up properly is likely to be the furthest from the pump. I'd do this with the CH turned on so that the pump will help to push any air out since the pipework goes up into the loft. If there's a bleed point on the pump it might be worth bleeding this first with the heating turned off. Good luck mate.

[Steve the gas]

Does it have a TRV on it ?

[morris minor]

Dave first, as to the first part of your Q the answer is no, I had to completly redisign the wiring, and Q 2 only one rad is taken off the pipe run B4 the pump for instance 28mm pipe comes out of the boiler up the wall and it has a tee and out of the T is a 8mm pipe going to the rad, and the other outlet on the tee continues along the ceiling and into the loft and into the pump and out the other side to a 6 way manifold and ont to the other rads. There is a return path via an other manifold babck to the boiler and this too has a T on it with the return from the rad thats not heating up. And no there is no air in the system. the other 2 pipe from the boiler are the DHW pipes and the flow of one of these have a pump.
Steve Gas. no it does not have a TRV on it.

[Dave From Leeds]

Hi again Morris,

Try shutting off all the other radiators, initially by their TRVs or feed valves if they don't have TRVs. Does the dodgy radiator heat up then? If so open the others back up and if the problem returns balance up the system as you suggested by turning down the lockshield valves on the other rads. If the radiator doesn't heat up when the others are shut off, it could be a partial blockage in its pipework or the radiator itself.

[Dave From Leeds]

Morris,
I've just re-read your latest post. You could still try what I suggested in my last reply but I don't anticipate much success, since I think that once you reinstate the others they will get too cold before this one warms up enough. In any case, forget what I said about a partial blockage.

From the configuration that you have described the radiator near the boiler cannot possibly be in the pumped CH circuit. It's just trying to get hot water from the boiler as a gravity feed. I think you need to repipe it into the two manifolds like all the others to get it to heat up properly. Alternatively re-site the pump to between the boiler and tee-off to the radiator then throttle back the lockshield valve on this radiator to prevent all the flow from going through it, otherwise all the others will then go cool/cold.

[Dave From Leeds]

Another thought. Don't completely shut off all the other radiators otherwise the pump will be running against a closed system!

[morris minor]

High Dave at the mo we have given up on trying to sort out the radbecause my daughter said she will leave it till the chap comes to service the oil boiler in the summer, and she will ask him as to what he thinks should be done to solve the problem