Cold upstairs radiators


Postby jetway » Mon Oct 20, 2008 6:16 pm

I have recently fitted a new upstairs bathroom radiator and two upstairs bedroom radiators all with trvs. When I tried to refill the system i had a problem getting any water through and traced the problem to a blocked pipe from the fe tank. I removed the blockage and reconnected the pipework, now the system fills very quickly and bleeds easily. When i run the heating now the downstairs rads heat quickly and give off good heat, the upstairs back bedroom and bathroom gets warmish after 15-20 mins and the other 2 bedrooms stay cold. The 2 bedrooms that stay cold are the new rads and they are both supplied with the same two pipes across from the back of the house. I followed these pipes from the back of the house where they supply the back bedroom and bathroom and the feed is hot out of the boiler through the hot water cyl and hot to the back bedroom and bathroom. then it goes cold on the long run to the front of the house. The return pipe is warm to hot in the same places as the feed and again is cold on the long run to the front of the house where the cold rads are. I have tried draining and refilling, draining water from the cold rads out the vents, closing all the other trvs and lockshieds on other rads. I have also drained down, cut the feed and return pipes at the start of the long run and blown down them to check for any blockage in this circuit all clear. I have an indirect system with a hot water cylinder and boiler approx 8 years old. Any advice would be apprieciated,
jetway
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Joined: Sun Sep 21, 2008 3:55 pm

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Postby plumbbob » Mon Oct 20, 2008 11:06 pm

Common problems are with either trapped air (I know what you say, but the symptoms are classic) or the system is unbalanced. Turn off the hot water, and ALL the hot radiators. This may cure the problem or at least point you in the right direction.

Make sure the bypass if fitted is only slightly cracked open.
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Postby jetway » Tue Oct 21, 2008 6:27 pm

thanks plumbbob, i have turned all rads off except bathroom which i think is bypass. I have turned off manual tap on hotwater coil exit pipe. I am running the heating but the pmp appears to be getting very hot and the water flowing thought the pump and nearby pipes is very noisy a sort of rushing noise nearly a bubbling or whistling noise. i left it running for about 20 mins and the cold rads supply pipes did start to get warm but the noise got louder in the pipes as if it was builing up pressure i suppose. How long would you say to leave it running like this and what do you think about the noise?
jetway
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Joined: Sun Sep 21, 2008 3:55 pm


Postby jetway » Tue Oct 21, 2008 6:33 pm

plumbbob. i have just looked at the pipework at the end of the long run to the cold rads. the 15 copper pipe feed runs about 4 meters away from the boiler and at the end goes in to a 90 facing straight up, it the runs straight up for about 2 inches then into a tee which goes left to one rad and right to the other. do you think this series of a 90, uphill, then a tee could cause a flow problem?
jetway
Posts: 5
Joined: Sun Sep 21, 2008 3:55 pm


Postby plumbbob » Wed Oct 22, 2008 9:11 am

I don't see why the uphill pipes or the tees should make any difference to the flows.

One point is if after a while of running, you find the pump body is getting hotter than the surrounding pipes, this indicates the pump is empty of water, and be careful as it can be damaged. Remove the large screw on the front of the pump. Behind you will see the impeller shaft, and any air in the pump will be expelled. When bled, water should dribble out.

If this is going to work, air should be forced through almost immediately. Still sounds like trapped air. You need to find a way to remove the air. TRy cracking open a joint near the pump. Maybe disconnect one of the cold radiator valves and point it into a bucket and open the valve to allow a good flow of water.
plumbbob
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Joined: Wed May 07, 2008 9:59 pm


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