Radiator not heating.

Postby Stewarty88 » Thu Jul 15, 2010 10:43 am

I'm having trouble with the radioatrs in the lounge. Initially, I couldn't get either of the two to heat. Having closed in every other radiator in the house, including one of the two in the lounge, I got the open one nice and hot. I then shut this one in and opened the other one but have had no luck with this. The incoming and outgoing pipes from this one are both cold.
Can anyone suggest the next course of action I should take?
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Simply Build It

Postby htg engineer » Thu Jul 15, 2010 8:32 pm

Could be:

Faulty radiator valve(s)

Remove radiator and open each valve - allow to run into a bucket. If there's good pressure at both valves - that rules out blockage and faulty valve.

Allow to run until all air (if any) has come out - it'll splutter.

Keep us updated on progress

htg engineer
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Postby Stewarty88 » Fri Jul 16, 2010 7:42 am

I got the radiator heating last night. It turned out to be a faulty TRV which I managed to replace. I think I need to properly balance the system now as when I opened up the other one in the lounge, this one lost some heat.

If the circ. pump was on its way out, could this be also causing poor heating? Not sure just how quiet the pump should be. There is a slight hum to it and as I have just bought the house, I'm not sure how old it is.

Thanks for your help htg!
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Postby eggers » Fri Jul 23, 2010 4:48 pm

yes, a poorly pump can certainly cause poor heating but adequate hot water. check what speed setting it is on and you could try popping it up a speed, but that would only be hiding the fault for a while (if the pump where dying i mean)
does the system have a by-pass fitted or a restrictor on the hot water cylinder return?
the pump will always hum quietly when running, new or old, and a change in the sounds can be a helpful tool when diagnosing a pump fault (but not definite diagnosis!) such as a louder whistling noise and poor flow which could be air in the pump, as a limited example.
How old is the system and when you changed the trv, how dirty was the system water? it may, for example, be a blockage on the primary flow from the boiler, if system is very dirty. I have seen it before!
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Postby Stewarty88 » Thu Jul 29, 2010 8:56 pm

The system has a by pass valve fitted. Yeah, the hot water is perfect, the heating is fine too, until too many radiators are on.

RE the age of the system, I'm not too sure. I just moved in a few weeks ago. I drained the system down not long after I was in to remove a radiator and the water was pretty damn clean. As it was when I removed the TRV.

The pump is a Grundfos Selectric 15/ 50 and is set to speed 3 already. Are these pumps fitted and set to the lowest speed (1) initially? As you say, the problem may have arisen before and been masked by maxing the speed up.

I'm going to have another bash of balancing the system. Failing this, I think I will change the pump for peace of mind. It seems to be quite a common fault judging by similar posts.

Thanks very much for your time and help, much appreciated!
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Postby eggers » Fri Jul 30, 2010 7:12 pm

could be the by-pass is at fault, but i would try the pump first. I think you got the idea and it's already at maximum speed and not heating all the rads (and your house is not excessively big) then it's the most likely cause.
Usually pumps are set a maximum speed straight out the box, the you just knock it down a speed or 2 depending on the size of the property (1 bedroom flat isn't going to need as much effort compared to a 4 bedroom house for example)
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