Coal fire not heating radiators properly

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13 Dec 2011
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Lincolnshire
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Hello everybody, I am hoping you can help me. I have a house with a coal fire, that heats the water and central heating. The hot water is kept in a copper tank upstairs and there is a small plastic tank in the attic for the central heating water, both are fed from a water tank in the attic. Everything was working fine, the fire heated the radiators really well with the airvent closed, and to have the fire on constantly, took 3 buckets of coal per day. Now, I have just had 3 new double core radiators fitted, (replacing single core ones and they are slightly smaller) and an extra one in my conservatory. Now, with the fire on the same setting, the radiators are not getting hot at all, and I have to open the vent, getting the fire hotter, to get any heat into the radiators. The plumbers who fitted the rads have been back and checked everything, and they say all is ok, (the pump is only a few years old and was checked to be fine), and they have just told me to turn the fire up, as there is extra water in the system, it needs extra heat to get it around the radiators. Now, the chimney breast is hot, but the hot water pump and pipes coming out of the chimney breast are barely warm. Before, the rads upstairs would get hot without having the pump on, but they don't anymore. I am getting through coal really quickly because of this. 3 buckets to 5 or 6 daily now just doesn't seem right! Surely, if the chimney breast is getting hot, then the pump should just pump the water round the system, or am I missing something? Would a bigger pump solve the problem, or is something else amiss here? They put a cleaner in when they emptied the system, so could that have caused a problem or blockage?. The system was only drained down about a year or so ago, and fernox has always been used.
 
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The plumbers who did your work sound clueless.

If you are piling coal in there the heat is going somewhere
most likely up the chimney.
If the pipes from the boiler are not hot the water isn't circulating.
I suggest flushing the system out with mains cold pressure
needs someone who knows what they are doing.

Depends what part of lincolnshire you are in I work near Doncaster
if you get stuck personal message me.
 
If you have suddenly more than doubled the output from your radiators, are you sure it's not simply that the fire is no longer capable of supplying enough heat?
 
Is the passage that goes under the back boiler clear of ash, and is the fire damper actually directing the heat from the fire that way?
John :)
 
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We have only added about an extra 40 litres to the system, as the new double core radiators are smaller than the old single core ones, and the radiator in the bathroom is still a single core one, with one extra radiator being added. the fire is a Parkray, I think, and the fire bars are 275 mm long, so its quite a big fire. The ash is removed either daily or every other day from the tray under the fire. All the other radiators were replaced with double core ones about 6 years ago, just these ones were not as we didnt have much money and only replaced the ones that needed it. Even if the fire is no longer big enough, surely, as the chumbey breast is warm, the pipes coming out of the chimney breast should be warm?, the pipes are nearly cold. And the radiators seemt o also now lose their heat really quick too
 
If the pipes aren't hot then the water simply isn't circulating......I'd suggest a severe blockage on one of the pipes as it enters the boiler.
John :)
 
Could the blockage have been caused when they drained the system down? They added a cleaner when they did it. The system was only drained down about a year ago with no problems. Could the blockage have been moved now? The house was built in 1954, so the pipes are obviously quite old, so potentially, would flushing the system stop the problem? Would this explain why the radiators get hot when the fire is turned up?
 
To be fair, so long as there is water actually in the back boiler, I would have expected to hear bubbling noises as the water started to boil and maybe cause the air bubble to shoot up one of the pies and to overflow into the loft header.
As you say both pipes are cold shows that they are either dry or no circulation is taking place.
I'd like to hear what others say!
John :)
 
How do I actually check to see if there is water in the back boiler? As the fire heats up to a nice temperature, the radiators do actually heat up, but not like they used to, and then they cool down quicker too!! tOtally confusing me now
 
Potentially, yes it could - it doesn't take much air to stop the circulation.
The only other alternative is to start cracking joints open, and risk them not resealing - so keep bleeding that air out and fingers crossed!
John :)
 
Also, ive got a grundfos 15-50 pump at the minute, and was wondering, with putting the extra radiators in the conservatory, would upgrading the pump to a 15-60 be beneficial? Was thinking the extra pumping head might help with circulation
 

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