One Radiator never gets really hot

R

RSMike

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I have a gas boiler ( oldish Potterton netaheat 80e) on a conventional gravity fed central heating system.

Small house, original system had 7 rads, then built a rear extension (single kitchen/dining room) and added a new rad, the problem is it has never really gets hot.

Now, I have been through all the usual stufff of bleeding air and balancing, had at least two plumbers over the years fiddle with the balancing, small improvements but still really to no avail.

Since added a small front Porch extension with another rad and this gets piping hot like all the other rads.

I think this problem rad is the last one on the system ( if that makes sense) and it is also the largest rad, could these things be a factor? , and what about the bore of the pipe supplying the rad, could that also be an issue?

Obviously don't need the heat just yet, but I'm sure in another month we will be feeling the early nip of winter, :)
Spent so much on additional electric heating last winter that I really need to get this sorted, just hope I don't have to go digging up floors to replace pipes or something.

Just wondereing if anyone out there has ever had similar problems?

Cheers
 
RSMike said:


I think this problem rad is the last one on the system ( if that makes sense) and it is also the largest rad, could these things be a factor? , and what about the bore of the pipe supplying the rad, could that also be an issue?
Click to expand...

These are two big issues. was another radiator feed tapped into for this probem rad or was it connected to main heating line?
 
One of my rads didn't heat and I was told when boiler was running to turn off all the other rads except the one that wasn't heating.... It worked after that.
 
Had a look at this today, there are a maze of pipes in my hot press where a lot of connections are coming together, but from what I can see this big rad is legged off the feed to another smaller rad in the bathroom, though very close (3-4 inhes) to where that feed is connected to bigger bore pipes that I assume are the main heating line ( these are coming directly off the immersion)

The pipe run then to the big rad is about 5 metres, using grey plastic pipe labeled HBP, with an outside diameter of 1.5 cm, all the older pipes/ connections are in copper.

The big rad panels (x2) are approx 148 x 52 cm.
 
Couple of things - from what you say the pipe bore to that rad could be too small for its size especially since you indicate it's at the end of the run. Another possibility is that your rad is blocked up with sludge, if yer handy with DIY ya could try turning off both valves and removing it and washing it out with a garden hose. The third possibility - I've actaully heard it happen, is that some cowboy plumber has gone to the trouble of hanging the rad on the wall and sticking two pipe into the floor for effect but not bothered to connect it up to the rest of the pipework!!!
 
I would go with possible airlock but most likely needs to be balanced, to send heat to this rad will most likely take a bit of time tweaking the system, I would start with the bathroom rad, nearest to where the connection was taken from.
By closing off all of the rads you will elimnate the possibility of the plastic pipe being creased, not unusual with plastic pipe.
 
Thanks for the replies guys, for starters, I will run a test with the bathromm rad completley off to see how that affects things.

On the sludge question, even though this rad and pipework is new the main part of the system is quite old (at least 25 years), I have heard there is a machine that pumbers have now to de-sludge systems.
Anyone have this done, and what were results?
 
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RSMike said:
Thanks for the replies guys, for starters, I will run a test with the bathromm rad completley off to see how that affects things.

On the sludge question, even though this rad and pipework is new the main part of the system is quite old (at least 25 years), I have heard there is a machine that pumbers have now to de-sludge systems.
Anyone have this done, and what were results?
Click to expand...


Power flushing. We do it and I must say the results are outstanding. Carefull consideration should be taken before you power flush though, power flushing an old system that is made up of gun barrel pipe is a no go.

Systems of sludge build up include, cold spots on rads, usually at the bottom and spreads like an arc. Slow heat up time. Well worth doing.

Your problem may be an installation one, and trying to retrospectively solve it can be difficult.
 
Thanks Davy, all my pipes are copper or plastic, so assume the power flush should be reasonably safe? , but I know what you mean, as the rest of the sysatem is heating up fine, this is probably not the main problem.

I tried a test with the bathrom rad off and I think the big rad was warmer but need to do a longer test to be sure.

Difficult to know whats best to do, possiblty rather than rip up floors to but in bigger bore piping, maybe better to just consifder putting in an additional rad closer to the main system ( which would also be messy, but more feasible)
 
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