Potterton Puma 80

[FarmerJohn]

Hi,

We have a Potterton Puma 80 combi which came with the house so I am not sure how old it is. The problem is that it takes ages for the radiators to warm up especially those at the end of the run. Just lately it appears to be getting worse.

When the central heating is switched on normally the boiler operates straight away and after a small delay the outgoing central heating pipe gets hot. This is a 22mm run upstairs where it branches into a number of 15mm runs for radiators on the second floor (four radiators) and also to a single 15mm run for the third floor (one radiator). Finally there are another two 15mm runs which come back down to feed radiators on the first floor (three radiators). I have replaced almost all of the old plastic pipe with copper since being there and have also fitted two new radiators.
If all eight radiators are on it can take up to two hours before the first floor radiators warm up and when they do they do not stay on for long. Its almost as if the pump or boiler heat output is not up to the job.

Does this configuration seem reasonable for this type of combi, I mean is there enough capacity in the boiler for eight radiators spread out over three floors?

Is there a way to be certain that there is no air in the system. I recently emtied it and refilled it again but got the same results? What is the purpose of the large black plastic hexagonal plug on the back of the pump? I can turn it by hand.

Regards FarmerJohn

 

[keego]

Sounds like it just needs balancing, look it up in the FAQ section.

 

[D_Hailsham]

We have a Potterton Puma 80 combi ...
Does this configuration seem reasonable for this type of combi, I mean is there enough capacity in the boiler for eight radiators spread out over three floors?

The puma 80 is a 24kW boiler, which is more than adequate for 8 rads, which will probably add up to about 10kW. The reason the boiler is "oversized" is that it needs this heat output to provide the instant hot water.

Is there a way to be certain that there is no air in the system. I recently emtied it and refilled it again but got the same results?

If the rads are just not getting very hot, it is unlikely to need refilling.
If a rad is cold at the top it needs bleeding. This should be done with the water cold, pump off and MV's set to MAN. (set to AUTO when finished!)

What is the purpose of the large black plastic hexagonal plug on the back of the pump? I can turn it by hand.

Probably just a cover. Which pump is it?

What temperature do you have the boiler thermostat set to?

As Keego says, probably just needs balancing. Do you have TRVs?

 

[FarmerJohn]

Hi,

Yes balancing was the problem. For some reason I had convinced myself that I needed to run all the radiators with the lockshield valves fully open.

Rebalanced as per FAQ and now the system is working correctly. Many thanks for all the replies.

Regards FarmerJohn