Potterton Puma 100e overcharging

3 Jan 2005
Reaction score
United Kingdom
Hi I have a potterton Puma 100e which has been going up the wall recently. It went off completely last night and sounded like the pump was jammed.
I removed the pump it seemed to spin freely and when i put it back together the boiler fired and ran.
The problem I have now is that I start with just over 1 bar pressure in the system Within minutes of turning on CH it is creeping over three bar into the red and I have to keep cracking down the pressure with the relief valve to keep the boiler running.
Of course this means when the CH is switched off again there is 0 pressure in the system.
Cant get my head round this one fellas any help would be greatly appreciated.
Sponsored Links
Unless you've left the filling loop open, which isn't very likely, it sounds like you have lost the pre-charge in the expansion vessel. This could be due to the diaphram rupturing or it might just need pumping up to about 1 bar.

Try opening the valve cap and pressing the valve. If water comes out the diaphram has gone.

If you're planning on recharging the PV, ensure that the system is emptied first.
As an emergency measure, reduce pressure to zero, then open the bleedscrew on an upstairs radiator. Then let more water drain out of the system until the rad is mostly empty. Close the valve at ONE end of the rad, close the bleedscrew, refill the system, bleed the other rads and set pressure to 1 Bar. Then try again to run the boiler. With a rad full of air to allow expansion, you will be able to prove that the expansion vessel is the cause of the problem (might not be) and hopefully will have a system that will work for a couple of days until you can either change the vessel or (probably easier) fit a second, external vessel.

By the way, using the PRV to relieve presure / drain water out of the system has probably already left it with a leak. You'll also need to clean / replace the PRV. Best way to drain a system is via a drainoff valve.
Thanks for the replies AB and CC. Sounds like a great idea using the rad as an expansion tank will definately give it a go. I think maybe its time for a new boiler soon anyway. Dont think the puma 100e is up to it and it is nearly 9 years old. Also I have a 7 week old baby to think about and shes not keen on being cold. Thanks again fellas.
Sponsored Links
CC's method works particularly well if you have a ladder-style towel rad in the bathroom. You can leave it working with BOTH valves open and it'll heat up properly where the water is, unlike a normal rad which relies on the flow over the top waterway.
Thanks Chris. Unfortunately I only have standard rads in the house I am just draining one as we speak. Thanks anyway mate.
Hi fellas
Quick update. Tried CC's idea with the upstairs rad and that seems to be doing the trick for now so thanks for that.
This obviously leaves the problem of what to do next. The larger CH expansion tank looks to be a sealed unit without a filling point and looks to be a pig of a job to change as it is tucked in the back of the boiler.
There is also a mini expansion vessel in the system which does have a valve on the top I don't suppose this is anything to do with my problem.
Any further help would be greatly appreciated.
small one is hot water :)

you can fit a extra vessel on the system as long as there are no valves etc beetween the vessel and the boiler :)
your expansion vessel is a large orange thing at the top / back of the boile, it should have a tyre valve towards the right, about 3 inches down (mine does i have same boiler)
Thanks breezer Found it now. Looks like this has happened before as the dust cap was sat on top of the boiler not on the valve.
To repressurise the system can i use a foot pump for a car. If not can you explain how I can do it.
Thanks for your help.
cooky said:
can i use a foot pump for a car. If not can you explain how I can do it.

thats exactly how the bg man did it, but reading these forums, if water comes out your expansion vessel has had it
Yes, use a footpump but make sure the system is empty and do it very gently - i.e. not like pumping up a tyre! :) make sure you don't go over about 13-14lbs, in fact 10 should do it.
Thats great. Will probably leave it until tomorrow now while the system is working OK. Think I would be about as popular as a fart in a spacesuit if we have no heating overnight. Will let you guys know how it goes.

Many thanks to all for the help today. First time on this forum. Can't believe how helpful you all are.
Cooky. ;)

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Sponsored Links