Yet another Potterton 80E problem to add to the collection:
The Central Heating is firing for 10-30 seconds, then switching off, repeating
this cycle ad nausaeum. We are also getting frequent lockouts when
Hot water is demanded, though I'm not sure if these problems are related.
Many thanks for any ideas the group can offer.
circulate water? Hot water would draw off a lot of the heat from the
exchanger provided flow rate is high enough, but central heating relies
on the pump to move the heat out and round, is it working well
enough/system clagged up?
Sounds like a pump problem might cause both problems.
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Similar problem here once. Annual service, guy turned up the pressure
after years of no change saying it would give faster heating, etc. That
led to lots of kettling so called another guy back who tweaked it back
down, but he could only guess at the previous setting. It's not a
modulating boiler, just a simple low/high thermostat switch.
Is gas pressure straightforward to twiddle?
Yes, as long as you've got a reasonable clue about what you're doing!
The installation handbook for your boiler should have a table which shows
heat output versus gas pressure. You have to:
1. decide how much heat output you need
2. connect a manometer ** to the pressure measurement point
3. tweek the governor with the burner on (and the boiler fully warmed up) to
give the correct pressure - as measured by the manometer
As a cross-check, you can time your gas meter pointer going round when the
boiler (but no other gas appliance) is running - to make sure that it is
consuming gas a rate commensurate with the desired settings.
** You can make a manometer out of a strip of wood, some plastic tube -
filled with water, bent into a U shape and fixed to the wood, and a piece of
graph paper between the tube and the wood to measure the difference in water
height between the two sides of the U
As an example, my boiler has a heat input of 23.7 Kw (80,900 BthU/Hr) at a
gas pressure of 4.0 inches of water (10 millibars). Since it's about 75%
efficient, its heat output under these conditions will be about 17.8 Kw
(60,700 BthU/Hr). The gas consumption would have to be calculated from the
calorific value (as stated on the Gas Bill) - in order to convert 23.7 Kw
into cu.ft/min - or whatever it is that gas meters measure these days.
It's actually a Baxi Solo 70/4 PF - which is now 10 or 12 years old. The
figures I quoted were for the intermediate setting. Its max input is 26.6 Kw
(90,900 BThU/Hr) and its max output 20.5 Kw (70,000 BThU/Hr) - hence the
When it was first installed, I was intending to extend my house (which I
have subsequently done twice!) and wanted to allow scope for extending the
heating system to match.
I had a go with my back boiler to cut down noise and short cycling.
I didn't have a manometer, just tried to stay on the safe side and make
sure ignition was ok.
The result was outstanding, short cycling gone and noise down.
I'll now duck in case I've done something extremely bad,
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