Hissing from pipes

[ajmcquaid]

Hi guys,
Wondering if you can help? Have a potteron puma that's doing some serious hissing. The main light is on , the boiler seems to be working but there is no hot water. Thames water are currently doing some major work in the area and our mains supply was turned off for most of the day for 'essential work'. I read a previous forum indicating that it could actually be noise from a mains leakage (and the noise travelling into the boiler??) Could it be that simple? Is there an air lock in the system?
Any info would be appreciated.

 

[ChrisR]

Check inside boiler. Fold panel down and you should see a red led come on on the pcboard when water is drawn.

If not, the hot water flow switch isn't operating. COuld be due to air in pipes but that 's unlikely or the water from the taps would spurt a lot. The hot water flow switch is a brass round flattish thing left of centre about 3 1/2" diameter with a hex shaft going to right. Electric switch is mounted on that. You should be able to see it working through the hole in the side of the hex. You can poke a small screwdriver in throughthe hole to operate switch manually - boiler should start. Turn water on first!

hot water flow switch sticks, though usually in the ON position. You can strip it to graease (silicone grease) or buy a new one for <£50 . Microswitch itself is extra - or may be the only bust bit.

 

[ajmcquaid]

Thanks Chris,
Today the water guys switched the mains off again for a couple of hours and the noise stopped. As soon as it was turned on again the boiler made alot of banging noise and when I loosened the little screw at the very top of the boiler alot of air came out. The hissing is still going on,the boiler switches on when the hot water tap is switched on but the water is at best a little warmer than cold. I was also told my overflow pipe outside the flat was ****ing out water at the same time as the bad banging noise. I don't really want to call anyone out if there was something simple I could do (by the way-I'm clueless)

 

[ChrisR]

OO er missus.

(later edit - mix of explanations and things to check here - see what you can glean and come back!)

The water main should NOT be connected to your heating system water!
Sounds like your filling loop is letting water go straight through. You are supposed to remove them- so this can't happen (and water can't go backwards from the CH into the main if the main is turned off).
Your mains water is going straight out of the pressure relief valve through the wall, which passes water at 3 bar ish. Check the gauge (underneath , on right) this should be stable around 1 bar, risng a bit when the boiler is hot (after turning off/ disconnecting the filling loop)

The vent on top is there to let air out of the heating system water. It isn't connected to the tap water. The heating system water should have NO air in it.

Your boiler is a little unusual in that the tap water uses the same heat exchanger as the heating system water, though the two don't mix.

The waterways in the CH bit of the heat exchanger have to be full or the water will boil. Having the tap on full will help for a while - depending how much air is in there.

So it could be quite a simple problem - or something unusual /nasty has happened like a leak between the two parts of the eheat exchanger.

Start withthe filling loop. If it has a tap at one or both ends just turning it across the direction of the pipe should close it (may need a screwdriver or small coin). That should stop the hissing! The PRV is likely to keep leaking - they don't shut well once they've been passing water for a while. That would mean you'd have to refill to get the pressure back up, but it won't stop your HW working in the v short term.

Iguess youhave no HW cos the burner's going out becasue it's overheating. I can think of lots of things which could be wrong - but you seem to have more than one.

DOes water come out of the hot tap - I know it's slow while it's cold (a wax thing opens when its hot).?
Does the heating work?

 

[ajmcquaid]

Hi ChrisR
The water from the cold tap has good pressure but the hot water tap isn't even close to a heavy stream. My overflow pipe outside is constantly running. The gauge on the bottom right of the boiler reads 4 psi. Its a potterson puma 80e and although I've been here 2 years, the building itself was built in the mid 90s-so it isn't that old. I think it may be the ball cock in the tank-when the mains was switched off, the water levels dropped as did the ballcock and maybe once the tank filled the ballcock remained lowered and unable to rise. Unfortunately I cant get access to the tank as its prob in the attic at the top of the building which is locked. I've turned off the mains water and the noise has stopped-I'm gonna get a huge bill if I dont-its been like this all week-end. Im waiting for a call back from the water company-hopefully they'll sort it out-I'll keep you informed.
Thanks again

 

[ChrisR]

If your bauge really reads 4psi (and not 4 bar!) then your boiler won't try to fire.
Your pressure relief valve is obviously "leaking" badly - you need a boiler engineer to fix it unless you want to delve yourself. It will keep the pressure low enough for the boiler to not fire if its pouring out. This is NOT an overflow pipe!!

Have you removed/ turned off the filling loop?

The tank you're talking about would not normally be connected to your combi at all.

The water compnay will not want to know about your boiler it's nothing to do with them, and their stuff is simply not connected to it.

The water flow from a puma WILL ALWAYS be low until the water is warm so that isn't a fault.

 

[ajmcquaid]

Hi Chris,
You were bang on the money-it WAS the filling loop!!
Thanks for the advice!

 

[ChrisR]

Godd - nice and cheap. But why no hot water?