could this be a sludge problem?

[obseen16]

Hi guys. went to a customers today who has a problem with the hot water circuit from boiler to coil. basically the boiler is overheating before the cylinder heats up. it is a pumped ch system but a gravity hot water.

when on hot water only the boiler fires for about 1 min and then overheats and cuts out. no fault lights flash and hot water is getting to the cylinder coil, as it is not an air lock could it be sludge in the system as on ch mode it works fine. my theory is that sludge has narrowed the pipe inside and so the hot water cannot escape the boiler quick enough so the boiler shuts off.

if this is the case is there any methods of getting the sludge out besides power flushing? its a VERY old system and leaks are probably guaranteed if its power flushed.

any advice appreciated,

Cheers guys.

J

 

[Puddle]

Have you checked the header tank,could be dry and cold feed blocked and system drained to below cylinder coil,heating would still work as enough water in system for this

what boiler is it ?

 

[mark_mc]

I have had this problem before, never went down the powerflush way.

I fitted a pump on the hot water side and put a check valve after the pump and after the pump on the central heating side, so that when one pump is on it does heat the other and so on.

it is diferent to wire with the two pumps but can be down,the only this is that would say the vent and cold feed for the heating is on the gravity hot water so will have to put on the heating side or fit a expansion vessel with quick fill, safety valve etc.

you may worry about the old pipework with pressurised heating so let you decide;

maybe check the expansion tank as with the cold feed connected to the hot water gravity sludge could easily block circulation from there, and clean on the heating system is always a good idea if open vent.

 

[ecowarm]

Have you checked the header tank,could be dry and cold feed blocked and system drained to below cylinder coil,heating would still work as enough water in system for this

what boiler is it ?

My thoughts exactly Puddle

 

[tamz]

Probably an air lock. Doesn't take much to stop a gravity.
Check layout and position of pipes carefully. The tee off for the expansion should be the highest point and fall back from there. If the pipe from expansion to cylinder rises at all it will cause problems.
Try splitting the nut at the flow connection on the coil to see if there is any air or alternatively the easiest way is to pull the stat from the boiler and let it boil for as long as your bottle holds

 

[Billy Bob Bob]

with regards to puddles suggestions(check the basics first) if not convert to fully pumped when its drained down check the coil they can be unblocked

 

[easyt]

How long has the system been in. OP says its a very old system. If it worked OK for years before then it should work OK now without a pump. Similarly if it hasn't been suffering airlocks in the past why should it now?

Probably an air lock. Doesn't take much to stop a gravity.

Next time I take a fall I'll remember those words as I hurtle to the ground.

 

[obseen16]

all very good points guys, the f+e tank is full of water, the boiler is an oldish glow worm floor standing fan flued boiler with auto ignition. cant think what the model is now, might try and drain the system and re-fill to see if that sorts it. i have drained this system before (12 months ago) and had no issues with it when re filling.

 

[tamz]

Next time I take a fall I'll remember those words as I hurtle to the ground.

Thats why you should never leave the house without your parachute

 

[tackleburger]

My bet is the feed from the F&E is at the cylinder return and that's where your blockage is get if so clear it and get some x400 in there.

 

[obseen16]

My bet is the feed from the F&E is at the cylinder return and that's where your blockage is get if so clear it and get some x400 in there.

ok what would be the best way of cleaning it out though? sever the pipe (rather not).

 

[Bungditin]

I had the same problem with a client of mine and it turned out to be an air lock.I managed to get a hose pipe attached to the cold feed and a isolation valve onto the vent on the expansion tank and pumped in water from the mains and made the system pressurised,then gradualy opened the isolation valve to expel the air in the system,took hours and patiance but it worked.

 

[Nas]

I had the same problem with a client of mine and it turned out to be an air lock.I managed to get a hose pipe attached to the cold feed and a isolation valve onto the vent on the expansion tank and pumped in water from the mains and made the system pressurised,then gradualy opened the isolation valve to expel the air in the system,took hours and patiance but it worked.

I've also experienced this and it turned out to be airlock.