central heating only comes on with h water, stumped engineer

[jackthom]

Hi Bill, the Grundfos is almost certainly the only pump.

If it is accessible can you confirm it is set to maximum speed and does it keep running after the boiler has tripped off in CH only mode.

If the pump has stopped at this point the problem is most likely an electrical one.

 

[bonkersbill]

The pump is set to 3 and does keep going pumping cold water round the CH

 

[jackthom]

When the short burst of very hot water from the boiler has been sent out by the pump, does the boiler fire itself up for another 30 sec soon after, without you having to do anything to the system ?

 

[bonkersbill]

No, i have to wait and im not sure what if anything helps to restart the boiler due to all the tests i keep running, if left for a while it will usually start up again. always starts when valve is not in CH only position so electrically it always works what ever i select at the programer if i manually move valve from CH only position.

 

[MANDATE]

Hi Bill!
You could put the boiler stat on high and try CH only again and see what difference it makes.
Still think a dose of cleaner might be worthwhile.
Still think pump itself might be the resistance and examination is the only way of knowing.
I know you have had this problem for 2 years, but has it ever worked correctly

 

[Agile]

Please dont anyone quote i need a good engineer, if i get to the bottom of why its not working and its beyond me to fix it, i will then get a 4th engineer to look at what ive found, had enough of engineers fumbleing around the same problem without any answers, at least here ive got a dozen or so looking at the problem.

Well I would say that you DO need a good engineer although I appreciate that you may be fed up with people coming round who cannot work it out.

I notice that you have not quoted your location! Can you add that to your profile? Also saying the town in the text.

Then perhaps one of the experts from this forum can come to you to suss it out for you. I dont imagine its going to be very difficult.

Tony

 

[bonkersbill]

Turned the knob up full on the fire and switched valve to CH, this after about 30 seconds made the pipes start rattling really fast to the side of the boiler, then boiler shut off. i'm not sure that it ever worked properly, the HW was set to come on when CH came on, we only put CH on when it was really cold, i can remember the rads would get warm in the summer when CH was never on. i will get some flush, is it just rad flush and do i put it in the CH tank in the attick and do i have to clean anything out after? How long before it will clean anything out?

 

[bonkersbill]

Would it be worth getting someone out to service the boiler?

 

[Agile]

You need someone to see what your problem is and whats needed to sort it out.

Tony

 

[MANDATE]

try googling 'central heating cleaner'.
Yes you do put it in the small tank in attic, but that is after you've drained enough water out of the system to ensure it gets well circulated when you have CH on with HW
Check instructions, probably need at least a week and yes it will need to be flushed out.
Note after a drain down, use lever to hold valve in mid position while re-filling, otherwise with CH port blocked off an air pocket may be formed

 

[MANDATE]

Hi Bill!
Just had another thought regarding your problem.
What if it's the lockshield valves on your radiators that are closed too much and causing the resistance as against a partial blockage in the pipe work.

I think I'd be tempted to open them a quarter turn, to see what effect it has.
At the moment the opening of the HW port and allowing some additional flow away from CH circuit seems to make the difference.

I'd also consider opening them more and more with a view to finding out if there is a point where there is sufficient flow to disperse the heat and stop stat from operating.

 

[MANDATE]

Hi Bill! Just checking to see if you have made and headway

 

[bonkersbill]

Hi, are the lockshield valves the thermostat adjusters on each rad, if so they are all open fully except one which i have turned off.

 

[algas]

Bill you said you replaced thr prog did you put the switch or jumper from G to P ?

 

[jackthom]

Hi, are the lockshield valves the thermostat adjusters on each rad, if so they are all open fully except one which i have turned off.

Hi Bill, the lockshield valves are the ones used to balance the system. They don't usually have a control knob and they generally have a plastic cover.

With the water flow problems you are having it would be best if all the radiator valves (both sides) were wide open.