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[jonathanh]

right - I know nothing about these systems (yet) but suspect I'm going to learn quickly.

Symptoms are

Bioler fires, pump works and it heats hot water.  turn the radiators on and you get nothing.  Relay in the controller sound like it is moving.  thermostat is working (tested that).  where next?  What is the most likely cause; controller or something else.  Can someone point me in the right direction to diagnose

thanks in advance

John

[Marks DTM Calib]

Need a bit more info about the system

Boiler: Combi, system or standard
Control pack: timer, stat, mid position motorised valves, seperate valves.

First guess even without the above answered would be you ahev a mid position valve and its not working.....this can normlay be set to a position manualy via a lever/switch on the side of it which should gte you heat in the short term as a work around.

[jonathanh]

Boiler: standard

control system is timer, stat and a single mid position valve.

Yep I was suspecting the mid pos valve as well - but it is moving, at least when hot water fires up

[Taxi_Driver]

If the valve moves to the W position when the hot water is on but doesnt go the mid position when heating and water on....I would suspect the controller. Or a break in the wire somewhere between the crontroller and valve.

[Mr Skrunts]

Air lock in a radiator, sounds daft but have you checked them.

[Andy B]

....
  turn the radiators on and you get nothing.   .....

When you say nothing ..... do you mean no hot rads or it all stops & you don't even get hot water?
If just no rads, does the 3-way/2-way valve to the rads move at all? What happens when you manually move the valve?
Try turning off all the rads and then open up just one rad at a time so the pump has to pump through that rad.
I've just had to use my air compressor to shift a blockage in my system .... a bathroom rad (fed via the primary hot water side) refused to get warm no matter how I had the system valved. I won in the end!

[jonathanh]

no air lock in the rads.  what i mean by heating on is that nothing happens: no pump, valve movement or boiler.  no response.

I'm suspecting the mid position valve so going to look at testing that for now

thanks for the help so far

[Marks DTM Calib]

As said, actuate the manual lever on the valve.

The way the valves should work is that the timer requests heat and the stat (connected in series with this) tells the mid position to move to the heat position.....the valve then moves and when it gets to the correct point in the travl it trips a micro switch which in turn fires the boiler.

The boiler then controls the pump.

So, either the synchron motor is buggered or the micro switch is shot.

[cem_devecioglu]

As said, actuate the manual lever on the valve.

The way the valves should work is that the timer requests heat and the stat (connected in series with this) tells the mid position to move to the heat position.....the valve then moves and when it gets to the correct point in the travl it trips a micro switch which in turn fires the boiler.

The boiler then controls the pump.

So, either the synchron motor is buggered or the micro switch is shot.

Marks DTM is there any subject that you dont know, you make me jealous  

[Marks DTM Calib]

As said, actuate the manual lever on the valve.

The way the valves should work is that the timer requests heat and the stat (connected in series with this) tells the mid position to move to the heat position.....the valve then moves and when it gets to the correct point in the travl it trips a micro switch which in turn fires the boiler.

The boiler then controls the pump.

So, either the synchron motor is buggered or the micro switch is shot.

Marks DTM is there any subject that you dont know, you make me jealous  

Central heating systems ar dead easy.....had to repair most of the control boards in the Potterton Profile boilers for the neighbours so studied the warped and mythical method of operation for a mid position valve!

And the symptoms described sudgest that this is probably the issue and by moving the lever on the side we will be able to pin point if its the motor or micro switch at fault.

[matt-sboro]

check for power on the grey wire at the mid pos valve - if you have 240 then check to see if you have 240 on the wire going to the syncron motor

if you are getting power to the syncon motor then just replace the syncron motor - if you dont then the pcb on the mid position valve has had it and you need to change the whole thing.

you might be lucky - you could have one with a removeable head

if not you will need to either need to drain the system or bung the cold feed and open vent in the header tank and then replace the whole thing  

[matt-sboro]

Central heating systems ar dead easy.....had to repair most of the control boards in the Potterton Profile boilers for the neighbours so studied the warped and mythical method of operation for a mid position valve!

And the symptoms described sudgest that this is probably the issue and by moving the lever on the side we will be able to pin point if its the motor or micro switch at fault.

common problem with pcbs - dry joints just need repairing - profiles and puma's seem to go fairly often

[Kevin Wood]

Central heating systems ar dead easy.....had to repair most of the control boards in the Potterton Profile boilers for the neighbours so studied the warped and mythical method of operation for a mid position valve!

Deep joy. We have those boilers in our estate. The neighbour's one has got bored of actually igniting and sits there for hours blowing unburnt gas out of the flue. He doesn't seem to care but it's a bit disconcerting when you've got an LPG conversion.

Called the gas board emergency number last time and sent the guy next door. Hasn't happened since.  

Kevin

[Marks DTM Calib]

Central heating systems ar dead easy.....had to repair most of the control boards in the Potterton Profile boilers for the neighbours so studied the warped and mythical method of operation for a mid position valve!

And the symptoms described sudgest that this is probably the issue and by moving the lever on the side we will be able to pin point if its the motor or micro switch at fault.

common problem with pcbs - dry joints just need repairing - profiles and puma's seem to go fairly often

Not seen any issues with dry joints (build quality actualy is pretty good on thecircuit boards).....every one so far has had 4 dried out electrolytic capacitors resulting in the fan cycling on and off.

Other than the fan bearings getting noisey (cheap and easy to fix), they seem bomb proof......and are surprising efficient (not that far off the modern condensing ones)

[jonathanh]

thanks everyone.  swapped the mid position valve (had a spare lurking around) and I'm now warming up....