powermax 155 - HW ok but no CH

[helishaker]

Central heating was working fine the other day but now all I get is a buzz from the programmer. I've tried manually turning the water pump screw but the impeller rotates freely. I've tried resetting the system several times but this has failed to sort the problem. Any ideas??????

 

[ollski]

may sound a stupid question but are you checking the right pump?, bottom of the appliance left hand side, there are also 2 reset buttons.

 

[bobw1956]

is the boiler the 155x.

is the CH pump working, after the heat store has reached its temp;

that will be the pump middle to left of boiler

 

[gazthepottertonengineer]

there is a few things you need to check if you are still getting hot water and boiler is firing up for hot water it obviously wont need resetting

it is more than likely either pump is seized relay to pump has failed or cold start stat is knackered

 

[helishaker]

I've checked the pump (the one one the left) and it is free.
I suspect the relay has failed because of the buzz when the central heating is selected. Where is the relay located?
Also, the suggestion that there are 2 reset buttons could be worth investigating - where are they??

 

[ollski]

presume you're getting voltage out of the room stat?

 

[gazthepottertonengineer]

as i said before if boiler is firing up for hot water then dont worry about those o/heat stats as they would stop boiler firing up follow lead from heating pump and you will see a blue box stuck to casing with velcro that is the relay

 

[helishaker]

I think the model you are refering to may be different to the one I have as there is no blue box stuck to the casing. I've followed the wires which go to a pcb, other than that I'm stuffed.

 

[gstens baxi]

The heating pump is wired to the cold start stat which is what determines wether the thermal store is up to temperature before letting the heating pump run. The problem is either the pump its self or the cold start stat.

the blue box is connected to the dhw flow switch....

 

[gazthepottertonengineer]

you are right as normal i did say cold start stat though

 

[helishaker]

The pump is running free when turned using a screwdriver and it was running OK the other day, which would suggest that the pump is not the culprit. There is this constant buzz from the programmer when the CH is selected - the room stat appears to be functioning correctly - it would seem that when there is a demand for heat, this is not processed but I can't identify where the fault lies. You suggest that it could be the cold stst - is there a bridge I can do across the connections on the front panel to prove the pump?

 

[ollski]

Have you not got a multimeter?. Try bridging it out across the orange and white wires.

 

[helishaker]

yep I've got a multi meter - 0 volts reading between orange (terminal 27) and white (terminal 25). Yes there is power at L1/N1 of 240 volt.

 

[ollski]

yep I've got a multi meter - 0 volts reading between orange (terminal 27) and white (terminal 25). Yes there is power at L1/N1 of 240 volt.

Check the stat common orange to neutral 240 and N.O white to neutral 240. If you have 240 on the N.O to neutral with ch calling then the stat is faulty.

 

[helishaker]

orange to neutral 0 volt - white to nuetral 0 volt