Back boiler won't fire up - faulty controller?

[SimonBea]

Hi, we have a baxi boiler which currently we can't get to fire up. We had the fuse go on the electrical switch for the controller (Drayton LP241) which we then had to change the fuse and then the actual switch itself. After this the boiler was permanently firing up and the only way to stop it was to turn off the fuse switch or turn down the temp on the cylinder. After a couple of days switching the controller off at the fuse switch now we can't get the boiler to fire up at all (pilot light is on). Our dilemma is we are having a new boiler installed in couple of weeks so don't want to fork out a lot to fix something we are scrapping.

I'm wondering if the faulty switch has fried the controller, I've seen a couple second hand on eBay and wondering if worth a swap? We are surviving with the emersion heater in the tank for hot water but temperatures are the moment not ideal with zero heating. I'm no electrician or plumber so is there any sense in my theory?


Thanks for any help
Simon

 

[terryplumb]

Sounds like the programmer blew the fuse. What testing was done to determine the switch was faulty ?
Only testing voltages at the wiring centre would determine what's going on ,do you have a 3 port motorised valve ( Y plan) ?

 

[SimonBea]

Hi, by coincidence we had electricians in the day it happened (fuse blew before they turned up) they replaced fuse and it blew again and then changed the switch over. Yes we have a 3 way valve above the pump, this still works, on the controller I can still switch heating on and the valve moves over, pump seems to be running just boiler doesn't kick in

 

[terryplumb]

Do you have a multimeter and can you safely measure mains voltages?

 

[SimonBea]

I do have one, but not something I've ever done, so that may be a no!

 

[DP]

Sounds like the programmer blew the fuse. What testing was done to determine the switch was faulty ?
Only testing voltages at the wiring centre would determine what's going on ,do you have a 3 port motorised valve ( Y plan) ?

Taking bets it was a 13 amp fuse

 

[CBW]

If need a 2 channel programmer (if that is indeed the fault) you can get new ones for a similar price for the used Drayton, straight swap. When you get the new boiler, will you not have a programmer?

 

[terryplumb]

Hi, by coincidence we had electricians in the day it happened (fuse blew before they turned up) they replaced fuse and it blew again and then changed the switch over. Yes we have a 3 way valve above the pump, this still works, on the controller I can still switch heating on and the valve moves over, pump seems to be running just boiler doesn't kick in

If the motorised valve is moving and pump is running it may not be the programmer ,but a boiler issue.
What baxi boiler model do you have and what's it's status ?

 

[SimonBea]

Hi, it's a baxi Bermuda inset 2. Pilot light on, gas fire works and was serviced recently.

If power is on then the valve always moves to hot water and pump always running, even if nothing set on on programmer, if I turn heating on the valve moves across to middle. But boiler doesn't fire up in either modes

 

[stem]

What if you turn off the HW and put CH on so that the valve moves from the middle to the far end of its travel to the CH only position.

The reason I ask this is because there are two things that start the boiler.

1. The hot water cylinder thermostat when HW only, or HW & CH are on
2. A microswitch inside the motorised valve when it's in CH only position

At the moment in the positions that you describe it could be the hot water cylinder thermostat that is faulty and not starting the boiler. If when it moves to CH only [check that it has moved fully across to rule out a faulty 3-port valve] you find that the boiler starts, it points to the hot water cylinder thermostat being faulty. If on the other hand it still doesn't start then it's looking like it's a boiler problem, it would be unlikely for the two items that control the boiler to both fail simultaneously.

If the 3-Port valve is moving to the correct positions that suggests that the Drayton LP241 is working because that's what it does. As per the above, other parts of the system control the boiler.

The same two things usually also control the pump so if you say the pump's running but the boiler isn't, I know where my money will be...

 

[SimonBea]

Hi, thanks for reply. I can't get it to CH only, it defaults to HW so sits either there or in the middle of I set CH on. With programmer set to nothing valve sits at HW.

 

[stem]

With programmer set to nothing valve sits at HW.

Correct

When the valve is not energised it sits at HW only and is held there by a spring
Whilst HW is on and is then joined by CH it winds halfway across to the middle position
With CH only on it should continue its travel right across to the CH only position

I'm guessing you can't get it to CH only because it's been wired incorrectly. Usually it means that the 'HW off' signal is missing from either the programmer or hot water cylinder thermostat.

Anyway, if you can't do the test I described, then the only way I can see forward is for someone who understands how the system is wired and what each and every wire does tests from the boiler back through the rest of the system with a multimeter to find the origin of the problem.

But as usually with your type of system the boiler and pump are usually wired together, if the pump's working and the boiler isn't, then the boiler would be my first port of call to test.

 

[Laurieo]

The thermostat valve under the boilers not been switched off has it ?.

 

[SimonBea]

Not sure what that is? Nobody has changed anything apart from the fused switch to the programmer when that went. Thanks for all replies, might just sit it out for couple weeks with the emersion heater till new boiler arrives

 

[Terrywookfit]

I would guess a trapped melted wire,