Baxi boiler 35/80 IE blowing fuses?

goodstuff!

The above baxi boiler will run for about 5 mins and then blow the fuse. I was told that water had leaked down onto the PCB but was dry when I got there. I gave the PCB a visual check and it seemed fine but obviously there could be an underlying problem other than a visual fault.
Has anyone had any problems with these controls before?
Could it be the Pump?
I'll be going back tomorrow when i have my tools and multimeter with me but i'm just looking for probable causes to help me find the fault.
Thanks.

JohnnieK

To blow a fuse there is a major short some where in the boiler. Windings of a fan or pump can cause this as to the pcb if a component was shorted. Is it the 3amp fuse or the quick blow that's going?

goodstuff!

I tested the boiler yesterday and everything seemed fine. I electrically disconnected each part of the boiler one by one, turned the power on and it still blew the fuse at the switched spur. Eventually i had the boiler completely disconnected and it still blew the fuse. I reconnected everything then bypassed the zone controller by hardwiring one zone and the hot water and everything seemed to work perfect for the half hour i was there. I left it like that and told the owner to keep an eye on it over the weekend, switching on and off with the spur, and contact me if anything happens.
He rang and said it will run now for about 45mins and then either blow the 3A fuse or trip the 10A MCB!!!!
The only thing left is a stat, wiring or a faulty MCB. But none of these should have and effect or variation on each other by anything i have disconnected or reconnected?
I'm getting a bit stuck on this now. Can anyone help?

Micky Dolenz

Get an RGI to inspect. It is illegal for you to work on a gas appliance even if you don't break into a gas way and are just working on the electrics.

God forbid but If the house burns down, the insurance would have a case not to pay out.

And I think it could be a thermostat or thermistor since it will run until the temp increases.

goodstuff!

goodstuff! wrote: »

Eventually i had the boiler completely disconnected and it still blew the fuse.

It ain't da boiler den.

Micky Dolenz

gary71 wrote: »

It ain't da boiler den.

How did I miss that? :P

Yeah, can't be the boiler.

External controls, try making and breaking all external switches, anymore than that get a boiler tech:)

Micky Dolenz

Micky Dolenz wrote: »

How did I miss that? :P

Your a busy man:)

meercat

as others have already said
i would suspect the pump

try and disconnect it and put it on a separate lead with its own fuse
if this fuse blows then you know for sure

goodstuff!

gary71 wrote: »

It ain't da boiler den.

Thanks:rolleyes:

goodstuff!

Micky Dolenz wrote: »

Get an RGI to inspect. It is illegal for you to work on a gas appliance even if you don't break into a gas way and are just working on the electrics.

God forbid but If the house burns down, the insurance would have a case not to pay out.

And I think it could be a thermostat or thermistor since it will run until the temp increases.

The RG Inspector was out on thursday, checked it over, gave the unit a service, told the owner it was an electrical fault, took his money and left!!!
I'm a qualified electrican, so hence i got the call.
As regards the the stat, i'd say it could be the problem, but why would it trip nearly straight away when wired through the zone controller and take nearly 45mins when bypassed?
For the 30mins i was there with the boiler running, it went through 2 full cycles with no problems at all. Thats why i was sure it was the controller sice i had removed it from the circuit!!

goodstuff!

meercat wrote: »

as others have already said
i would suspect the pump

try and disconnect it and put it on a separate lead with its own fuse
if this fuse blows then you know for sure

Thanks but the pump is built into the boiler unit and is working fine.

goodstuff!

goodstuff! wrote: »

but why would it trip nearly straight away when wired through the zone controller and take nearly 45mins when bypassed?
For the 30mins i was there with the boiler running, it went through 2 full cycles with no problems at all. !

All the external controls are just switches but are dependent on temperature apart from the programmer/clock.
The switchs of the hot water cylinder or room stats can be opened or closed depending on the temperature they are sensing, for example if you arrived and the cylinder had achieved temperature already the cylinder stats isn't calling, after awhile if the hot water is drawn off lowering the temperature of the cylinder which then makes the cylinder stat which could then short circuit:)

dersawazzie

Any luck ?