Baxi Solo 3 PF

[Darren Griffin - PocketGPSWorl]

I have a 17 month old Baxi solo 3 boiler which started throwing fuses yesterday. Initially when I realised the heating had gone off I found a circuit breaker in the CU had tripped, reset this and all was OK. Next day the same thing happened but once the circuit was reset this time only the 'Boiler On' light on the control panel illuminated, no 'Fan On' light and no Pilot or Burner lights.

I located the installation manual and identified the circuit board fuse, this had blown so I replaced it with the spare and once again all worked normally for an hour or until this time the 3A fuse on the isolation switch blew (Baxi state this should be 5A?). Once again replacing this worked for about 20 mins until it blew both the isolation switch 3A and the circuit board fuse.

Any ideas what may be causing this and where can I source a replacement fuse for the circuit board which is marked F4AH250V?

TIA

[Set Square]

You can probably get fuses from the likes of Maplin or RS Components - but you clearly need to find and fix the root cause - otherwise fuses will just keep blowing.

Hopefully those (like Geoff) with a detailed knowledge of this boiler will respond - but it sounds to me like a problem either with the PCB or gas valve - or possibly the fan.

[geoff]

In message , Darren Griffin - PocketGPSWorld writes

It sounds to me that the fan is short circuit

i.e. knacked

The fuse is telling you that you have a problem (looks like the fan). Until you solve the problem, you'll keep on blowing fuses

The fuse is a 4A fast blow

look at my site

[Darren Griffin - PocketGPSWorl]

Thanks Geoff, is there an easy way of confirming that this is the cause? If I can be ceratin it is then I can contact you regarding a recon replacement.

[Darren Griffin - PocketGPSWorl]

Geoff, even with the fan unit unplugged the system blows the fuse in the isolation switch?, with the thermostat set to OFF I switch the isolator ON and a fter a few seconds the boiler ON light illuminates and the fuse blows.

[geoff]

Only by disconnecting the fan (at the fan as the connector on the pcb also has the air pressure switch connections)

If the fuse doesn't blow, it's probably the fan

The boiler won't go any further through it's sequence as the APS has to change state for anything else to happen

[geoff]

Do you have a wire trapped somewhere?

Is there water damage on the board?

What happens if you disconnect the pump?

[Darren Griffin - PocketGPSWorl]

No obvious signs of damage on the PCB, no arcing, burns or any water damage ceratinly. If I disconnect the Pump supply from the PCB (fan is now reconnected) I no longer get any blown fuses, Boiler ON light illuminates but I have left the thermostat OFF.

Appreciate your help here, I assume this means the fault points towards the pump and I should be looking in the airing cupboard now?

[Set Square]

Probably. You could bottom this out by disconnecting the pump from its current supply (junction box, or whatever) and putting a 13amp plug with 3 amp fuse on the end of its lead. Plug this into a 13amp socket (with the help of an extension lead if necessary) and see what happens. If the fuse blows, it's pretty conclusive.

[Darren Griffin - PocketGPSWorl]

I'm about to give up on fixing this and call a pro, the only problem is, is this an electrician's job or a heating engineer? I'm not rolling in cash and would like to get this fixed in one hit, I don't fancy paying for a hetaing engineer only for him to say it needs an electrician after I have forked out for his call out fee :(

[geoff]

If that's where it is, yes.

It certainly seems to be the first thing to look at

If you are confident enough with electricity, you could try connecting it up to the mains (via a plug with a 5A fuse in (unless you like big bangs))

If it blows the fuse, you've found your problem

[geoff]

If you look at the cost of calling someone out, it would be cheaper to just buy a pump and replace the old one

When you find the pump, tell us whether it has a valve on each side of the pump - if so you can change it without draining down the system.

When I say easy, it depends how easy it is to undo the connectors

You can be sure that there is enough expertise in this group to lead you through doing it (unless you listen to IMM, in which case it's bound to leak)

[Darren Griffin - PocketGPSWorl]

Thanks Geoff, I'll test the pump first thing and report back, gotta be worth a try!

[Darren Griffin - PocketGPSWorl]

OK, firstly I now appear to have blown the PCB, tested last night without pump connected and all was OK, switched off, connected pump, switched on and there was a pop, noticed fuse on PCB had blown so replaced and even without pump conncted this time there was no light indicating Boiler ON, removed PCB and there is a small burn mark towards rear around two resistors, so I'll be needing a recon replacement from you for starters! (Baxi Part: 231711).

As for the pump, disconnected, attached plug (with 5A fuse) and connected to mains, as soon as it is switched on the master trip in the CU activates although the 5A fuse does not blow! This obvioulsy suggests the pump has a problem but my electrical knowledge is not good enough to explain why the fuse remains intact. The good news is there are valves directly above and below the pump so a full system drain is not necessary.

Would you agree that the pump appears to have been the culprit here? I'll source a new replacement, it's a Grundfos Selectric UPS 15-50 and hopefully this should be relatively simple to replace. As for the PCB, I'll contact you directly regards a replacement.

[Set Square]

Why, oh why didn't you follow the advice of testing the pump on its own FIRST? You'd have saved yourself the cost of the new PCB for the boiler!

The pump almost certainly has a short between live and earth. The mains socket you plugged it into is probably protected by an earth leakage breaker - which tripped before the fuse blew. The central heating - along with freezers etc. - is probably on a circuit which doesn't have earth leakage protection - causing the fuse to blow instead when the pump was normally connected.

You'll need a large spanner (or adjustable) to undo the nuts on the pump - and they might take a bit of shifting. It often helps to have an assistant to hang on to the pump while you tap the spanner round with a copper mallet. Make sure that you replace the (rubber or fibre) washers between the valve flanges and pump body - and try not to strain the surrounding pipework more than absolutely necessary - since this can induce leaks elsewhere.

[Darren Griffin - PocketGPSWorl]

I know, it was stupid but in my defence I found a number of wires in the airing cupboard junction box were loose and could be pulled out easily so having tightened and checked those I foolishly thought I'd test in the vain hope that this may have fixed it, of course it didn't and a blown PCB is the price I'll have to pay for my idiocy!

[John]

shut off the service valves and hope they don't leak through the spindle when you move them if they are more than a couple of years old. (Try to do the job when merchants are open to buy replacements if they do). Sometimes the nuts move easily but often they require a bit of tapping with a small hammer to break the crud seal which may have formed on the threads. With a bit of practice you can strike it on the "corners" to persuade it to undo. Ensure the new pump goes back in the same flow direction as per arrow on body and apply grease to the threads to facilitate future removal. Most pumps come with 2 new joint gaskets in the box but make sure the faces of the old unions are clean. Its sometimes easier to fit the wiring while the pump is loose and easy to work on. Refill and vent the pump through the spindle plug then away you go.

[geoff]

Has the short circuit of the pump blown a track on the board?

The CU operated faster than the fuse blowing, or it is a short to earth.

So you can remove the pump after closing the valves

I'm not an expert on pump removal, but maybe a bit of WD40 or plus gas on the threads now might be a good idea to let it penetrate for a while before trying to undo it

It looks very much like it

Two nuts (don't forget the washers) and the L N E connections.

There is a 3 way rotary switch on the pump which is probably set to II. You should set the new one to the same power setting

Make sure you fit the new pump the same way round as the old one (which may sound pretty obvious, but I thought I'd mention it anyway)

[Darren Griffin - PocketGPSWorl]

Geoff, have taken a phot of the PCB to indicate the area where damage appears to have ocurred. There do not appear to be any damage tracks, just faint brun marks on front and back around the three components indicated by the arrow.

[geoff]

I can't see anything obvious, (If you had kept the board still, it would have helped), but the tracks associated with the pump don't appear to have blown, it's a component failure