Baxi Bermuda 45/4 Electronic - Intermittant problem

Hi, I've had this back boiler installed and working for 5-6 years now without any problems (Pumped CH with Gravity HW incl.2 way Motorized valve and Cyl Stat) , the boiler is serviced annually (due april).

A couple of days ago at around 11.00pm (after being "on" all day) the system began banging and clattering due to over heating - Although the programmer (Horstmann C27) was set as usual on the 24H setting neither the HW or CH were asking for heat but the boiler was running! I switched the system off, let it cool down then re-started it.

Everything was fine until last night at around 9.00pm when the same thing happened. This time I was in the same room as the B/boiler and heard a "boinging" sound on a couple of occasions as the boiler fired up ( sounded like a relay was not operating correctly) I shut down the system before the water overheated, let it cool down and re-started - again everything is ok today.

My initial thoughts are that it could be either a relay on the PCB that is causing the problem or the thermostat - or both?

Any Ideas??

Kev

Reply to
awtltd
Loading thread data ...

You've presumably got a C-Plan system, as per the first plan shown in

formatting link
?

With this plan, the boiler is switched on by the micro-switch in the zone valve. When the zone valve is open (HW mode) the boiler is connected to permanent live. When the valve is closed (CH mode) the boiler is connected to the pump - and only comes on when there is a CH demand from the programmer and room stat.

It seems that, in your case, the boiler is running withouy either the valve being open or the pump running - which is clearly not supposed to happen. Does your boiler have a permanent live connection in addition to switched live? If so, there *could* be an internal malfunction causing it to fire when it shouldn't. If not, it can *only* be that it is receiving an external demand when it shouldn't. A distinct possibility is that the zone valve is closing when the HW demand is satisfied, but its micro-switch is sticking in the valve-open position. It seems to me that your symptoms are an exact fit for this scenario.

Reply to
Set Square

Hi, I think that makes sense.

So, probably the easiest way to test this is by replacing the Valve Head as by manually opening/closing the valve is not guaranteed to show the problem.

Cheers,

Kev

Set Square wrote:

Reply to
awtltd

You could try hitting the valve head when it happens, and see if the boiler then switches off. Or can you run it with the cover off to see what the micro-switch is doing? If it *is* this, you should be able to induce the fault by turning both stats right down.

Can you also test whether or not the boiler is receiving a switched live signal when the problem occurs? That would determine whether the problem is internal to the boiler or external.

Reply to
Set Square

Well, I couldn't replicate the fault last night - I'll keep an eye on it and report bacxk next time it happens.

Cheers,

Kev

Reply to
awtltd

HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.