Trianco Eurostar combi boiler going off

[Clayson]

Morning all,
Can anyone shed some light on said boiler? It’s going off on unexpectedly. This is only the second time it’s done so in 3 weeks, boiler doesn’t go in to lockout. The first time was just after having heating oil tank topped up, but far as I can see oil is flowing freely to pump. The way I restarted the boiler was just switching off and on at the mains. Could something be overheating? The water pump still seems to be spinning after boiler goes off. It’s back on working fine now, but want to pin point the fault before it happens again. Thanks for any help

 

[SJB060685]

Can you elaborate more when you say going off on unexpectedly please. The boiler isn’t going to lockout you say?

 

[Tea-Break]

If it’s not the normal ‘cycling’ to maintain store temperature (as I’m sure you’re familiar with).
The only thing it can be is either of the high limit stats tripping. Then again you have not mentioned
resetting them (one usually under the control panel)
Not sure where the other is, but they both require manual resetting??

 

[SJB060685]

I believe on this particular boiler both high limit and store stat are underneath panel. However he has not mentioned manual reset at all, nor does it sound like a burner lockout, hence why I asked please elaborate more. Is this happening when there is a demand for heating or hot water

 

[Clayson]

Thanks for reply’s. Both times have been during the night, get up and cold house no heating on, but I can here water pump whining away still until turning thermostat down. I’ve not reset anything, no red light on control box. I tried turning it off on the time switch programmer(the one on boiler packed up so have new time programmer installed near by on wall) and then back on continuous running but nothing boiler still didn’t fire up, so turned it of just at the mains switch on wall and is running again, still running fine now. Could the water pump be sticking?

 

[Clayson]

When I mention boiler going off, I mean not firing At all, it just shut off and wouldn’t restart, but didn’t go into lockout

 

[Tea-Break]

If the pump had ‘stuck’ or stopped working, for any reason. The temperature would build up and trip the high limit stat.
Could be the diverted valve not opening fully?
Unfortunately, unless the problem is obvious it is difficult to diagnose blind.

 

[Tea-Break]

Ok right, this now appears to be a burner issue then.

 

[SimonG]

Would need testers on it to see where power was going and not going.

 

[SJB060685]

No I disagree Tea-Break. If this was a burner issue I would expect lockout. I’m looking at the wiring diagram now and it says when a roomstat is added to remove link A between terminals T and H, this link by passes any roomstat, switches valve to CH, brings pump on and allows boiler to cycle. If this link is not removed and wired correctly then there’s no thermostatic Control. Something isn’t wired right.

 

[SJB060685]

Sorry Tea-Break I thought he said a new room stat was wired in, not a programmer . Below is the wiring diagram as it should be, anyone who knows how to read these things will be able to trace wires and work out what feeds we have where like SimonG said. Looking at the wiring diagram it is possible the pump and boiler would get a feed and the motorised valve may not open.

 

[Tea-Break]

In the absence of a technician on site to check through wiring/component function, we can only guess 😵

 

[SJB060685]

I totally agree. Personally I would be checking correct wiring to start, after that I would consider faulty valve or stats failing to bring boiler on. Sorry to misunderstand you earlier, it’s Super Bowl Sunday and I’m pi**ed right up

 

[Tea-Break]

No worries 🙂

 

[Clayson]

Thanks, it Has had a new diverter valve fitted last year as old one was leaking. I haven’t had time too look any further but it’s still running fine now so will see how it goes. The thermostat is a Honeywell dial type, lookin at it looks as it’s been installed for sometime, but it still clicks in and out when boiler stopped working. Was actually looking at getting new thermostat with prog built in if any one could recommend one?

 

[SJB060685]

If the roomstat is clicking in and out that usually means it’s ok. If you’re not confident yourself to investigate the wiring any further then please get a good engineer in. Following the wiring diagram is easy if you have an understanding already. You could have a dodgy room stat, you could have a dodgy CH stat not bringing boiler feed on, you could have a loose wire in wiring centre not supplying power to pump and valve, the relay could be at fault, as could the valve already mentioned. The problem is this is an intermittent fault and Sod’s law is might not play up while investigating.