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After a bit of advise.. On Sunday the Boiler blew.
Boiler is an Ideal Classic FF350
Programmer is a Danfoss TP715
Junction unit is a Danfoss WB12
Water had been on, and running fine. Switched the heating on, and 10mins later there was an electrical bang from the kitchen where the boiler is mounted. This has blown the relay on the PCB for the fan, (new PCB arriving today). The PCB neon was not illuminating, so there was obviously no power reaching the boiler. A test with a multimeter confirmed this.
However, and this is what is confusing me, the boiler is not wired directly into the switched 3amp spur below it. The spur feeds the programmer, this then runs up the back wall of the kitchen, I assume to the junction box in the airing cupboard upstairs. The supply then returns and the boiler is connected using a terminal block to this ?
There is no power on this supply, feeding the boiler. There is power on the switched spur and the programmer is powering up fine.
Why is the boiler not just connected directly to the switched spur ? (like the installation guide suggests) ?
What is stopping the live supply which was originally feeding the boiler ?
Any help would be appreciated as we are without heat and water at the moment !
There is no continuity on the live from the spur to the feed originally used for the boiler.
(Just to add - I have wired the boiler up to a 3pin plug directly and it powered up the board and ran for a short time).
Some old boilers used to be fired up by switching on/off the main live feed via the programmer. I.e all there was on the boiler was a Live, Neutral and Earth, And no switched live input.
Plumbers can get in the habit of wiring newer boilers up like this as they often can get away with it (less wires, and they can re-use an old installation's wiring). Or the boiler's internal relay packed in so it was bridged and the main live feed used as a switched feed instead as a cheap repair. But you can get away with it, its just facilities on modern boilers like pump overrun, fan overrun and fault code logging don't work.
Either way, if the boiler has a seperate connection teminmal for a switched live (probably a feed and return) then that should be used.
I think its a case of running about with the multimetre until you find the rogue component. Mechanical thermostats can melt if overloaded or if the contacts start to arc (they can corrode and start to bounce). So check the tank stat and room stat. And recheck all teminal connections in the controller and juncton boxes are sound.
Whats the pump(s) doing during all of this? And are any auto-valves working normally (if you have them)?
It could well be the boiler only needs one live feed; It worked like tht before so I don't think thats the issue: I guess it being called a "classic" denotes it being able to be used in old fashioned installations where the main live to boiler is switched by the programmer. If thats the case ignore part of what I said about it being wired wrong - as it could well be ok.
I think in this case, the pump should run wherever the boiler is running. So I presume the pump isn't running either.
If there absolutely no live in the junction box when the programmer is calling for heat, hot water and all the stats are cranked up (both HW and CH), I would look at what comming out of the programmer, as that should be feeding the junction box on at least one terminal with with respect to neutral (oh, make sure the neutrals are all good).
Typically (bear with me on this). Feed from the programmer goes to the junction box, which will then go through a thermostat (if its set for HW only - it will be the tank stat, if its CH - room stat). That it will go back to the junction box then to the mid-position valve, then back to the junction box to the terminals that feed the pump and boiler.
So, Spur-->Programmer-->Junction Box-->Stat (HW or CH depending on selected mode)-->Junction box-->Auto-Valve-->Junction box-->Pump+Boiler.
Well, thats how I would expect to see it...but its been ages since I messed with boiler electrics. But I hope it helps.
I think the programmer probably is the curlprit as well tbh. as there should be some form of live in the junction box when heat is being called for.
Anyway, stats: Several ways to test stats. One way with the power switched off, one can check the resistance between the terminals. With teh stat turned fully one way should be nearly zero ohms resistance (on), turned fully the other way will be infinite resistance (off).
A tank stat will usually have a normally closed and normally open connection...basically one connection does the opposite of the other (so one will be zero resistance whilst the other is infinite, and vica versa).
Either way, even if a stat was faulty, there will still be a live in the jucntion box from the programmer
Last edited by Shark Man; 18 June 2008 at 14:04.
Reason: on off on off on off ;-)
Fan already tested and runs fine.. From what I have read, the PCBs are prone to going on these.. (plus I have noticed that the kettle wasn't far from the cupboard where the boiler lives, the steam has possibly upset it).
So just hoping that the programmer turns up today or tomorrow!
Fitted the new programmer. Hot water works fine. Switched the Heating on - Fuse blew. Tested the Mid Position valve - cant find any faults with it, however once removed and circuit bridged the heating and pump are working perfectly. So new Actuator required.
Finally getting sorted. Thanks for all the advise. Should be fully sorted early next week, but at least we now have hot water. (we don't need the heating at this time of year anyhow).