Halstead Best 50 boiler problem,

[julesd]

Hi,
I'm at my wits end with my central heating system.
I booked two plumbers who didn't show and i've got a 2yr son & angry wife in a cold house. Any advice would be so appreciated.

O.k.

I've got a Halstead Best 50 boiler (about 5 yrs old) & Danfoss Randall FP715 programmer.

The Problem - Went to turn the heating on, scrolled through to the on selector, Heard a click in the airing cupboard somewhere as the Power blew.

Replaced the 3amp in line fuse - back on, same again, when asked to kick system in - instantly blew again.

Nothing leading up to this, working perfect.

noticed display on programmer a bit funny, showing unknown symbol.

Spoke to tech at Danfoss, He reckoned it was probably the programmer.

so i went out and bought the same model kit as it was only £30 more than just the programmer.

I carefully replaced all the parts:

FP715 Si Programmer,
Motor valve
Cylinder Stat
Room Stat

Still the problem persisted.
Thought o.k - how about the pump.
Brother in-law had a spare so we dry wired it in place
Still same problem,

Investigated further, checking the RCD board as to what else is wired on the same trip.
The heating system in on one of the 'sockets' trip.

Systematically checked everything else on on that trip - all o.k

So i isolated the mains supply for the heating system running directly from a new breaker only that on it, to rule out anything else on that ring.

Still the same problem..... Hmmm.

Just to check the programmer - disconnected that from the circuit and just powered that up, It was perfectly fine and didn;t blow the 3amp.

So recapp....

I have replaced:
PRogrammer, Motor Valve, Cylinder Stat, Room Stat, Checked Pump.
Isolated Mains supply, Checked power to programmer when removed from circuit and this is working fine.

My next step is to check the boiler is receiving 230volts,
Could ths be a fan or PCB problem??? I can't get the boiler powered up as the 3amp just blows. what should i do?

many thanks for reading this and anything you can suggest would be of great help.

many thanks
Jules

 

[gas4you]

Remove boiler switched live and try again. If nothing blows then you know it's a boiler fault. Disconnect fan wires and again test.

Keep logically testing until you find the problem.

 

[julesd]

Hi Dave,

Thanks for getting back to me,

Still no joy,

I removed the 'Switch Live' from the boiler connection. - Still Blows

so then

I removed the 'Pump Live' from the boiler connection - Still blows.

So then i simply removed the main 'Live' - and has still blown.

I'm Baffled.,....?? any other ideas?

The mains for the central heating is still isolated, so it must be something in this circuit.

 

[gas4you]

Repeat the above but disconnect the neutrals as well in order.

Have known faults to be neutral to earth instead of live to earth

 

[julesd]

Still no Joy.

Neutral & Switched Live Disconnected at boiler - Still blows
Neutral & Pump Live Disconnected at boiler - Still Blows
Neutral & Main Live Disconnected at Boiler - Still Blows.

I would have presumed ( & hoped) by basically removing the boiler the 3Amp would not blow and the programmer would be powered, very strange.

 

[ChrisR]

SO what have you got, a fused spur feeding a junction box, or what?
If you use the opposite logic, ie disconect everything and reconnect things one at a time until a fuse blows, you'll use fewer fuses.
It's always posible it's that picture you hung on the wall - the nail went through a couple of wires!

I'd pull out the supply wires so they're dead and use a meter with a beeper to look for shorts . If there's an intermittent contact you hear it when you poke things.

 

[julesd]

Hi, thanks for time.

I unwired everything from the control block (the array of wires now tidyd up on a connector block.

Found the trouble cable, 1 red wire!
Everything stable and power remaining on until this wire connected up, then blows straight away.

It runs from the programmer Terminal 4 which is: 'HTG ON' i presume this is heating on. I don';t seem to be able to trace where this goes,
would i be correct in assuming this runs to the boiler and not the thermostat?

 

[Terrywookfit]

Htg on will open the M/v via the roomstat!!

 

[julesd]

So why would that be tripping it?

Any idea as to fix this?

Forgive my stupidity.

 

[gas4you]

Now you've found it is this wire you need to test this remaining ciruit seperatley.

The wire in 4 with this will go to the 'common' in the room stat

The switched live from the room stat will return to 5 if wired in a standard Honeywell system. There will probably be a brown wire from 5 to the motorised valve. This supplies power to turn the motor in the valve.

As ChrisR says you need to test each section of this wiring as it does sund now as there is a short in in somewhere.

 

[geoffersgra]

I Have had a simular fault with a Baxi solo system boiler. After many hours turned out to be a dead short in the pump its self. Try disconnecting it at the pump. Just a thought. The pump had not seized but must have shorted electriically.

Regards

Geoff Abraham
GRA Heating Services

 

[kevplumb]

err check the date

i think it might be sorted by now

and i would remove that ad from your sig

before god sees it

 

[geoffersgra]

Point taken

Geoff