Back Boiler blowing fuse hot water only

[paulcantfixit]

Hello,

I have an annoying problem with a back boiler and struggling to get to the bottom of it.

Moved in to a rented house 6 months ago that has a Potterton Fireside 35/51 back boiler.

Over the last month found that when heating hot water only the 3 amp fuse blows in the socket. It is strange as this does not happen when the central heating is on. It started doing it now and again but now does as follows:- turn on hot water, boiler fires, continues to fire, burner goes out as temp reached?, clocks to fire up second time and blows 3 amp fuse.

The house is rented and to be fair to the landlord an electrician came out first and could not find the problem, said it was an earth leak and needed a heating engineer. An enginner has been over but after spending 2 hours on a free call out said it had him baffled.

We have an electric immersion heater and its Summer so the landlord has now decided to drag heals.

If anyone has any idea I would be very greatful.

Thanks.

 

[stevetheplumber]

any one spending 2 hours there for nothing isnt a heating engineer

 

[paulcantfixit]

Sorry, I am not sure what you mean.

Is my problem something that you have encountered in the past and can help me with?

Thanks.

 

[jtsplumbing]

If its only blowing on 2nd time position then it must be the time control !! what timer have you got ??

 

[paulcantfixit]

We have a Danfoss 102 timer next to the fuse socket. The engineer that came wired in a brand new one and it still blew fuses as described.

 

[paulcantfixit]

To confirm it is not blowing on the second time position on the programmer, it is blowing after the burner has shut off, presumbaly reaching temperature, then it goes to fire up after cooling down and then blows the 3 amp fuse.

 

[Billy Bob Bob]

what type of system do you have paul? do you have a 3 port or 2 valve fitted somewhere?

 

[paulcantfixit]

The parts in this system are boiler, hot water cylinder, tanks in loft, room thermostat and programmer.

There are no valves on our system the pump does not run when hot water only is on.

 

[AWheating]

do you an rcd at your consumer unit? if it was an earth fault it should trip your rcd before your fuse goes unless the rcd is faulty.

 

[Billy Bob Bob]

The parts in this system are boiler, hot water cylinder, tanks in loft, room thermostat and programmer.

There are no valves on our system the pump does not run when hot water only is on.

so by the sounds of it you have a pumped heating system and gravity hot water this is coming back to the programmer or boiler

 

[paulcantfixit]

The rcd in consumer is not tripping. I dont think the electrician went anywhere near the consumer unit.

 

[paulcantfixit]

Yes that is correct. The pump, which is under the TV in the lounge, has only ever run when central heating is on. The cyclinder in the airing cupboard has two large pipes entering its side there are no other components with it. We use the programmer to switch hot water on and off.

 

[stevetheplumber]

only thing i can think of that may be different on the second fire would be the boiler stat from cold its made the circuit before the power is applied and the action of switching is occuring in the programmer
when it breaks circuit on temp rise and then temperature drops again this time the switching will be within the termoststat
try it from cold and switch on and of from the prog a few times by spinning the dial if this doesnt blow fuse then try it with the boioer stat on of a few times
thats all i can think of without being there

 

[zzzjim]

( Not a great idea , but best i've got )

Check for trapped wiring getting caught by movement caused by expansion in gravity pipes

( had lighting cable in steel ,caught attic end once )

 

[mountainman]

( Not a great idea , but best i've got )

Check for trapped wiring getting caught by movement caused by expansion in gravity pipes

( had lighting cable in steel ,caught attic end once )

Not a bad idea either!

A decent heating heating engineer should be able to trace the fault in less than 2 hours but not as a freebie though.

 

[AWheating]

The rcd in consumer is not tripping. I dont think the electrician went anywhere near the consumer unit.

an electrician there to test the electrics never went near the consumer unit?? strange that is.

As your electrician stated it was an earth fault i would have thought it stange he/she did not think it was strange that the rcd was not tripping as they are there to trip on earth faults and would trip before your fuse spur if working properly. has the electrics been tested in the property recently?

 

[zeebeedee]

Had a similar issue once, only tripped when the system was getting hot, turned out some idiot had ran the cable to the back boiler on the exhaust hood, the wire was melted beyond recognition

 

[paulcantfixit]

Thank you for all your responses.

Now the pilot light wont light, dont think the gas is on as nothing seems to come through when I hold in the grey knob. So not going to touch it until another engineer comes out to inspect it.

I will report back what problem was when found.

 

[paulcantfixit]

I have no knowledge of the electrics being checked. Being a rented house we have a gas safety certificate, thats it. Also being a rental we have to rely on the landlord and letting agent to organise the engineer visits.

 

[diamondgas]

gas valve could be a bit iffy? Older firesides had TV supressors that would pop fuses now and again ... Or as mentioned a cable that's melted may be the culprit 🙂

 

[mountainman]

gas valve could be a bit iffy? Older firesides had TV supressors that would pop fuses now and again ... Or as mentioned a cable that's melted may be the culprit 🙂

Showing your age there Diamond, I remember fitting those capacitors mainly to Baxis and Glowworms and a melted cable was commonplace :93:

 

[zeebeedee]

gas valve could be a bit iffy? Older firesides had TV supressors that would pop fuses now and again ... Or as mentioned a cable that's melted may be the culprit 🙂

Tv supressors??????

 

[diamondgas]

Tv supressors??????

Yep! They were fitted to stop interference on the TV screen when the boiler stat turned on and off!! If not fitted you'd see lines of interference jump across the TV. TV's were usually fitted to one side of the fireplace where the back boiler was 🙂

 

[zeebeedee]

Yep! They were fitted to stop interference on the TV screen when the boiler stat turned on and off!! If not fitted you'd see lines of interference jump across the TV. TV's were usually fitted to one side of the fireplace where the back boiler was 🙂

That's amused me that!

 

[diamondgas]

That's amused me that!

This wiring diagram shows the capacitor fitted to a 45/3M .... View attachment 7532 that's what we would call the TV suppressor coz it stopped the lines 🙂