Fuse blowing

[daddioy]

Hi guys
I have an Ideal Mexico boiler situated in the conservatory, it has frost stat, room stat and RWB2 controller. Pump is on the 1st floor next to emersion cylinder, hot water can be gas or electric.
A new pump was fitted around 2 months ago.

System started to blow fuses a few weeks back an electrician friend checked it over quickly and could find nothing obvious.
I wired in a new 3 port valve tried it fuse blew straight away.
left it for a week before i killed it!! took out new 3port wiring and wired in the old valve ( i didnt actually remove the valve)

Fired up all ok for about an hour and half then blew!

Took out controller and bypassed that with 2 links last night, worked for an hour then blew!

changed fuse today and again worked for around 50 mins then blew!!
no obvious leaks anywhere near electrics. everything checked except the tank stat.

Any ideas

Driving me nuts

 

[PrenticeBoyofDerry]

What size fuse you putting in the spur?

 

[MANDATE]

I believe this type of problem has been addressed a few times before and the most likely culprit appears to be the pump. may be your electrician friend can test it.
I suppose it might be related to the windings shorting out when heated, or maybe water getting to terminals. I don't know, I'm just reporting what I've read on this forum.

 

[MANDATE]

//www.diynot.com/forums/viewtopic.php?p=46905#46905

 

[matt1e]

if its working for a while then blowing fuses then I would check the cyl stat and room stat as it looks as though there is a short introduced when one of them switches over to its satisfied terminal
If you have had a new room stat fitted check that the neutral (if there is one) or earth has not been put into the wrong terminal
does the fuse blow straight away if the hot water is in the off position on the programmer
you need to have a multimeter to be honest as it could be a number of things

Matt

 

[daddioy]

3amp fuse

pump is new and no water leaks anywhere

will check the stats next

thanks

 

[daddioy]

right, traced it down to the tank stat blowing fuse when it reached temp, .
bypassed controller with 2 loops and disconnected the "make when temp reached" wire on the stat and got the boiler running so have heat only strange thing was when room stat asking for heat the 3 port valve started clicking!
bought new stat and controller as i was suspicious of that being damaged, Wired the common to the"make when temp reached" wire on the stat to test it and the fuse blew. wired the new 3 port valve and behold the fuse didn't blow so the culprit was the 3port valve after all!!
fitted the new tank stat, valve still clicking! tried the new controller still the same( the old controller was all ok after all)!

so now i have no fuses blowing but when i turn up the room stat i get a clicking 3port valve. If i turn the cylinder stat down the boiler and pump switch off even though the room stat is calling for heat?
clicking happens with old and new valve so its not the valve

any ideas? before i blow it all up

Kevin

 

[seco services]

so now i have no fuses blowing but when i turn up the room stat i get a clicking 3port valve. If i turn the cylinder stat down the boiler and pump switch off even though the room stat is calling for heat?
clicking happens with old and new valve so its not the valve

any ideas? before i blow it all up

Kevin

What valve make/model ?

 

[leytonjc]

double check your wiring, you may have the demand and common the wrong way round at the cylinder stat.

 

[daddioy]

old valve was a honeywell new is siemens cmv3

tried changing wiring just worked backwards lol ( came on when temp reached and off when heat needed.

wondering if i have got it wrong with the 3 port to the block sometime?

 

[seco services]

tried changing wiring just worked backwards lol ( came on when temp reached and off when heat needed.

wondering if i have got it wrong with the 3 port to the block sometime?

 

[Phill Peck]

As said above could be pump or one of the stats

My concern is your boiler what sort of Mexico is this non room sealed boilers should not be in a conservatory

 

[daddioy]

All sorted, i had got 2 wires wrong when connecting back and forth with the 3 port valve! checked wiring dia and wires and found the mistake.
Boiler is vented through the wall in the conservatory was here when we moved in.

thanks for all the suggestions guys

Kevin