cyclinder stat blowing fuse

[Wiresandthings]

Plumbers + electrics = disaster!! Similarly electricians + plumbing = usually disaster!!

It needs tracing through from experience

 

[ayjay]

i give up

 

[JonnySegway]

Before I continue I will admit I did not carry out as thorough testing as I should have. I had just finished another job for him, just as I had packed up the van and was about to drive away "could you go and look at a problem for me..." I then had a very short window to get the job sorted out. Enough excuses....

When I started testing, nothing made sense at all, I couldn't identify any cables leaving the programmer and arriving at the junction box. I didn't want to start taking everything apart so I simply went through each step.

Disconnected the hot water side of the programmer: power stayed on. With HW ON channel disconnected everything stayed on.

Then disconnected each item on the HW side. The usual culprit I find is the pump but the fuse still blew with that attached. When I disconnected the cylinder stat the fault was removed. It was at this point I tested the cable I had disconnected at the programmer (blue) with the cable I had just disconnected (red) and realised there was a join somewhere. Indeed; on digging around I find another (hidden) junction box, which explains my initial problem with identifying cables when testing and making sense of how it had previously been wired.

We changed the stat, ran the hot water and central heating, everthing was okay.

In an ideal world I would probably return and rewire the whole thing so that there is only one 10-way junction box but we are not in an ideal world.

I was just enquiring as to whether people here have encountered a common problem with regard to cyclinder stats in order to at least give me a starting point when I return. I am quite prepared to put several hours aside on Monday to just start testing everything one by one but thought it doesn't hurt to have some advice in advance as my experience with these systems is limited

 

[Petej999]

Why did you think the cylinder stat was the problem? What tests did you do?

 

[Petej999]

Agree no good just changing bits without testing first

 

[DPG]

It was 8 years ago so I wouldn't worry about it.