Banging Noise from CEntral Heating

[Riot]

Ok...the noise sounds scary so I thought I would get some advice before calling an engineer tomorrow to have a look. I fitted a new thermostat and i fired up the boiler and everything seemed to work fine. Half an hour later i turned it off and on again, and i started to get really loud banging noises. I turned it off 10 seconds after...as I am not sure if it could be dangerous.

So what could be causing that? Could it be that i messed up with the wiring? (don't think so...but i could always put the old thermostat in order to check). The pilot seems to be alight...and the boiler is an old Servowarm if that helps.

Anyway, it is freezing so any advice is welcome at this point.

Thanks

 

[swbjackson]

Normal cause of this is overheating within the boiler. Could be a pump failure or you may have dislodged something when you wired the new stat in.

 

[swidders]

can't think of a reason why a new stat should affect the system, but for peace of mind put the old one back and try again. at least then you can rule this out

 

[Riot]

I know...which makes me wonder whether I messed up. This is the thermostat (http://www.grasslin-controls.co.uk/assets/graphics/static/STT%20RF.pdf), and the wiring diagram is shown on page 10 (i used the 230V switching).

The boiler had 4 wires going to the old programmer (black, brown, yellow/green and blue). I connected the following on the thermostat:

- On the Live Supply: Connected the black (from the boiler) and red (from the fused switch)
- On the live Output: Connected the brown (from the boiler)
- On the Neutral Supply: Connected blue (from boiler) and black (from mains switch)
- and Finally, the earth from the mains to the earth of the boiler

Any errors there? If not, then I'll go and undo my masterpiece of wiring so at least I can rule out the boiler.

Thanks

 

[swidders]

I'll not waste you time - don't really know but hopefully someone will advise. Sorry for any false hope!

 

[Riot]

When it's 16C in the room, time is not important anymore lol

 

[bengasman]

my guess is that you somehow managed to switch the boiler on without activating the pump or opening the valve

 

[Riot]

Which points towards an error in the wiring, shall I presume?

Thanks

 

[swidders]

sounds a bit like it to me. but like i said, i'm no expert.

 

[namsag]

The orginal clocks on these had a built in pump overrun timer in them / cant remember exactly how the pump was wired through it , but it sounds like you have messed it up.

 

[Riot]

Thanks for filling me with confidence!! On a serious note, when you say 'clocks', do you mean the old servowarm programmer or something else?

I have definetely messed up the wiring. i am going now before going to bed to put the old programmer on, and try to figure out tomorrow how to wire it properly.

Thanks for your help.

 

[namsag]

yep Servowarm programmer. old mechanical clock
been a long time since wired another clock into one of these but think a wire comes back from the gasvalve/stat to give power to pump (through the clock)when heat is sensed after heating goes off.
Pretty certain used to leave existing clock in situ on constant and wire new one in altering the lives for switching and having a permenant live

But ay have it completly wrong
but there is definetly a pump over run that needs connecting up

 

[Riot]

Thanks. Makes sense now that you explained; and i think that's the culprit as I can hear water actually boiling in there before the noises start. I guess its beyond my capabilities; I'll accept defeat and call an electrician tomorrow to sort it out

Annoying thing is that i couldn't find any wiring diagram for this boiler, as it is so old.