Central heating blows a fuse..

[Phil]

Just turned my heating on after 4 months.....and after about 5 minutes the fuse (to boiler and pump) blows.

It works OK with just water on. It works OK with heating+water. (pumped, gas, header tank etc)

Now - I know there is a lack of water in the system - the feed from the header tank is blocked - and when I took off a radiator a year ago it has not filled properly. It subsequently worked fine - just lots of gurgling noises.

Now - my theory - is that when I just have the heating on there is so little water that the pump "races" and blows a fuse ????????

[Christian McArdle]

Before you continue to destroy various central heating components, you should fill your system with water. You may now need a new pump. Hopefully, the boiler shut down worked before the heat exchanger went dry.

Christian.

[Grunff]

Anyone want to take bets on the order in which components will fail?

[Christian McArdle]

I would think definitely the pump first. The zone valves and electronics won't care. The boiler might, if it doesn't have protection against running dry. The radiators won't take kindly to being half full of warm water and oxygen. They'll probably corrode from within, along with the pipework.

What's your guess?

Christian.

[Grunff]

Yeah, sounds about right - pump(s) and maybe boiler, I'm sure the boiler will have a thermal cutout, but you never know, that too might fail. Long term, the heat exchanger and the rads.

[Christian McArdle]

I'm just worried that the thermal cutout might need water in the pipe to detect the heat. I would hope that there is a specific cutout on either water pressure, or maybe the exhaust flue temperature that could overcome this possibility, if it is a real problem.

Christian.

[The Natural Philosopher]

Electrical motors draw overcurrent when stalled, not when 'racing'

[Christian McArdle]

But the windings could possibly overheat and short out if there is no water flow. I don't know enough about the pump motor specifics to know if this would occur.

Christian.

[adder]

Mine used to do this (blow the fuse). The pump was full of sediment and stuff and I reckon once it heated up it would stall and blow the fuse. The final solution was to install the pump the correct way up so it didn't store all the air inside it!