On Tuesday, 3 March 2020 06:35:26 UTC, Stephen wrote:
Hello,

I went away for a couple of weeks and I didn't know how cold the house
would get so rather than turn off the heating, I left it set low for
frost protection so I didn't come back to burst pipes. When I got
back, the house was very cold and the boiler was dead. I investigated
with a volt stick and found that current was going to the boiler from
the FCU but no further. I looked on the PCB and there is a 1.6A fuse
that had blown. I didn't have any replacements: the best I had was a
couple of 1A fuses from a shaver socket adaptor. The boiler tries to
start but there is a funny noise and then the fuse blows. It doesn't
help that I was using 1A fuses rather than 1.6A.

I only got a second or two before the fuse blew, but I think the noise
came from the pump. Would that make sense? I've read that pumps can
seize. If it was seized, would it stall a draw a higer current than
usual and blow the fuse? I read that you can unscrew the large screw
onthe shaft of the pump and try to move the pump spindle. The boiler
is an ancient Seme and I know I need to save up and replace it with a
modern condensing boiler. The pump has a bolt head in the centre of
the shaft which I managed to loosen and I could feel the shaft
rotating but some black water came out.

I am waiting for some replacement fuses to arrive. I'm wondering
whether the pump was seized and whether I have managed to loosen it.
Do you think it is worth taking the pump off to give it a rinse? I was
surprised the water that came out was so dark as I added inhibitor and
a magnetic filter.

Do you think I should get a new pump just in case? The one fitted is
probably the original and very old.

I read that sometimes valves stick when you go on holiday but as this
is a combi boiler and the heating is on one zone, the only valve is
the diverter that switches between CH and HW and since I get neither
CH nor HW, I'm sure the problem lies somewhere else.

Thanks in advance!

Pumps can seize, and yes undoing the centre screw is sometimes enough to free them. Gunky water is normal. I'd disconnect the pump & fire the system up, but only for several seconds as the boiler will get no flow & overheat very quickly. Then you'll know if the pump is the problem.


NT