On Thursday, 5 March 2020 08:27:28 UTC, Stephen wrote:
On Tue, 3 Mar 2020 09:58:57 +0000, alan_m
wrote:



Pumps usually seize only if they have been left unused for a period of
time such as in a system where the pump is only used for central heating


Hello,

Thanks for all the replies.

The pump is only used for CH. I had the CH thermostat turned dwen low
for frost protection, so I don't know how often the boiler fired up
while I was away. I must have fired at least once to blow the fuse.

I never thought to power the pump independently, thyatnks for that,
I'll try that if there is ever a next time.

What limited me on the day was that I didn't have any 20mm fuses,
other than a 1A one from a shaver adaptor and they are not very easy
to find. I'm surprised at this because you would think they would be
very popular in shaver adaptors, especially now everyone has electric
toothbrushes, as well as shavers. I think office clocks still use
BS646 fuses too.

I've managed to order some 1.6A fuses, so it's a maytter of trying
them when they arrive.

The pump does not have the central screw. Instead it has a hex head
bolt. I'm not sure if that's how it came or whether that's an "after
market modification" by a previous owner/plumber, but it seems to do
the same job. I couldn't remove it completely, but once I had loosed
it, the shaft seemed to turn rather than the screw.

I suppose it wouldn't hurt to drain it and top it up with fresh
inhibitor. I'm just not sure whether this was a warning that the pump
is on its way out and whether to replace that at the same time.

I was once advised by a plumber's wife (to save the call out charge) to hit a seized pump with a hammer a few times. Did the job and it carried on working.

Jonathan