Central heating pump help please

Hi all, just recently the central heating in our house stopped working. It would appear that the pump is acting up, as the boiler (Glowworm Ultimate 50BF) still heats the hot water, and the room temperature thermostat still 'clicks' when it is turned. The pump, however was red hot to the touch. One of my neighbours is a young chap who works for British Gas, so he came in to have a look. By this time, I had turned the boiler off and the thermostat down, and the pump had cooled down too. When he came in, he gave the pump a clout with a rubber mallet, and turned up the flow rate to max (I couldn't see this, as it was on the reverse side of the pump). Lo and behold, the heating started working again. However, the other night there was a horrible smell of burning electrical components, so I turned everything off. The pump is a Commander 'S' SMC, and the neighbour reckons it's about 25 years old. The problem is, apparently the size of the bore. He brought around a new pump to replace the old one, but the bore on the old one is about 1", whereas the new one is probably metric 12mm or similar. Question is - is it possible to get either a new pump with the old size bore, or could I get reducers to change to the new pump's bore? Needless to say, the pump is in an awkward position, and would mean the removal of kitchen cupboards to replace it.The old pump has a valve on either side, by the way. Any help, thoughts etc. greatly appreciated! Regards John
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On Tue, 22 Mar 2005 12:23:12 +0000, John Orrett wrote:

Based on the boiler model, you would have a typical sized house. So you need a 'normal' pump so a '5metre' unit will do but '6m' won't be wrong. Usually pumps are 130mm between flanges on the couplings, some larger and/or older pumps may not conform to that. Forget all about the 'bore' the pump has to join to 22mm pipe work (very likely assumption). If the existing couplings won't hack it then the system will have to be drained and new couplings used.
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Ed Sirett - Property maintainer and registered gas fitter.
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Ed Sirett wrote:

Thanks for the reply Ed; yes, we are in a 3 bed semi! So it theoreticaly should be a case of drain the system, take old pump out, fit reducers at either end, and then install new pump (presumably having to cut off a bit of pipe either side to allow the reducers?). I assume that reducers from 22mm to 12 mm (ish) are available? Regards John
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In an earlier contribution to this discussion,

I don't understand your problem! I don't know what sort of pump you saw with 12mm connections - but it was unlikely to be a central heating pump!
AFAIK, virtually all CH pumps have flange connections with a 1.5" BSP thread. [See http://www.screwfix.com/app/sfd/sea/searchresults.jsp ;jsessionid=YPQ0STWQ0EVJLCJO2C1SIIQ?_dyncharset=UTF-8&q=&n113&pn=1&pd=1&pi=1&cn=1&cd=1&x=8&y as an example].
You then have a valve similar to http://www.screwfix.com/app/sfd/sea/searchresults.jsp ;jsessionid=YPQ0STWQ0EVJLCJO2C1SIIQ?_dyncharset=UTF-8&q=&n987&pn=1&pd=1&pi=1&cn=1&cd=1&x&y on either side of the pump - which screws onto the threaded flange and connects to the 22mm pipework.
You can normally close the valves to retain the water in the system, unscrew the valves from the pump and insert a replacement pump - all without draining down. The only provisos are (a) that the valves work and (b) that the replacement pump is the same physical size in respect of distance between flanges.
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Set Square
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Set Square wrote:

http://www.screwfix.com/app/sfd/sea/searchresults.jsp ;jsessionid=YPQ0STWQ0EVJLCJO2C1SIIQ?_dyncharset=UTF-8&q=&n113&pn=1&pd=1&pi=1&cn=1&cd=1&x=8&y
http://www.screwfix.com/app/sfd/sea/searchresults.jsp ;jsessionid=YPQ0STWQ0EVJLCJO2C1SIIQ?_dyncharset=UTF-8&q=&n987&pn=1&pd=1&pi=1&cn=1&cd=1&x&y
Hi Set Square - I see where you are coming from!Thanks for the links, that made things much clearer. I didn't realise that the pump valve gate was a separate unit. I thought it was an integral part of the pump. So presumably it should just be a case of close both valves, turn off the electrics ,unscrew the pump from the pump valve gates and remove the wiring, and then reinstall? I'll put a bit of WD40 on the valves in the meantime. I'll check the distance between flanges also! Thanks again, John
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John Orrett wrote:

gate
So
the
the
Just in my experience those gate valves never fully close off the supply so have lots of towels around and act quickly!
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Yup. After about 20 years of never being used, mine barely made any difference. And then discovered the brass to steel action between one of them and the pump had seized the cap nut solid. So had to cut it off. The new pump - although the same make, and nominally the same model, in combination with the new valves, was somewhat sorter overall, meaning I had to extend the pipework. So much for a ten minute job. :-)
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snipped-for-privacy@yahoo.co.uk wrote:

Ta :-) John
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Anyway, unless you know it's been done recently, draining down and adding fresh inhibitor does two jobs for the price of one.
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*I got a sweater for Christmas. I really wanted a screamer or a moaner*

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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On Wed, 23 Mar 2005 10:43:25 +0000, John Orrett wrote:

That's the theory. I practice with kit that's been around for 25 years you _will_ end up draining the system and fitting new couplings and pump.
The rubber washers between the pump and coupling flanges will have been turned to charcoal over the time, but new ones come with the new pump.
HTH
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Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
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Ed Sirett wrote:

I thought it sounded too easy! Maybe I'll ask our local central heating merchant to come around and do it! I'm sure it probably needs inhibitor in it anyway, so maybe it wouldn't be a bad ideaa draining down and starting again. Our local neighbour reckons British Gas are charging 450 for a powerflush! Thanks again for the advice, John
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