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John Stumbles
 
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Default Testing a central heating pump

On Fri, 06 Jan 2006 13:39:13 +0000, Tony Williams wrote:

In article ,
Set Square wrote:
Most pumps seem to come with dire warnings about not running them
dry.
Anyone know why this is? Does a pump rely on water to cool it -
albeit using 'coolant' at 80-odd degrees? Or is water needed to
lubricate the bearing in some way?


The cast iron rotor on our c/h pump is definitely
water-lubricated.

It would sometimes be useful to test a pump dry - by running it
for a minute or so -before fitting it, and I'm trying to assess
the consequences of so doing.


Run dry it *will* score in just a few seconds. Since I
was mending our our pump it was apart, and I was able to
use a drop of 3 in 1 on the bearing surfaces. Ran up ok
without any complaints.


If you want to be safe you could dunk the wet end in a bowl while you test
it. In fact as long as you've wetted the bearing it should be OK to
run for a minute or so. I can think of at least one CH pump that's been
run dry to the extent of telling anyone in earshot about it, and is still
running OK now.