I'm currently looking for a pump to boost the HW pressure downstairs and
things being what they are, it's probably going to be bought on ebay.

The thing is, there are many more twin impeller pumps to choose from than
single impeller pumps. So, my question is, does it damage a pump to only
use one side? Most twin impeller pumps seem to be identical to their single
impeller cousins (apart from the extra pump chamber) but of course there my
be differences in the bearings.

If it's not good to use just one side, I don't suppose there's anything
wrong with pairing up the inlets and outlets is there?

Tim

Tim Downie wrote:

If it's not good to use just one side, I don't suppose there's anything
wrong with pairing up the inlets and outlets is there?

That would be my preference. Saves running one side dry.

--
Cheers,

John.

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In article ,
"Tim Downie" writes:
I'm currently looking for a pump to boost the HW pressure downstairs and
things being what they are, it's probably going to be bought on ebay.

The thing is, there are many more twin impeller pumps to choose from than
single impeller pumps. So, my question is, does it damage a pump to only
use one side? Most twin impeller pumps seem to be identical to their single
impeller cousins (apart from the extra pump chamber) but of course there my
be differences in the bearings.

If it's not good to use just one side, I don't suppose there's anything
wrong with pairing up the inlets and outlets is there?

I suspect you'd end up with smoke from the dry side.

I guess you could double up to increase the flow, or run them
in series to increase the pressure.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

"Andrew Gabriel" wrote in message
...
In article ,
"Tim Downie" writes:
I'm currently looking for a pump to boost the HW pressure downstairs and
things being what they are, it's probably going to be bought on ebay.

The thing is, there are many more twin impeller pumps to choose from than
single impeller pumps. So, my question is, does it damage a pump to only
use one side? Most twin impeller pumps seem to be identical to their
single
impeller cousins (apart from the extra pump chamber) but of course there
my
be differences in the bearings.

If it's not good to use just one side, I don't suppose there's anything
wrong with pairing up the inlets and outlets is there?

I suspect you'd end up with smoke from the dry side.

I guess you could double up to increase the flow, or run them
in series to increase the pressure.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

All of the twin impeller pumps that I've owned over the years, specifically
warned against running the pump with the chambers dry.

Arfa

"Tim Downie" wrote in message
...
I'm currently looking for a pump to boost the HW pressure downstairs and
things being what they are, it's probably going to be bought on ebay.

The thing is, there are many more twin impeller pumps to choose from than
single impeller pumps. So, my question is, does it damage a pump to only
use one side? Most twin impeller pumps seem to be identical to their
single impeller cousins (apart from the extra pump chamber) but of course
there my be differences in the bearings.

If it's not good to use just one side, I don't suppose there's anything
wrong with pairing up the inlets and outlets is there?

The bearings (usually) require water. Running a twin impeller pump with one
side dry would (probably) seize the dry side and put unbalanced wear forces
on the shaft anyway.

Doubling up in series probably wouldn't gain you much pressure and might
cause some vibration/noise modes depending on the dynamics of the
flow/pressure. Paradoxically, you would get a better perceived pressure gain
by running both sides in parallel as, although the hydrostatic pressure
would be the same, the pressure drop with flow would be reduced, leading to
a better pressure in use (IMHO), and everything would be balanced. Having
said this, at low flows there will be a lot of turbulence from the impellers
driving over capacity, which *might* increase the noise. If you have to have
a twin impeller, run both sides in prallel is the answer!


--
Bob Mannix
(anti-spam is as easy as 1-2-3 - not

Bob Mannix wrote:
"Tim Downie" wrote in message
...
I'm currently looking for a pump to boost the HW pressure downstairs
and things being what they are, it's probably going to be bought on
ebay. The thing is, there are many more twin impeller pumps to choose
from
than single impeller pumps. So, my question is, does it damage a
pump to only use one side? Most twin impeller pumps seem to be
identical to their single impeller cousins (apart from the extra
pump chamber) but of course there my be differences in the bearings.

If it's not good to use just one side, I don't suppose there's
anything wrong with pairing up the inlets and outlets is there?

The bearings (usually) require water. Running a twin impeller pump
with one side dry would (probably) seize the dry side and put
unbalanced wear forces on the shaft anyway.

Doubling up in series probably wouldn't gain you much pressure and
might cause some vibration/noise modes depending on the dynamics of
the flow/pressure. Paradoxically, you would get a better perceived
pressure gain by running both sides in parallel as, although the
hydrostatic pressure would be the same, the pressure drop with flow
would be reduced, leading to a better pressure in use (IMHO), and
everything would be balanced. Having said this, at low flows there
will be a lot of turbulence from the impellers driving over capacity,
which *might* increase the noise. If you have to have a twin
impeller, run both sides in prallel is the answer!

Thanks all for the replies. Didn't win the pump I was hoping for but will
keep looking.

Tim

On Thu, 27 Nov 2008 11:02:22 +0000, Tim Downie wrote:

Thanks all for the replies. Didn't win the pump I was hoping for but
will keep looking.

If you're in the Reading area I've a 2 year old bog standard twin
impeller shower pump I've just taken out of a job (put in a mains pressure
HW supply). A brown beer token secures :-)

OTOH if you want a really good pump for not outrageous dosh you can't do
much better than the Salamanders that Screwfix do for 100 notes.

--
John Stumbles -- http://yaph.co.uk

I am neither for nor against apathy