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How much PSI can this pump produce?



 
 
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  #1  
Old August 23rd 06, 01:04 PM posted to alt.home.repair
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Posts: 6
Default How much PSI can this pump produce?

I have a Magnetek 1081 PB4 Booster Pump, 3/4 hp, 3450 rpm - part
#173840-20 attached to my pool to run a pool cleaner. I don't have the
official specs for it so would anyone know how to calculate how much PSI
this pump can/should produce?

Thank you.
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  #2  
Old August 23rd 06, 01:34 PM posted to alt.home.repair
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Posts: 220
Default How much PSI can this pump produce?


"Stuart Benoff" wrote in message
...
I have a Magnetek 1081 PB4 Booster Pump, 3/4 hp, 3450 rpm - part
#173840-20 attached to my pool to run a pool cleaner. I don't have the
official specs for it so would anyone know how to calculate how much PSI
this pump can/should produce?

Thank you.


I think most pumps are rated Gallons per minute GPM. pool system run at
a very low PSI 10 to 20.


  #3  
Old August 23rd 06, 01:52 PM posted to alt.home.repair
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Posts: 6
Default How much PSI can this pump produce?

Sacramento Dave wrote:
"Stuart Benoff" wrote in message
...

I have a Magnetek 1081 PB4 Booster Pump, 3/4 hp, 3450 rpm - part
#173840-20 attached to my pool to run a pool cleaner. I don't have the
official specs for it so would anyone know how to calculate how much PSI
this pump can/should produce?

Thank you.



I think most pumps are rated Gallons per minute GPM. pool system run at
a very low PSI 10 to 20.



That's interesting because the cleaner that it's attached to says that
it needs between 20 and 25 PSI for it to be completely effective. You'd
think that they would say between X and Y GPM?
  #4  
Old August 23rd 06, 02:58 PM posted to alt.home.repair
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Posts: 5,834
Default How much PSI can this pump produce?


"Stuart Benoff" wrote in message
...
I have a Magnetek 1081 PB4 Booster Pump, 3/4 hp, 3450 rpm - part
#173840-20 attached to my pool to run a pool cleaner. I don't have the
official specs for it so would anyone know how to calculate how much PSI
this pump can/should produce?

Thank you.


Pressure gauge in the line


  #5  
Old August 23rd 06, 03:31 PM posted to alt.home.repair
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Posts: 857
Default How much PSI can this pump produce?

According to Stuart Benoff :
Sacramento Dave wrote:
"Stuart Benoff" wrote in message
...

I have a Magnetek 1081 PB4 Booster Pump, 3/4 hp, 3450 rpm - part
#173840-20 attached to my pool to run a pool cleaner. I don't have the
official specs for it so would anyone know how to calculate how much PSI
this pump can/should produce?

Thank you.



I think most pumps are rated Gallons per minute GPM. pool system run at
a very low PSI 10 to 20.


That's interesting because the cleaner that it's attached to says that
it needs between 20 and 25 PSI for it to be completely effective. You'd
think that they would say between X and Y GPM?


Flow rate is dependent on PSI, so they pick the one that's of most
importance to the device to spec it. This device cares more about
pressure than flow rate.

With a freshly cleaned sand filter, my pool pump produces about
15PSI on the manifold's pressure guage. As the sand filter
gunks up, the pressure rises.

My pump will produce about 35PSI if the outlet is completely plugged.

[We've tee'd the discharge system into a fire hose. If you shut
the fire hose's nozzle off, pump pressure hits 35PSI.]
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.
  #6  
Old August 23rd 06, 03:55 PM posted to alt.home.repair
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Posts: 6
Default How much PSI can this pump produce?

Chris Lewis wrote:
According to Stuart Benoff :

Sacramento Dave wrote:

"Stuart Benoff" wrote in message
...


I have a Magnetek 1081 PB4 Booster Pump, 3/4 hp, 3450 rpm - part
#173840-20 attached to my pool to run a pool cleaner. I don't have the
official specs for it so would anyone know how to calculate how much PSI
this pump can/should produce?

Thank you.


I think most pumps are rated Gallons per minute GPM. pool system run at
a very low PSI 10 to 20.




That's interesting because the cleaner that it's attached to says that
it needs between 20 and 25 PSI for it to be completely effective. You'd
think that they would say between X and Y GPM?



Flow rate is dependent on PSI, so they pick the one that's of most
importance to the device to spec it. This device cares more about
pressure than flow rate.

With a freshly cleaned sand filter, my pool pump produces about
15PSI on the manifold's pressure guage. As the sand filter
gunks up, the pressure rises.

My pump will produce about 35PSI if the outlet is completely plugged.

[We've tee'd the discharge system into a fire hose. If you shut
the fire hose's nozzle off, pump pressure hits 35PSI.]


I'm trying to determine if there is a problem with the pump. When I put
a pressure gauge on the line it reads 14-15 PSI however, this is a
'booster' pump not the mail pool pump. It's designed to send
pressurized water to the pool cleaner. The cleaner requires 20-25 PSI
and recommended a pump of this size. So, I'm trying to determine if the
pump is undersized or whether or not there's a problem with the pump.
  #7  
Old August 23rd 06, 04:31 PM posted to alt.home.repair
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Posts: 857
Default How much PSI can this pump produce?

According to Stuart Benoff :

I'm trying to determine if there is a problem with the pump. When I put
a pressure gauge on the line it reads 14-15 PSI however, this is a
'booster' pump not the mail pool pump. It's designed to send
pressurized water to the pool cleaner. The cleaner requires 20-25 PSI
and recommended a pump of this size. So, I'm trying to determine if the
pump is undersized or whether or not there's a problem with the pump.


The question is whether the booster pump reads 14-15 PSI _with_ the
pool cleaner attached. Does it? Or are you measuring the pressure
without the pool cleaner attached with the pump discharging some other
way? Are you measuring the pressure at the pump or at the cleaner?
Try attaching the cleaner and _then_ see what the PSI is at _both_
the pump and cleaner ends.

[I'm not familiar with the use of pool cleaners working on the
pressure side of the pump. It _may_ also be that your plumbing is
undersized or restricted. In which case, the PSI at the pump
end will be okay, but at the cleaner end it won't be.]

Think of it this way - a device like the pool cleaner needs to be
specified at a specific pressure AND flow rate. Eg: "to operate
properly, this device needs 1GPM or more at a pressure of 15PSI
or more".

Secondly, the plumbing between the two devices matter - it has
to be large enough to permit the GPMs that the cleaner needs
without excessive PSI loss.

Industrial equipment is rated/matched that way. So are, for example,
tools for use with air compressors (eg: "this tool consumes
x CFM at y PSI").

The PSI of the output of a pump varies inversely with the GPM
the outlet is permitting.

Pumps _tend_ to have a given "PSI vs GPM" curve given the
HP rating of the pump. In the middle "design range" (of GPMs),
it's pretty much determined by the HP of the pump.

It's not linear, but at least for the most part, two pumps with
the same HP rating _should_ push just about the same amount of GPMs
at the same PSI as each other.

So, if it's the right HP, it (probably) _should_ work.

But, without knowing the GPM requirements of the cleaner or the expected
GPM vs PSI curve of the pump, it's difficult to be absolutely certain
whether a given combination _should_ work or not, and the best bet is
probably to call the manufacturer[s] (cleaner manufacturer _first_),
explain your situation mentioning model numbers etc, and they should be
able to tell you whether the cleaner or the pump are working in spec or not.

The cleaner manufacturer is probably intimately familiar with the
behaviour of the cleaner with every pump on the market. If they
tell you "we have lots of cleaner customers using that pump
satisfactorily", you _know_ that something's wrong with one
(or both) of the devices. They may tell you that there's
something specifically "odd" about that pump that means it won't
work. Or they may tell you that the plumbing is too small.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.
  #8  
Old August 23rd 06, 05:18 PM posted to alt.home.repair
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Posts: 6
Default How much PSI can this pump produce?

Chris Lewis wrote:
According to Stuart Benoff :


I'm trying to determine if there is a problem with the pump. When I put
a pressure gauge on the line it reads 14-15 PSI however, this is a
'booster' pump not the mail pool pump. It's designed to send
pressurized water to the pool cleaner. The cleaner requires 20-25 PSI
and recommended a pump of this size. So, I'm trying to determine if the
pump is undersized or whether or not there's a problem with the pump.



The question is whether the booster pump reads 14-15 PSI _with_ the
pool cleaner attached. Does it? Or are you measuring the pressure
without the pool cleaner attached with the pump discharging some other
way? Are you measuring the pressure at the pump or at the cleaner?
Try attaching the cleaner and _then_ see what the PSI is at _both_
the pump and cleaner ends.

[I'm not familiar with the use of pool cleaners working on the
pressure side of the pump. It _may_ also be that your plumbing is
undersized or restricted. In which case, the PSI at the pump
end will be okay, but at the cleaner end it won't be.]

Think of it this way - a device like the pool cleaner needs to be
specified at a specific pressure AND flow rate. Eg: "to operate
properly, this device needs 1GPM or more at a pressure of 15PSI
or more".

Secondly, the plumbing between the two devices matter - it has
to be large enough to permit the GPMs that the cleaner needs
without excessive PSI loss.

Industrial equipment is rated/matched that way. So are, for example,
tools for use with air compressors (eg: "this tool consumes
x CFM at y PSI").

The PSI of the output of a pump varies inversely with the GPM
the outlet is permitting.

Pumps _tend_ to have a given "PSI vs GPM" curve given the
HP rating of the pump. In the middle "design range" (of GPMs),
it's pretty much determined by the HP of the pump.

It's not linear, but at least for the most part, two pumps with
the same HP rating _should_ push just about the same amount of GPMs
at the same PSI as each other.

So, if it's the right HP, it (probably) _should_ work.

But, without knowing the GPM requirements of the cleaner or the expected
GPM vs PSI curve of the pump, it's difficult to be absolutely certain
whether a given combination _should_ work or not, and the best bet is
probably to call the manufacturer[s] (cleaner manufacturer _first_),
explain your situation mentioning model numbers etc, and they should be
able to tell you whether the cleaner or the pump are working in spec or not.

The cleaner manufacturer is probably intimately familiar with the
behaviour of the cleaner with every pump on the market. If they
tell you "we have lots of cleaner customers using that pump
satisfactorily", you _know_ that something's wrong with one
(or both) of the devices. They may tell you that there's
something specifically "odd" about that pump that means it won't
work. Or they may tell you that the plumbing is too small.


The pump is sending water to the wall outlet and then the cleaner is
attached to the wall. The 14-15 PSI reading is from the wall outlet
without the cleaner attached. When I take the measurement from the end
of the hose that attaches to the cleaner it's at 11 PSI. The hose is a
5/8" hose and is about 22 feet long.

The pump is a Magnetek 1081 PB4 Booster Pump, 3/4 hp, 3450 rpm - part
#173840-20 but I can't find the specs for it online.

I also did as you suggested and called the manufacturer of the cleaner.
Their 3/4 hp pump is capable of 67-80 GPM but they couldn't help with
the specs for my Magnetek pump and didn't have any info stating that
this pump wouldn't work with their cleaner. I'm still looking for a
phone number for Magnetek. Their website refers people to AO Smith
(http://www.aosmithmotors.com/html/contactUs.html) so I wrote to them
because they don't have a published phone number.

Thank you.
  #9  
Old August 23rd 06, 05:53 PM posted to alt.home.repair
Bob
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Posts: 119
Default How much PSI can this pump produce?


"Stuart Benoff" wrote in message news:echv51
The pump is sending water to the wall outlet and then the cleaner is
attached to the wall. The 14-15 PSI reading is from the wall outlet
without the cleaner attached. When I take the measurement from the end
of the hose that attaches to the cleaner it's at 11 PSI. The hose is a
5/8" hose and is about 22 feet long.


All these measurments are going to vary with the water flow. You need
to measure with the cleaner attached and operating, with no leakage which
will lower the reading. Where the booster pump gets its water will affect
the reading. If it connects to the water return line to the pool, it will start
with low pressure. If it connects to the outlet of the pump, before the
filter, it will start with higher pressure and end up with a higher boosted
pressure.

Bob


  #10  
Old August 23rd 06, 06:27 PM posted to alt.home.repair
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Posts: 857
Default How much PSI can this pump produce?

According to Stuart Benoff :

The pump is sending water to the wall outlet and then the cleaner is
attached to the wall. The 14-15 PSI reading is from the wall outlet
without the cleaner attached.


Is the wall outlet free flowing or plugged?

When I take the measurement from the end
of the hose that attaches to the cleaner it's at 11 PSI.


Same question.

The hose is a 5/8" hose and is about 22 feet long.


I think you need to connect the cleaner to the line and then
measure pressure, at both ends. The drop from 14-15 to 11
seems a bit high, suggesting the hose is undersized.

5/8" garden hose? Use 3/4" high quality hose. Some 5/8"
hoses are quite flow restricted, especially those with cheap
end fittings. This could be your problem right there.

The pump is a Magnetek 1081 PB4 Booster Pump, 3/4 hp, 3450 rpm - part
#173840-20 but I can't find the specs for it online.


3/4HP Magneteks appears to be one of the pumps of choice for pool
cleaners according to the number of hits on Google. Eg: they're
bundled with Polaris and other units.

So it should be working with yours.

I also did as you suggested and called the manufacturer of the cleaner.
Their 3/4 hp pump is capable of 67-80 GPM


67-80GPM at 20PSI? Good grief, that's _high_ for a 3/4HP unit. I'd
expect a pump delivering that performance to be 2HP or more.

You simply _cannot_ push 67 GPM thru even 3/4" copper pipe with any
sort of efficiency, the friction losses are _enormous_[+]. 13 GPM is
more like an acceptable upper limit thru pipe that size. 1/2" pipe
is around 8 GPM max, and garden hose (smaller "real" diameter compared
to nominal inside diameter) will be less. Especially since
some cheap garden hose has very restrictive hose fittings. Watch
out for restrictive valves too (if there are any valves in the line).
Use full aperture ball or gate valves. Washer type stop valves
are quite flow restrictive.

Are you sure they didn't say 6.7-8.0 GPM? _That_ is reasonable,
and suggests that the hose (if you supplied it) is likely at fault.

[+] There is a "practical speed limit" for efficient pushing of
water through pipe, above it, the friction loss becomes ridiculously
high. With 3/4" copper/PVC, that "speed limit" is achieved at roughly
13-15GPM. Trying to exceed 13-15GPM in 3/4" pipe means that you have
to size the pump FAR larger than necessary (and thus waste a lot
of money) to get the device to work. If you don't size the pump
that large, the device simply doesn't get the water volume it needs.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.
 




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