air in pump

[Luca Brazi]

Just switched out a Mag 3 for a Mag 7 in a closed loop SCWD
circulation system and the blasted thing is churning out microbubbles
and rattling unbearably (neither of which the Mag 3 did). It is
slightly better when I restrict flow a bit on the output side, but
that rather defeats the purpose of using the new pump now doesn't it?
There is a simple U tube connected to the pump inlet by about 2.5 feet
of 3/4" hose. There's got to be air getting in somewhere but I can't
find any leak. I didn't experience a similar "break in" with my Mag
3. Microbubbles means the leak, if any, has to be before the
impeller, right? Anyone with more experience want to tell me what's
happening here?

[Mort]

"Luca Brazi" > wrote in message
om...
> Just switched out a Mag 3 for a Mag 7 in a closed loop SCWD
> circulation system and the blasted thing is churning out microbubbles
> and rattling unbearably (neither of which the Mag 3 did). It is
> slightly better when I restrict flow a bit on the output side, but
> that rather defeats the purpose of using the new pump now doesn't it?
> There is a simple U tube connected to the pump inlet by about 2.5 feet
> of 3/4" hose. There's got to be air getting in somewhere but I can't
> find any leak. I didn't experience a similar "break in" with my Mag
> 3. Microbubbles means the leak, if any, has to be before the
> impeller, right? Anyone with more experience want to tell me what's
> happening here?


I could really be reaching here and I'll prolly get slapped for saying this
but....


In a hydronic heating system (closed loop) there are occurances where if the
pump is oversized or the line is undersized the pump will actually reduce
the pressure on its suction side to the point where the water will begin to
turn to vapor. (ie=make bubbles) This could explain the rattling.

I seriously doubt this is the case. I'd be surprised if a Mag pump could
even do this but a mag 7 is considerably larger than a 3. Why the change?

What type of hose is it that you are using? Is there anything else
connected by a tee or otherwise near the outlet of the pump?

~Mort

[Jon C Rupert]

"Mort" > wrote in message
. com...
>
> "Luca Brazi" > wrote in message
> om...
> > Just switched out a Mag 3 for a Mag 7 in a closed loop SCWD
> > circulation system and the blasted thing is churning out microbubbles
> > and rattling unbearably (neither of which the Mag 3 did). It is
> > slightly better when I restrict flow a bit on the output side, but
> > that rather defeats the purpose of using the new pump now doesn't it?
> > There is a simple U tube connected to the pump inlet by about 2.5 feet
> > of 3/4" hose. There's got to be air getting in somewhere but I can't
> > find any leak. I didn't experience a similar "break in" with my Mag
> > 3. Microbubbles means the leak, if any, has to be before the
> > impeller, right? Anyone with more experience want to tell me what's
> > happening here?
>
>
> I could really be reaching here and I'll prolly get slapped for saying
this
> but....
>
>
> In a hydronic heating system (closed loop) there are occurances where if
the
> pump is oversized or the line is undersized the pump will actually reduce
> the pressure on its suction side to the point where the water will begin
to
> turn to vapor. (ie=make bubbles) This could explain the rattling.
>
> I seriously doubt this is the case. I'd be surprised if a Mag pump could
> even do this but a mag 7 is considerably larger than a 3. Why the change?
>
> What type of hose is it that you are using? Is there anything else
> connected by a tee or otherwise near the outlet of the pump?
>
> ~Mort
>

You may have a good point. I think the technical term is cavitation. It
can destroy a pump and it typically happens when the pump is not properly
sized for the system.

[Luca Brazi]

"Jon C Rupert" > wrote in message >...
> "Mort" > wrote in message
> . com...
> >
> > "Luca Brazi" > wrote in message
> > om...
> > > Just switched out a Mag 3 for a Mag 7 in a closed loop SCWD
> > > circulation system and the blasted thing is churning out microbubbles
> > > and rattling unbearably (neither of which the Mag 3 did). It is
> > > slightly better when I restrict flow a bit on the output side, but
> > > that rather defeats the purpose of using the new pump now doesn't it?
> > > There is a simple U tube connected to the pump inlet by about 2.5 feet
> > > of 3/4" hose. There's got to be air getting in somewhere but I can't
> > > find any leak. I didn't experience a similar "break in" with my Mag
> > > 3. Microbubbles means the leak, if any, has to be before the
> > > impeller, right? Anyone with more experience want to tell me what's
> > > happening here?
> >
> >
> > I could really be reaching here and I'll prolly get slapped for saying
> this
> > but....
> >
> >
> > In a hydronic heating system (closed loop) there are occurances where if
> the
> > pump is oversized or the line is undersized the pump will actually reduce
> > the pressure on its suction side to the point where the water will begin
> to
> > turn to vapor. (ie=make bubbles) This could explain the rattling.
> >
> > I seriously doubt this is the case. I'd be surprised if a Mag pump could
> > even do this but a mag 7 is considerably larger than a 3. Why the change?
> >
> > What type of hose is it that you are using? Is there anything else
> > connected by a tee or otherwise near the outlet of the pump?
> >
> > ~Mort
> >
>
> You may have a good point. I think the technical term is cavitation. It
> can destroy a pump and it typically happens when the pump is not properly
> sized for the system.

The pump is on a 29gal approximately 2.5 to 3 feet below the tank's
top. There is a simple U tube connecting with 3/4" black vinyl tubing
running straight down to the inlet. From the outlet it runs up one
foot to the SCWD (ball valve in the middle) and the SCWD connects to U
shaped outlets than hang over the edge in each of the tank's back
corners. Given a 3' vertical run and the SCWD taking ~20% off the
flow rate, I estimated that the pump would be circulating around 300
to 350 gph. Since the connections on the pump are 1/2" MPT and FPT I
figured that 3/4" hose would provide sufficient water volume to the
pump. It certainly worked with the Mag 3, but I wasn't getting enough
circulation in the tank and wanted to up the water movement without
adding powerheads. Thanks for responding so quickly.

[Dragon Slayer]

cavitations is when a pump is running and not pumping, its most commonly
caused by an air pocket not an undersized pump.

kc


"Jon C Rupert" > wrote in message
.. .
>
> "Mort" > wrote in message
> . com...
> >
> > "Luca Brazi" > wrote in message
> > om...
> > > Just switched out a Mag 3 for a Mag 7 in a closed loop SCWD
> > > circulation system and the blasted thing is churning out microbubbles
> > > and rattling unbearably (neither of which the Mag 3 did). It is
> > > slightly better when I restrict flow a bit on the output side, but
> > > that rather defeats the purpose of using the new pump now doesn't it?
> > > There is a simple U tube connected to the pump inlet by about 2.5 feet
> > > of 3/4" hose. There's got to be air getting in somewhere but I can't
> > > find any leak. I didn't experience a similar "break in" with my Mag
> > > 3. Microbubbles means the leak, if any, has to be before the
> > > impeller, right? Anyone with more experience want to tell me what's
> > > happening here?
> >
> >
> > I could really be reaching here and I'll prolly get slapped for saying
> this
> > but....
> >
> >
> > In a hydronic heating system (closed loop) there are occurances where if
> the
> > pump is oversized or the line is undersized the pump will actually
reduce
> > the pressure on its suction side to the point where the water will begin
> to
> > turn to vapor. (ie=make bubbles) This could explain the rattling.
> >
> > I seriously doubt this is the case. I'd be surprised if a Mag pump
could
> > even do this but a mag 7 is considerably larger than a 3. Why the
change?
> >
> > What type of hose is it that you are using? Is there anything else
> > connected by a tee or otherwise near the outlet of the pump?
> >
> > ~Mort
> >
>
> You may have a good point. I think the technical term is cavitation. It
> can destroy a pump and it typically happens when the pump is not properly
> sized for the system.
>
>

[Luca Brazi]

(Luca Brazi) wrote in message >...
> "Jon C Rupert" > wrote in message >...
> > "Mort" > wrote in message
> > . com...
> > >
> > > "Luca Brazi" > wrote in message
> > > om...
> > > > Just switched out a Mag 3 for a Mag 7 in a closed loop SCWD
> > > > circulation system and the blasted thing is churning out microbubbles
> > > > and rattling unbearably (neither of which the Mag 3 did). It is
> > > > slightly better when I restrict flow a bit on the output side, but
> > > > that rather defeats the purpose of using the new pump now doesn't it?
> > > > There is a simple U tube connected to the pump inlet by about 2.5 feet
> > > > of 3/4" hose. There's got to be air getting in somewhere but I can't
> > > > find any leak. I didn't experience a similar "break in" with my Mag
> > > > 3. Microbubbles means the leak, if any, has to be before the
> > > > impeller, right? Anyone with more experience want to tell me what's
> > > > happening here?
> > >
> > >
> > > I could really be reaching here and I'll prolly get slapped for saying
> this
> > > but....
> > >
> > >
> > > In a hydronic heating system (closed loop) there are occurances where if
> the
> > > pump is oversized or the line is undersized the pump will actually reduce
> > > the pressure on its suction side to the point where the water will begin
> to
> > > turn to vapor. (ie=make bubbles) This could explain the rattling.
> > >
> > > I seriously doubt this is the case. I'd be surprised if a Mag pump could
> > > even do this but a mag 7 is considerably larger than a 3. Why the change?
> > >
> > > What type of hose is it that you are using? Is there anything else
> > > connected by a tee or otherwise near the outlet of the pump?
> > >
> > > ~Mort
> > >
> >
> > You may have a good point. I think the technical term is cavitation. It
> > can destroy a pump and it typically happens when the pump is not properly
> > sized for the system.
>
> The pump is on a 29gal approximately 2.5 to 3 feet below the tank's
> top. There is a simple U tube connecting with 3/4" black vinyl tubing
> running straight down to the inlet. From the outlet it runs up one
> foot to the SCWD (ball valve in the middle) and the SCWD connects to U
> shaped outlets than hang over the edge in each of the tank's back
> corners. Given a 3' vertical run and the SCWD taking ~20% off the
> flow rate, I estimated that the pump would be circulating around 300
> to 350 gph. Since the connections on the pump are 1/2" MPT and FPT I
> figured that 3/4" hose would provide sufficient water volume to the
> pump. It certainly worked with the Mag 3, but I wasn't getting enough
> circulation in the tank and wanted to up the water movement without
> adding powerheads. Thanks for responding so quickly.

Still spewing microbubbles after running for 18 hours so I
disconnected it and put the Mag 3 back on. Circulation and no noise
or microbubbles. I remain confused but am willing to accept that 3/4
hose is too small a diameter for this span. So the question is: would
a system of sufficient diameter and vertical travel to avoid the
cavitation problem with a Mag 7 have any more GPH of flow than does
the Mag 3 with the existing dimensions?

Another option might be to split the hose with a "T" before the SCWD
and use a ball valve to divert a % of the outflow directly into the
tank through a third return. Principal cost of the experiment would
only be time and frustration but has anyone out there done anything
similar or know why it wouldn't work?

[Marc Levenson]

Yes, that will work as well.

Here's my closed loop, in case you've not seen it:

http://www.sparklingfloorservice.com/tank/closedloop.html

Marc


Luca Brazi wrote:

> Another option might be to split the hose with a "T" before the SCWD
> and use a ball valve to divert a % of the outflow directly into the
> tank through a third return. Principal cost of the experiment would
> only be time and frustration but has anyone out there done anything
> similar or know why it wouldn't work?

--
Personal Page: http://www.sparklingfloorservice.com/oanda/index.html
Business Page: http://www.sparklingfloorservice.com
Marine Hobbyist: http://www.melevsreef.com

[RickS]

I have found that many pumps that are designed for submerged or external use
tend be noisy/"rattly" when used externally. On my 54, I tried the Mag 7
externally and it was just that...very noisy and very "rattly". Now,
interestingly enough, I then tried a Mag 9...and that was fine, so go
figure. I have noticed though, that model to model, the noise level of Mags
does vary. I just set up a system with 3 external Mags. The 9's were quiet
enough, but the 12 was much noisier in comparison. In one of my tanks I
have a Mag 12 submerged and it can't be heard.

I have found that with any of these pumps run externally as well, that it
does help to do what Marc says to get any trapped air out of the pump.


"Marc Levenson" > wrote in message
...
> Does it help to turn off the system for about 10 seconds, then restart?
I'm
> running mine on a Mag 5, but I have a Mag 7 in the garage waiting to be
> installed.
>
> I don't have as much head pressure, as mine rises 3" to the SCWD and then
> another 8" to the top edge of the tank.
>
> Marc
>
>
> Luca Brazi wrote:
>
> > Just switched out a Mag 3 for a Mag 7 in a closed loop SCWD
> > circulation system and the blasted thing is churning out microbubbles
> > and rattling unbearably (neither of which the Mag 3 did). It is
> > slightly better when I restrict flow a bit on the output side, but
> > that rather defeats the purpose of using the new pump now doesn't it?
> > There is a simple U tube connected to the pump inlet by about 2.5 feet
> > of 3/4" hose. There's got to be air getting in somewhere but I can't
> > find any leak. I didn't experience a similar "break in" with my Mag
> > 3. Microbubbles means the leak, if any, has to be before the
> > impeller, right? Anyone with more experience want to tell me what's
> > happening here?
>
> --
> Personal Page: http://www.sparklingfloorservice.com/oanda/index.html
> Business Page: http://www.sparklingfloorservice.com
> Marine Hobbyist: http://www.melevsreef.com
>
>