March 809 HS pump flow rate

[Søren T]

Today I received a pump from USA (I live in Denmark) - a March 809 HS 230 Volt.

I have set it up and I have run some tests.

According to the specifications the pump should give a maximum of 5,3 GPM, but I only get half of that.

I have measured the inlet and outlet ports of the pump and they are 10 mm. All my hoses, fitting and ball valve have an inner diameter of 10 mm.

The test runs were done with a no head.

Have any of you guys measured the flow your March pumps ?

Why do I not get the 5,3 GPM, but only the half ? Am I doing something wrong? I am thinking that I have been send a wrongly marked 809, since this pump only gives a maximum of 3,1 GPM.

I have two pictures of the pump, fittings and hoses at :http://www.tygesen.esenet.dk/pump1.jpg
and http://www.tygesen.esenet.dk/pump2.jpg

cheers,
Søren

 

[SuperiorBrew]

I think that is under ideal conditions, you are adding lift and head pressure to the mix.

 

[Søren T]

As I see it, I ran the test at almost ideal condition and with no head pressure.

Getting only half the flow rate is disappointing.

 

[kladue]

What is the "RPM" listing on the pump motor, if ~1400 then it is the low speed motor and pressure drop in the tubing is the problem, check the 809 PL pump curve.

 

[Søren T]

It's a 3000 RPM according to the sticker on the pump. The curve is here. The flow rate I am getting resembles a head of 9 feet.

 

[Søren T]

flow rate here http://www.marchpump.com/documents/curves/809-BR-HS.pdf

 

[kladue]

You are probably up against the pressure drop caused by the high rate of flow in the 10 mm tubing, probably should 16-20 mm for that kind of flow rate. Also the pump curve shown is for the higher rpm us motor not the metric motor which would be lower due to lower rpm. Here is a link to a pipe and tubing pressure drop calculator in Excel that will help you understand what happened http://www.midwayis.com/excel/Pressure_Drop.xls

 

[mr x]

If you are using the set-up shown in the pic, you are probably having pressure drop in the suction side of the hose. I suspect most manufacturers spec their max flows with no restrictions on the inlet or outlet, which never happens in reality.

Also, does that tank have a good size vent?

 

[Søren T]

I think you are right about the pressure drop in the suction side of the hose. Today I removed the hose fitting and the bend on the tap, and mounted the pump directly on the ½” ball valve. The water came gushing out. After that I mounted the same hose on the outlet and I was back to 3 GPM. This pump apparently adds very little pressure when pumping, so the solution must been larger hoses.

Thanks.

 

[BrewBeemer]

Does Denmarks power company run on 50 cycles per/second vs 60 cycle here in the USA? That alone will reduce pump speed to 83% of normal rpm's not adding small restrictive lines and head pressure.

 

[Søren T]

Yes, I belive we run at 50 Hz. Maybe thats why the 230 V version is marked 3000 RPM, while the 110 V says 3400 RPM.

 

[BrewBeemer]

Now this is troubling to me as reducing the rpm's of a motor from 60 Hz to 50 Hz is 83% reduction of the rpm's, a 3,400 rpm motor will become a 2,822 rpm motor going fron 60 to 50 Hz. This would be a good question to present to the March company with their pumps.

 

[wihophead]

The formula to calculate synchronous speed is....rpm = 120 x Frequency/ No. of Poles

The synchronous speed of a 2 pole motor at 60hz is 3600RPM so the rating of 3400 must incorporate 200RPM slip.

The synchronous speed of a 2 pole motor at 50hz is 3000RPM and if you incorporate the same slip it would be 2800RPM

So you are right on the money.....

 

[modenacart]

You have to know the losses in your system and that is the gpm your pump will run at. You need the curve for the losses versus gpm and you plot that on the performance curves for the pump and it will tell you the flow the pump will put out.

 

[awest74]

You all seem to know alot about the March pumps, I wonder if you can help me with an issue. Dont want to hijack this thread, but am desperate. I have a march 809 and for some reason I cant get it to pump hot liquids at all. I have 1/2 ID hose, and have tried Silicon, Silicon reinforced, and garden hose.

I can run it with room temp liquids and get to the mash and the liquor tank ( 3 -4feet above boil kettle outlet ) with no problem, but as soon as I try to move 175F water, I have to move the HLT below the boil keetle. The pump is located about 1.5 feet below the lowest vessel. I know it isnt the prime, since after I get it running If I move it back, the pump slowly dies. I dont think air is getting into the lines, since there seems to be none in the hoses and I have even re-tighted all the connectors when warm.

I am about to buy either high temp rated hoses or a new pump, but dont want to waste more money if I can avoid it. I have seen many carts posted here, just using re-inforced silicon tubing from home depot with there pumps, and no one else seems to complain about this problem.....

I do use CPC QDs on all connections.

Please advise.

thanks in advance,
Adam

 

[awest74]

Seems I ned to learn more about tubing, I think the stuff I am using isnt silicon, just vinyl. Seems to cheap to be Silicon, think thats the issue?

thanks again,
Adam

 

[mr x]

I know this seems like a no brainer, but you are sure the hose isn't getting soft from the heat and pinching or collapsing somewhere.

 

[awest74]

I know it isnt getting pinched, or collapsing, it is getting soft, but I checked all connections to make sure they didnt loosen with the heat and let air in. I guess its possible that it is letting in small air bubbles all over the hose......

I know this seems like a no brainer, but you are sure the hose isn't getting soft from the heat and pinching or collapsing somewhere.

 

[BrewBeemer]

Treat those March pumps like small fractional hp 1/2, 3/4 to 1 hp surface mounted centrifugal shallow well pumps. They operate on volume vs pressure like your city water service has. Any restriction in piping (well applications especially) or tubing and fittings example March pump for brewing has a large effect on your flow volume.
As per above posts 1,800 and 3,600 rpms are standard especially 3,400 for well pumps. Motor specs usually name taged 1,750 and app 3,580 rpm's on 60 cycle in the US. Little rpm differences or drop on centrifugal pump impeller speed results in rather large pump efficiency output drops. Unless I missed another reply posted above use 1/2 tubing and be careful on your pump adapter selection preventing small internal adapter inside diameter restrictions. I had a couple adapters that I drilled out the inside diameter then chamfered the ends for a smoother fluid flow transition. I hope this reply comes out understandable as the last time I posted I was the laughing stock of many members while on Percoet hence i'll just shut up and lurk only again. I've spent a few years digging wells and installing piping and sprinkler systems that operated on high volume low pressure off well pumps. Back to lurking under my rock what do I know?

 

[modenacart]

Treat those March pumps like small fractional hp 1/2, 3/4 to 1 hp surface mounted centrifugal shallow well pumps. They operate on volume vs pressure like your city water service has. Any restriction in piping (well applications especially) or tubing and fittings example March pump for brewing has a large effect on your flow volume.
As per above posts 1,800 and 3,600 rpms are standard especially 3,400 for well pumps. Motor specs usually name taged 1,750 and app 3,580 rpm's on 60 cycle in the US. Little rpm differences or drop on centrifugal pump impeller speed results in rather large pump efficiency output drops. Unless I missed another reply posted above use 1/2 tubing and be careful on your pump adapter selection preventing small internal adapter inside diameter restrictions. I had a couple adapters that I drilled out the inside diameter then chamfered the ends for a smoother fluid flow transition. I hope this reply comes out understandable as the last time I posted I was the laughing stock of many members while on Percoet hence i'll just shut up and lurk only again. I've spent a few years digging wells and installing piping and sprinkler systems that operated on high volume low pressure off well pumps. Back to lurking under my rock what do I know?

Makes sense. The pump will flow at a specific flow rate based on the pressure drop of your system. The more restrictions in your system, the lower your gpm will be. You have to plot the performance curve verses the pressure drop curve for your system to predict what that flow rate will be. The other way is to run the pump on your system.