Amp draw

TonyS

Do we reduce the amp draw on a small wet rotor circulator  when we start closing a valve on the outlet side to regulate flow? I know this is the case with submersible pumps on well systems but I never checked to see if it works the same on circulators.

JStar

Yup.

Should work the same way.

Mark Eatherton

Low impedance wet rotor motors...

Draw the same amperage with a locked rotor as they do with no load, so in short, no.



With larger PUMPS (not circulators) your idea wold be valid, but you still have to assume worst case scenarios.



ME

TonyS

Now Im going to have to

hook up my amp meter to the circulator tommorow. LOL

Techman

amps

Does a Taco 007 fall into the low impedence motor catagory? Would the amp draw increase by throttling closed the valve on the outlet of the 007?

TonyS

Check this out

http://www.cyclestopvalves.com/geninfo_2.html        Check out the videos on amp draw too. I use these cycle stop valves and they really do work better than variable speed.

bob_46

Amps

All the centrifugal circulator/ pumps or for that matter blowers that I have worked with draw

fewer amps when throttled down.

Mark, how do you explain Fig. 7-42 in Siggy ? Most all the wet rotor pumps that I have seen have permanent split capacitor motors. I don't know about the ECM's but I would think the less work they do the less power they would use.

Unknown

Amps and low Hp Circs

During Brain Box training sessions Mark Hunt and I do, we do comparrisions of constant speed "pocket circs" (007, UPS 15-58 Star 16 types) to ECM, runing an analysis of power consumption of full flow (about 8 ro 10 USGPM) and 75% flow, 50% 25% and dead head (zero flow).



Watts of a 3 speed "typical" residential circ on high speed typically run around 105 at full flow and drop to about 85 at dead head.  Watts/volts approx approx equal amps.  There is math that can support this (BHP = head x flow/3960 x effeciency) but I like to let the watt and flow meter do the talking.



ECM circs typically runs 36 watts at full flow and 5 at dead head.

Mark Eatherton

My comment is based on field experience...

For example, a Taco 007 serving a Weil McLain Gold boiler. Problem at hand, no heat, but boiler is hot.



Checked pump for voltage. Voltage present.



Check pump for proper amp draw and confirmed proper amp draw, but still not heating, and pump motor is hotter than hell.



Pull pump apart and found locked rotor on cartridge.



Replaced cartridge, and re-checked amperage draw and found it to be the same as the previous locked rotor motor.



TO be honest, I have not actual sat down with a volt/amp meter and played with the pump, so it is entirely possible that there would be some change in amp draw with some motors, but that is my experience in the field.



I had thought at one time about the possibility of doing these tests on a test stand,in an attempt to be able to make a field call about how many GPM's these wet rotor pumps would be moving, based on voltage and amp draw, but after running into the locked rotor Taco, I gave the idea up.



If I am all wet, I stand corrected.



ME

Mark Eatherton

ME Too...

I went down to my "lab" and checked out my own pumps operations.



Taco 007 serving DHW needs.

120 VAC



Free flow rate (as verified with visual in line flow meter) is 3.5 GPM

Amp draws are as follows;



3.5 GPM = .32 amps

3.0 gpm = .32 amps

2.0 gpm = .31 amps

1.0 gpm = .31 amps

dead head = .31 amps



2nd pump is a Grundfos 1542 serving space heating needs.

Free flow GPM = 2.25

2.25 gpm = .54 amps

2.0 gpm = .54 amps

1.5 gpm = .53 amps

1 gpm = .51 amps

dead head = .50 amps



Assuming a power factor of 1, the corelating wattage draws would be amps times volts, so the Taco uses 38.4 peak watts, and 37.2 minimum watts under the above testing scenarios.

The Grundfos uses  64.8 maximum vs  60 watts minimum under the above tested scenarios.



So, obviously, the less work it is doing, the less power it consumes, but the differential in actual wattage does not vary as a direct proportion to the variations in flow.



Hence the reason I never persued trying to come up with a chart that could be used in the field to verify flow based on amperage being drawn.



Also, 4 100ths of an amp could result from poor instrumentation or other outside influences.



HTH clear things up a bit.

Your milage may vary :-)



ME