STS1072R vs STS1072RV1; capacitor hump; "Conservationist" mo

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Diver

Diver

0
May 5, 2011
480
South of Boston
My wife got me a two speed replacement motor for our superpump as a birthday gift  I gave her a direct link to a web site and it was a link for STS1072R motor. However the one that we received was STS1072RV1, which is slightly different model but still a direct replacement for my pump.

I tried to research the differences but couldn’t find a lot of info and what I found is somewhat confusing. Attached is an excerpt from AOSmith pdf.

So maybe someone with good knowledge can help me understand couple of things:

1. R motor has nameplate HP of 3/4-1/8 for Hi/Lo and RV1 version has 3/4-1/10 for Hi/Lo (SF is omitted for simplicity since it’s the same for both models). So it looks like it will deliver less power for low speed, which I’m happy about, but then looking at full AMPs it’s 6.4/1.9 for first motor and 5.4/2.2 for second one! I would think that the AMPs for lower speed for second model would be lower than for the first one since it seems to be more energy efficient model to begin with and lower speed has even less power. But the AMPs are higher!
2. The RV1 model has a big capacitor on the body of the motor (pictured). I know there is a start capacitor under end cap for both models, but I’m not sure what is the purpose of this other one. The PDF says “Energy Efficient capacitor start, capacitor run “Conservationist” motor” so maybe the capacitor is for the “conservationist” mode, but I don’t really know what that means.

So overall it seems that RV1 is newer more energy efficient motor that is replacing the older R model and I should be happy that I got better motor than that I paid for. However I still don’t understand the 2.2 AMPs on low speed – that doesn’t seem to make sense.

I’d appreciate if someone can shed some light on this for me.
 

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Re: STS1072R vs STS1072RV1; capacitor hump; "Conservationist

The big capacitor on top is a Run capacitor, it make the motor more efficient by improving the Power Factor.

The rated amps are the full load amps, not the normal running amps.
 
Re: STS1072R vs STS1072RV1; capacitor hump; "Conservationist

James,

Thanks for clarification. I read a bit about run and start capacitors and now it makes more sense.

As for full load amps, i was thinking it could be maximum load amps, but then i thought it would still should be proportional to the other numbers.

What's the good way to measure running amps? I believe there is a way to calculate the flow and watts based on piping configuration and filter pressure. Another one would be to use an AMP meter clamp, but i'm not sure if it would work well with a conduit that leads the wires to the motor.
 
Re: STS1072R vs STS1072RV1; capacitor hump; "Conservationist

Low speed is sometimes capacitor-start/capacitor-run and sometimes capacitor-start/induction-run. Perhaps that explains the difference, but I'm not sure.

There seems to be some conflicting information from various sources, including A.O Smith as to exactly what type the motors are. Can you post all of the information from the motor label?

You can measure running amps using a clamp type ammeter on one of the legs of the supply. Ideally, it should be a "true RMS" meter to account for the Power Factor.

Note: I'm not sure how precise the rated measurements for amps and horsepower are, anyway. There might be a significant difference depending on test conditions, design specs, assumed operating conditions etc.
 
Re: STS1072R vs STS1072RV1; capacitor hump; "Conservationist

i will take a picture of the nameplate tonight.

"You can measure running amps using a clamp type ammeter on one of the legs of the supply."

since this is 230V motor, two hot wires are used to power it up (there is no neutral, which sounds weird to me, it looks like ground wire is used to complete the circuit). so should the clamp go over two hot wires that are engaged for a specific winding of the motor?
 
Re: STS1072R vs STS1072RV1; capacitor hump; "Conservationist

A 240 volt circuit uses two wires in exactly the same way a 120 volt circuit uses two wires. The only difference that matters here is that neither wire is anywhere near ground potential in a 240 volt circuit, while in a 120 volt circuit one of the wires (neutral) is somewhere around ground potential.
 
Re: STS1072R vs STS1072RV1; capacitor hump; "Conservationist

JasonLion said:
A 240 volt circuit uses two wires in exactly the same way a 120 volt circuit uses two wires. The only difference that matters here is that neither wire is anywhere near ground potential in a 240 volt circuit, while in a 120 volt circuit one of the wires (neutral) is somewhere around ground potential.
Click to expand...

Jason,

I agree with your statement. I understand that neutral and ground are actually connected at the circuit panel. My question was regarding clamping an AMP meter around one hot wire to measure AMPs that go to the motor powered by two hot wires (240volts). Do you still think that clamping one hot wire in this case would give me current AMPs for the motor?
 

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Re: STS1072R vs STS1072RV1; capacitor hump; "Conservationist

It looks like the manufacturer is phasing out the 3/4-1/8 model, so very likely they are re-designing or having issues with it. Depending on the power factor, you are looking at a difference between the two of 300 milliamps, or probably about the equivalent of a 60 watt light bulb. I wouldn't worry about it.
 
Re: STS1072R vs STS1072RV1; capacitor hump; "Conservationist

Ohm_Boy said:
It looks like the manufacturer is phasing out the 3/4-1/8 model, so very likely they are re-designing or having issues with it. Depending on the power factor, you are looking at a difference between the two of 300 milliamps, or probably about the equivalent of a 60 watt light bulb. I wouldn't worry about it.
Click to expand...

Ohm_Boy,

I wasn't worried much about it, i just tried to understand somewhat conflicting information. The second model seems to be more energy efficient, has lower powered low speed and still has higher max amps - that just looked odd to me.

thanks for chiming in!
 
Re: STS1072R vs STS1072RV1; capacitor hump; "Conservationist

JasonLion said:
A 240 volt circuit uses two wires in exactly the same way a 120 volt circuit uses two wires. The only difference that matters here is that neither wire is anywhere near ground potential in a 240 volt circuit, while in a 120 volt circuit one of the wires (neutral) is somewhere around ground potential.
Click to expand...

Jason,

I now understand where my confusion was... There is a neutral wire in one speed motor and I was thinking that that wire was used to complete the circuit. In two speed motor, there is no neutral, so i was thinking that it must be the ground wire that completes the circuit. But it's two hot wires that make it complete and since they are now part of this circuit, clamping one wire to measure the amps make sense!

sorry for the confusion :)
 
Re: STS1072R vs STS1072RV1; capacitor hump; "Conservationist

well, i got the answer to my question from AO Smith today plus some more additional information that i think i should share since with the people who participated in this topic. Below is one of the internal emails within AO Smith engineering department regarding my inquiry as to why more efficient model of the motor consumes more power on lower speed (see my first post in this topic). I also attach a spec sheet that was included in the response I got. what i find strange from the spec pic is that watts are dropping as speed increases. i'm probably reading it wrong.

----

Original STS1072R had over-inflated low speed horswepower. It had listed 1/8 HP or 0.125HP when by affinity laws it should have been 0.09 or 0.10 HP.

STS1072RV1 HIGH = permenent split capacitor, LOW= capacitor start induction run
the hi speed run capacitor gives better efficiency on hi speed. since low speed is induction run there is not much improvement on efficiency on low speed.

The efficiency improvement of the RV1 was on hi speed. Any improvement on efficiency on low speed, if any, would be negligible.


I understand where the question is comming from.
Why is MAXLOAD 2.2A higher amp rating at only 0.150 SFHP on STS1072RV1 when the original had MAXLOAD 1.9A rating at 0.187 HP SFHP on STS1072R?

The amp ratings on the nameplates are MAXLOAD AMP ratings. This is maximum amp draw at one of 3 load and voltage points.
1. 207V, 0.98 X SFHP
2. 230V, SFHP
3. 253V, 1.03 X SFHP.

STS1072R 0.125 X 1.5sf = 0.187 service factor horsepower MAXLOAD AMPS 1.9A
STS1072R 0.10 X 1.5 sf = 0.150 service factor horsepower MAXLOAD AMPS 2.2A


The simple explanation is the nameplate amp ratings are MAXLOAD AMP ratings and you can't necessarily compare them side by side since these two motors have different electrical designs. Depending on the electrical design saturations, the amps could go up or down at 207V 0.98XSFHP or 253V 1.03XSFHP load points. You would need to compare nominal 230V SFHP load points at same horsepower load between the two motors for a true comparison of amp draw.


I only have the torque curve on STS1072R. I do not have the torque curve on STS1072RV1 (winding spec 0116758 -- it looks like 0345590 was the original sample by Jevon Reynolds).
 

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