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#1 02-10-2012 11:33:00

greg
Newbie
Registered: 10-05-2008
Posts: 8

Electrical Question

I've got a single phase 1/12 HP motor that's pulling 2.6A @ 119V. The power factor is .44. So calculated draw (not including PF) is 309W but indicated draw is about 136 watts. My question is if the actual electricity consumption of the motor is the calculated or indicated watts. That may be a dumb question but I know in a 3 phase world a lower PF costs you money.

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02-10-2012 11:33:00

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Re: Electrical Question

#2 02-10-2012 11:33:46

eddieser
Helper
Registered: 11-14-2009
Posts: 18

Re: Electrical Question

Sounds like your motor doesn't have much load on it.

It is 309 VA (309W at 1.0 pf or 250W at 0.8 pf), but you're pulling
136 W. Depending on the utility company, you either pay them in kWh
only (DWP doesn't care about your low pf) or kWh *plus* power factor
penalty (which is wasted VARs).

If you're paying the pf penalty, then you either make sure your motor
is properly loaded, or add pf correction capacitors to inject negative
VARs into the system. But you have to be careful not to add too much
cap, or you'll overcompensate, get hit with penalty for sending the
VARs into the grid and possibly burn out your motor when unloaded
because the voltage goes up.

If this was a big motor, I worry about the penalty, but for a tiny
little 1/12hp motor.... nah! It's like a fly on an elephant!

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#3 02-10-2012 11:51:48

chuck
Rookie
Registered: 10-22-2008
Posts: 66

Re: Electrical Question

Even though the calculated watts may be 309, other factors come to play such as where the motor is installed, what it is being used for (ie. pump, fan, direct drive or pulley driven). These can change what the motor will draw....
What application is this motor used for ??
Kind a low power factor.... not very efficient.... which is why that motor pulls the amount of amps it does....
I am used to motors with higher efficiency ratings.....

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#4 02-10-2012 11:52:39

bj
Rookie
Registered: 05-18-2009
Posts: 88

Re: Electrical Question

if you double the voltage input to that motor, does it become more efficient?

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02-10-2012 11:52:39

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Re: Electrical Question

#5 02-10-2012 11:55:46

greg
Newbie
Registered: 10-05-2008
Posts: 8

Re: Electrical Question

Thanks for that info. I'm still not quite clear on the actual load I'm paying for so here's the hard data my "kill-a-watt" meter is telling me. And Charles, I am also used to bigger (<=50HP) 3 phase motors with power factors like .85 - .90 so I surprised with this little mouse of a motor.

This motor is for hot water recirculation in my house. I'm finally getting around to figuring out why my Edison bill is so high and this motor and the pool motors are the prime suspects. My kill-a-watt meter indicated 2.6A @ 119V and 136W. I thought it was odd that it was only using 136W with a draw of 2.6A (given V x A that should be 309W) and then noticed the power factor of .44 which I really thought was odd. So I multiplied (V x A x PF) and that yields the 136W that the meter is indicating.

So I'm wondering if my electric meter is seeing the 136W or 309W usage? The kill-a-watt apparently factored in the PF in it's 136W reading but I have a feeling the meter is seeing the entire 309W. Referring to Eddie's comments I don't know if I or Edison pays for the low PF. The 1/12 HP motor sounds trivial but even at the 136W that's 100 kwh/mo. or 225 kwh/mo. at the full 309W. Obviously I need to get a timer and presumably a more efficient motor.

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#6 02-10-2012 12:06:00

westside
Helper
Registered: 10-05-2008
Posts: 34

Re: Electrical Question

Yup. It's all about the juice!

I used one of these:

http://www.amazon.com/Watts-Power-Analy … 000CSWW92/

that we kinda bought for doing "server sizing".

My electric bill is less than the past two years. I went and reviewed
some things to turn off, others to keep more of an eye to when they're
on. Swapped out some hi-usage lights with compact fluorescent where
feasible.

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#7 02-10-2012 12:25:19

Stein
Helper
Registered: 05-27-2009
Posts: 48

Re: Electrical Question

Here is the HW recirculation setup that I installed about 2 years ago....
Purchased it at Home Depot.....
While the pump says Watts on it.... It is actually produced by Grunfros from Germany....
We use Grunfros pumps at work.... They are well built and efficient....

http://www.homedepot.com/webapp/wcs/sto … =100426993

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#8 02-10-2012 12:30:27

kev
Enthusiast
Registered: 09-27-2008
Posts: 102

Re: Electrical Question

Man, my power bill is jacked. Almost 270 for the electric only, not inc gas.

Probably from the xmas lights.

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#9 02-10-2012 12:31:08

Stein
Helper
Registered: 05-27-2009
Posts: 48

Re: Electrical Question

Generally my electric bill is about $135 a month....
Been working on reducing the bill where I can over the past several months.... by using energy efficient light bulbs, recirculation pumps and locating high usage appliances....
Still trying to find more ways to reduce the bill....

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#10 02-10-2012 12:52:21

kev
Enthusiast
Registered: 09-27-2008
Posts: 102

Re: Electrical Question

the circ pump might be nice, does it really cut back? I have a long
run from kitchen to the water heater.

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#11 02-10-2012 12:53:35

Stein
Helper
Registered: 05-27-2009
Posts: 48

Re: Electrical Question

Saves money on water and sewer usage for the amount of gallons wasted while the water runs when you are waiting for the water to warm up....
The timer allows for the circ pump to be programmed for the times you need the hot water....

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#12 02-10-2012 12:57:08

miami
Helper
Registered: 10-05-2008
Posts: 25

Re: Electrical Question

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#13 02-10-2012 12:57:39

kev
Enthusiast
Registered: 09-27-2008
Posts: 102

Re: Electrical Question

Yea, the return line would suck. between the floors to the middle of
the house. Hmm..

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#14 02-10-2012 12:58:29

miami
Helper
Registered: 10-05-2008
Posts: 25

Re: Electrical Question

There's always a way. PEX tubing is awesome for those situations. I
use it more and more instead of copper these days. Much quieter too.

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#15 02-10-2012 12:59:45

Stein
Helper
Registered: 05-27-2009
Posts: 48

Re: Electrical Question

Interesting design and applications....
Not sure how long those models have been around, or how much it costs, but the one that I used was available locally for a decent price....
Thanks for the info....

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#16 02-10-2012 13:00:34

Stein
Helper
Registered: 05-27-2009
Posts: 48

Re: Electrical Question

No return line needs to be installed...
It is a controlled by a thermostatic recirc manifold... that is
installed at the furthest point from your water heater...

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#17 02-10-2012 13:01:48

kram
Rookie
Registered: 05-24-2009
Posts: 95

Re: Electrical Question

So I'm looking at this recirc. You're basically bleeding off hot water
into the cold side. I would think that this would use less water, but
more electricity and more gas as the water that goes out gets replaced
by cold water which needs to be heated. How are the savings on it?

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#18 02-10-2012 13:03:03

kram
Rookie
Registered: 05-24-2009
Posts: 95

Re: Electrical Question

kev wrote:

Man, my power bill is jacked. Almost 270 for the electric only, not inc gas.

Probably from the xmas lights.

It's those wild parties and the new aircompressor, plus your plasma
setup. :) I'd bet 40-50 of it went into heating your hottub.

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#19 02-10-2012 13:08:17

Stein
Helper
Registered: 05-27-2009
Posts: 48

Re: Electrical Question

Obviously electricity is only used when the pump runs.
The motors are efficient drawing only .22A.
Savings come from a lot less water and sewer usage.

Nice to have hot water immediately at the shower.
Ask your wife how important that is to her !!!
There are additional benefits I wont get into on the forum....

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#20 02-10-2012 13:10:39

nads
Rookie
Registered: 05-29-2009
Posts: 89

Re: Electrical Question

If you are in a city which owns its utility. you may be screwed....

Look at how many kilowatts you use.

If you have central air, and you have edison sign up for the reduced rate program. They put a radio controller on it to allow them to turn off your AC in peak periods.

I save a lot on my electricity but have not yet noticed a shutdown.

Besides, if your house is already cool there is little change in house temperature in the two hours it might be down.

And the cost savings are incredible....running AC all the time keeping my house really cool my Summer bill was never over $100 (i also got a new energy efficient AC/Heater for $5k, figure I saved $1500 the first summer)

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#21 02-10-2012 13:11:25

nads
Rookie
Registered: 05-29-2009
Posts: 89

Re: Electrical Question

What does recirculation do to the costs?

Can a simple dedicated solar water heater better serve that area that has the poor hot water issue?
I imagine a small solar water heater right above the sink can better serve the hot water need without the additional cost.

Same for the Jacuzzi, a small solar water heater which has a thermostat valve that opens at 80 or 90 degree to keep the jacuzzi warm so very little electricity is expelled getting it to temperature.

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#22 02-10-2012 13:14:04

fragchaser
Newbie
Registered: 07-08-2009
Posts: 10

Re: Electrical Question

I've got a gunfros pump (43gpm) on the radiant heating system and it's an impressive unit. It's a tiny integrated unit that's both powerful and efficient. Looks similar to the Watts unit but about twice the size.

I'm curious about the Watts unit as I thought those recirculators do their work through the cold water circuit therefore warming the cold water? Also since they put hot water into the cold water lines your consuming water that's gone through the water heater for cooking/drinking that I've always considered to be a no-no.

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#23 02-10-2012 13:17:15

fragchaser
Newbie
Registered: 07-08-2009
Posts: 10

Re: Electrical Question

I haven't seen that one. These things definitely pay for themselves fast. Did a search on that one and found a site that specializes in power monitoring:

http://www.powermeterstore.com/index.php

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#24 02-10-2012 15:16:29

josh
Helper
Registered: 10-05-2008
Posts: 27

Re: Electrical Question

Our runs about $100-$120.    The best thing we ever did was sign up for the SCE remote shut off service for the A/C.    Dropped our bill big time.   

Right now we have two fridges.     The one out in the garage is a pretty old energy sponge.    Been considering getting rid of it just to save some energy and replace it with a much smaller one but just dont have money to spend on that right now.

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#25 02-10-2012 15:17:35

westside
Helper
Registered: 10-05-2008
Posts: 34

Re: Electrical Question

Yeah, looked at the remote shut off, but thought it might kill our pet
(temp sensitive to above about 77 degrees F) so we passed.
Personally, I'M temp sensitive above about 77 degrees, now that I
think about it!

(Wife accuses me of getting him just so I can keep the house
cooler! ;-)

Argh! Don't have a picture handy - he's a chinchilla...

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