appliance PROBLEM voltage drop 220-230ft run HELP!

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HVACRMAN

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Phoenix, AZ
Scenario:
Applicant freezer commercial RLA is 12-13 115V 220-230ft run. electrican ran 10ga for 200ft then used 12ga wire for the last run 20-30ft. the compressor is over heating and taking out the start relays. voltage drop at LRA is 90volts. I keep telling the owner the wiring is too small for the length of run. and she doesn't belive me. I did my own load calucation and it confirms the wire is too small and should be using a 6-8ga wire continuos run with NO break or smaller size wire in between runs.


originally the run was 12ga @220-230ft burnt out my start relay start cap & runcap I replaced the starting compnents. I explaned to the owner the wire is too small. the electrician rewired the circuit to 10ga but hear this THE GUY HALF ASS went 200ft then RE-USED 12ga the last 20-30ft. The freezer ran better, but not good enough. I went back the 3rd time and it burnt out the start relay, start cap & run cap again. I have since voided out the warranty because of the continous problem of wire size too small. & to top it off 2 different wire sizes. any damage should be paid by the electrician or the electrical engineer who sized it.

will someone qualitfied help me out? I've talked tp several professional and they all agree the length is too small but she says her people are right. the numbers I input on the calulations DON'T LIE, I keep telling her (as I'm bang my head against the wall).
 
Voltage ratings these days are based on a nominal 120 volts; it?s not 115 anymore.

I calculate a voltage drop of 7.49 volts total. The first 200 feet of #10, at 13 amps, drops you 6.46 volts. The last 20 feet of #12, at 13 amps, drops another 1.03. That results in 93.8% voltage available at the load. That is a bit too low.

I don?t have a problem with two different wire sizes, as long as the overcurrent protection device is sized for the smaller wire. I calculated that if you ran #8 wire for the first 200 feet and finished the run with 20 feet of #12, the total voltage drop would be 5.1 volts. This would give you a voltage at the load over 95% of rated. That should be acceptable. But I agree with you that #6 run all the way would be better.
 
My numbers agree with charlie's and would call #8 very marginal and #6 the better choice.

Who are "her people" and can you meet with them? They have obviously calculated something wrong or were given the wrong information.
 
Commercial applicance freezer WIRING SIZE CALCULATIONS HELP!

Commercial applicance freezer WIRING SIZE CALCULATIONS HELP!

HVACRMAN said:
Scenario:
Commercial applicance freezer RLA is 12-13 120V 220-230ft run. electrican ran 10ga for 200ft then used 12ga wire for the last run 20-30ft. The compressor is over heating and taking out the start relays. @ LRA 66voltage drop is 90 volts. I keep telling the owner the wiring is too small for the length of run. and she doesn't belive me. I did my own load calucation (here on Mike holts calculation page) and it confirms the wire is too small and should be using a 6-8ga wire continuos run with NO break or smaller size wire in between runs. So unless your calulator is better some where else let meeeee know.


Originally back in November 08. The electrical run was 12ga @220-230ft burnt out my start relay start cap & runcap. I then replaced the starting compnents thinknig mabe old but I did notice the amp draw @89 with a 80 voltage drop @ LRA. I explaned to the owner the wire is too small. the electrician rewired the circuit to 10ga, but hear this THE GUY HALF ASS went 200ft then RE-USED 12ga the last 20-30ft. The freezer ran better, but not good enough.

I went back the 3rd time early April in fact last week and it burnt out the start relay, start cap & run cap again. I have since voided out the warranty because of the continous problem of wire size too small. & to top it off 2 different wire sizes. any damage should be paid by the electrician or the electrical engineer who sized it. No one want to accept accountablity. the compressor is probably damaged by now and will continue to burn out starting components or worse compressors.

Will someone qualified help me out? I've talked tp several professionals and they all agree the length is too small, but she says her people are right(so call electrician in AZ thats a laugh should say fly by night). The numbers I input on the calulations DON'T LIE on Mike holt calculation page. I keep telling her (as I'm bang my head against the wall).
Click to expand...

The proof is the unit runs great at 50ft or less,when tested. I'm not an electrican, but I have my degree and 25yrs experience in HVACR to know & see what's right and whats wrong. in the HVACR field we have to follow guideline & laws of physics in our field. We just don't dream them up or use rule of thumb. as some commentors have indicated.
 
HVACRMAN said:
We just don't dream them up or use rule of thumb. as some commentors have indicated.
Click to expand...
Maybe I am misreading what you have said, but it appears to me all the people who responded to this thread were on your side. Don't yell at us, yell at the goob who put in the small wire. :)
 
HVACRMAN said:
The proof is the unit runs great at 50ft or less,when tested. I'm not an electrican, but I have my degree and 25yrs experience in HVACR to know & see what's right and whats wrong. in the HVACR field we have to follow guideline & laws of physics in our field. We just don't dream them up or use rule of thumb. as some commentors have indicated.
Click to expand...
The numbers don't lie. In additon to what has been calculated, the 50 ft test is just another piece of evidence you can use when talking to "her people".

If you can't get through to them, ask her if there is someone else she knows and trusts that you can talk to. It sounds like you are going to have to have someone she trusts to agree with you since she can't accept the simple facts on her own and does not seem to trust you.

Perhaps you can print out this thread for her as another source.

Finally, you may never be able to convince her. Some people are just that way.

add: If you print this thread out, you might want to edit out any disparaging remarks directed at her & hers as she may not be thick skinned as most of us here.
 
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HVACRMAN said:
I keep telling the owner the wiring is too small for the length of run. and she doesn't belive me.

I have since voided out the warranty
Click to expand...

Now that she's out of warranty, make it simple for her. Ask her how many more times you'll need to come out changing the same parts over and over before the new wire would of payed for itself.
 
commercial appliance

commercial appliance

i apologize for the misunderstanding I ment this vent out to the elctricians who were / are involved for all this mess.
 
lets see,
Single phase 120 volts formula
VD=(2kil)/cm

Cm=(2kil)/vd

vd=voltage drop
k=12.9 resistance constant for copper at 75 degrees
l= distance or length of run
cm= circularmills from Table 8 Chapter 9 2008 NEC

RLA is 12-13 115V 220-230ft run
assuming this is the branch circuit and not feeder, recommended max voltage drop is 3% of nominal voltage NEC 215.2(A)(3) Fine print note #2 and 210.19(A)(1) fine print note #4. that is 120 X 0.03= 3.6


cm= (2 X 12.9 X 13 X 230)/3.6=19,780

Awg 6 circularmills is 26,240 Awg 8 circularmills is 16,150.

You need Awg 6. ;) So Mike Holt guys did I do it right?? If so take these formulas and calculations to her and others.
 
It appears to me you made a good faith effort reparing this unit. You have gone up and above the call of duty. Tried to explain something to the customer that they dont understand and explained that the warranty on this unit is voided do to incorrect wiring. You could inform the customer if the correct wiring is installed you would be willing to make the repairs.
 
By my calculations (I don't use the over-conservative numbers from the NEC) there is only a 6 volt drop on the line, which is only 5% and should be within the rating of the motor. However, that doesn't mean you don't have an under-voltage problem, but the #10 wire is only a contributing factor.

You need to measure the actual voltage at the motor and verify if it is below the rated voltage of the compressor. However, I would also measure the voltage at the load center and find out if it is within spec.

Just because the motor is overheating and you are blowing start capacitors, does not automatically mean it is an under voltage condition. Have you checked the operation of the motor start capacitor circuit? If the start capacitor is not dropping out of the circuit, the amperage drawn will remain very high and it will knock out the cap and overheat the motor.
 
Rick Christopherson said:
By my calculations (I don't use the over-conservative numbers from the NEC) there is only a 6 volt drop on the line, which is only 5% and should be within the rating of the motor. However, that doesn't mean you don't have an under-voltage problem, but the #10 wire is only a contributing factor.

You need to measure the actual voltage at the motor and verify if it is below the rated voltage of the compressor. However, I would also measure the voltage at the load center and find out if it is within spec.

Just because the motor is overheating and you are blowing start capacitors, does not automatically mean it is an under voltage condition. Have you checked the operation of the motor start capacitor circuit? If the start capacitor is not dropping out of the circuit, the amperage drawn will remain very high and it will knock out the cap and overheat the motor.
Click to expand...
Hey Rick.

What inputs did you use? I used the IEEE exact VD method and got the following for 120 volt, single phase, 100% pf, 13 amp load:
200 ft of #10 = 6.24 volts = 5.2% for the section, 113.76 volts load-end
20 ft of #12 = 1.04 volts = 0.91% for the section, 112.72 volts load-end
Total = 7.28 volts = 6.07% drop overall

add: it may be a start problem, as I think he said he was dropping to 90-something
 
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As others post, the voltage drop is marginal under normal running conditions, and probably grossly excessive under starting conditions.
Remember also that the voltage may be on the low side at the start of the long wire run, the utilty supply might be only 114 volts (120-5%), and if the circuit is supplied from a sub-panel an additional few volts might be lost.

The best solution would be to have an electrician re-run the circuit in larger wire.

If the refrigeration compressor has been damaged and needs replacement, perhaps a 230/240 unit could be used, and the circuit re-configured for a nominal 240 volts. (the NEC places restrictions on cord and plug connected appliances at 240 volts, therefore it might have to be hardwired, though the code article re this is un-enforceable)
A 240 volt unit will draw about half the current (presuming same HP) , this will halve the drop in volts, to one qaurter as a percentage of the higher supply voltage.
(For example, drop on 120 volts supply might be 12 volts or 10%. On a 240 volt supply the drop would be halved to 6 volts, which is only 2.5% of 240 volts)

Another option might be to feed the circuit at 208 or 240 volts, and use a transformer at the appliance to step down to 120.
It should be possible to select the transformer tappings to give say 130 volts off load, to compensate, to an extent, for voltage drop on load.
 
HVACRMAN said:
voltage drop at LRA is 90volts.
Click to expand...

Is this what you meant to say? Voltage at the motor during startup is 30-volts or less? Or did you mean to say the voltage at the motor is 90-volts which would mean the voltage drop is 30+/-.

It would help if we knew what the current draw at start-up is and what the voltage is at the same time. What's the voltage with no load? What's the voltage and current when it's running? What's the voltage at the panel when it's running?

It seems to me there is more wrong than the just wire size. Generally, a motor should be able to handle a 10% VD from 120-volt nominal.
 
090418-1405 EST

HVACRMAN:

You need to make some voltage and current measurements. At least voltage which is quick and easy.

With freezer off measure the voltage at the main panel, and at the outlet to the freezer.

Next connect a 1500 W room heater to the freezer outlet. It will be about 12 A. Measure the voltage at the main panel and then at the freezer outlet with and without the heater plugged in.

What you want to measure is the change in voltage at the source (main panel) with and withoiut the load. This tells you how much of whatever change you see at the freezer outlet is due to the source impedance as viewed at the main panel.

Then you want the change in voltage at the freezer outlet from the known load change. By subtracting the voltage change at the main panel from the change at the freezer outlet for that change of load you can determine the change due to the resistance of the wiring and joints from the main panel to the freezer outlet. Since this heater load is about the same as the freezer should be, then correlate this measured voltage change with what others have calculated. If there are bad joints, then your measurements will show up as a greater change than the theoretical change.

Note: in some areas the line voltage at the main panel may vary considerably from one moment to the next, and when you make small voltage difference measurements it is necessary that you know the voltage before and after any change you make.

Next do the same test with the freezer as the load.

If you have something like a Fluke 87 III you can use the MIN/MAX mode and get an estimate of voltage during startup.


Here are some non-comparable measurements. The measuring instrument was a Fluke 87 III and in MIN/MAX. I can not tell you how their MIN/MAX works. This I need to find out.

These measurements are at my son's shop. The service is an open delta with a wild leg. The single phase transformer is 100 KVA, the one transformer supplying the wild leg is about 50 KVA. There is about 200 ft of wire from the transformer to our main panel. My voltage measurements in the following experiments are from 1/2 (120 V) of the single phase supply from an outlet close to the main panel and from a breaker different than the motor breaker, except in the DeWalt experiment.

Experiment 1:
A Quiincy QT-5 air compressor. Near zero pressure in the tank. Motor Baldor 5 HP rated 205 - 230/460, 14 - 13.8/6.9 A 1750 Rpm.

Pump off 122.4 V
Min 119.2 V
While pumping 121.6 V.
Voltage drop during startup = 3.2 V.
During peak inrush the voltage might have been lower. This depends upon what Fluke actually measures for MIN.

If the motor was drawing 13.8 A at the 121.6 V, then I estimate at least 55 A for startup.

Note: these voltages are not at the motor. There is not a lot of wire to the motor, 30 to 40 ft maybe, and probably #8. Motor starts very quickly.


Experiment 2:
A moderate size belt sander. Not much inertia or mechanical load at startup. Motor Leeson 20 HP rated 208 - 230/460, 53 - 48/24 A 1750 Rpm.

Off 122.4 V
Min 116.0 V
While pumping 121.8 V.
Voltage drop during startup 6.4 V.



Experiment 3:

DeWalt radial arm saw without maximum size blade. Thus, lower inertia.
1.5 HP, 120/ 208-240, 17, 8.5 A, 3450 RPM.

In this experiment the meter is plugged into the same outlet as the saw. Thus we see the voltage at the motor.
Off 122.4 V
Min 92.0 V
While running and not cutting 120.3 V.
Voltage drop during startup 30.4 V.

From previous experiments when a larger blade was on the saw and there was a long startup time the voltage drop was greater.

There is something over 100 ft from the main panel to the saw, and it is #12 wire.

.
 
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