Electrical Service Question

[Angelic]

Hi,
I am new to your forum and and hoping to get some advise on a problem I am having. I have worked with electrical installations of all kinds over the years, but my primary focus is in electronics repair of varied equipment. I recently acquired a piece of equipment that requires 208 volts, 30 amp, 4368 watts. The part of building where this unit is being tested is approximately 150 feet from the service panel with 10 gauge wire. The equipment I am testing starts and performs as should until I reach about 75% of capacity and then shuts down. I have not had any problems before, but have not ran equipment that has pulled this many watts. The service I have available is show below. My question is: Are my problems possibly coming from voltage drop over the 150 feet run. And am I utilizing my available service correctly. I am connected to 1 & 2.

 

[MAC702]

...Are my problems possibly coming from voltage drop over the 150 feet run...

This entirely depends on the voltage tolerance of the device in question. Many devices are extremely tolerant and can operate with at least 10% drop.

If you are connected 1 - 2, you should have 240V, not 208V.

At 30A and 150', this calculator says that would be a 4.5% drop at 208V: https://www.calculator.net/voltage-...ce=150&distanceunit=feet&amperes=30&x=32&y=25

 

[texie]

Hi,
I am new to your forum and and hoping to get some advise on a problem I am having. I have worked with electrical installations of all kinds over the years, but my primary focus is in electronics repair of varied equipment. I recently acquired a piece of equipment that requires 208 volts, 30 amp, 4368 watts. The part of building where this unit is being tested is approximately 150 feet from the service panel with 10 gauge wire. The equipment I am testing starts and performs as should until I reach about 75% of capacity and then shuts down. I have not had any problems before, but have not ran equipment that has pulled this many watts. The service I have available is show below. My question is: Are my problems possibly coming from voltage drop over the 150 feet run. And am I utilizing my available service correctly. I am connected to 1 & 2.

Your load is rated for 208 volt, your supply is 240 volts. Do you know if the load is approved for 240 volt?

 

[Angelic]

Your load is rated for 208 volt, your supply is 240 volts. Do you know if the load is approved for 240 volt?

Would it possibly be better to use the high leg with a ground?

 

[Angelic]

This entirely depends on the voltage tolerance of the device in question. Many devices are extremely tolerant and can operate with at least 10% drop.

If you are connected 1 - 2, you should have 240V, not 208V.

At 30A and 150', this calculator says that would be a 4.5% drop at 208V: https://www.calculator.net/voltage-...ce=150&distanceunit=feet&amperes=30&x=32&y=25

This is a fairly complex machine. It is a centrifuge that is also refrigerated. The centrifuge works fine at rpms upto 15000 with ac. But over that after the ac compressor kicks in it shuts down. I am studying the manual and there appears to be a section on adjusting the input voltage. I have never done that before and am not exactly sure how that works.

 

[Angelic]

This is a fairly complex machine. It is a centrifuge that is also refrigerated. The centrifuge works fine at rpms upto 15000 with ac. But over that after the ac compressor kicks in it shuts down. I am studying the manual and there appears to be a section on adjusting the input voltage. I have never done that before and am not exactly sure how that works.

How would be the best way to regulate the line voltage that is coming in from my existing service?

 

[JFletcher]

Welcome to The Forum. Can you post a picture of the name plate, or its information?

You have a single phase, 208 volt, 21 amp (4368W) motor load connected to #10 branch circuit conductors running 150' to 30 amp breaker from a 240-volt supply, correct? Is this machine rated for 50 or 60 hertz?

While most small motors can run happily on 208 to 230 volts, perhaps yours cannot, or the controls cannot tolerate such an over voltage.

I would delve into the manual to find out if there is any sort of way inside the machine to accommodate for your higher voltage. I have seen PTAC units with a 208/240v selector switch on the control transformer. There may also be different taps on that transformer.

While using the high leg and neutral would give you an incoming 208 volts, this is a very uncommon setup that requires a few special considerations before implementation.

 

[Angelic]

Welcome to The Forum. Can you post a picture of the name plate, or its information?

You have a single phase, 208 volt, 21 amp (4368W) motor load connected to #10 branch circuit conductors running 150' to 30 amp breaker from a 240-volt supply, correct? Is this machine rated for 50 or 60 hertz?

While most small motors can run happily on 208 to 230 volts, perhaps yours cannot, or the controls cannot tolerate such an over voltage.

I would delve into the manual to find out if there is any sort of way inside the machine to accommodate for your higher voltage. I have seen PTAC units with a 208/240v selector switch on the control transformer. There may also be different taps on that transformer.

While using the high leg and neutral would give you an incoming 208 volts, this is a very uncommon setup that requires a few special considerations before implementation.

Hi and thanks for your response.
Here is what I got from the manual.
Mine is taged 208v.

As soon as you receive your RC-5C PLUS, carefully inspect it for
any shipping damage that may have occurred. If you find any
damage, please report it immediately to the transportation company
and file a damage claim, then notify Thermo. If any parts are missing,
contact one of the Thermo district offices or the local representative
of SORVALL ® products. You will find a list of offices on the back
cover of this manual.
Electrical Requirements
The appropriate power source must be available to plug the
centrifuge into. Check the nameplate on the back panel of the
centrifuge to determine the electrical configuration of your
centrifuge, which should be one of the following:
200V, 60Hz, 30A, single phase
200V, 50Hz, 30A, single phase
208V, 60Hz, 30A, single phase
220V, 50Hz, 30A, single phase

230V, 60Hz, 30A, single phase
230V, 50Hz, 32A, single phase
230V, 50Hz, 32A, polyphase
240V, 50Hz, 30A, single phase
Check the supply line voltage with a voltmeter, then verify that the
voltage indicated on the nameplate is in agreement with the mea-
sured line voltage. If the measured line voltage is not within 10% of
the voltage specified on the nameplate, do not connect the power
cord and operate the centrifuge. Damage to the centrifuge may
result. To connect the centrifuge to a voltage other than what is
specified on the nameplate (including polyphase), it will have to be
rewired and its power cord may have to be replaced. Contact Thermo
to have a Field Service Engineer do the rewiring.
Single phase RC-5C PLUS Centrifuges are equipped with a three-
wire power cord with three-prong connector to fit a NEMA 6-30P
receptacle or equivalent or, on 230V 50Hz centrifuges, an IEC 60309-
type three-pin receptacle (32A, 2-pole and earth). 230V 50Hz polyphase
RC-5C PLUS Centrifuges are equipped with a four-wire power cord
with five-pin connector to fit an IEC 60309-type five-pin receptacle
(32 A, 3-pole, neutral and earth).

 

[MAC702]

... the nameplate ... 208V, 60Hz, 30A, single phase
...
Check the supply line voltage with a voltmeter, then verify that the
voltage indicated on the nameplate is in agreement with the mea-
sured line voltage. If the measured line voltage is not within 10% of
the voltage specified on the nameplate, do not connect the power
cord and operate the centrifuge. Damage to the centrifuge may
result. ...

Did you measure your supply voltage? You say you are connected in such a way (1 to 2) that should provide 240V. It looks like 3 to ground should give you 208V.

Is an actual electrician doing the installation? I don't repair electronics because it's a different specialty.

240V is over 15% higher than 208V. A lot of equipment is safe within that entire range. But some isn't, and your label seems very specific.

 

[JFletcher]

Did you measure your supply voltage? You say you are connected in such a way (1 to 2) that should provide 240V. It looks like 3 to ground should give you 208V.

Is an actual electrician doing the installation? I don't repair electronics because it's a different specialty.

240V is over 15% higher than 208V. A lot of equipment is safe within that entire range. But some isn't, and your label seems very specific.

I agree though the information that Angelic posted seems to suggest that the equipment can be field modified to run on 230 volts, which is a heck of a lot better option then using the high leg and neutral to get it.

~~~~~~~~~~~~~~~~~~~~~~~

Simply put, your machine cannot operate at the supply voltage. if the machine is still under warranty, I would have the manufacturer tech come out, even though he is likely only going to change a jumper or two or move a selector switch.

The three problems that spring to mind from using the high leg to the neutral is that:

A) one of your conductors is now a grounded conductor. Per 200.6 (B), this conductor must be white or marked white at the time of installation.

B) since you are above 120 volts to ground, your breaker must be a full rated breaker and not a slash rated one.

C) wiring the high leg to the neutral, many transformers only allow a 5% of their capacity loading. Putting a 21 amp load 208 volts from high leg to neutral would tax even an older 75 KVA with no other loads on it.

The first two are easy fixes, the last one is pretty much going to require you to have a 240 to 208 volt step down transformer if the equipment cannot be internally modified to accept your facilities 240 volts.

 

[MAC702]

I agree though the information that Angelic posted seems to suggest that the equipment can be field modified to run on 230 volts, which is a heck of a lot better option then using the high leg and neutral to get it....

Good catch. Agreed!

 

[Angelic]

Did you measure your supply voltage? You say you are connected in such a way (1 to 2) that should provide 240V. It looks like 3 to ground should give you 208V.

Is an actual electrician doing the installation? I don't repair electronics because it's a different specialty.

240V is over 15% higher than 208V. A lot of equipment is safe within that entire range. But some isn't, and your label seems very specific.

I have not had time over the holiday to work with it, but will do more testing tomorrow. And know I am not doing the install. I simply clean up ,test,and repair used equipment. And yes with all of the possible voltage options listed in the manual this one may be more sensitive.

 

[Angelic]

Good catch. Agreed!

I to am hesitant to go with the high leg. In the past I have had some bad unexpected results when used with electronic components.

 

[Angelic]

I agree though the information that Angelic posted seems to suggest that the equipment can be field modified to run on 230 volts, which is a heck of a lot better option then using the high leg and neutral to get it.

~~~~~~~~~~~~~~~~~~~~~~~

Simply put, your machine cannot operate at the supply voltage. if the machine is still under warranty, I would have the manufacturer tech come out, even though he is likely only going to change a jumper or two or move a selector switch.

The three problems that spring to mind from using the high leg to the neutral is that:

A) one of your conductors is now a grounded conductor. Per 200.6 (B), this conductor must be white or marked white at the time of installation.

B) since you are above 120 volts to ground, your breaker must be a full rated breaker and not a slash rated one.

C) wiring the high leg to the neutral, many transformers only allow a 5% of their capacity loading. Putting a 21 amp load 208 volts from high leg to neutral would tax even an older 75 KVA with no other loads on it.

The first two are easy fixes, the last one is pretty much going to require you to have a 240 to 208 volt step down transformer if the equipment cannot be internally modified to accept your facilities 240 volts.

No warranty on this machine. The manual that I have is over 300 pages and it is taking a while for me to digest. I am sure that a company tech would do just that. Come out change a few connections an send me a huge bill. Since I am unfamiliar with this one it will take some study. And since I have no step down transformers in that range I will first look at the possibility of internally adjusting the unit. After I do some careful line voltage testing. The voltage that I receive here sometimes varies significantly and also may affect the operation of units like this one.

 

[al hildenbrand]

I to am hesitant to go with the high leg. In the past I have had some bad unexpected results when used with electronic components.

As you should. A high leg to neutral load connection, in four-wire delta three phase, is a "bootleg connection". It is just plain messy.

 

[sblk55]

High leg 240

High leg 240

We recently installed 4 product X-rays from Thermo. One of the other elections wanted to use the hi leg and neutral. I did not feel that this would be what thermo would want so we called them and they said it would work either way. And we do have 2 working each way.

 

[Angelic]

We recently installed 4 product X-rays from Thermo. One of the other elections wanted to use the hi leg and neutral. I did not feel that this would be what thermo would want so we called them and they said it would work either way. And we do have 2 working each way.

So you are saying that it is ok to use the high leg in this application to get 208V, 60Hz, 30A, single phase.

What was the other way that was used?

 

[JFletcher]

We recently installed 4 product X-rays from Thermo. One of the other elections wanted to use the hi leg and neutral. I did not feel that this would be what thermo would want so we called them and they said it would work either way. And we do have 2 working each way.

You have four major differences over the original posters installation. One, you got manufacturer approval to connect your equipment either 208 or 240 volts. Two, your equipment is not so sensitive as to require one or the other. Three, you presumably had licensed electricians do load calculations for the transformer loading as well as the installation, and finally I do not see X-ray equipment being nearly as high of a load or as continuous as a centrifuge.

Although your incoming voltage is too high, you have a used, out of warranty centrifuge at a repair shop... There is almost an equally likely possibility that the problem is something in the machine.

you did not state if this is your centrifuge, or something from a customer that you are repairing and have to return.

 

[Angelic]

You have four major differences over the original posters installation. One, you got manufacturer approval to connect your equipment either 208 or 240 volts. Two, your equipment is not so sensitive as to require one or the other. Three, you presumably had licensed electricians do load calculations for the transformer loading as well as the installation, and finally I do not see X-ray equipment being nearly as high of a load or as continuous as a centrifuge.

Although your incoming voltage is too high, you have a used, out of warranty centrifuge at a repair shop... There is almost an equally likely possibility that the problem is something in the machine.

you did not state if this is your centrifuge, or something from a customer that you are repairing and have to return.

This is my machine. I purchase 2nd hand equipment from a local laboratory. Most often the units are in working condition and do not require anything but a good cleaning - set-up and testing. I them turn around and sell this equipment on the open market. Before I go to far down this rabbit hole I need to check the freon level just to make sure this is not causing the unit shut down. I have not done any load calculations as of yet, but have an engineer friend who works for Square D that may be able to help. Thanks again for all of your input.