Another 240 Volt GFCI Question

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kegkong

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Hi folks,
Just getting back into brewing after decades long absence.
I've searched all over the forum as well as have read the electric tutorial sticky but many of the thread links are gone so I don't yet have a complete picture.

Installation of a 240 v 30 amp breaker is not an option and neither do I wish to go the Spa box route. I wish to use the dryer socket, but as in many older homes the dryer and socket are, from what I can gather, the three pin NEMA 10-30 (?)
20200322_115331.jpg


I have two Blichmann 240v Brewcommanders, each of who's power input cords are 10 gauge 3 wire, fitted with NEMA L6-30P connectors.

So there are two problems; matching the plug/socket types, as well as the GFCI issue.

For the GFCI, it has been virtually impossible to find an inline unit with this combination, although I have seen on Amazon (via North Shore Safety) an inline unit with NEMA L6-30 on both ends (link may expire at any moment).

https://www.amazon.com/North-Shore-...srs=15837011011&ie=UTF8&qid=1587494780&sr=8-6



gfci L6-30.jpg


They also sell the same unit with flying leads for almost half the price, but I really don't want to mess with finding the plugs and doing the wiring, even though I'll admit, it looks easy. I prefer to have molded plugs and avoid problems due to my own incompetence. Anyway, I reckon my life is worth more than $150.

I have to admit i was surprised that the Brewcommander uses the 3 pin configuration, but I assume the black, white and green wires are the same as the wires in the 10-30 socket and that somewhere behind the wall there is a neutral and a ground jumpered together? and therefore this GFCI is compatible as long as I can find an adapter to bridge L6-30 to 10-30?

Assuming so, I found on ebay: https://www.ebay.com/itm/30-Amp-NEM...248156?hash=item3d708c4d9c:g:OicAAOSwSudcVHuX

Nema Adapter.jpg


My question therefore is does anyone see a functional discrepancy with plugging this adapter into the dryer socket and then plugging the male end of the GFCI into the adapter? Again, I realize that this isn't the cheapest solution, but I'm not really concerned with that part of it. I only need to know if there would be any deleterious effect on the GFCI functionality with this configuration. I'm also aware that a four pin solution is superior as regards safety, however, since the Blichmann controllers use three pins I assume the additional risk is not terribly high.

Any assistance would be greatly appreciated.

Cheers,
 

Deadalus

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Why does Blichmann build them like that? It seems like the unit is designed to use a three wire old dryer 3 prong line by switching out the receptacle.

From the description of the unit.
"For some folks, this is a perfect configuration because they have a 240v circuit that only has 3 wires (hot, hot, ground). They can find a standard 120v circuit to feed the pump input even if it requires an extension cord."

A dryer doesn't need a GFCI per NEC as far as I know even if it is 10/3 w ground. It seems like they are saying go ahead without the GFCI. Maybe it says something in the product manual? Or not saying anything because the inline is so expensive?
 
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kegkong

kegkong

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Why does Blichmann build them like that? It seems like the unit is designed to use a three wire old dryer 3 prong line by switching out the receptacle.

From the description of the unit.
"For some folks, this is a perfect configuration because they have a 240v circuit that only has 3 wires (hot, hot, ground). They can find a standard 120v circuit to feed the pump input even if it requires an extension cord."

A dryer doesn't need a GFCI per NEC as far as I know even if it is 10/3 w ground. It seems like they are saying go ahead without the GFCI. Maybe it says something in the product manual? Or not saying anything because the inline is so expensive?
Hi, many thanks for responding. Yes, in fact the product manual warns that it should not be operated unless both the 120v as well as the 240v supply lines are plugged into a GFCI circuit. The statement about the dryer is what attracted me to the unit. They even offer a power cord that has the dryer plug on one end and the L6-30 on the other but I realized immediately that it wouldn't help me because I could not find any GFCI offerings with that kind of configuration. The L6-30 seems to be some kind of more common industrial application. Every place I call that had a potential solution wanted me to buy 1000 units. It was a rude awakening. :(

OK, maybe there is no neutral line, but wouldn't that in this case, be effectively the same as having neutral and ground jumpered? I mean, would that affect the function of the GFCI? It's all so confusing.

Also, is the number of milliseconds needed for the GFCI to break the circuit important?

Cheers,
 
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kegkong

kegkong

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doug293cz

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OK, maybe there is no neutral line, but wouldn't that in this case, be effectively the same as having neutral and ground jumpered? I mean, would that affect the function of the GFCI? It's all so confusing.

Also, is the number of milliseconds needed for the GFCI to break the circuit important?

Cheers,
Neutral and ground are jumpered (technical term used is "bonded") at the main service panel. The difference between a ground and neutral at an outlet is the neutral is expected to carry current in normal operation, and thus may have a potential slightly above ground due to wire resistance. A ground is not supposed to carry any current in normal operation in order that anything that is grounded is at ground potential (for safety.) The GFCI can work without a neutral in a 240V system if wired correctly.

I haven't seen GFCI's spec'ed at different trip times. Do you have examples?

Brew on :mug:
 
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kegkong

kegkong

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Neutral and ground are jumpered (technical term used is "bonded") at the main service panel. The difference between a ground and neutral at an outlet is the neutral is expected to carry current in normal operation, and thus may have a potential slightly above ground due to wire resistance. A ground is not supposed to carry any current in normal operation in order that anything that is grounded is at ground potential (for safety.) The GFCI can work without a neutral in a 240V system if wired correctly.

I haven't seen GFCI's spec'ed at different trip times. Do you have examples?

Brew on :mug:
Hi doug, wow, thanks for the clarification. That makes sense that the two should be bonded at the panel. I must have missed the part about neutral carrying current in the primer.
During my searching I thought I recalled seeing youtube examples of where the bonding occurred at the socket, or perhaps it was inside the old dryers with the NEMA 10-30 plug, but I may have just been confused.

In that Amazon link you showed me, if you scroll down it has a product description thus:

"... Frequency: 60 Hz Trip Level: 5 +/- 1 mA Phase: Single Response Time: 25 mS max @ 500 Ohm fault..."

I just assumed that it meant if a fault was detected the circuit would require 25 milliseconds to cut power, so I didn't know whether that was a good number or a middling one. I've also seen other devices which claim 5 milliseconds "...Response Time..." but I've looked at so many websites I cannot recall exactly where i saw the other number. If I've misinterpreted the meaning and if it doesn't matter then not a problem.

So just to clarify, in the general case of the NEMA L6-30 and in the specific case of the Brecommanders is the green wire of the plug meant to carry a neutral or a ground, and does it matter with regard to the Interrupter?

As always, you patience and assistance is appreciated.

Cheers,
 

doug293cz

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Hi doug, wow, thanks for the clarification. That makes sense that the two should be bonded at the panel. I must have missed the part about neutral carrying current in the primer.
During my searching I thought I recalled seeing youtube examples of where the bonding occurred at the socket, or perhaps it was inside the old dryers with the NEMA 10-30 plug, but I may have just been confused.

In that Amazon link you showed me, if you scroll down it has a product description thus:

"... Frequency: 60 Hz Trip Level: 5 +/- 1 mA Phase: Single Response Time: 25 mS max @ 500 Ohm fault..."

I just assumed that it meant if a fault was detected the circuit would require 25 milliseconds to cut power, so I didn't know whether that was a good number or a middling one. I've also seen other devices which claim 5 milliseconds "...Response Time..." but I've looked at so many websites I cannot recall exactly where i saw the other number. If I've misinterpreted the meaning and if it doesn't matter then not a problem.

So just to clarify, in the general case of the NEMA L6-30 and in the specific case of the Brecommanders is the green wire of the plug meant to carry a neutral or a ground, and does it matter with regard to the Interrupter?

As always, you patience and assistance is appreciated.

Cheers,
Yes some dryers do some not quite kosher things with the ground (using them as a neutral to carry a small amount of current for 120V loads in the dryer.) NEC has grandfathered this, but I think it is discouraged/forbidden for new construction. In a dryer that is designed to work on either 3 wire or 4 wire, neutral and ground are bonded in the dryer when using 3 wire. Otherwise they are isolated.

I know that 5mA is the nominal trip level required for GFCI's to meet code, and that they are allowed 1mA tolerance on the high side - must trip at 6mA, or the unit doesn't meet code. I haven't really looked at trip time specs, so I need to do that.

In a three wire 240V application, the third wire is always ground. The GFCI works by measuring the currents flowing in the current carrying wires (line 1, line2, and neutral - if present.) If the current in one direction is different than the current in the other direction, then there is a current leak somewhere, and the GFCI trips. The "Test" button on the GFCI works by shorting one of the hot wires to ground or neutral thru a resistor that will give 6mA of current. This short current bypasses the current sensor in the GFCI, thus creating the current imbalance the GFCI is looking for. In a three wire system, the test button shunts some current to ground. In a four wire system, I believe the standard for the test button to shunt to neutral, but either ground or neutral will work.

Brew on :mug:
 

Cato1507

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Hi folks,
Just getting back into brewing after decades long absence.
I've searched all over the forum as well as have read the electric tutorial sticky but many of the thread links are gone so I don't yet have a complete picture.

Installation of a 240 v 30 amp breaker is not an option and neither do I wish to go the Spa box route. I wish to use the dryer socket, but as in many older homes the dryer and socket are, from what I can gather, the three pin NEMA 10-30 (?)View attachment 676805

I have two Blichmann 240v Brewcommanders, each of who's power input cords are 10 gauge 3 wire, fitted with NEMA L6-30P connectors.

So there are two problems; matching the plug/socket types, as well as the GFCI issue.

For the GFCI, it has been virtually impossible to find an inline unit with this combination, although I have seen on Amazon (via North Shore Safety) an inline unit with NEMA L6-30 on both ends (link may expire at any moment).

https://www.amazon.com/North-Shore-...srs=15837011011&ie=UTF8&qid=1587494780&sr=8-6



View attachment 676807

They also sell the same unit with flying leads for almost half the price, but I really don't want to mess with finding the plugs and doing the wiring, even though I'll admit, it looks easy. I prefer to have molded plugs and avoid problems due to my own incompetence. Anyway, I reckon my life is worth more than $150.

I have to admit i was surprised that the Brewcommander uses the 3 pin configuration, but I assume the black, white and green wires are the same as the wires in the 10-30 socket and that somewhere behind the wall there is a neutral and a ground jumpered together? and therefore this GFCI is compatible as long as I can find an adapter to bridge L6-30 to 10-30?

Assuming so, I found on ebay: https://www.ebay.com/itm/30-Amp-NEM...248156?hash=item3d708c4d9c:g:OicAAOSwSudcVHuX

View attachment 676810

My question therefore is does anyone see a functional discrepancy with plugging this adapter into the dryer socket and then plugging the male end of the GFCI into the adapter? Again, I realize that this isn't the cheapest solution, but I'm not really concerned with that part of it. I only need to know if there would be any deleterious effect on the GFCI functionality with this configuration. I'm also aware that a four pin solution is superior as regards safety, however, since the Blichmann controllers use three pins I assume the additional risk is not terribly high.

Any assistance would be greatly appreciated.

Cheers,
I use the North Shore in line GFCI w/manual reset and it works great. Mine is a 240v 20amp for my 3750 Boil Coil. I got the model with the exposed wires and ordered the plugs i needed. They provided wiring diagrams and it just took me a couple minutes to put it in operation.
It was a much cheaper option than paying an electrician.
 
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kegkong

kegkong

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I use the North Shore in line GFCI w/manual reset and it works great. Mine is a 240v 20amp for my 3750 Boil Coil. I got the model with the exposed wires and ordered the plugs i needed. They provided wiring diagrams and it just took me a couple minutes to put it in operation.
It was a much cheaper option than paying an electrician.
Hi Cato, thanks for the confirmation. Yes, I agree. If I were not able to find the unit with the molded plugs I probably would have gone with that version. Adding the ebay adapter will just make everything plug-n-play.

Cheers,
 
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kegkong

kegkong

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Yes some dryers do some not quite kosher things with the ground (using them as a neutral to carry a small amount of current for 120V loads in the dryer.) NEC has grandfathered this, but I think it is discouraged/forbidden for new construction. In a dryer that is designed to work on either 3 wire or 4 wire, neutral and ground are bonded in the dryer when using 3 wire. Otherwise they are isolated.

I know that 5mA is the nominal trip level required for GFCI's to meet code, and that they are allowed 1mA tolerance on the high side - must trip at 6mA, or the unit doesn't meet code. I haven't really looked at trip time specs, so I need to do that.

In a three wire 240V application, the third wire is always ground. The GFCI works by measuring the currents flowing in the current carrying wires (line 1, line2, and neutral - if present.) If the current in one direction is different than the current in the other direction, then there is a current leak somewhere, and the GFCI trips. The "Test" button on the GFCI works by shorting one of the hot wires to ground or neutral thru a resistor that will give 6mA of current. This short current bypasses the current sensor in the GFCI, thus creating the current imbalance the GFCI is looking for. In a three wire system, the test button shunts some current to ground. In a four wire system, I believe the standard for the test button to shunt to neutral, but either ground or neutral will work.

Brew on :mug:
OK, thanks again for the clear explanation. I'd be interested in what your research reveals regarding the trip times.

Cheers doug,
 

Bobby_M

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This is the absolute cheapest way to do it. Sometimes dryers will make GFCI trip so it's better to add the GFCI protection inline after the dryer outlet. I was able to fit this breaker into a Carlon 4x4x2" plastic junction box by cutting a square hole in the cover. You'll send your 3 wire cable through here.. Leave the ground uncut and passing through, then the two hots go through the breaker. It also gives you a way to positively shut down the power, which the BrewCommander does not have.

 

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