Placement of CT [donut ] on 50 AMP panel

[Esmitee]

I didn't want to hijack Mike's thread anymore so I moved the discussion here.
It's started from this post.
https://www.homebrewtalk.com/forum/...-herms-240v-30-amp.622007/page-4#post-8213099

OK, here's the drawing. It's a (not unrealistic) representation of current flow in a50A control panel. I left out all of the switches, contactors, PID's, lights, etc. The arrows show current flow direction during 1/2 of the AC cycle. During the other 1/2 of the cycle current flow is in the opposite direction.

• The wire segment with 48A is part of 4 loops
• The wire segment with 47A is part of 3 loops
• The wire segments with 46A are part of 2 loops
• The wire segments with 23A are part of 1 loop
• The wire segment with 2A is part of 2 loops
• The wire segments with 1A are part of 1 loop

If you put the input black and red wires thru the current detection coil, you would measure 2A. If you put the input black, red and white wires thru the coil, you would measure zero amps, and in fact, this is exactly what is done inside your 240V GFCI circuit breaker.

Ok Doug, so if I interpret your diagram correctly. I should place the CT on my RED hot line before my main contactor because I have the most "loops" on this side.
I'll explain how my power is distributed in the picture.

# 1 is a 6 AMP breaker supplying power to the door. Pids, switches, key switch and lights.On the RED Leg

# 2 is a 5 AMP fuse supplying tower to pump # 1. On the RED leg

# 3 is a 5 AMP fuse supplying power to just the case fan and the AMP/VOLT meter. On the BLACK leg

# 4 is a 5 AMP fuse supplying power to pump #2. On the BLACK leg

So I guess I should put the CT on the RED LEG because the RED LEG would have the most loops?

I'm guessing, the way I have the power separated like this, and putting the CT on the RED LEG, the V/A meter will not read the power on the BLACK leg?

 

[MintonHVAC]

I didn't want to hijack Mike's thread anymore so I moved the discussion here.
It's started from this post.
https://www.homebrewtalk.com/forum/...-herms-240v-30-amp.622007/page-4#post-8213099

OK, here's the drawing. It's a (not unrealistic) representation of current flow in a50A control panel. I left out all of the switches, contactors, PID's, lights, etc. The arrows show current flow direction during 1/2 of the AC cycle. During the other 1/2 of the cycle current flow is in the opposite direction.

• The wire segment with 48A is part of 4 loops
• The wire segment with 47A is part of 3 loops
• The wire segments with 46A are part of 2 loops
• The wire segments with 23A are part of 1 loop
• The wire segment with 2A is part of 2 loops
• The wire segments with 1A are part of 1 loop

If you put the input black and red wires thru the current detection coil, you would measure 2A. If you put the input black, red and white wires thru the coil, you would measure zero amps, and in fact, this is exactly what is done inside your 240V GFCI circuit breaker.

Ok Doug, so if I interpret your diagram correctly. I should place the CT on my RED hot line before my main contactor because I have the most "loops" on this side.
I'll explain how my power is distributed in the picture.
View attachment 556548
# 1 is a 6 AMP breaker supplying power to the door. Pids, switches, key switch and lights.On the RED Leg

# 2 is a 5 AMP fuse supplying tower to pump # 1. On the RED leg

# 3 is a 5 AMP fuse supplying power to just the case fan and the AMP/VOLT meter. On the BLACK leg

# 4 is a 5 AMP fuse supplying power to pump #2. On the BLACK leg

So I guess I should put the CT on the RED LEG because the RED LEG would have the most loops?

I'm guessing, the way I have the power separated like this, and putting the CT on the RED LEG, the V/A meter will not read the power on the BLACK leg?View attachment 556548

So by hooking up your current Transformer the way you have it will not read 240 volt loads.

And will only partially read 120 volt loads if you're 120 power is coming from one leg.

If you pull 120 from L1 and L2 it will cancel each other out.

The best way is to only Pull 120 from one leg and put the CT only on that leg.

It will still read your 240 vac loads and your 120 vac loads.

The way you currently have the current Transformer on both L1 and L2, the phases cross each other 180 degrees and cancel the signal.

Hope that helps.

 

[doug293cz]

@MintonHVAC has it exactly correct. In your case it doesn't matter much whether you choose the black or red leg. Either way you can only read the current to one pump. The total of all the other loads in you panel is probably less than 1A.

Brew on

 

[Esmitee]

So by hooking up your current Transformer the way you have it will not read 240 volt loads.

And will only partially read 120 volt loads if you're 120 power is coming from one leg.

If you pull 120 from L1 and L2 it will cancel each other out.

The best way is to only Pull 120 from one leg and put the CT only on that leg.

It will still read your 240 vac loads and your 120 vac loads.

The way you currently have the current Transformer on both L1 and L2, the phases cross each other 180 degrees and cancel the signal.

Hope that helps.

Thanks Minton, yes, it helps.
Yes I found out on the other thread, that the CT won't work as pictured.
I'm going to move it to ONLY have the RED cable go through it.
By doing that, your saying it will only read the 120v circuits (and 240v) connected to the the RED leg, and will not read the BLACK leg 120v circuits, Or will it?

Or should I rewire all the 120v circuits to the RED LEG and then all of the 120 circuits will be read?

 

[doug293cz]

Yes, if you put the coil on the red hot feed, you will not measure any of the 120V load current flowing in the black hot feed. Yes, if you rewire all of the black 120V loads to the red hot bus, then you can read the total current in your panel when the coil is on the red hot feed. All 240V load current flows in both the red and black hot feeds, so all 240V load current will be measured with the coil on either feed wire.

Brew on

 

[Esmitee]

Yes, if you put the coil on the red hot feed, you will not measure any of the 120V load current flowing in the black hot feed. Yes, if you rewire all of the black 120V loads to the red hot bus, then you can read the total current in your panel when the coil is on the red hot feed. All 240V load current flows in both the red and black hot feeds, so all 240V load current will be measured with the coil on either feed wire.

Brew on

Thanks Doug, I really appreciate how you take Your time to make others really understand!
All I have to do to fire up my panel now, is wire my spa panel to my house main panel, and I should be ready to go. But before I do that, I'm going to move pump # 2, to share pump # 1 fuse, so all 120v will be on the RED leg, except # 3, the case fan and volt meter. That draws nothing.
When I 1st use and test my panel, I want to be able to view all of the power consumption and amps being actually used when I turn on both 5500w elements and both pumps to see in reality what it is.
Perhaps after a brew or 2, I may change the CT to the BLACK leg and just monitor the 220v for the elements.
Although it really doesn't matter , I guess I should have used the BLACK leg for my 120v circuits, as that would have been the proper way that you would see in electrical diagrams.

 

[doug293cz]

...
Although it really doesn't matter , I guess I should have used the BLACK leg for my 120v circuits, as that would have been the proper way that you would see in electrical diagrams.

Actually the best practices way is trying to balance the 120V loads between the two hot feeds, just as you originally did. But, that makes it difficult to measure the total current flow. If measuring total current is important to you, then placing all of the 120V loads on one hot feed is acceptable.

Two pumps on one fuse may require larger than a 5A fuse. A typical chugger is rated at 1.4A, but the starting current surge is higher. You may find you need to use a 10A fuse for two pumps. If you used 16AWG wire or larger for the pump wiring, then a 10A fuse is acceptable.

Brew on

 

[Esmitee]

Actually Doug, that was my intention and also the way I used those lugs to distribute the power, made the most sense to me. I never gave any thought to the CT placement, because as you seen, I thought both wires would go thru. Lol

Actually those 3 fuse holders have 10 amp ceramic fuses in them. I got them from a solar panel installation that we removed. I also got a lot of wire from that job and I used 12 gauge wire for allmost all the 120v wiring,because I had it and didn't have to buy any, so I should be okay.

 

[augiedoggy]

I am probably wrong here but I see the wire terminals you have bolted to the main backer plate but I dont see the screws and bolts that hold them in place isolated from the backer plate? are those screws and bolts only screwed into the blocks which im assuming are some sort of nylon insulation blocks? it just looks kind of scary having those big hot terminal blocks sticking up in the panel with 240v going through them.. I realize if you dont open the panel while its hot its not a big concern but if anything came loose in there, I would be concerned the odds of something conductive coming in contact with them would be much higher than a normal insulation where the terminal block hot points are recessed or covered behind insulation of some form.

 

[Esmitee]

I am probably wrong here but I see the wire terminals you have bolted to the main backer plate but I dont see the screws and bolts that hold them in place isolated from the backer plate? are those screws and bolts only screwed into the blocks which im assuming are some sort of nylon insulation blocks? it just looks kind of scary having those big hot terminal blocks sticking up in the panel with 240v going through them.. I realize if you dont open the panel while its hot its not a big concern but if anything came loose in there, I would be concerned the odds of something conductive coming in contact with them would be much higher than a normal insulation where the terminal block hot points are recessed or covered behind insulation of some form.

Hey Augie, Indeed it looks very scary.... as is, But it"s really not.
The 2 lugs sit on 1 1/2" thick PVC, it's 2 pieces of 3/4" . The piece that touches the enclosure, is screwed in from the back of the box with (6) 5/8" screws, the top piece of 3/4" is screwed down into the 1st layer with 1 1/4" screws that are offset from the bottom screws. The lag bolts that fasten the lugs only penetrate the PVC 1". BTW, PVC is an excellent electrical insulator , and something like 320 F melting point. I googled it.

As far as the lugs being exposed like they are, I agree with you. As you state, an accident of any kind could happen. I do think at some time, maybe for testing, I would have the door open and the panel energized. That red lug is about a 1/2" away from the side of the enclosure, I was concerned about that too.

Not in the picture, I have a 1/4" thick clear Plexi shield in the shape of an upside down "L". It goes up the side of the box and over the lugs. I don't want to FRY!

Thanks for writing a post about it, because, others may just think it"s not a valid safety concern looking at the picture and think it"s acceptable without a protective shield!

 

[Esmitee]

Does anyone know what terminals #1, #2, and #8 are for on the Auber Dspr 120? 1 and 2 for an alarm? Nothing said about them in the manual that comes with it? They must be for something.

 

[doug293cz]

Does anyone know what terminals #1, #2, and #8 are for on the Auber Dspr 120? 1 and 2 for an alarm? Nothing said about them in the manual that comes with it? They must be for something.

Terminals 1, 2, 8, 13 & 14 don't connect to anything on the DSPR120. There is no external alarm output on the DSPR120.

Brew on

 

[ajdelange]

Forgive me if this is already buried in the words, photos or diagrams but the way to sense the entire current drawn by the system is to cross the two hots and place the doughnut over the cross. Orienting the doughnut verticallay (with the axis of its hole horizontal) and assuming L1 comes in at the top left of the picture and L2 at the top right, route the L1 lead through the doughnut from left to right and the L2 conductor through the doughnut from right to left. If you draw this and then trace the currents you will see that the doughnut will sense the sum of the L1 and L2 currents irrespective of whether they are common mode (L1-L2) or differential (L1-N, L2-N). Multiply the current (phase - amperes) indicated by 120V to determine total power consumed.

 

[doug293cz]

Forgive me if this is already buried in the words, photos or diagrams but the way to sense the entire current drawn by the system is to cross the two hots and place the doughnut over the cross. Orienting the doughnut verticallay (with the axis of its hole horizontal) and assuming L1 comes in at the top left of the picture and L2 at the top right, route the L1 lead through the doughnut from left to right and the L2 conductor through the doughnut from right to left. If you draw this and then trace the currents you will see that the doughnut will sense the sum of the L1 and L2 currents irrespective of whether they are common mode (L1-L2) or differential (L1-N, L2-N). Multiply the current (phase - amperes) indicated by 120V to determine total power consumed.

It's partially addressed in this post from the thread that spawned this thread. However, that post doesn't cover the part about multiplying the sum of L1 & L2 currents by 120 to get total power usage. I guess it depends on whether you want to look at current or power, since the sum of currents method will over report current.

Brew on

 

[ajdelange]

I don't see how it over reports currents unless he doesn't want to see pump etc. current in which case he could run the neutrals back through the doughnut in the directions opposite to those of the phases which supply the 120 V circuits.

 

[doug293cz]

I don't see how it over reports currents unless he doesn't want to see pump etc. current in which case he could run the neutrals back through the doughnut in the directions opposite to those of the phases which supply the 120 V circuits.

Let's look at the simple case of a single 240V/5500W element with no switches or other components. There will be 22.9A flowing in L1, 22.9A flowing thru the element, and 22.9A flowing in L2. With the sense coil around either L1 or L2, but not both, the meter will read 22.9A, which is the current flowing thru the element. If L1 and L2 go thru the coil in the "same" direction, then the meter will read 0A, even though the current in the element (and L1 and L2) is 22.9A. If L1 and L2 both go thru the coil but in "opposite" directions, the meter will read 45.8A, even though the current in all segments of the loop is only 22.9A. That is over reporting current.

It turns out (as you noted) that if you do power calculations that assign half the voltage drop to L1 and half to L2, then the power comes out correct with the wires going thru the coil in opposite directions, since 120V * 45.8A = 240V * 22.9A = 5500W. But, the current in the loop is still 22.9A. So, it's a question of what do you want to measure, current or power? Someone who doesn't have a full understanding of this could easily get concerned that 45.8A on their 30A breaker was a big problem.

Brew on

 

[Esmitee]

Terminals 1, 2, 8, 13 & 14 don't connect to anything on the DSPR120. There is no external alarm output on the DSPR120.

Brew on

ahh, woulda been nice to tie an alarm to it, you would think Auber would have provided 1 simple alarm output. I'm never going to hear that cheesy internal alarm or see that micro flashing light!

 

[Esmitee]

Guys, your above conversation is well above and beyond my scope of electrical knowledge.
All I know is I moved the CT to the red leg, and I moved 1 wire to the red side. the meter appears to be working correctly!

 

[doug293cz]

ahh, woulda been nice to tie an alarm to it, you would think Auber would have provided 1 simple alarm output. I'm never going to hear that cheesy internal alarm or see that micro flashing light!

That's the difference between models. The DSPR300 is the same as the DSPR120, but with external alarm relays. The DSPR310 adds programmable mash steps and more timer functions. The user is responsible for understanding the different models, and purchasing the one that meets their needs. Check with Auber, they might allow you to do a trade (plus the price delta and some handling charges), or you could sell the 120 and buy either a 300 or 310.

Brew on

 

[doug293cz]

Guys, your above conversation is well above and beyond my scope of electrical knowledge.
All I know is I moved the CT to the red leg, and I moved 1 wire to the red side. the meter appears to be working correctly!

That will work for you. Don't worry about the angels dancing on pin-heads.

Brew on

 

[Esmitee]

That's the difference between models. The DSPR300 is the same as the DSPR120, but with external alarm relays. The DSPR310 adds programmable mash steps and more timer functions. The user is responsible for understanding the different models, and purchasing the one that meets their needs. Check with Auber, they might allow you to do a trade (plus the price delta and some handling charges), or you could sell the 120 and buy either a 300 or 310.

Brew on

I knew the 300 had a bunch of extra stuff on it, I'll get by without the alarm output, but come on, a cheapo Rex c100 has an alarm

 

[doug293cz]

I knew the 300 had a bunch of extra stuff on it, I'll get by without the alarm output, but come on, a cheapo Rex c100 has an alarm

Personally I would rather have the elegant operational modes of the DSPR120 than a simple PID like the c100, even with its alarms.

Brew on

 

[ajdelange]

So, it's a question of what do you want to measure, current or power?

When this configuration is used (popular in stand by generators where the manufacturer is to cheap to spring for a 2nd CT) the desire is to measure phase-amperes which, given that the phase-N voltages are known, gives total power.

Someone who doesn't have a full understanding of this could easily get concerned that 45.8A on their 30A breaker was a big problem.

Such a breaker is labeled 30 30 so it should be pretty obvious that its nominal capacity is 60 phase-amps. That's how you would count it in sizing a service. In any case, while I see what you are concerned about, it is my opinion that anyone incapable of understanding electricity to this level should not have his hands in electrical panels.

 

[Esmitee]

Personally I would rather have the elegant operational modes of the DSPR120 than a simple PID like the c100, even with its alarms.

Brew on

Yes Indeed! I got the 120, mainly for "Ease of USE". It is very easy to use and fits my needs perfectly!

 

[Esmitee]

I am probably wrong here but I see the wire terminals you have bolted to the main backer plate but I dont see the screws and bolts that hold them in place isolated from the backer plate? are those screws and bolts only screwed into the blocks which im assuming are some sort of nylon insulation blocks? it just looks kind of scary having those big hot terminal blocks sticking up in the panel with 240v going through them.. I realize if you dont open the panel while its hot its not a big concern but if anything came loose in there, I would be concerned the odds of something conductive coming in contact with them would be much higher than a normal insulation where the terminal block hot points are recessed or covered behind insulation of some form.

Hey Augie, Indeed it looks very scary.... as is, But it"s really not.
The 2 lugs sit on 1 1/2" thick PVC, it's 2 pieces of 3/4" . The piece that touches the enclosure, is screwed in from the back of the box with (6) 5/8" screws, the top piece of 3/4" is screwed down into the 1st layer with 1 1/4" screws that are offset from the bottom screws. The lag bolts that fasten the lugs only penetrate the PVC 1". BTW, PVC is an excellent electrical insulator , and something like 320 F melting point. I googled it.

As far as the lugs being exposed like they are, I agree with you. As you state, an accident of any kind could happen. I do think at some time, maybe for testing, I would have the door open and the panel energized. That red lug is about a 1/2" away from the side of the enclosure, I was concerned about that too.

Not in the picture, I have a 1/4" thick clear Plexi shield in the shape of an upside down "L". It goes up the side of the box and over the lugs. I don't want to FRY!

Thanks for writing a post about it, because, others may just think it"s not a valid safety concern looking at the picture and think it"s acceptable without a protective shield!

View attachment 564374
I had to show this pic of the clear protection cover, that protects the main incoming power lugs.