Generator Watt Meters?

[larry4406]

We have endless discussions on generators - most centered on how and how not to connect them to the house. This is not the question here.

Anyone install watt meters to monitor the loads on the legs of their 240V generators?

I have been looking at the Reliance MB125. It uses current transformers (CT's) on Line 1 and Line 2 from the generator to monitor the load on each leg.
http://www.nooutage.com/mb125.htm

I have a 7500W Generac (13.5W surge).

This reviewer states that the CT's are not large enough to fit his generator wire (he used 2-2-2-4) so he had to swap out the CT's.

I was planning on using MHF (4-wire feed) for my setup so I am thinking I will likely have the same problem. I have not sized the wire yet but the total conduit path length will be somewhere in the range of 90-120' (portable generator will be outside on a pad, under an enclosure, 30' or so away from the house).

Am I better off just buying loose CT's sized to the wire I use and loose meters? Any thoughts on how to do this short of buying the Reliance MB125 and then likely having to replace the CT's?

 

[m32825]

Look at this and related products, may open up new options: Power monitor

 

[rlitman]

FYI, while split CTs can be stuck on live wires without disconnecting them, non-split versions are much more accurate.

 

[larry4406]

FYI, while split CTs can be stuck on live wires without disconnecting them, non-split versions are much more accurate.

Thanks for this info. Mine would be a new install so easy to feed conductors thru a non-split CT.

 

[larry4406]

Look at this and related products, may open up new options: Power monitor

Thanks for the link I will follow it.

 

[rlitman]

Yep, and you'll safe a few bucks that way too.

 

[Ole Slewfoot]

Real equipment uses Amp meters.

 

[couch67]

Larry I have always wanted to ask - are those 3D beer goggles?

 

[alfredeneuman]

Real equipment uses Amp meters.

A current transformer (CT) is part of an ammeter.

 

[mm08822]

Look at this and related products, may open up new options: Power monitor

Would need to select a product with 2 ct's for a 3-wire ckt - 120/240v.

 

[mm08822]

We have endless discussions on generators - most centered on how and how not to connect them to the house. This is not the question here.

Anyone install watt meters to monitor the loads on the legs of their 240V generators?

I have been looking at the Reliance MB125. It uses current transformers (CT's) on Line 1 and Line 2 from the generator to monitor the load on each leg.
http://www.nooutage.com/mb125.htm

I have a 7500W Generac (13.5W surge).

This reviewer states that the CT's are not large enough to fit his generator wire (he used 2-2-2-4) so he had to swap out the CT's.

I was planning on using MHF (4-wire feed) for my setup so I am thinking I will likely have the same problem. I have not sized the wire yet but the total conduit path length will be somewhere in the range of 90-120' (portable generator will be outside on a pad, under an enclosure, 30' or so away from the house).

Am I better off just buying loose CT's sized to the wire I use and loose meters? Any thoughts on how to do this short of buying the Reliance MB125 and then likely having to replace the CT's?

If you want to build your own, I would proceed as follows:

2 – 50 Amp ct’s (0-5 amp output), solid core, .5” id
2 – 50 Amp meters (0-5 amp input)
Why 50’s ? Handle start-up surges w/o constantly ******* meter

Run the power leads from generator input circuit straight into distribution panel.

Use a 6” x 6” x 4” pvc surface mounted box to house meters if panel is surface mounted
Otherwise use 2 old work boxes with 2 gang blank cover – mount meters in cover if panel is flush mounted
Run the 4 ct wires into the distribution panel.
Solid core ct’s each passed over L1/L2 conductors in distribution panel

Maybe you can find a digital version of this for 120/240 3-wire ckt, but the above method is simple and been around for decades.

 

[mike93lx]

My Reliance panel has meters built in. It's been helpful for balancing loads and really understanding how much generator i actually need.

 

[larry4406]

My Reliance panel has meters built in. It's been helpful for balancing loads and really understanding how much generator i actually need.

Looking at the Reliance brand panels is what peaked my interest and that is when I found their panel that I linked to. Your experience with balancing the loads is what I would like to be able to do.

 

[larry4406]

If you want to build your own, I would proceed as follows:

2 – 50 Amp ct’s (0-5 amp output), solid core, .5” id
2 – 50 Amp meters (0-5 amp input)
Why 50’s ? Handle start-up surges w/o constantly ******* meter

Run the power leads from generator input circuit straight into distribution panel.

Use a 6” x 6” x 4” pvc surface mounted box to house meters if panel is surface mounted
Otherwise use 2 old work boxes with 2 gang blank cover – mount meters in cover if panel is flush mounted
Run the 4 ct wires into the distribution panel.
Solid core ct’s each passed over L1/L2 conductors in distribution panel

Maybe you can find a digital version of this for 120/240 3-wire ckt, but the above method is simple and been around for decades.

Any links to the parts you suggest? Googling this my head hurts - rabbit hole of resisters across legs of CT's, etc.

Example:
https://www.amazon.com/dp/B005CWO20A/?tag=atomicindus08-20
https://www.amazon.com/dp/B005CWO20A/?tag=atomicindus08-20

 

[alfredeneuman]

An important thing to remember when working with CTs is never run current through the CT window when not connected to a meter or the leads shorted together (shunted).
It can subject the CT to a voltage extreme which is likely to ruin the CT

 

[mm08822]

Any links to the parts you suggest? Googling this my head hurts - rabbit hole of resisters across legs of CT's, etc.

Example:
https://www.amazon.com/dp/B005CWO20A/?tag=atomicindus08-20
https://www.amazon.com/dp/B005CWO20A/?tag=atomicindus08-20

The ct’s I’m talking about have a 5 amp secondary output at full scale. You’ll see specs like 50:5, 0-5/0-50A etc.

The meters I recommended have a full scale deflection at 5 amps with a scale of 0-50A.

Hoyt meter https://www.alliedelec.com/hoyt-electrical-instrument-works-st-70u-5aac-50aac/70232997/

Shurite Meter https://www.alliedelec.com/shurite-8503z-50/70136642
Shurite cut sheet https://www.alliedelec.com/m/d/9d0e739e5daecea779ba4e673fa38349.pdf
https://www.amazon.com/dp/B011ON9O6C/?tag=atomicindus08-20

Other meters of this type start to get pricey very quickly. Options are limited in the low $ range.

50:5 ct CR2RL-500 $16.00
http://www.crmagnetics.com/commercial-current-transformers/wire-lead/current-output/solid-core/cr2
https://www.amazon.com/dp/B005CWHXO2/?tag=atomicindus08-20

If you go this route, make sure the ct output circuits are never opened/left open when the conductors in the ct window are energized. Short the ct output if needed.

A pricier option can be found back at your original site. http://www.nooutage.com/ngv25.htm
This looks to be a cobbled set-up of components, but all the development work is done for you. Not sure which components are listed.
I like that multi-function meter used, but couldn’t find it anywhere else on the net.

There is plenty of ~$20 systems on Amazon from Drok and others. However, nothing shows and type of ETL or other certifications. Not sure I trust those.

You may also want to consider getting rid of the mhf and sizing the wire smaller to accommodate the supplied ct's.

 

[larry4406]

The ct’s I’m talking about have a 5 amp secondary output at full scale. You’ll see specs like 50:5, 0-5/0-50A etc.

The meters I recommended have a full scale deflection at 5 amps with a scale of 0-50A.

Hoyt meter https://www.alliedelec.com/hoyt-electrical-instrument-works-st-70u-5aac-50aac/70232997/

Shurite Meter https://www.alliedelec.com/shurite-8503z-50/70136642
Shurite cut sheet https://www.alliedelec.com/m/d/9d0e739e5daecea779ba4e673fa38349.pdf
https://www.amazon.com/dp/B011ON9O6C/?tag=atomicindus08-20

Other meters of this type start to get pricey very quickly. Options are limited in the low $ range.

50:5 ct CR2RL-500 $16.00
http://www.crmagnetics.com/commercial-current-transformers/wire-lead/current-output/solid-core/cr2
https://www.amazon.com/dp/B005CWHXO2/?tag=atomicindus08-20

If you go this route, make sure the ct output circuits are never opened/left open when the conductors in the ct window are energized. Short the ct output if needed.

A pricier option can be found back at your original site. http://www.nooutage.com/ngv25.htm
This looks to be a cobbled set-up of components, but all the development work is done for you. Not sure which components are listed.
I like that multi-function meter used, but couldn’t find it anywhere else on the net.

There is plenty of ~$20 systems on Amazon from Drok and others. However, nothing shows and type of ETL or other certifications. Not sure I trust those.

You may also want to consider getting rid of the mhf and sizing the wire smaller to accommodate the supplied ct's.

mm08822 - thanks for the reply! Lots of good info here. I also saw the $20 systems on Amazon and thought them to be sketchy.

The pricier NGV25-SW unit you linked to http://www.nooutage.com/ngv25.htm shows red and black connections with in-line fuses to the wires from the generator in addition to the CT's. I assume this is for measuring the voltage between the two legs. How would these be connected?
http://www.nooutage.com/images/NGV25-SW-conn.gif

I will look into using wire other than MHF to accommodate smaller CT's as you suggest. This whole generator project is part of running wire to my barn. I will have an intermediate pull point in the yard (110' conduit path from house panel) and then another 140' to the barn.

I want to build a generator shed at this intermediate pull point and place my portable Generac 7500W unit there. Dig up the yard once, conduit for power to the barn, conduit for generator feed to house, outlet for battery trickle charger, conduits for communications, etc.

I want to have the watt meters in the attached garage adjacent the electric panel where the generator connects. It would also be nice to have a remote start button, remote shutoff, choke on/off, fuel on/off, etc all from the comfort of my being in the attached garage at the panel. Thus my other thread regarding generator sheds https://www.garagejournal.com/forum/showthread.php?p=7558134

 

[mike93lx]

mm08822 - thanks for the reply! Lots of good info here. I also saw the $20 systems on Amazon and thought them to be sketchy.

The pricier NGV25-SW unit you linked to http://www.nooutage.com/ngv25.htm shows red and black connections with in-line fuses to the wires from the generator in addition to the CT's. I assume this is for measuring the voltage between the two legs. How would these be connected?
http://www.nooutage.com/images/NGV25-SW-conn.gif

I will look into using wire other than MHF to accommodate smaller CT's as you suggest. This whole generator project is part of running wire to my barn. I will have an intermediate pull point in the yard (110' conduit path from house panel) and then another 140' to the barn.

I want to build a generator shed at this intermediate pull point and place my portable Generac 7500W unit there. Dig up the yard once, conduit for power to the barn, conduit for generator feed to house, outlet for battery trickle charger, conduits for communications, etc.

I want to have the watt meters in the attached garage adjacent the electric panel where the generator connects. It would also be nice to have a remote start button, remote shutoff, choke on/off, fuel on/off, etc all from the comfort of my being in the attached garage at the panel. Thus my other thread regarding generator sheds https://www.garagejournal.com/forum/showthread.php?p=7558134

my ridgid generator has a panel that can be remotely located. It allows you to start and stop, see run time, power consumption and has a couple 120v plugs. The connector for the controls and start/stop is a 4-pin flat trailer and 120V is carried by a cord with a L14-20 twist lock. kind of a neat setup, although I've never needed it.

 

[mbear]

Do you need continuous real time monitoring are could you just use a clamp on ammeter to check things out once your up and running ?

 

[larry4406]

Do you need continuous real time monitoring are could you just use a clamp on ammeter to check things out once your up and running ?

I want permanent meters in place. Generator panel interlock kit/backfeed setup is where I am heading thus I want to be wise in which breakers I enable.

 

[mm08822]

mm08822 - thanks for the reply! Lots of good info here. I also saw the $20 systems on Amazon and thought them to be sketchy.

The pricier NGV25-SW unit you linked to http://www.nooutage.com/ngv25.htm shows red and black connections with in-line fuses to the wires from the generator in addition to the CT's. I assume this is for measuring the voltage between the two legs. How would these be connected?
http://www.nooutage.com/images/NGV25-SW-conn.gif

I will look into using wire other than MHF to accommodate smaller CT's as you suggest. This whole generator project is part of running wire to my barn. I will have an intermediate pull point in the yard (110' conduit path from house panel) and then another 140' to the barn.

I want to build a generator shed at this intermediate pull point and place my portable Generac 7500W unit there. Dig up the yard once, conduit for power to the barn, conduit for generator feed to house, outlet for battery trickle charger, conduits for communications, etc.

I want to have the watt meters in the attached garage adjacent the electric panel where the generator connects. It would also be nice to have a remote start button, remote shutoff, choke on/off, fuel on/off, etc all from the comfort of my being in the attached garage at the panel. Thus my other thread regarding generator sheds https://www.garagejournal.com/forum/showthread.php?p=7558134

The NGV25-SW schematic shows a dedicated 2p cb supplying voltage to it. Then fuses in series with the cb. I would not waste 2 spaces in a panel for that, but rather tap an existing 2 pole circuit that would be running while on the generator. (Could even tap a 2p cb used for a surge protector.)
The schematic also is missing a neutral connection. Not sure how you can measure L1 or L2 separately w/o a neutral connection. That raises another q. Exactly what is happening when “Both” is selected? Not enough info to tell if this meter is measuring 2 separate voltages and their respective currents and the meter is correctly calculating the wattage in total drawn from the generator or the switch is just switching voltage sources and ct’s in/out of a single meter input. If the latter, then there is some error. Having the meter cut sheets would help to understand capabilities. Having the schematic would also help.

Nooutage is in northern va. You may want to call them if you have any interest in pursuing their mousetrap. If close enough – maybe go visit and get a live demo. Bring your clamp-on to verify.

 

[m32825]

Are your meters going to be right next to your breaker panel?

 

[larry4406]

Are your meters going to be right next to your breaker panel?

Yes. One stud bay over.

 

[m32825]

Yes. One stud bay over.

That will be nice. You can flip breakers and quickly see the load. My main panel is outside and everything else is off subpanels. I would need something that talks to an app on my phone.

When I first got my generator I obsessed over all the loads, but after a bit of time with a couple clamp meters I was able to figure out what combinations would work.

I don't need real-time metering but that doesn't keep me from wanting it!

 

[larry4406]

That will be nice. You can flip breakers and quickly see the load. My main panel is outside and everything else is off subpanels. I would need something that talks to an app on my phone.

When I first got my generator I obsessed over all the loads, but after a bit of time with a couple clamp meters I was able to figure out what combinations would work.

I don't need real-time metering but that doesn't keep me from wanting it!

Yeah I figure that adding the meters is a relatively small effort compared to the conduits and wire for the barn and generator pad. Been using the generator for several years without meters but would like to do a better job. Placing the meters adjacent the panel seems like the most logical choice for instant monitoring.

From the several posts here, it looks like I will really be monitoring amps/leg vs watts/leg but will still be able to balance/monitor the loads which is the objective. This seems to be the simplest approach.

The meter and CT options mm08822 posted/linked seem straightforward.

Do some of you folks also monitor voltage? I don't want to over complicate this too much. As mm08822 pointed out the voltmeter would need to connect to a dual circuit breaker that is generator feed.

Looking more at the NGV25-SW option it appears that you monitor one leg at a time and would need to constantly flip the switch back and forth to monitor the legs. This seams like a PIA and having dual meters side by side seams much easier. Also trying to make this somewhat "wife friendly" without going down the automatic whole house generator path.