ADDING 25KW SINGLE PHASE TRANSFORMER TO MEP-005A

[msgjd]

it sounds like a 3 phase panel might be the best way to balance out the load between the legs. I think the lightbulb came on. that gives me 120 and 240 balancing using the 3 phase. again thank all of you .

that absolutely will give you that as well as better control of the loads and properly protect your branch-circuit conductors from overcurrent

as others have said, the actual voltage between phases is 208V but most 240V 1-phase equipment has no issue running on that other than an increase in amperage proportionate to the HP or wattage .. With what you indicate you're running, it would be a minimal increase

 

[edemoss]

that absolutely will give you that as well as better control of the loads and properly protect your branch-circuit conductors from overcurrent

as others have said, the actual voltage between phases is 208V but most 240V 1-phase equipment has no issue running on that other than an increase in amperage proportionate to the HP or wattage .. With what you indicate you're running, it would be a minimal increase

would i adjust the rheostat to 208v or 240v or somewhere in the middle i am assuming 208 but just checking

 

[DieselAddict]

It’s best to keep it near 208v since the 120v side will also increase if you push the voltage up.

 

[Scoobyshep]

would i adjust the rheostat to 208v or 240v or somewhere in the middle i am assuming 208 but just checking

208 is the target. Increasing it will increase the leg to neutral voltage as well.

If you have nothing using the neutral (120v devices) increasing the voltage won't cause too much trouble. There is a limit to how far you can push it before it'll trip the over voltage shut down.


Depending on the load devices you can increase the voltage slightly, I personally wouldn't go above 130 phase to ground.

Do not rely on the set gauges. Use a digital multimeter.

 

[KN6KXR]

I work in this field. Lots of experience and training and such. Here are my thoughts for what they are worth:
-All the facilities I work in are 3-phase 480 and 208. There is no "split phase" like residential where the waves are 180 apart. it's all balanced three phase with the waves 120 apart. We run PLENTY of 240 stuff on 208 and there are never any issues. Every once in awhile some lab folks doing a test where they just HAVE to simulate 240 and we provide a xformer for them. Otherwise you won't have problems. As noted it'll draw a little more amperage for the same output but more likely the devices just won't perform to the full nameplate spec. As noted balance the loads.
-Bonding of neutral and ground is required at the service entrance and prohibited elsewhere. The intent is to drive all current back to the main breaker and prevent alternate paths. This will be factory OEM at your service entrance. Unless you have an ATS that breaks the neutral, like in a separately derived system, do NOT bond the ground and neutral at the generator as this will introduce such a point (that would allow objectionable currents). Most generators are a "floating neutral" from the factory for this reason. The exception is a stand alone system for the field such as a MEP or other portable generator where it is the service so you bond them then. When hooking to an established distribution system, where the ground and neutral are already bonded at the main, do NOT connect them at the genset but DO drive a spike/rod/UFER and ground the genset in accordance with NEC or local code (some places around me require TWO 8 foot rods spaced 10 feet apart). If it's stand alone then do the spikes and such and DO bond the neutral to the ground. And BTW ground always "makes first and breaks last" make it your motto it might save your butt someday....
-Every once in awhile somebody says that running two of the three legs of a 3 phase genset is bad for it. So far I have never seen any proof of this. Theoretically there is no reason for this to be possible. Certainly it's INEFFICIENT but there is no risk of damage. As proof of this I would point out all the totally unbalanced three phase systems out there. I don't see a bunch of transformers blowing up and I have definitely seen some lopsided stuff so.... Not an issue. Waste of money? You bet. Overloaded legs? Yep. Nuisance trips? Sure. But damage to the generators or transformers no.

It's not a simple thing. Takes not only time to understand this but a bit of a knack for it. Not everyone is cut out for it. At the same time please don't ask me to drywall, paint or roof anything. I suck at those.

Ask questions, get advice, consult manuals. Get an Ugly's reference and keep it handy. If most of the "electricians" I knew would read that little book (and have a little humility) things would go much smoother out there. Then again maybe I should be careful what I wish for I make a decent living cleaning up those messes!

 

[Scoobyshep]

I work in this field. Lots of experience and training and such. Here are my thoughts for what they are worth:
-All the facilities I work in are 3-phase 480 and 208. There is no "split phase" like residential where the waves are 180 apart. it's all balanced three phase with the waves 120 apart. We run PLENTY of 240 stuff on 208 and there are never any issues. Every once in awhile some lab folks doing a test where they just HAVE to simulate 240 and we provide a xformer for them. Otherwise you won't have problems. As noted it'll draw a little more amperage for the same output but more likely the devices just won't perform to the full nameplate spec. As noted balance the loads.
-Bonding of neutral and ground is required at the service entrance and prohibited elsewhere. The intent is to drive all current back to the main breaker and prevent alternate paths. This will be factory OEM at your service entrance. Unless you have an ATS that breaks the neutral, like in a separately derived system, do NOT bond the ground and neutral at the generator as this will introduce such a point (that would allow objectionable currents). Most generators are a "floating neutral" from the factory for this reason. The exception is a stand alone system for the field such as a MEP or other portable generator where it is the service so you bond them then. When hooking to an established distribution system, where the ground and neutral are already bonded at the main, do NOT connect them at the genset but DO drive a spike/rod/UFER and ground the genset in accordance with NEC or local code (some places around me require TWO 8 foot rods spaced 10 feet apart). If it's stand alone then do the spikes and such and DO bond the neutral to the ground. And BTW ground always "makes first and breaks last" make it your motto it might save your butt someday....
-Every once in awhile somebody says that running two of the three legs of a 3 phase genset is bad for it. So far I have never seen any proof of this. Theoretically there is no reason for this to be possible. Certainly it's INEFFICIENT but there is no risk of damage. As proof of this I would point out all the totally unbalanced three phase systems out there. I don't see a bunch of transformers blowing up and I have definitely seen some lopsided stuff so.... Not an issue. Waste of money? You bet. Overloaded legs? Yep. Nuisance trips? Sure. But damage to the generators or transformers no.

It's not a simple thing. Takes not only time to understand this but a bit of a knack for it. Not everyone is cut out for it. At the same time please don't ask me to drywall, paint or roof anything. I suck at those.

Ask questions, get advice, consult manuals. Get an Ugly's reference and keep it handy. If most of the "electricians" I knew would read that little book (and have a little humility) things would go much smoother out there. Then again maybe I should be careful what I wish for I make a decent living cleaning up those messes!

I have seen the aftermath of the abuse of a generator that has had 2 heavily loaded legs and one not loaded. Windings were distorted. It's rare, and it takes time to happen, and it's easy to prevent.


You need to be extremely careful driving another ground rod. This is more important for permanent installs. It's best to check with someone local as every jurisdiction has its nuances (despite using the same codes).

 

[G744]

I have many single and 3 phase demands on the property running just fine on 208V rather than 240V.

Our grid service is WYE configured 120/208, so is the backup DRASH genset.

Have no worries, guy.

 

[edemoss]

It’s best to keep it near 208v since the 120v side will also increase if you push the voltage up.

that is what i thought thank you very much for your help.

I have seen the aftermath of the abuse of a generator that has had 2 heavily loaded legs and one not loaded. Windings were distorted. It's rare, and it takes time to happen, and it's easy to prevent.


You need to be extremely careful driving another ground rod. This is more important for permanent installs. It's best to check with someone local as every jurisdiction has its nuances (despite using the same codes).

you have given me things to think about and i appreciate it.

 

[msgjd]

Get an Ugly's reference and keep it handy.

Nice ! I totally forgot about Ugly's ! When my youngest son started his stage show tech biz about 15 years ago he had questions around the clock about connection polarity and ratings of lead cords, loading of portable gennies, circuits, and whatnot.. I told him to go online and buy an Ugly's.. That ended the non-stop calls and texts

 

[msgjd]

Plan Bulldozer is part of the Heavy Constructors Association they help counties and muncipilities during emergencies.

Once upon a time combat engineer Guard units had every piece of heavy construction equipment imaginable to do this service .. Not so anymore due to state/local politics and state budgets .. The units are now few and far between, that's if any HEAVY horizontal construction Nat'l Guard battalions exist anymore.. The ones in 3 northeastern states around me went Light-Mobile

You are certainly filling a void, and thank you !

During an ice & snow storm emergency involving FEMA about 20 years ago with downed trees and powerlines blocking every road in an isolated ill-equipped mountain town , I offered the services of a few of my M51 dumps to the local EMO to haul logs, limbs, debris, etc.. Guy was too arrogant to accept help other than from his own little "click" having 1-tons and a couple F700's .. The highway dept was reluctant to remove sanders and risk the DPW's trucks for the job.. Most of the scattered and sparsely-populated town was without utility power for up to 17 days (in the dead of winter) because of the road-clearing "progress" .. Yep, there's plenty of gennies around but the transplants sure weren't prepared

 

[G744]

True that...

Severeal times I've offered to help out local organizations for free when needs arised.

More than once they accepted, then some connected guy got bent out of shape at me.
Turned out he had an under-the-table $ deal, and I "screwed" that up. Fuk 'em.

 

[KN6KXR]

I have seen the aftermath of the abuse of a generator that has had 2 heavily loaded legs and one not loaded. Windings were distorted. It's rare, and it takes time to happen, and it's easy to prevent.


You need to be extremely careful driving another ground rod. This is more important for permanent installs. It's best to check with someone local as every jurisdiction has its nuances (despite using the same codes).

I'm willing to wager overloading was the root cause not being unbalanced. Like I said the physics of electricity just doesn't back it up. What's really likely is they looked at the 3 phase rated kVA and then hooked up a single phase equivalent. For example a 25 kVA genset is only good for about 16 kVA at single phase. Combine that with the misunderstanding about continuous and intermittent load duty ratings and we have a pretty good recipe for disaster. Why does NEC 790 (solar panels) require everything to be sized 125% of table value? Because 80% of 125% is 100% and solar is a continuous load. Misunderstanding around single and three phase power, VA vs W, continuous and intermittent loading creates a lot of issues out there. Unless specifically stated for continuous if you run over 80% you WILL eventually melt it. Not to mention other factors such as rise over ambient, motor locked rotor ratings, power factor issues, THD effects, etc... It's actually amazing more stuff out there isn't totally melted.

My observation is that in the last 20 years fewer and fewer young people are getting the same quality instruction I got. I try to teach the younger guys I work with when I have a chance (and they'll listen). I do stuff like bought the whole crew I work with Ugly's references. When I roll up on a guy doing electrical work we talk for a minute, break out the books, design the job the right way. I tell all the young guys in the trades to learn this stuff really well because being good at it is great job security.

 

[Scoobyshep]

I'm willing to wager overloading was the root cause not being unbalanced. Like I said the physics of electricity just doesn't back it up. What's really likely is they looked at the 3 phase rated kVA and then hooked up a single phase equivalent. For example a 25 kVA genset is only good for about 16 kVA at single phase. Combine that with the misunderstanding about continuous and intermittent load duty ratings and we have a pretty good recipe for disaster. Why does NEC 790 (solar panels) require everything to be sized 125% of table value? Because 80% of 125% is 100% and solar is a continuous load. Misunderstanding around single and three phase power, VA vs W, continuous and intermittent loading creates a lot of issues out there. Unless specifically stated for continuous if you run over 80% you WILL eventually melt it. Not to mention other factors such as rise over ambient, motor locked rotor ratings, power factor issues, THD effects, etc... It's actually amazing more stuff out there isn't totally melted.

My observation is that in the last 20 years fewer and fewer young people are getting the same quality instruction I got. I try to teach the younger guys I work with when I have a chance (and they'll listen). I do stuff like bought the whole crew I work with Ugly's references. When I roll up on a guy doing electrical work we talk for a minute, break out the books, design the job the right way. I tell all the young guys in the trades to learn this stuff really well because being good at it is great job security.

The over current protection should prevent that. It has more to do with magnetic fields in the head (source: the rewind shop in work with). All I can do is pass the information on.

The problem with the younger generation is the older generation. It's our job to teach them as much as we can. It doesn't help that we have become a disposable society. Instead of repairing something we just replace it. In depth diagnostics is a dying art.

 

[Guyfang]

What kind of RO is that in the picture?

 

[2Pbfeet]

What kind of RO is that in the picture?

Which picture? I must have missed an RO photo...

All the best,

2Pbfeet

 

[Guyfang]

This looks like an Army RO.

 

[msgjd]

True that...

Severeal times I've offered to help out local organizations for free when needs arised.

More than once they accepted, then some connected guy got bent out of shape at me.
Turned out he had an under-the-table $ deal, and I "screwed" that up. Fuk 'em.

yep, i later found out they were getting paid behind the scenes , even the EMO got a piece of the pie via a subsidiary he had with someone else's name on it, there were plenty of shady "conflicts of interest" within the town that came to light in time

 

[2Pbfeet]

This looks like an Army RO.

View attachment 937495

Thanks for clarifying that. My apologies, I have only seen the large military RO, Reverse Osmosis, systems. That looked like a small US civilian style transformer to me.

All the best,

2Pbfeet

 

[Guyfang]

VERY handy item.