Power conditioner / voltage regulator with a generator

I am sure this is not the correct place to post this, probably not even the correct site entirely. But this is a vast resource of industrial knowledge in general... so here goes. Please feel free to point me to a better electrical power website if you know of one.

I have a 11Kva diesel genset that I power my house with when we lose power (which is quite frequent). The generator has a mechanical voltage regulator but no AVR (that was an option that this particular unit did not have). I monitor the voltage, hrz and amps and generally speaking its not bad, but I do drop voltage a little when there is a large demand.

I also happen to have a Stabiline BCR1210OU power conditioner (10Kva), that I was going to use in my shop to boost 208 to 240v but never did. As we are running out of space in the shop, I moved the power conditioner to my house and figured I would install it after the generator so I have nice steady voltage. Otherwise its a really heavy paperweight.

All seems great....EXCEPT.... The manual for the power conditioner says it can run a 120V load but it should be connected between output tap #1 and the 120V tap - which is basically a Center tap on the output coil. And the 120v load should not exceed 1/2 the rated Kva of the unit (which makes sense as its half of the coil). I can post the schematic if I get any interest in this inquiry.

Since I am powering my electrical panel with this unit, in addition to 240v loads, I will have 120v loads on both output legs by nature of the way the breaker panels are set up. So, my question is.... Can the power conditioner handle 120v on the LEG #2 using the same 120V center tap. Now before you tell me, this is a question for Superior Electric (maker of the unit), I should mention that I have emailed them multiple times and have not gotten an answer yet.

So I am hoping to tackle this with a collection of broad electrical knowledge. Basically this unit is large transformer with a primary and secondary (output) coils and there are a series of smaller coils that buck or boost voltage to the primary input coil, which in turn affects the voltage on the output coil. However, looking at the schematic the voltage adjustment is input on the left side of the coil (based on the schematic) which lines up with the output coil between output LEG 1 and the 120v Center tap. On the right side of the coil we have a series of taps on both the input coil and output coil where input and output voltages can be adjusted - for example if we want to go from 208V in to 240V out. its really just how much of the coil windings you are tapping into on both the input and output sides.

Are you still with me so far...? So what I am saying is, I THINK, the reason that the manufacture wants the 120v load on only one side of the the circuit is because that is the side that will see voltage regulation. The other side will certainly have voltage between LEG 2 and the center tap, but that voltage is fixed based on the input and output taps used. Assuming my theory is correct, I can certainly test the voltage on both sides, but how do I know if the 120V center tap can handle the current that may be generated from either end of the coil. An electrician friend of my has told me that the left side to center and right side to center will cancel each other out, but I haven't gotten my head around that yet)

So here's to hopping that someone on this forum has any idea what I am talking about...

Thanks
clint

clinter36 said:

I have a 11Kva diesel genset that I power my house with when we lose power (which is quite frequent). The generator has a mechanical voltage regulator but no AVR (that was an option that this particular unit did not have). I monitor the voltage, hrz and amps and generally speaking its not bad, but I do drop voltage a little when there is a large demand.

I also happen to have a Stabiline BCR1210OU power conditioner (10Kva), that I was going to use in my shop to boost 208 to 240v but never did.

Click to expand...

Depends on how hard you expect to abuse your emergency "grid", load side of that conditioner.

These goods expect a great deal more reserve and resilience as to imblance on what they "perceive" as their "grid" side than your Diesel genset and its generator head are likely to be able to deliver.

Given any thought to even what it takes to simply energize the unloaded primary of a 10 KVA-rated transformer-clan critter off a mere 11 KVA Gen-set?

THUNK HUMMMMMM! a familiar sound? That's the sound of Diesel fuel being pissed-way, Pilgrim.

My MEP-803a is a nominal 10 KVA @ 8,000 ft above sea level, generally considered a 12 KVA, where I sit about 352 feet up. so we are not all that differently set up.

I can option to 208 Wye and hand-dial it up tp 220 Wye if need be for running machine-tool motors. Which I don't, during an outage. YMMV.

There WILL be drop under ANY significant load. 3-P is just my own gen set's best situation for easiest balance.

Keep in mind that the common 200A @ 240 VAC residential service is approx 48 KVA, and has a Helluva lotta grid BACK of it, even so.

You want a gen set that COPES with loads? You have it.

You want a gen set that hides their effects? You need 60 KVA to 120 KVA, not 11 KVA.

Wise? Not in my view.

Oversized gensets want to wet-stack. Investment and maintenance are higher, Diesel isn't free, and you'd have more of it to store and "polish".

Where we need to "do this" - for telco and data sites - there is a massive battery bank in float and some seriously costly no-break power UPS+conditioner packages involved.

"Real Money" seriously costly, you have Fortune 100 finance houses, major banks, and governmental agencies in the racks..

I can't justify that for a residence. Even what I have is overkill, given folks can adapt to no electricity at all, just like we did for the first billion years or whatever.



We just make a few minor alterations in lifestyle for the duration of an outage when one hits and are happy that "minor" is all they are.

Nothing under-roof, here, is that picky about power anyway or it would not BE under my roof.

The power you get from the utility is from a center tapped transformer. The center tap is grounded and called neutral. You can do the same, as long as its 120 to center on both sides and 240 across the lines. In single phase panels, the load is balanced with the 120 volt loads as the 240 loads are allways balanced. As thermite said, what you need is capacity. Even grid connected systems have voltage fluctuations, sometimes alot. Depends on how close you are to the transformer on the pole, and how overloaded the system already is. Where i live in Nicaragua, you are lucky to get 106 or 108 volts from hot to neutral. The system is overloaded. Is this power conditioner going to respond to changing loads? And if it does, where is it going to get that power from? You only have so many watts going in. You cant get any more out, in fact, the transformer has some loss, so it may be worse. Have you counted how many watts you are using? Can you prioritize some things to lessen the load at peak times? Your local utility just cuts in a peaking plant, if the have one thats not already running. You dont have that option, so conservation is your tool, like it is for many utilities today.

On single phase 120/240 the neutral which is the center tap does on see just the difference in the two phases. If the 120 volt load on both phases are equal the neutral will see no current flowing. So yes if the voltage regulation is done on one side then the both the 120 on that one side and the 240 across both phases will be regulated while the 120 on the other side will not be.

My dad and I were both electricians. When he was about 80 he had a friend help him change his house service, hot as we both have done many times. My dad turned around and saw his friend lift the neutral with the power still on. Dad said "Oh Shit!" and he was right. The voltage imbalance took out his TV, VCR, Microwave oven, and alarm clock!

garyhlucas said:

On single phase 120/240 the neutral which is the center tap does on see just the difference in the two phases. If the 120 volt load on both phases are equal the neutral will see no current flowing. So yes if the voltage regulation is done on one side then the both the 120 on that one side and the 240 across both phases will be regulated while the 120 on the other side will not be.

My dad and I were both electricians. When he was about 80 he had a friend help him change his house service, hot as we both have done many times. My dad turned around and saw his friend lift the neutral with the power still on. Dad said "Oh Shit!" and he was right. The voltage imbalance took out his TV, VCR, Microwave oven, and alarm clock!

Click to expand...

ROFL!

Dad and I did quite a few without pulling the meter as well.. but damn... never gave that issue a thought.

Thanks!

We always opened the main, then gutted whatever it was we had inherited as was NOT Square-D "QO" FIRST!

I mean.. it was all going to have to be reterminated onto the new "QO" breakers anyway. Usually more work-to it yet, but...

Funny about "experts", some days.

Guy in a utilty work uniform with a badge knocks on my door, wants permission to use my front of the house hose bib for ground - something he is part of a krew doing testing needs for their gear.

Told him it would do him no use, go round the back and find one of the Earthing rods, right near the air-con unit.

Get a lecture about how all cold-water lines are grounded, yadda, yadda.

Finally interrupt to say "they were at one time. But that spigot is NOT grounded - it's abandoned."

Lecture resumes that it doesn't matter if the water is shut-of.. yadda, yadda.

"Yah, well, there IS a valve..."

"As I said.. , yadda, yadda..

"....but there is about fourteen or fifteen feet of ignorant AIR between this-here hose bib and that partic'lar valve."

"Cut out the Copper and re-used it several years ago."

Y'know? I b'lieve he still thought I had to be ignorant?

Well.. fair 'nuf. I AM. Just not about that truant hose bib.

Its still 120 to neutral because 120 x2=240. So if one leg to the other is 240, and one leg to neutral is 120, the other leg to neutral will be 120. One side may be carrying more load, and the regulator is compensating for it, but both will be 120 volts. The open neutral as your dads friend created, lowers the voltage on the heavily loaded side, and raises the voltage on the lightly loaded side. They still add up to 240, weather they are 100 and 140, or 200 and 40, they will add up to 240. Its that high voltage that blows the electronics.

I was just thinking about this, and it is when the output is connected for a voltage other than 240 that it matters about the other side. If it is connected for 208, then the 120 side will be 120, and the other 88 volts, making it unsuitable for 120 volt loads.

This is a case where posting the schematic would be helpful.

It seems a bit goofy, if I were doing the thing, I would be tempted to do the regulation on the primary side, which would take care of both 120V outputs. The idea of regulating just one is a bit odd. And I am not clear on how that is accomplished in your device, many would change taps on the fly, as the substation does, that seems to be different..

JST said:

This is a case where posting the schematic would be helpful.

It seems a bit goofy, if I were doing the thing, I would be tempted to do the regulation on the primary side, which would take care of both 120V outputs. The idea of regulating just one is a bit odd. And I am not clear on how that is accomplished in your device, many would change taps on the fly, as the substation does, that seems to be different..

Click to expand...

The NEED, perceived need, or rationale of using it (because it exists, mayhap?) even more so?

Coupla times I've had branch offices to kit-out with 'puters back when 'puters were pickier. The problem wasn't sag or a noisy utilty-mains service. Both just happened to be within half a floor of the lift motors and switchgear for 26 and 37 story buildings, four shafts.

Best "Ferrups" for each in the bottom of the rack, and the servers were happy.

But that was over 30 years ago. Most newer gear, their own PSU is more protective.

Dunno WHAT the OP is actually trying to protect, or FROM what, on a light-duty 120 VAC service?

Feeling bad about buying a gadget as has not found a USE might be overshadowing technical considerations?

Whom, here, has never been THERE?