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Transfer Switch

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MattM

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#1
I bought a 40KW Muti-Quip diesel generator for emergency use. Now I need to get a 400 amp manual transfer switch.

I've been doing some research on the web but thought to ask for advice here.
 

higgite

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#2
If I may ask, why do you need a 400 amp transfer switch? Will you be using it to switch over to the generator from a 400 amp utility service? That's an awful lot of current for hobby machines, but to each his own. :)

Tom
 

MattM

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#3
Good question. That 400 amps supplies our entire house. I know it is way overkill but I got a good deal on an almost new genset. With the 40kw it can be wired directly into the main service box, no need to select individual circuits. The electrician said it would be a lot less expensive to wire.
 

woodchucker

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#4
so if your current house is 200amp, then you only need a 200 amp transfer switch.
All you need is a lockout type switch.
 

mksj

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#5
I have installed a few generators, and also considered one for my current house. I agree with Matt, it is much easier to have a generator big enough for the whole house load, rather than have separate breakout circuits in a sub panel that are handled by the generator. The transfer switch needs to be sized for the whole hose load. Older panels/houses were often 200A, newer house (larger) house tend to have higher amperage panels, my house service entrance is designed with a 200A main panel and an additional 100A breaker can be added if needed so I would need a 300A transfer switch. So the problem is that 200A automatic transfer switches are fairly common and they run $600-700. These are usually automatic type so they have a genset exerciser, sense line drop outs and also wait a specified time before before transfer back to house power and then have a cool down period for the generator. The common brands are Kohler, Honeywell, ASCO, Eaton, Winco, Generac, etc.. A manual transfer switch runs about $400. So at the 200A level it probably pays to go with an automatic. But above 200A the price of the automatic transfer switches in the 300-400A are 2-3X more expensive than the 200A. A manual 300-400A switch runs about $800, more if for a service entrance. If you cannot breakout the power after your main house breaker then you need a service entrance rated transfer switch and UL approved, which is very pricey. My last house I was able to put the transfer switch after the main house breaker, but many service entrance panels the main breaker is incorporated into the mains panel and you then need to use a service entrance transfer switch which is much more expensive. Not to be pessimistic, but if the panel is not rated correctly or is wired wrong and something happens, your insurance can deny coverage.

I would go with a transfer switch sized to your current main panel, a 400A is way overkill unless you have a large shop or heavy equipment, in witch case you would be better to just take care of the house power. A 200A transfer switch would be adequate for a 40kW genset. As far as what I recommend, the first 4 brands above, Generac is somewhat iffy in my experience. I would get the correct sized transfer switch and you need to determine if it can be installed, and if you need a service entrance type. At 200A, I would go with an automatic switch if the genset can be wired for auto start. The automatic systems also have sensors for things like low oil, overspeed/under speed, etc.
 

MattM

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#6
I have installed a few generators, and also considered one for my current house. I agree with Matt, it is much easier to have a generator big enough for the whole house load, rather than have separate breakout circuits in a sub panel that are handled by the generator. The transfer switch needs to be sized for the whole hose load. Older panels/houses were often 200A, newer house (larger) house tend to have higher amperage panels, my house service entrance is designed with a 200A main panel and an additional 100A breaker can be added if needed so I would need a 300A transfer switch. So the problem is that 200A automatic transfer switches are fairly common and they run $600-700. These are usually automatic type so they have a genset exerciser, sense line drop outs and also wait a specified time before before transfer back to house power and then have a cool down period for the generator. The common brands are Kohler, Honeywell, ASCO, Eaton, Winco, Generac, etc.. A manual transfer switch runs about $400. So at the 200A level it probably pays to go with an automatic. But above 200A the price of the automatic transfer switches in the 300-400A are 2-3X more expensive than the 200A. A manual 300-400A switch runs about $800, more if for a service entrance. If you cannot breakout the power after your main house breaker then you need a service entrance rated transfer switch and UL approved, which is very pricey. My last house I was able to put the transfer switch after the main house breaker, but many service entrance panels the main breaker is incorporated into the mains panel and you then need to use a service entrance transfer switch which is much more expensive. Not to be pessimistic, but if the panel is not rated correctly or is wired wrong and something happens, your insurance can deny coverage.

I would go with a transfer switch sized to your current main panel, a 400A is way overkill unless you have a large shop or heavy equipment, in witch case you would be better to just take care of the house power. A 200A transfer switch would be adequate for a 40kW genset. As far as what I recommend, the first 4 brands above, Generac is somewhat iffy in my experience. I would get the correct sized transfer switch and you need to determine if it can be installed, and if you need a service entrance type. At 200A, I would go with an automatic switch if the genset can be wired for auto start. The automatic systems also have sensors for things like low oil, overspeed/under speed, etc.
 

MattM

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#7
Very helpful.

The house has 400amps incoming which is split into two 200 amp sub panels. The sub panels (which are 90% full) are some distance from the genset. The genset is close to the main service entrance. We certainly don't need all 400 amps anytime much less in an outage.

I'm thinking in the case of an outage (or once a month) to light up everything and put a healthy load on the genset. Having had boats with diesels and having owned a marine diesel rebuild company I know diesels like to run hot and under load.

Like I said this is way overkill.
 

GoceKU

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#8
Matt i would suggest visit couple of scrap yards that buy industrial machines, and i would suggest find switch with two positions, 0,1,2 so you can switch between city power and generator power, i also own an 30 kw diesel generator i only have 100 a three phase 380 v selector switch.
 

MattM

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#9
Matt i would suggest visit couple of scrap yards that buy industrial machines, and i would suggest find switch with two positions, 0,1,2 so you can switch between city power and generator power, i also own an 30 kw diesel generator i only have 100 a three phase 380 v selector switch.
Can't do that. Must be a "legal" "approved" unit before a licensed electrician will install it and I'm not at all comfortable working around 400amps.

I did however install such a switch on an off-grid system but I was only dealing with 6.5kw and 30amps. Out there we, "Didn't need no stinkin permits" (or licensed electricians).
 

GoceKU

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#10
Can't do that. Must be a "legal" "approved"
Matt if you are thinking of investing you'll do it right anyway, no one wants to burn their house down with bad wiring, i know this is a very common with the solar systems installations now, here in europe the power company only cares that the power must pass thru the meter what you do with it, they really don't care, i have a main breaker and an selector switch, in the beginning i use to disconnect the main breaker and simply plug in my generator in the three phase socket in my garage, this is not wise because the automatic fuse are not made to work backwards but the generator has its own fuses.
 

MattM

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#11
The genset was delivered yesterday. Advice I got from an electrician was that I could use two single pole double throw manual switches to activate my two 200 amp panels. This seems reasonable to me. I don't mind going out to the shop and throwing two switches.

What's wrong with this?
 

GoceKU

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#12
There's nothing wrong with using two switches if nothing is switch on, however you can't use two switches to start an three phase electric motor or a machine, because depending on the phase you switch first it will change direction of rotation.
 

tq60

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#13
Nothing wrong with that so to speak but.....


Back in past life we has many stand by plants as well as portable use sites where trailer unit is plugged in.

Standby were fully automatic where others were manual.

Manual had either a large switch that was panel sized 2 pole 2 position with load as common and line and generator as either or positions of the switch.

Next company used a much cheaper design in that it used a pair or paired interlocking breakers that only allowed one or the other to be selected and these were the main entry breaker for the panel.

The main point here is there are many options but one item is critical in that there must be no possible way under any idiot operating the controls to place the generator to line.

For this size unit do look for and spend to buy certified unit.

Sent from my SAMSUNG-SGH-I337Z using Tapatalk
 

JPigg55

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#14
You will need to verify for your area, but here I know a generator transfer switch has to have the same rating as your incoming service since both power sources go through it.
That said, if your incoming 400 amp service splits into two 200 amp service panels, you might get away with using a 200 amp transfer switch for each the individual sub-buses.
From what I remember when I had my standby generator installed, a 200 amp auto transfer switch ran about $1000, but a manual one ran about $400.
That was probably 6-8 years ago so the prices are probably somewhat higher now, but from what I saw I think two 200 amp switches would be cheaper than one 400 amp switch.
If you don't need both sub buses, you could just connect to one of them and only need one transfer switch.
I'd definitely talk to your electric company. They will probably be a better source for information on what would be legal/required.
 

MattM

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#15
There's nothing wrong with using two switches if nothing is switch on, however you can't use two switches to start an three phase electric motor or a machine, because depending on the phase you switch first it will change direction of rotation.
I get my 3phase from a rotary converter.
 

Linghunt

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#16
High amp switches can get expensive. I hate this option but breakers are often used for switches. specially in LOTO.

Do you have a main 200A breaker in each subpanel? Does the Generator have proper current limiters?

Ask your electrician about grounding of the generator how he plans to do bonding.

The more "automatic" you go the more complicated and costly.

I did one job where the generator was backup to a cell/wireless/internet tower. When the power went out [winter storms in Northern CA], we had battery backup and a generator to charge the batteries.

The system would check for power outage and swap over. The smart system send a message so technician that it was down and stamp time for him to get there with more fuel for generator. We found a German device that could trip off of low voltage signals and it would send wireless signal back to software control. Other checks in there as well

Think of a small concrete block room at the bottom of cell tower that is 2 hours from service guy's house on a mountain road. If the tower goes down, the boys playing video games will be off line and pissed off. Important stuff.

Joking aside, this kinda stuff is part of what is needed in those hurricane areas. Not much you can do if the top of the mountain is gone and the tower is n the Bermuda triangle.
 

MattM

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#17
This is a cell tower takeout. Only has ten hours on it.

I do have main 200 amp breakers in each 200 amp panel and could go that direction but I have been strongly advised against it. If the power company finds out it would be mightily pissed.

Finally got an electrician to come out. He agreed that it would be "legal" to use two manual (knife) switches. Hopefully he will get back to me with a price. The unit is only 35' from the service entrance. No digging a trench, can run directly through the carport.

I fired up the unit. It is one sweet running machine. Can't wait to get it hooked up and have the power go out.
 

Blackjackjacques

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#18
I have the same exact circumstance but using a 35 kW generator. My normal utillity service is 400A 500 MCM and also splits into two 4/0 feeding 200 A panels with local disconnects. To ease installation and approvals, I opted for a whole house system with the utility meter nippled to a 400 A ABT. This arrangement also eased utility failure takeoff and generator battery trickle charging connections, etc. However, having two 200A disconnects may require more real estate and may possibly cost more than just using a single 400 A ABT.
 

Linghunt

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#19
Let us know how it turns out and what you do, knife switches was my 1st thought.

When you turn them off, do a visual check that the blades are disconnected. I've seen a failure on a 3 phase system where one leg was still connected. Tech turned it off for upgrade job. Measuring around it was funky and then we found the failure. I think it was a 225 A service inside a large building. I don't remember where it broke on the lug or hardware.

Measure and visual for me on those.
 

juiceclone

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#20
eBeast seems to have a lot of 2 and 3 pole double throw knife switches. ....I just ordered a 100 amp one.. u might look for a 200 amp one? they seem well insulated and suited to safely isolate and switch to gen power. can't speak for legal..usually when it's not expensive enough, someone finds a way to stop u...
 

Linghunt

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#22
eBeast seems to have a lot of 2 and 3 pole double throw knife switches. ....I just ordered a 100 amp one.. u might look for a 200 amp one?
I think I'm missing it, but not heard of eBeast. a quick search didn't help.
 

Doodle

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#24
I have been watching this and had some chuckles. I know you have 2 200 amp panels but what is you average connected load in amps? My guess would be on a rough day you might do 40. I would suggest you find out what your minimum, average, and peak loads are and what the durations are. If you supply only the power you really need, you can load shift and get by with much smaller equipment saving much money. If you want to be able to safely transfer maximum loads with an automatic transfer switch and not kill any linemen in the process (which is murder by the way), then get out your checkbook and put the very best money can buy into a safe system.
 

Blackjackjacques

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#26
The guidance proposed herein to simply just use "knife switches" introduces several problems:

1. The switches shown here are likely not listed and if they are, not intended for such service. Listed disconnects are often spring-loaded devices to minimize transition time from OFF to ON and ON to OFF, etc to minimize liklihood for arcing, and often employ features such as arc chutes, etc to squelch resulting arcing. I don't know where one would use the shown switches, maybe perhaps to interrupt a bank of solar cells, etc. - but frankly, they look like cheesy. Proper disconnects are governed by UL 98 and this is what you will want to use.

2. You will need a listed enclosure to contain the switches, and the container/switch must be configured such that the switch can be actuated with the enclosure door closed as a means of containing any possible explosion. If located outdoors, the enclosures must meet NEMA 3R (rain tight) and preferably, NEMA 4 or 4X (splashproof/corrosion proof) depending where located.

3. While it may be true that your actual loading may be far short of the 400A utility service provided, such things as complying with the Code (NEC), and the wiring logistics, runs, interface, etc such as to satisfy the AHJ , the power company, as well as make the design practical --will drive your design. For instance, if you do use two typical 200A disconnects (e.g., DPST) with the present house wiring to connnect the generator to the house, you will also need means to disconnect the utility service from the load panels. You can use a DPDT configuration, but to match the 400A design rating of the utility connection, such a switch shall minimally be rated for the larger current - in this case 400A - even if your emergency load demand is only 10A, etc. The simplest design in this case is to feed a common node such as an ABT or even MBT from both the utility and the generator with the transfer device rated for whatever is the larger. A 400 A automatic bus transfer (ABT) can be had new for about $2K. You can likely pick one up a good used one for much less.
 
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JPigg55

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#27
I do have main 200 amp breakers in each 200 amp panel and could go that direction but I have been strongly advised against it. If the power company finds out it would be mightily pissed.
Finally got an electrician to come out. He agreed that it would be "legal" to use two manual (knife) switches.
I fired up the unit. It is one sweet running machine. Can't wait to get it hooked up and have the power go out.
I know what you mean. When I installed my standby generator (15 kw Briggs with Auto Transfer switch) I remember thinking "I spent $5000 (completely installed and tested) for something I hope I never need", but it sure was nice the first time the power went out and I heard the generator kick on.

Just a couple thoughts here to ask yourself.
I'm guessing your generator has the auto start/stop feature based on its previous use. Using manual transfer switches, I'm not sure what other wiring connections would be required to maintain this feature. Without it during a power outage, you'd first have to go out and start the generator and then go close in the transfer switches. Check, but I think with this type of set-up, you will have to install lock-out switches for your main feeds by your electric company to prevent backfeeding the grid..
Second, this is a diesel driven generator. You'll have to be sure and have plenty of diesel on hand to feed this monster as well as stabilizer it to keep it from going bad. Gas station pumps require power to operate as well and most don't have back-up generators. So running to the local filling station for diesel during a power outage isn't an option
While you may need 40 kw of capacity to run everything, ask yourself what you would really need during an outage. My generator is set up to run on propane and is rated at 1.5 gals/hr at 50% load. Even at idle (no load), engines require fuel to run and, as you said, diesels don't like just sitting at idle. I live in the country so I have a 1,000 gal propane tank for my house and generator. Max fill on the tank is about 80%-85% so completely full it would run my generator for 16 days with a 50% average load running 24 hrs/day.
I did a quick search on your generator and I found a few 36 kw ones listed on eBay with asking price of around $26,000 plus. I don't know what kind of deal you got on it when you purchased it, but if I was in your shoes, I'd try and sell it. Based on these prices, even if you got half ($13,000), you could buy a standby generator with auto transfer switch installed and have money left over. I'd also recommend using natural gas fueled (if you have service) or propane (if not). Natural gas companies only shut off gas in the event of an earth quake or local fire. Propane can be stored on site in large quantities with no need of treatment, stays good forever.

Either way, I know when the power goes out ~10 seconds later, my generator kicks on, runs through a self test (~20 seconds), and then the transfer switch kicks over and the lights come back on. I don't even have to get my butt out of the chair. When power comes back it transfers back, cools down the generator, and shuts itself down.
The only issue I've had is during times when the power "Flickers" (lights go off and on really quick a couple times). The generator senses this as a transfer switch failure and locks out which I have to go out and manually reset.

Good luck with your endeavor.
Oh BTW, when I searched for a generator and switch, this is the place I found with the best prices. https://www.electricgeneratorsdirect.com/power/briggs-and-stratton-generators.html
I didn't buy from them as I decided to go with a Briggs & Stratton generator. The local dealer delivered, installed, set-up, and tested the generator and transfer switch for about $600 more than I could buy them from this place and it was going to be another $150 for residential tailgate delivery or else it would show up on a big truck and I would be responsible to unload it.
 
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Linghunt

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#28
I would be scared to buy and use one of those. Refer to the points blackjack made so well.

I see an arch blast potential coming off of that if switched under load and the person is hanging right next to it on that handle.


My hands on guys would have full PPE setups and never stand in front of the switch enclosure with door open.

Per that companies policies, they would go to electrical safety courses annually and see these types of videos as part of the package. Puts the fear of electricity into you.

Nice thread BTW and great comments.
 

BROCKWOOD

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#30
Very good read on an important subject! I would pay to dispose of those Chinese disconnects if I had them. Those are death waiting to happen even with an experienced tech operating them. I'm just looking forward to the part of this story where the commercial grade underground fuel tank gets installed!
 
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