How the heck does a typical home transfer switch work?

How the heck does a typical home transfer switch work?

Mine isn't working so I need to figure out how it works first.

o My mains is two hots plus a neutral (i.e., it's not 3 phase) o There are two duplicate transfer boxes (presumably one per hot phase?) o Each box has a beefy fist-sized double-ended solenoid o Each box has what looks like a plastic relay o And then each box has a fuse strip & a junction strip

That's pretty much it, where I'm not sure which "side" of the main circuit breaker this two-box transfer switch is on yet.

Before I can troubleshoot, I need to know how it works.

  1. The beefy double-ended solenoid is labeled: "Generac transfer switch pn #71340, 250VAC/100A" "This transfer switch is for use with control module ass'y #75595 - #79844 - #83494"

  1. The plastic relay is labeled o Deltrol controls, 166F DPDT, coil 12 VDC, o 1/3 HP 13 AMP 120 VAC o 1/2 HP 13 AMP 277 VAC o 3/4 HP 3 AMP 600 VAC o 10 AMP 28 VCD o 8600, 20552-81, 9346

  2. The 4 fuses are each labeled either Buss BBS-4 or BBS-5.

  1. The junction strip is labeled o Utility 1 o Utility 2 o Load 1 o Load 2 o blank o 23 o 194

What is the role of each of those 4 parts in this transfer switch?

Reply to
Arlen G. Holder
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How about a real Gernerac model number? The part and assembly numbers on the visible nameplates don't seem to point to a particular model.

I couldn't find a model number, so how about a search by serial number?

Incidentally, you should consider labeling the cables, wires, terminals, fuses, etc.

Why two transfer switches?

Got a schematic of how you wired it? If not, trace the wires and make one.

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Jeff Liebermann     jeffl@cruzio.com 
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Reply to
Jeff Liebermann

Thanks for offering suggestions and asking questions.

I didn't wire it, but I'm pretty sure this is standard stuff.

It's just typical stuff I don't know - but I'm sure it's to typical code, which means everyone wires them similarly I would think since there's no rocket science going on.

I "think" the reason for the two panels is that each panel supplies half the house, which seems to be how it works when I pull the Buss fuses.

But that's exactly why I asked if anyone knew how the TYPICAL setup works, since this has to be as typical as typical gets for such things, given it has to be to code which means everyone does it similarly.

Back to your question, I don't know what an "emergency panel" is, as there's nothing "emergency" about this. PG&E power goes out once a month out here, for about a day on average, for about 10 to 12 times a year, where this setup isn't flipping those two fist-sized solenoids automatically.

I can manually flip them, and the setup works - but not automatically - but I'm NOT asking about that - as the problem will literally scream out where it is if I only knew how these things are typically wired.

Googling for what you mean by 'emergency panel", it "seems" that what you mean by "emergency panel" is the same as what I mean by "transfer switch", where I get the name of "transfer switch" right off the boxes themselves.

In short, I "think" this is set up as typical as typical can be, which means anyone who knows how these things are set up would be able to explain it, where I get Jeff's point that I can follow the wires, but that still doesn't tell me WHAT each thing does - just where the wires go (and there are a zillion of them).

I "think" the two panels are for two sides of the house, where I "assume" one panel has one hot and one neutral, while the other panel, I assume, has another hot and another neutral.

Otherwise, why would the two panels be so exactly symmetric?

Reply to
Arlen G. Holder

Thanks for the additional questions as this pretty much has to be typical stuff - but I just have no experience with debugging transfer switches.

This is the model number of the generator, if that's what you're asking

That Generac Generator is pretty typical stuff out here, if a bit puny, which is a Generac model 09067-9 8KW (67Amps) propane generator.

Maybe the model number on this placard is ONLY for the solenoids?

This, for example, is the placard on the side of the panel inside:

And this sticker is also on the inside of the panel: I couldn't find a model number, so how about a search by serial

Now that's interesting! (I can call 888-922-8482 tomorrow.)

The link shows that there "should" be a transfer switch serial number! But I don't see any number that would be a serial number yet.

However while looking I found covers which have slightly different cards:

I agree. But first I have to figure out what they are.

I don't know. It's got to be standard stuff. Everything has to be to code.

I suspect each box controls one hot wire, as when I pulled the Buss fuses, one side of the house turned off when the generator was running with no power coming in from PG&E.

Both boxes seem almost perfect symmetric, so I think it's just one hot for each box. But that's why I asked about a typical setup, as this must be to code.

It came with the house, and it's to code since the house has all the permits filled, and it used to work but then stopped working about a year or two ago.

What happens is that the power goes out, and then the generator turns on, but the two fist-sized solenoids don't trigger. I can trigger them manually by putting this handle which is screwed to the box into the big solenoid.

Moving that lever down in each solenoid turns the transfer switch on. But that's supposed to happen automatically when the power goes out and the generator turns on.

While I was looking for the serial number, I found the closest thing to a schematic, which is this placard on the inside of the cover (which has been off for a long time since the transfer switch no longer turns on automatically when the power goes out.

*AUTOMATIC TRANSFER SWITCH FOR USE ON STANDBY SYSTEMS* Suitable for control of motors, electrical discharge lamps, tungsten filament lamps, and electric heating equipment where the sum of the motor full-load ampere ratings and the ampere ratings of other loads do not exceed the ampere rating of the switch and the tungsten load does not exceed 30 percent of the switch rating. *AUTOMATIC SEQUENCE* *UTILITY FAIL* - Utility voltage sensor senses when utility voltage level is below 60% of nominal. Engine start sequence is initiated after a 6-second time delay.

*ENGINE WARMUP* - Time delay to allow for engine warmup before transfer. Fixed at 15 seconds.

*STANDBY VOLTAGE* - Standby output voltage must be above 50% of nominal voltage before tansfer is allowed.

*TRANSFER* - Switch transfers load from utility to standby supply; occurs after standby voltage is above set levels.

*UTILITY PICKUP* - Utility voltage sensor. Voltage pickup level is 80% of nominal voltage.

*RETRANSFTER* - Time delay after utility voltage supply is above pickup level before load is transferred from standby to utility. Fixed at 6 seconds.

*ENGINE COOLDOWN* - Time delay for engine no-load cooldown. Fixed at 1 minute.

System will operate automatically every seven days from the time of initial setting to ensure proper operation. Consult Owner's Manual for further explanation of Transfer System operating and features. Systems shall be tested periodically on a schedule acceptable to the authority having jurisdiction, to assure maintenance in proper operating condition. Enclosure is type 1, suitable for indoor installation. When protected with 200 ampere maximum (110a rated device) or 400 ampere maximum (200a rated device), Class J, T fuses, this switch is suitable for use on a circuit capable of delivering not more than 200,000 RMS symmetrical amperes, 250 volts maximum.

When used with 200 ampere maximum circuit breaker 100 ampere device; 400 ampere maximum curcuit [sic] breaker 200 ampere device; (type G.E. TJK or Westinghouse HLC) this switch is suitable for use on a curcuit [sic] capable of delivering not more than 10,000 RMS symmetrical amperes, 250 volts maximum.

Connect utility, standby generator supply and customer load as shown.

*Transfer Switch:* N1 N2 N3 === Utility Supply T1 T2 T3 === Customer Load E1 E2 E3 === Standby Supply

Terminal connectors tightening torque is 50 in-pounds (100a rated device) or 250 in-pounds (200a rated device). Control wiring terminal connectors tightening torque is 11 inch-pounds. 79959 D

Reply to
Arlen G. Holder

Thanks for that document:

I just found this also, but it's the wrong model number: o Generac Owners Manual for Automatic Transfer Switch 888-436-3722 o Model Numbers RTSI100M3, RTSI200M3, RTSN100R3, RTSN200R3, RTSN400R3

Same with this one, which seems to be the wrong model number: o Generac Owners Manual for Automatic Transfer Switch 888-436-3722 o Model Numbers RTSW100G3, RTSW100J3, RTSW100K3, RTSW200G3, RTSW200J3, RTSW200K3

Unfortunately, I can't find a model number for the General Transfer Switch yet, but only model numbers for the big double-fisted solenoids.

I will call Generac tomorrow though.

Reply to
Arlen G. Holder

Hi Clare, That was a GREAT question since I just looked and it's NOT what I thought.

I always thought I had 200Amp mains service, but I looked at the mains breaker which clearly says it's a 300Amp breaker, and on that same mains panel are three separate 100 Amp circuit breakers (plus a couple of 30 Amp spares).

So the service must be 300 Amp mains service, where I looked again at the two double-fisted solenoids in the transfer switches, each of which says it's 100 Amps.

That makes sense because when the transfer panels were working, they only ran "most" of the house, in that they didn't run the pool (which is one of the 100 Amp breakers I spoke about above on the main panel).

Given that, here's what I "think" I have. o 300 Amp mains service (broken into 3 100 Amp circuits) o Transfer switch handles only 200 Amps (100 Amps per "box")

Does that sort of sound like it might make sense?

Reply to
Arlen G. Holder

You can't possible be that stupid. This is just another one of your long rambling posts that goes on and on so you can listen to yourself.

Kindly go f*ck yourself.

That's your cue to (wrongfully as usual) call me Snit, because you just HAVE to reply.

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Reply to
Fox's Mercantile

Nope. I'm looking for the model number or name of the transfer box so I can read the docs which should have wiring and installation instructions. Not much I can offer unless I know what you have.

Methinks I found the install manual:

"Installing Automatic Generator Generac Guardian" Part 1 Part 2 Part 3 The transfer box they used looks like yours. Start at 2:12. Notice that the terminal blocks are labeled.

I did some digging and found that the only excuse for 2 transfer switches is two generators, or two different sources of backup power such as generator and solar inverter.

I hate be the bearer of bad news, but you potentially have a miswired mess. I'm fairly sure it would not pass an electrical inspection in its present form. If you have time and money, find someone with a clue and let them fix the mess. My guess(tm) is they would recommend ripping it all out and starting over with the wiring and installation.

Good luck.

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Jeff Liebermann     jeffl@cruzio.com 
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Reply to
Jeff Liebermann

Hi Clare,

You are correct the generator is a puny 8KW Generac, model 09067-9

This propane generator is so tiny that it's only capable of 67 Amps, so I'm not sure why there are two 100Amp transfer switches yet, but the house is

300 Amp mains service, where the pool is 100 Amps, and the house takes a circuit breaker each of 100 Amps.

It used to work, but now, when the power goes out (which happens about monthly out here in the mountains), the generator kicks in automatically, but the house doesn't get the current because the double-fisted solenoids don't turn on automatically.

I have to turn the solenoids on manually, which is the problem I'm trying to debug by asking how these two 100A transfer switches typically work.

I did find the model number, just now, after climbing on a stool

This model number is hand written as Generac 79848A (DD).

Googling for that model number, it does show up on Ebay. Generac Transfer Switch 100 Amp 250 VAC One Owner Used #71340 #79848A Switch is CSA Certified for use with control module assembly #79844, #75595 and #83494

Generac Transfer Switch 100 Amp 250 VAC One Owner Used #71340 #79848A $408.45 Buy It Now 32d 16h 48m 37s, Click to see shipping cost, 30-Day Returns, eBay Money Back Guarantee Seller: sparkyinpa (13,861) 99.6%, Location: Reading, Pennsylvania, Ships to: US, Item: 153421838181 Condition: Used, Condition: This transfer switch is in good working condition was removed because the generator was upgraded. Inside is very clean. Message us for shipping quote., Model: 71340, MPN: #71340 #79848A, Brand: Generac, Rated Amperage: 100 A, Type: Automatic

There are pictures with that Ebay listing which look almost exactly the same as mine does, so I'm pretty sure that's the model number.

*GENERAC TRANSFER SWITCH*

*HOLE ON BOTTOM*

*DOUBLE-FISTED SOLENOID* PN 71340, 250VAC, 100Amp Assembly _79848A_

*GUTS OF THE TRANSFER SWITCH*

*2Amp SlowBlow? BUSS SBS2 FUSES* (Mine are SBS4 and SBS5)

*PLACARD ON SIDE SAYING 600 Volt 2Amp*

*DOUBLE-FISTED SOLENOID CLOSEUP with manual lever*

*OWNERS MANUAL*

Reply to
Arlen G. Holder

I kept looking and found the model number of _each_ transfer switch!

The model number of _each_ transfer switch is: 79848A

Googling for that model number finds an exact lookalike for _one_ box

Here is just one of the eight pictures of that lookalike 79848A:

That's pretty close!

The manual switch is different, and the generator is different - but it's similar, where I will go through that excellent video with my Fluke.

I checked my main panel, which is definitely 300 Amp mains service (I had always thought it was 200 amps, but it clearly has a 300 Amp main breaker, plus 3 separate 100 Amp breakers, where the house has two of them and the pool has one).

The last guy who worked on that generator is in Santa Cruz, based on the label on the outside panel, which I found buried under stuff.

This DEFINITELY WORKED so it's NOT miswired. The only problem is that the solenoids are not automatically kicking on.

Here's what SHOULD happen:

  1. PG&E power goes out about monthly
  2. The Generac generator automatically turns on
  3. The two transfer switches should automatically turn on
  4. The house should have two 100 Amps (the pool does NOT have power) [Although the generator is puny - it's only able to output 67 amps!]
  5. When PG&E comes back about 24 hours later - the generator turns off
  6. The transfer switch transfers the two 100 Amps back to the mains

Everything above is working EXCEPT - I have to MANUALLY flip the double-fisted solenoids.

If I switch just ONE of them, I get only half the house. If I switch the SECOND one also, then I get the full house.

So my main problem is troubleshooting why the double-fisted solenoid is not automatically turning on.

Reply to
Arlen G. Holder

What amp service do most people have?

I just put some chalk on the raised letters of my mains circuit breaker which showed the mains breaker to be 200 Amps (not 300 Amps as I stated prior).

There are three separate 100 Amp breakers, each going to a different panel.

So I think, at this point, that the reason for the TWO 100A Generac model

79848A transfer switches is simply that each one handles 100 amps nominally.

Now I just need to figure out how to debug why this two-fisted solenoid isn't switching on automatically - but it does switch on when I flip it manually.

Reply to
Arlen G. Holder

Correction.

I just put some chalk on the raised letters of my mains circuit breaker which showed the mains breaker to be 200 Amps (not 300 Amps).

There are three separate 100 Amp breakers, each going to a different panel.

So I think, at this point, that the reason for the TWO 100A Generac model

79848A transfer switches is simply that each one handles 100 amps nominally.

Now I just need to figure out how to debug why this two-fisted solenoid isn't switching on automatically - but it does switch on when I flip it manually.

Reply to
Arlen G. Holder

Thanks Clare. That makes sense then as to why the puny generator is only 67 Amps, but since the Mains is 200 Amps, it needs two transfer switches of nominally 100 Amps each.

Thanks for that analysis, which I can't argue with.

Some of these voltages appear to be hard coded, based on this sticker

I'll start looking up where to source spare parts, after calling Generac tomorrow (1-800-GENERAC) to see if they still sell parts for this 79848A.

One problem I realized is that I lost 2 of the Buss fuses, which "may" be why both transfer switches aren't turning on when the power goes out and the generator turns on.

Funny thing is that advertisement for a similar transfer switch seems to have the "green" Buss 600Volt fuses spec'd at 2 Amp based on this picture of the Buss SBS-2 (green color code) for sale

Notice those are "SBS-2" green 600Volt fuses (not BBS!).

The sticker on the side panel of that transfer switch for sale, and on my side panel both say the same thing, which "implies" 2 amp fuses at 600VAC.

My fuses appear to be red (not green), and they appear to be o BBS-4 (not SBS) o BBS-5 (not SBS)

So what's odd is that mine are higher amperage, but also a different three letter code (mine are BBS while the one for sale is SBS).

I tried to get these fuses at Home Depot, Lowes, and Ace today, but none of them stock these fuse sizes in the 600 VAC rating.

I realized I'm _missing_ two fuses, where, I don't recall, but maybe I removed them to test them and never put them back? It would have been a long time ago (a year or two) so the _first_ thing I'm gonna do is source those Buss fuses after figuring out why some are 4amp and some are 5amp.

I'm not sure _why_ some are the red 4 amp and some are 5 amp though (while the originals seem to be green 2 amp).

Googling, SBS does NOT stand for "slow blow" but for fast-acting!

Reply to
Arlen G. Holder

Let me guess... State Electric Generators formerly in Harvey West Park? They moved to Scotts Valley: High prices and so-so work. You could do worse. State does much better work than what I saw in your photos which suggests that they were fixing something.

Try this video. Notice that the relays switch based on the condition of one input wire labeled "transfer". "Generac automatic transfer switch explained, demo" The "transfer" line on the terminal strip comes from the electronics that detects that the utility power has dropped and that the generator has produced stable power for XX number of seconds. When it gets both of those, it grounds the "transfer" wire, which closes the relay, etc. In other words, your problem is not in the relay box, but rather in whatever you're using for electronics to detect utility and generator power (and timers). In the above video, it's the black box with all the terminals and colorful labels. I don't see such a box full of electronics in your photo: Find the "transfer" terminal, disconnect whatever is connected to it, ground it, and see if it acts like the relay in the video.

Incidentally, 200A service should use 2/0 copper (or 4/0 Aluminum or CCA) minimum. In some counties, it's 3/0 copper minimum. That doesn't look like 2/0 in the photo. More like #4. Color me very suspicious.

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Jeff Liebermann     jeffl@cruzio.com 
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Reply to
Jeff Liebermann

You are pretty good Jeff, as these are the two stickers on the cover

I generally obfuscate where I live, but suffice to say I can probably see your house from where I am, or close to it. :)

I'm glad the narrator said he couldn't find out how it worked online, which is exactly the type of answer I'm asking about here.

At 34 seconds he explained what that cryptic "194" meant! And he explained what that cryptic "23" meant on my panel! Where: o 23 === ground o 194 === +12VDC So I can now test the two-fisted solenoid by putting 12 VDC across them, which is what the generator should do, which will "transfer" the power from line power to generator power. (This is what I've been doing manually with the mechanical lever.)

The narrator then showed that when the PG&E power is restored, the generator will _remove_ that 12VDC, which flips the two-fisted solenoid back to "line" power.

The one bit of confusion is that he said at 90 seconds that each solenoid is controlling 240 volts, but I think it might only be controlling 120 volts (but I'm not sure if it's controlling 120V or 220V yet).

He then explained the transfer is controlled from the "plastic relay".

I agree his box is different than mine, where mine is just like this one:

Mine and that one for sale are "simpler" looking than his is.

I think it should be easy to put 12VDC onto pins 23 & 194, but I need to get a bunch of those BBS-4 and BBS-5 fuses first.

So my current plan is: a. Source the two missing BBS-4 (or?) BBS-5 fuses. b. Then test with 12VDC to see if the double-fisted solenoid operates

If that makes it work, then my problem is likely the "sensing" circuitry, where this sticker explains all that sensing circuitry is hard coded, I think:

You have a good eye, where all I can say is that I didn't wire it. I did INCORRECTLY say it was 300 Amp mains service, where, when I shined a light on it and put chalk on the mains breaker, it turns out to be 200Amp service.

What's odd is that there are _three_ 100 Amp sub panels!

Which seems kind of strange, but I didn't wire anything and all the permits that were pulled were closed, so, it must make sense (code wise).

Two of those 100 Amp panels are in the house, and one is at the pool.

I need to call Generac (800-GENERAC) where I'm confused about the fuses o Why BBS-4 _and_ BBS-5 fuses?

Once I source those hard-to-get fuses, I will test the 12VDC at cryptic pins 23 & 194.

If the double-fisted solenoid does not trigger...

then we know that the sensing circuit isn't working to put 12VDC across those two pins.

Thanks for that wonderful video.

I'm a bit leery of what I can test with the MAINS connected though, since the power is currently running fine ... so I will need to be careful since it's only once a month that the PG&E power goes out for me to run the full test.

Reply to
Arlen G. Holder

This is closer, but not exactly either, I think:

Apparently, they recommend testing the transfer switch _monthly_

This has a transfer switch testing sequence

I found a paper copy of the 32-page owners manual, part number 98374 which is titled "Generac II Emergency Power Systems Owner's Manual" (revision 0, dated 11/22/1995) and which contains a generic parts list and exploded diagram for both the generator and transfer switch (apparently they come as a matched set).

The four fuses in the exploded diagram just say 2 Amps 600Volts, but I wonder if mine are double that because there are two transfer switches (where on the net, the video Jeff provided _also_ used red 4 amp fuses!).

I found that two outfits will sell generac parts to the public online:

I'll call Generac tomorrow to get more details.

888-GENERAC (888-436-3722) extension 4, extension 2 1-262-544-4811
Reply to
Arlen G. Holder

+1
Reply to
Micky-Bob

Don't Feed The @#$%^&*()_)(*&^%$ Troll!

Reply to
peterwieck33

Methinks your first problem is finding the box that controls the automagic transfer switch (which contains the sensing, timing, and switching logic). Something like this: "Automatic Transfer Switch Controller Tutorial" It's probably inside the generator enclosure. Just look for another rats nest of wires. The thresholds, timing, interlock, etc settings are usually adjustable.

I have two guesses:

  1. The +12VDC that runs the relay is probably missing because the starter battery in the generator is dead, or the fuse that protects it is blown. That might explain the missing fuses. It might also be that State Electric took one look at the mess and ran away. There might be some lower voltage coming from the charger trying to charge a dead (shorted) cell.

  1. Every controller I've seen has a self-test and/or test-run feature. You should be able to test the transfer switch with the test-run button instead of reworking the wiring.

Also, I have some suggestions:

  1. Don't play with the transfer switch with the utility AC power applied. The life you save may be your own. The undersized wires feeding the transfer switch should go to a double breaker on the main panel. Flip it open, check that there is now no AC on the contacts or anywhere in the rats nest of wires, and then troubleshoot.

  1. Draw as schematic diagram and label everything. If this were my headache, that's the first thing I would do.

  2. If you know a local electrician, who won't turn you in to the county, have him look at the wiring and make some recommendations.
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Jeff Liebermann     jeffl@cruzio.com 
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Reply to
Jeff Liebermann

Jeff:

The creature that calls itself Arlen G. Holder is trying hard for a Darwin Award.

For its sake, and ours, please let it win!

Peter Wieck Melrose Park, PA

Reply to
peterwieck33

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