How the heck does a typical home transfer switch work?

Hi Jeff, I agree with you, and I can clearly see that there is a rat's nest inside the generator, which must be doing the initial sensing of the power in the first place, as you mentioned.

I think my task is EASIER than looking at that rat's nest inside the generator though, since all I need are the wires coming OUT of the generator.

I'm not sure yet where to FIND those wires inside the transfer switch, but I think the first (and only?) place I need to look is at what the pins of that "plastic solenoid" do... since that solenoid seems to send the purple and blue wire 12VDC to the "double-fisted solenoid" to switch power from the mains to the generator.

I understand and appreciate this assessment, where there's LOTS I didn't mention (which is always the case in such things), mainly the fact being I "think" it was me who pulled those fuses long ago and forgot to put them back (I think I was testing them but I don't actually recall).

Also, you're actually correct that the battery in the generator WAS dead, since I had disconnected it to charge it, and then I had left it disconnected where the charge eventually bled off. I actually had to jumpstart the generator when the power last went out, but I have since charged the battery (I'm gonna put quick connect clamps on the battery at some point, which will help in the charging process since I have multiple spare batteries I swap in and out of that generator).

This is good to know, for two reasons:

  1. This is dangerous stuff so having safe tests is required, and,
  2. Most of what I read suggested testing MONTHLY (which is crazy frequent)

Thanks for that advice, Jeff, as I'm well aware of the power, but I'm not sure yet how to test a transfer switch. It does seem prudent to test the transfer switch ISOLATED from BOTH the mains and the generator.

Preventing the generator from turning on should be easy as it has a power switch and it requires the battery so it's easy to prevent it from turning on.

I'm not totally sure simply turning OFF the mains will isolate the transfer switch - but that's simply because I'm currently ignorant of the wiring diagram (which is one reason you said to do that first).

If the power goes from the power pole to the utility meter to the main 200 Amp breaker switch, and THEN to the transfer switch, then doing all tests with the main 200Amp circuit breaker off is prudent. (Obviously I'd doublecheck with the Fluke DMM.)

Yup. I agree. I had wanted from this question on Usenet to first get a general idea of how these transfer switches work - which - I think I kind of now have - but the exact wiring of every connection is still needed before I can effectively troubleshoot.

Generac sent me the owners manual for my 09067-9 generator, which contains exploded diagrams, for example, here's the exploded diagram of the 09067-9 Generator Control Panel: And the wiring diagram for the 09067-9 generator itself:

And here's the exploded view for the 79848A transfer switch: And the wiring diagram for the 79848A transfer switch:

Once, I called a well pump guy, and told him I had a problem, which he fixed, but I told him before he came out to charge me based on the fact I would be standing there right next to him as he debugged, asking him questions while he did the work in front of me.

It was then that I noticed he simply replaced entire circuit boards, simply by the process of pulling them out, putting the new one in, and finding that it worked, so he was about to take the old circuit board "home" with him, where I said if I'm paying for the new one, I want the old one (I still have it). Some day I'll figure out specifically what's "wrong" with it. :)

A similar thing happened with the heater repairman, who simply replaced the main circuit board, but he insisted that there was a core charge which _he_ wanted back - and that he's have to charge me for that - so he got the core charge, not me.

I learned from that that these guys replace the entire board rather than figure out what's wrong ON the board.

Given that replacing things seems to be what the repair techs do also, in this case, I think I have three options, two of which are what many people use, while the third option is the approach I'm currently trying:

  1. Replace everything, one by one, until the damn thing works
  2. Pay State Electric or Spiess Electric to fix it (in my presence)
  3. Debug the damn thing (after first figuring out how it works)

Personally, I like to debug first, where simply UNDERSTANDING how the circuit works usually causes the offending part to SCREAM OUT that it's broken.

To that end, I'll follow your advice and start marking up the panel with a label of the purpose of each of the myriad connections.

Reply to
Arlen G. Holder
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Thanks for that helpful advice where I gave up trying to source at a local hardware store since I had tried three local box stores, none of which sold the Buss BBS-4 or BBS-5 600V fuses o Ace, Home Depot, Lowes

I called Generac today, where I was surprised to find that they don't have an "opening" time - their customer support is open 24/7/365, which is surprising in this day and age, don't you think? o 888-GENERAC (888-436-3722) extension 4, extension 2 (or 262-544-4811)

They confirmed there is no separate manual for the 79848A transfer panels; the transfer panels are covered in the 32-page owners manual (PN 98374) for the Generac 09067-9 8KW propane generator itself (where the manual is mostly about the generator but it does have a few pages about the transfer switch).

There IS a parts diagram though, which gave me the Generac part numbers o PN 63617 Transfer Relay o PN 73590 BSS-2 Fuse 2A o PN 71340 100Amp 2pole Relay etc.

Generac told me the cheapest place to get the parts is usually o But they also said there is a good Generac parts lookup engine at o

Where I ran a quick price survey of the three parts above for reference: o PN 63617 Transfer Relay $18 at Jacks, $25 at Tree o PN 73590 BSS-2 Fuse 2A $6 at Jacks, $9 at Tree o PN 71340 100Amp 2pole Relay $243 at Jacks, $287 at Tree etc.

The nice thing about Usenet is that I like to give back to the team, as you're aware (where I respond to all that are helpful at the same time I try to ignore the worthless trolls) - where these two outfits "seem" to be generally useful to source manufacturure parts for MORE than just Generac. o o

Do folks here know of other outfits useful for sourcing common brand name part numbers for these types of electrical parts (pumps, motors, openers, etc.)?

Reply to
Arlen G. Holder

The wiring diagram of the generator shows the (missing) controller, with all the connections to the automatic transfer switch. Pg12 of the manual, lower schematic, shows wires 23 and 194 going to the transfer switch. Since the other end of these wires goes only to the solenoid (relay) coil, I would presume that these should have 0V across them when the transfer switch is on utility power, and 12VDC(?) when it on generator power. Put an LED and resistor across both solenoid coil terminals so you can see what's happening without fumbling with a volts guesser.

Unfortunately, there's no schematic for the controller logic board which runs the show. Near the controller logic board is SW1, which is the "start/stop" switch. That should NOT activate the relay on the transfer switch. This is the generator test switch which I previously indicated was on all such autostart generators.

SW2 is labeled "Set Exercise Switch" which is something like a "test" switch but also is not intended to test the transfer switch. There should be something in the manual on how to use this switch. Here's a video that might offer a clue on what I think is a similar generator: "How To Set Exercise Time on Generac Air Cooled Generator Pre Nexus Controller APSwrap" There's quite a bit on how a proper test switch should operate:

This is a typical generator test which demonstrates proper operation: "Home Generator Transfer Test"

Also on the schematic is the fuse F1 (15A), which appears to protect the controller 12VDC battery line. Check this fuse if you have a good

12VDC battery, but no controller function. If this 15A fuse is actually blown, you potentially have a high current short somewhere in the generator on the 12VDC line. Be careful tracking this one down.

Remember, you have but one life to give for your backup power system.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
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Reply to
Jeff Liebermann
  1. Note that it's a "Transfer Switch" and not an "Automatic Transfer Switch"

A Transfer switch is noting but a "BIG Relay" which is designed so mains and utility power CANNOT be connected at once if a part failed.

Emergency panel

If the generator is too small for the house, then you put the loads that need power in an emergency on a single panel. (e.g. refrigerator, sump pump etc)

The "automatic" part might do a number of things such as:

  1. monthly/weekly test
  2. monitor oil level
  3. Exercise generator or generator and transfer.
  4. make sure utility power is stable before taking generator offline.
  5. Implement cool down phase.
  6. The generator exercise period may top off the battery.
  7. Monitor voltage/frequency
  8. manage starting

So, voltage and frequency out of range will prevent transfer. Oil level will prevent generator from starting automatically.

You may have two sub-panels and a pool. The pool does not get generator backup. Looks like your missing stuff like fuses. You may just have a 12 V signal that tells it to transfer. It may or may not need power to keep it in one position. I did not look at the details.

Reply to
Ron D.

My transfer switch is a pair of 30A breakers for the genny and an aluminum sheet that slides up and down, so that the main breaker and the genny breakers can never be turned on at the same time.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
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Reply to
Phil Hobbs

I have the same set up at the house.

200 Amp pass through panel with 200 amp main breaker. Then the 60 amp breaker for the 15 KW generator.
--
"I am a river to my people." 
Jeff-1.0 
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Reply to
Fox's Mercantile

UPDATE:

Hi Jeff,

As you're aware, PG&E has cut our power here near Santa Cruz and the hills surrounding Silicon Valley, where the fact I'm able to post this means I figured out what the problem was with the power from the generator not getting to the house.

I had _thought_ it was the transfer switch, simply because a couple of those SBS-2 600V 2Amp fast acting ferrule fuses were missing, but it turns out that when I replaced the two missing fuses, nothing changed.

It turns out that half of the part #5 was broken inside (invisibly so) o Generac Part Number #74969 35Amp Circuit Breaker

I'm not sure if that's the same part as "CB1" in bottom right of this page:

But it's Generac Part Number 74969 35 Amp Circuit Breaker (2 ganged poles), which disconnects 120VAC power based on my measurements on the breaker.

This is what it says on the circuit breaker itself: Carling Switch Inc. AA2.B0.24.635.5D1.C FL AMP 35 MAX VOLTS 227 (? hard to tell) HERTZ 50/60 DELAY 04 (? hard to tell) TRIP AMPS 43 (? hard to tell) Mexico 9513 (probably the 13th week in 1995)

Where the complete circuit diagram is outlined already in this older post:

In summary, there were two problems concurrently:

  1. The fuses were missing in the transfer switch
  2. Half the circuit breaker was internally broken

The result was that there was no electricity in the house when the PG&E power went out until I replaced the fuses; and there was only electricity to half the house. The 35Amp ganged circuit breaker has two "LINE" and two "LOAD" terminals, where, each circuit breaker innervates half the house.

--
Solving electrical problems with advice from helpful posters on Usenet.
Reply to
Arlen _G_ Holder

Too bad, that by pure blind luck, certainly not skill, that we continue to be cursed with your presence.

Reply to
peterwieck33

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