Daveh85
Hi all,

I’ve had two SMM modules go bad over the past two months. Both on 30amp fuses, the entire panel protected by a surge protector. What could cause this? The top circuitry is fried as is the low voltage coil. What’s odd is that we’ve had no outage, only the usual weekly maintenance runs on the generator.

Any ideas? Oh and these were installed about 9 months ago.

Thanks.
Quote
grsthegreat
no idea. ive installed 100's of these, and have had only 2 failures and those were buzzing units. if only 9 months old they are covered under warranty.
Quote
Daveh85

We’ve had another module go bad since first reporting. All have failed on the coil of the contactor and low voltage protection side of the circuitry. Could it be a bad batch?


Some details about the loads. They are all 240v, 2 were 30amp and 1 was 20amp. They are Eaton breakers and we have a whole home surge protector. 


Thoughts?

F944841A-19C1-4033-8C72-CF4A8C50152B.jpeg  80F4903E-4986-4D3A-BD1F-3AC74627F6E1.jpeg  F94F771D-3F8F-4BC4-8564-0CA6B3120CD1.jpeg  898A6154-410C-4F31-B92F-C6BD918C2EA0.jpeg  D9AB319A-E41A-4EAF-A1BE-7391D2CCCF68.jpeg  720B2260-42A6-4D5A-8E82-F36AF88BF113.jpeg  234B9E65-2237-4A51-99FC-2970CEF5A456.jpeg 

Quote
JayH

Problem appears to be bad design. R6 through R9 are overheating. Those look like 1206 size parts. R6 and R7 are 130K resistors. The only way they could get enough voltage to overheat to that extent would be if they're across the 240 volt line. It looks like they're part of a switching regulator. You can see the RF filter inductor and bridge rectifier on the board. Unless I miss my bet, they're feeding the raw line voltage through a voltage divider of R6 through R9 as part of the power supply. Those four resistors need to be physically much larger, at least as big as R14 nearby. Flameproof through-hole parts mounted above the board with an air gap would be better. If they keep them surface mount, a ground plane under the board would also help.

Seeing some discoloration on circuit boards under heat-producing parts isn't really all that unusual and these might function like that for a while. Once the carbonization  gets conductive enough to get the attention of the 240 volts, it's going to be game-over pretty quickly, and it would be a spectacular failure indeed except for the small dark brown rectangular device near the connector, which is a fuse. That board could probably be fixed.

The contactor relay is continuously powered in normal operation and some discoloration of the varnish over time is also typical. It's not a low-voltage coil, it's line powered. Note that it's a compromise coil for 208 or 240 volt operation which means that it's near its upper limit at 240V continuous duty. Is the relay coil open?

Quote
Daveh85
You're on the money Jay. I checked the continuity and it's open. 

Does anyone have one of the "newer" 7000 SMM Modules that they can snap a picture of? I'm wondering whether anything changed in the latest rev.
Quote
grsthegreat
ya, i can take a pic of it later today. also, you are in usa? 60 hz not 50hz?
Quote
grsthegreat
just checked my inventory control, and ive installed 135 of these older units and had 4 failures. 3 failures were due to shreaking contactors. I show 1 failure due to one wire leading to contactor melting and shorting out. i never did figure out what caused that. 20200208_102257.jpg  20200208_101858.jpg  20200208_102013.jpg  20200208_102021.jpg  20200208_102041.jpg 
Quote
Daveh85
grsthegreat wrote:
ya, i can take a pic of it later today. also, you are in usa? 60 hz not 50hz?


Thx for sharing the pics. Looks like much of the board is identical, though it’s a higher rev and I’m sure there are subtle differences. The four we have are all here in the US, all going bad during the winter months. They are installed in a conditioned space that is 70F.

Do Generac engineers review these posts by any chance?
Quote
grsthegreat
no idea.
Quote
JayH
Pictures of the new board show the same issue. The newer one has looser tolerance parts for the suspect resistors. Older boards look like 1% tolerance (three significant digits plus multiplier) newer are 5% (two significant digits plus multiplier). This board will likely suffer the same issue in time.

Daveh85, do all of your failed boards show heat damage in the same area?
Quote
BillM
I can't speak about them failing but I for one wish they actually worked as they were marketed and continue to be marketed to work as.  I have one, and it has a lockout switch.  Which I have learned means very little because in my installation it means absolutely nothing.  My Guardian 22kW runs and the SMM won't lockout the load.  I suppose if the generator was truly overloaded it might.  I'll never know since I haven't been able to get that to happen.  If you want a vote that it's a ridiculously designed product you have my vote.  Generac eventually wrote me a check to compensate me for my time and trouble when I fought this module, in this forum as well.  When I bought mine, it didn't have the 'addendum' to pretend the lockout switch doesn't exist.
Quote
JayH

BillM wrote:
I can't speak about them failing but I for one wish they actually worked as they were marketed and continue to be marketed to work as.  I have one, and it has a lockout switch.  Which I have learned means very little because in my installation it means absolutely nothing.  My Guardian 22kW runs and the SMM won't lockout the load.  I suppose if the generator was truly overloaded it might.  I'll never know since I haven't been able to get that to happen.  If you want a vote that it's a ridiculously designed product you have my vote.  Generac eventually wrote me a check to compensate me for my time and trouble when I fought this module, in this forum as well.  When I bought mine, it didn't have the 'addendum' to pretend the lockout switch doesn't exist.


It's an interesting design, and in many ways rather clever. The assumption is that the generator won't be running at exactly 60.00 Hertz. The SMM monitors the frequency. What the lockout switch is supposed to do is to sense the generator frequency as slightly inaccurate and shed the load.There aren't any control wires to the SMM, only the AC line, so frequency and voltage are all it can measure.

Without the lockout switch operated, it ignores slight differences from 60.00 and instead looks for a dip in frequency or a substantially low frequency (indicating an overload) and sheds the load then. When frequency returns to a normal range for the generator it re-energizes the load.

What your situation tells me is that your generator is doing extremely well in terms of frequency stability and the SMM isn't able to distinguish between utility and generator power. The SMM works well for me in a situation where I don't want to lock out the load on generator unless there's an overload condition, but I may take it apart to see if the same overheating issue exists.

Quote
BillM
JayH wrote:

Without the lockout switch operated, it ignores slight differences from 60.00 and instead looks for a dip in frequency or a substantially low frequency (indicating an overload) and sheds the load then. When frequency returns to a normal range for the generator it re-energizes the load.

What your situation tells me is that your generator is doing extremely well in terms of frequency stability and the SMM isn't able to distinguish between utility and generator power. The SMM works well for me in a situation where I don't want to lock out the load on generator unless there's an overload condition, but I may take it apart to see if the same overheating issue exists.



Generac, who sent two engineers to my house, one came from the Whitewater plant and the other came from Waukesha HQ to look at my installation, replaced my SMM (4th replacement in 90 days plus, all 'good' units in hindsight).  Table 2, page 4 of the manual and further explained on Page 9 says (without qualification to load being light or overloaded), that with the lockout position set to on, while on generator; "Power is NOT available on module output (contactor output).  Contactor is OPEN"  The highlighter (upper case) words are how they are in the manual.  We went on generator, lockout switch on.  We had a 5 ton A/C on.  We had every light (5200 sq ft home) on, and a car charging and though my lights dimmed twice.  Once when the generator took the load and then a second time when the SMM came out of it's 5 minute auto-delay and while on generator gave the EVSE all 32 amps it wanted.  We could hear the generator scream for it's mother on both instances but the SMM never once dropped the load.

Here's where it turned into a 3 Stooges situation.  I bought the SMM in October of 2018.  I installed it in front of an electric car charger (EVSE).  I don't want my car or the EVSE to take power while on gen as a general rule.  I have other cars, so I can always manage.  But I loved the idea that by flipping a switch I could change my mind.  I noticed through my monthly load tests, that things weren't going as planned/designed.  I was getting txt's from the car about it's charging in a time when it shouldn't be.  I asked for help from my Generac Service Provider, they went silent, they told me that I had to pay labor.  I said; "take my money".  They never showed and disappeared.  I wrote two more Generac service providers in my area, offering to PAY for them to look at it to see where I screwed up in the installation.  One never showed, one never returned any calls.  I then went to Generac directly.  Got no where.  Filed a complaint with the Attorney General consumer protection division.  In the meantime, I posted my problem here.  Went back and forth, replaced the module.  Saw the 7000 came out.  Replaced it with that one.  None of them came with the fancy addendum that said the switch does nothing that I learned after some time on THIS forum.  My first SMM was bought in October of 2018.  The technical bulletin came out in January of 2017.  The technical addendum that is dated January 2017 says to ignore the switch, it does nothing.  I gave up, I had my answer, a very kind member here who I won't identify but his initials are Mattyman, posted the addendum here online.  Thank you Matty.  See July 11, 2019 posts.  At this point, I was pissed and just gave up.  My mental note was to replace it with a PMM someday.  I ran extra wire so I could use them for the PMM control wire.  But wait, there's more.  Generac finally called me after the AG complaint hit them.  They sent two guys out, with a new SMM.  There SMM didn't have the addendum either and I tried to tell them about it but they assured me that I misunderstood the addendum and that it will operate as the manual and logic suggests.  It is, afterall, a lockout switch.  I let them test.  They said my SMM, the 3rd one, is also broken.  They replaced it.  Tested.  No change.  At this point while they were replacing the SMM I found the addendum on THIS forum and printed it for them.  I handed it to them.  Silence.  I'll skip the rest because it is even more bizarre.  But here's how it ended;  They reimbursed me for the SMM, $500 to cover the cost of installing it.  Left the SMM in place, but they did offer to remove it.  And, I got a shirt AND a hat.

Quote
grsthegreat
the 7000 series requires a jumper move to enable lockout. this is weird. my jacuzzi has had the older style smm on it for 3-4 years. works great. not sure what causes your issues. the PPM module works just like the SMM, but wont shed the load permanently.
Quote
grsthegreat
JayH wrote:
Pictures of the new board show the same issue. The newer one has looser tolerance parts for the suspect resistors. Older boards look like 1% tolerance (three significant digits plus multiplier) newer are 5% (two significant digits plus multiplier). This board will likely suffer the same issue in time.

Daveh85, do all of your failed boards show heat damage in the same area?
Just for giggles, i opened up the unit running my Jacuzzi tub for nearly 4 years. not a spec of discoloration on board.
Quote
grsthegreat
And for the guy that wants a load shed for car. have you looked into a company called PSP products ( pspproducts.com ) They have a huge selection of aftermarket load shed units that can work on a variety of generators. I use their 100 amp latching load shed units for many years.

https://www.pspproducts.com/gld-50/
Quote
BillM
grsthegreat wrote:
And for the guy that wants a load shed for car. have you looked into a company called PSP products ( pspproducts.com ) They have a huge selection of aftermarket load shed units that can work on a variety of generators. I use their 100 amp latching load shed units for many years.

https://www.pspproducts.com/gld-50/


Yes, I chose the SMM because I liked the famous 'switch' so I could if I ever had a long outage and NEEDED the car charged ..... I could easily go that route and still get overload protection.  
Quote