Generac starting without power loss and will not transfer back to utility after reset

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FREEBALL

Senior Member
Location
york pa usa
Having an issue with a Generac that fired up the other morning for no particular reason. After the homeowner reset, it said utlity power loss detected and after 10 second wait it fired up again. No power outage was present. Im thinking sensing circuit and fuses that control this but wanted to know if anyone else had any ideas or familiarization with this. The control board was replaced 2 months ago. It is a model 5873 17kw NG Generac, the model has been discontinued. Im going to job on Tuesday.
 

ceb58

Senior Member
Location
Raeford, NC
Having an issue with a Generac that fired up the other morning for no particular reason. After the homeowner reset, it said utlity power loss detected and after 10 second wait it fired up again. No power outage was present. Im thinking sensing circuit and fuses that control this but wanted to know if anyone else had any ideas or familiarization with this. The control board was replaced 2 months ago. It is a model 5873 17kw NG Generac, the model has been discontinued. Im going to job on Tuesday.

Sounds like it, check the fuses on N1 N2. If generator doesn't read 220v it thinks power is out.
 

FREEBALL

Senior Member
Location
york pa usa
Thanx GoldDigger yeah I am afraid to find out what caused that lol :happyyes:thanx for your thoughts I will let you know how I make out. Take care and be safe.
 

FREEBALL

Senior Member
Location
york pa usa
GoldDigger, yup the fuses are both blown. I wanted to wait to replace them to do some research. It seems the cold weather kit is also wired from the sensing circuit. And the night in question the temps were below 34 in the outer areas so Im leaning towards this to be the answer. Im trying to figure out if maybe the conductor size is too small for the added load. I wouldn't think so but nobody had the fuses today so it gives me time to research. It says the heating units are self operating meaning they control themselves when the temp gets to low. I think total watts were like 35watts. Im wondering if they could've possibly built up enough heat and with too small of a conductor, inability to dissipate the heat, that the fuses blew. I pulled in a 16/7 cable in conduit at the advice of the generac company in the area, against my wishes, I used single conductor 14g in conduit on previous install. The fuses fast acting. I think this design is less than favorable, nothing should be on the sensing circuit, if so then whatever else is on should be fused after the sensing unit IMO. What are your thoughts.
 

ceb58

Senior Member
Location
Raeford, NC
There should not be any thing extra on the N1 N2 sensing circuit. It is only fused at 5 amps. That is what the T1 circuit is for. It is used to supply power to the battery charger and can be used for the cold weather kit
 

FREEBALL

Senior Member
Location
york pa usa
yea but after reading installation instructions from Generac it tells you to install this on the 240v sensing circuit since this is the only 240v from supply and the kit is 240v. The homeowner only plugged his heat into prewired connections, Generac instructs you to do this, why I don't know, So I believe I have to troubleshoot some heat.
 

FREEBALL

Senior Member
Location
york pa usa
does anyone know what the load is of the sensing unit on a 5873 generac the tech on phone did not. He said its less than 5 amps but studdered when I asked how can you apply another load i.e. heating elements, without knowing this.
 

GoldDigger

Moderator
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Location
Placerville, CA, USA
Occupation
Retired PV System Designer
The wires would have to get very hot to heat the connected fuse enough to lower the fuse trip point significantly. A bad connection to both fuse blocks might cause them both to overheat. But a more likely cause for both fuses blowing would a fault from the sensing circuit to ground or neutral in the control board.
I would not just replace the fuses without putting in series a current limiting resistance (like two light bulbs.)
 

ceb58

Senior Member
Location
Raeford, NC
Did some investigating and found that the battery heating pad, that goes under the battery, dose connect to N1 N2. There have been others that found the connector can become corroded or the weight of the battery would cause a short in the mat blowing the fuses.
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
Did some investigating and found that the battery heating pad, that goes under the battery, dose connect to N1 N2. There have been others that found the connector can become corroded or the weight of the battery would cause a short in the mat blowing the fuses.

Other options for similar Generac include carburetor heater and fuel regulator valve heater (for LPG/LNG models). These probably are a low lower power normally, but could short out too.
 

GoldDigger

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Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
thanx ceb58 and golddigger should I use like a 250 watt bulb on each leg you think

That might work. But if the fuses are fast blow the inrush of a cold 250W bulb might allow a short circuit to blow the fuse anyway.
Depending on what the normal current load in the circuit is, I might go with something smaller.
Or just use the bulbs to bypass the empty fuseholder.
 

FREEBALL

Senior Member
Location
york pa usa
well Im not as concerned about the fuses as I am the control board. Are you saying you think Id be ok with the fuses I bought extra in the event there is an issue
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
well Im not as concerned about the fuses as I am the control board. Are you saying you think Id be ok with the fuses I bought extra in the event there is an issue
Yes, as the damage to the control board, if any, has probably already happened.
It is very hard to find fuses that work fast enough to protect semiconductor equipment.

(Transistors are objects that blow out very quickly to prevent damage to fuses.)
 

FREEBALL

Senior Member
Location
york pa usa
well I ran continuity on n1 and n2 and had nothing to ground but that was with a multi meter. And I was thinking the same that damage may already be done. Im going to disconnect the heating elements, check connections and install the fuses and go from there I believe.
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
:thumbsup:
well I ran continuity on n1 and n2 and had nothing to ground but that was with a multi meter. And I was thinking the same that damage may already be done. Im going to disconnect the heating elements, check connections and install the fuses and go from there I believe.
 

FREEBALL

Senior Member
Location
york pa usa
GoldDigger/ceb58, well I was successful atleast for now I hope. I replaced the fuses ran the Gen. through all tests and not a problem. I couldn't get an accurate reading on the heat pads for the oil filter or battery elements but got about 1.5 amps on the sensing circuit with them connected. I would like to know what the sensing circuit is to draw but I guess I will never know. I still do not know what caused this though, I thought maybe the voltage somehow dipped down to a point that would increase the load of the heat pads and thus blow them and then the Gen. sensed a loss of power but not sure. Anyway all worked well. With just a modest bill for the work. I know this wasn't an issue of mine but felt a little sympathy with all this guy has gone through. Thanx for your help.
 
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