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Tcwndsr

Generator High Voltage

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I have a Generac 55G in an 02 National RV. I went to use it yesterday but my Progressive EMS flashed a voltage of 160 on the display before shutting down due to the high voltage error. I checked it today with my meter and it showed the voltage sitting at 6 volts for 30 seconds or so before spiking to 160 and then returning  to 6volts. It runs smoothly but sounds like it’s under a load before the voltage spikes. There is no transfer switch involved, the generator is wired to a 50 amp outlet in the electric bay which I would plug my shore cord into. I think my EMS saved my bacon, can’t imagine what would have been fried by 160 volts if it had passed through to the rest of the coach. Some brief research is pointing me towards the voltage regulator, what do those with more electrical knowledge think?

Thank you!

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I am not terribly high in the knowledge area so others can be much more definitive but I will comment that this sounds like a problem I had with a floating neutral so part of your answer will be told in checking voltages working back from the progressive. Where did you check the voltages? At the generator?

 

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13 minutes ago, Daveh said:

 sounds like a problem I had with a floating neutral

Ditto

I would start by checking connections

Clay

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TC, its too early and there's too many unknowns as of yet, but to start with I believe some of those Generac 55G's are "configurable" as 240 volt, do you know how yours is configured??  If its 240 it would measure 240 L1 to L2.

I would assume it came from the factory with a BONDED Neutral (NOT a Floating,  they make small gensets with both Floating and Bonded Neutrals) but since its for RV use I would want it to have a Bonded Neutral.

You might want to check to insure it has a Bonded Neutral and also check the connections from genset to the outlet and in the outlet box are all wired correct and tight. In 240 volt RV pedestals if the Neutral isn't present you can end up with instead of 120 and 120 on each leg  you may get 200 and 40 grrrrrrrrrrrr 

I agree with your assessment the Voltage Regulator may be at fault but check the wiring first

An EMS is expecting a Bonded Neutral system and 120 volts on each leg, yours is doing its job it sounds like

PS This manual if for you genset may help:   https://www.norwall.com/product_pdfs/3799_5751_specs.pdf

John T   

Edited by oldjohnt

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3 hours ago, Tcwndsr said:

Some brief research is pointing me towards the voltage regulator, what do those with more electrical knowledge think?

As a career electrical tech I have to agree. A floating neutral only impacts the voltage when under load and the total voltage of the two legs added together would be 240V. If you measured 160V between each leg and neutral it isn't a floating ground and the generator voltage control is the most likely cause. If you have the means to do so, check the frequency as well since the generator running too fast might cause the high voltage but it would also increase the frequency. 

Are we correct to assume that you had proper voltage in the past and this is a new problem?

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I’m electrically disabled but learning so bear with me...

It runs at 6 volts for about 30 seconds, spikes to 160 for about 10 seconds then drops back down to 6. This cycle is pretty consistent.

i just tested L1 to L2 as John T suggested, got 0.00 reading on the meter, switches to -0.00 when it cycles to 160 v. Maybe that reading is telling us something? I don’t know if it’s a floating or bonded neutral, wouldn’t know how to tell the difference. I checked the wiring in the box, ground to frame, everything under the access panel and everything seemed to be tight and relatively clean.

I don’t think I have a way to check frequency, pretty sure a multi-meter doesn’t do it. My EMS reads frequency but it shuts down before it cycles through the readings. It doesn’t seem to be running faster than normal and yes, this is a new issue. I just did an oil change about 6 weeks ago and ran it under load for 30-45 minutes at that time with no problems. I exercise it regularly as recommended.

I had an issue with slightly low voltage about 2 years ago but corrected that easily by adjusting the regulator.

Thanks guys!

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This outlet you are connected to, is it something that is part of the generator or did you have it hardwired to the generator? Is there a way to substitute another outlet or remove it and check the wires directly. 

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This discussion may help. I think John has you on the right course. If you can rule out wires touching (OR EVEN LOOSE---TIGHTEN DOWN EVERYTHING EVEN OUTLET WIRES--LOOK FOR EVIDENCE OF BURNING OR FAULT) then probably voltage regulator.  Remember the source of the floating neutral may not be evident and even a loose wire can cause this problem. So double check and tighten stuff even if it looks good.   http://www.irv2.com/forums/f258/generac-q55g-146vac-output-387895.html

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4 hours ago, Tcwndsr said:

i just tested L1 to L2 as John T suggested, got 0.00 reading on the meter, switches to -0.00 when it cycles to 160 v. Maybe that reading is telling us something? I don’t know if it’s a floating or bonded neutral, wouldn’t know how to tell the difference. I checked the wiring in the box, ground to frame, everything under the access panel and everything seemed to be tight and relatively clean.

TC Thanks for the feedback and here's my response to your new info:

1) If the genset is NOT configured for 240, as I suspect, you would indeed measure 0 Volts across two legs of the same phase same voltage subject to how its wired.

2) How to tell if its a Floating or a Bonded Neutral: Take a continuity tester or an ohm meter and measure between Neutral and the iron case/frame of the Genset. If its a Bonded Neutral there will be no resistance IE a basically short circuit Neutral to case/frame, but if its a Floating Neutral its an open (high ohms approaching infinity on some meters) circuit. There are good reasons why a Genset may have a  Floating or Bonded Neutal but that's another topic.

3) Open Neutral. Its more of a hazard in a 120/240 50 Amp configuration then a 120 volt only. In a 120/240 like a 50 amp RV pedestal has if the Neutral is open there's still 240 L1 to L2 but if you connect L1 loads and L2 loads which are as typical different resistances and they draw current you end up with different voltages on each leg IE you could get 200 volts on L1 and 40 on L2. Obviously if there's no load applied there's no V = I x R voltage drop WELL DUH  you say lol. If its a 120 only supply if the Neutral is open there's no return current path and the device simply doesn't work.

4) An Open or resistive Neutral is NOT the end all and cause of many voltage problems as many lay persons tend to believe. In electrical power distribution terminology the Neutral is most often BONDED AND NOT FLOATING. However there can be an open (more hazardous in 120/240 then 120 only) or a loose/resistive connection which can cause a V = I x R Voltage drop when under a load. If the genset still exhibits those weird voltages direct on it not hooked to any outlets and loads I suspect a voltage regulation problem NOT an open or loose/resistive Neutral...…..

NOTE I am NOT any genset expert by any means so no warranty. I'm only a long retired n very rusty electrical power distribution design engineer and 49 year RV owner and past dealer, so consult with generator experts and service technicians. If the genset internal wiring and connections are all okay and the voltage problems still exist right at the genset itself with no outlets or loads attached, it could be the voltage regulation system (among a ton of other) is at fault, but there are just too many possibilities and too many unknowns to figure it out remotely.

 Best wishes and good luck

John T   

  

Edited by oldjohnt

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4 hours ago, Tcwndsr said:

i just tested L1 to L2 as John T suggested, got 0.00 reading on the meter, switches to -0.00 when it cycles to 160 v. Maybe that reading is telling us something?

How & wher did you measure the 6V followed by 160V? Were you measuring between L1/L2 and neutral? Using a good digital meter, I assume? If those readings between L1 & L2 were in the times of 6V & 160V then it would sound like John is right about the two legs being in phase and not set for 240V. I have very little experience with a Generac but here is a copy of the service manual.  On page 4 of that manual, it mentions that the voltage from the generator before field boost is 7 - 12V, which may be what you are first observing. On page 5 it addresses the configuration of single or dual voltage. Starting on page 19 there is a troubleshooting flowchart, but you really need to have a frequency meter to do the tests. Starting on page 27 are a series of diagnostic tests. 

 

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I checked the voltage at the outlet wired to the generator, measuring between both L1/L2 and neutral. I wasn’t able to open the link to the service manual, can you post that again, Kirk? Thanks

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6 hours ago, Tcwndsr said:

I wasn’t able to open the link to the service manual

I wasn't either, try this link, it worked for me http://www.generator-parts.com/manuals/generac-rv/0E7225.pdf

On page 7 of the manual linked above it talks about RECONNECTION and my best pure "guess" is from the factory it came with two 120 volt legs and no 240 (see Figure 1.8 Page 7) . If that's the case (I have no idea setting here) if alls working I would expect 0 volts if measured across L1 & L2 .

FWIW even this may be above your skills and no help to you whatsoever,  In the manual linked above I found this interesting:

NOTE   If you read that below, I think Kirk may be onto something when he stated  "On page 4 of the manual it mentions that voltage from the generator before field boost is 7 to 12 volts"   !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

 

FIELD BOOST

When the engine is cranked during startup, the

engine's starter contactor is energized closed. Battery

current is then delivered to the starter motor and the

engine cranks.

Closure of the starter contactor contacts also delivers

battery voltage to Pin 13 of an Engine Controller circuit

board. The battery current flows through a 47

ohm, 2 watt resistor and a field boost diode, then to

the Rotor via brushes and slip rings. This is called

“Field Boost” current.

Field boost current is delivered to the Rotor only while

the engine is cranking. The effect is to “flash the field”

every time the engine is cranked. Field boost current

helps ensure that sufficient “pickup” voltage is available

on every startup to turn the Voltage Regulator on

and build AC output voltage.

NOTE: Loss of the Field Boost function may or

may not result in loss of AC power winding output.

If Rotor residual magnetism alone is sufficient

to turn the Regulator on loss of Field Boost

may go unnoticed. However, If residual magnetism

alone Is not enough to turn the Regulator on,

loss of the Field Boost function will result In loss

of AC power winding output to the load. The AC

output voltage will then drop to a value commensurate

with the

 

AND ON PAGE 9 I FOUND THIS: Your Excitation circuit breaker could have a problem IT STATES IF EXCITATION CURRENT FLOW IS LOST THE AC OUTPUT VOLTAGE WILL DROP TO 7-12 VOLTS      But what about that 160 volt reading ???????????????????????

 

EXCITATION CIRCUIT BREAKER:

The excitation circuit breaker (CB3) is self-resetting

and cannot be reset manually. Should the breaker

open for any reason, excitation current flow to the

Rotor will be lost. The unit’s AC output voltage will

then drop to a value commensurate with the Rotor's

residual magnetism (about 7-12 VAC).

 

HOWEVER that doesn't explain your 160 volt reading IE leads me more towards a Voltage Regulator problem ???? 

Figure 2.7 Page 10 shows the Voltage Regulator and perhaps it or the Excitation Circuit Breaker mentioned above may ??????????? be your problem.

Since I'm not there to take measurements and are for the most part  operating in the dark I THINK YOU NEED A QUALIFIED SERVICE TECH TO TAKE IT FROM HERE because while a Voltage Regulator or other components may be the problem there may be other minor issues such as a loose resistive connection. At least take a look at the Regulator and its connections (remove clean and re attach) and the excitation circuit breaker and any and all other wiring connections inside (unplug clean and re attach the connectors)

 

Sorry I'm running out of smarts and this is getting above my pay grade but will still help more if I can  

 

John T

 

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The two manuals have a lot of similarities, this one lists 55 (The Genset in question) and 65 and 75, Models 4702, 4703, 4705, 4706, 4707

http://www.generator-parts.com/manuals/generac-rv/0E7225.pdf              "generac-rv" part of the URL

 

This one lists IM, NP and Q Series with engine controller circuit board 92234

http://www.generator-parts.com/manuals/generac-rv/0E7225.pdf             "generac-rv" part of the URL

 

Both are similar technical in depth manuals, Do you know exactly which Genset you have (55, Model 47xx, Series IM, NP or Q, and what circuit board) ??????????????????? Those numbers can be hard to find grrrrrrrrrrrrrrrrrrr

Verify which Make and Model and Series and what engine controller yours has, LOOK AT BOTH MANUALS and use the one suited for your particular Genset.

BOTH have troubleshooting flow charts HOWEVER if the original poster isn't technically savvy and doesn't have all the necessary testing equipment he may or may not be able to diagnose the problem on his own...…..And I sure cant sitting here lol 

I would still check, maybe (if you are technically proficient) remove, clean and re attach the cable connections, inspect all the wiring, and re check voltages. While the Voltage Regulator or Excitation Circuit may ?????????? (along with a ton of others) prove to be the problem, other minor easily correctible wiring or connection issues might also . If this doesn't help I suggest a trained professional service technician  be used.

John T

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It is a Series Q-55G, with controller circuit board 92234. 

I kind of understand some of what you’re saying about the field boost, excitation circuit. It seems like the excitation circuit is going too high, 160 instead of 120, and then kicking itself back down to the field boost of 6 volts. I guess the question is why it isn’t just going to 120 and holding there.

I do have limited testing equipment and abilities so don’t know if I can nail down what the actual cause of this is. I will double check and clean the connections as suggested and take a look at the troubleshooting charts. I probably won’t be able to get to that until this evening.

The other problem may be finding a service tech, i do know that Generac doesn’t support their old RV generators anymore and won’t offer even the simplest help over the phone. 

Thanks again for all the time and effort you guys are putting into this, I realize there’s only so much you can do to help get this fixed remotely.

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6 hours ago, Tcwndsr said:

The other problem may be finding a service tech, i do know that Generac doesn’t support their old RV generators anymore and won’t offer even the simplest help over the phone. 

Generac may well support their authorized service people more than the end-users. Many RV equipment vendors operate that way, possibly to protect the authorized dealers & their service departments.

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I read through the troubleshooting, excellent info there especially if you know what you’re doing. It seems like the excitation circuit breaker is doing its job - sensing hi voltage, dropping it back to 6volts and then resetting itself. I assume this happens after power goes through the voltage regulator (?). So the regulator is either not sensing the high voltage or malfunctioning and sending the high voltage along the line anyway. The guide mentions the red led on the regulator (pg 10), I’ll have to take a look and see what the status of that is. It was pouring rain when I got home this afternoon  so couldn’t really do anything.

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14 hours ago, Tcwndsr said:

It seems like the excitation circuit breaker is doing its job - sensing hi voltage, dropping it back to 6volts and then resetting itself.

TC, it sounds like you're fairly proficient and may be able to track down your problem congratulations !! and thanks for the feedback..

 In regards to your post above, take a look at what the manual says regarding the "excitation circuit breaker"

  EXCITATION CIRCUIT BREAKER:

The excitation circuit breaker (CB3) is self-resetting

and cannot be reset manually. Should the breaker

open for any reason, excitation current flow to the

Rotor will be lost. The unit’s AC output voltage will

then drop to a value commensurate with the Rotor's

residual magnetism (about 7-12 VAC).

Not being there and based on the above taken from the manual, it indeed appears if the breaker opens the AC output would drop to 7- 12 volts as you have reported  HOWEVER I think its the Voltage Regulator (NOT the excitation circuit breaker) that "senses voltage" and the Voltage Regulator also controls voltage level (120 not 160). I don't know if the VR is opening the breaker when it senses high voltage (doesn't seem like a precise or accurate voltage regulation scheme) or exactly how it functions when it senses 160 volts ????????? NOT being a Generator Tech I suspect the VR is supposed to regulate the output voltage by controlling rotor current much more precisely, but if it malfunctions and sends excess current the result is high 160 volts output !!!!!!!   Maybe that's what's opening the excitation circuit breaker??? darn if I know, but the instant drop from 160 down to 6 or 7 volts makes sense …... 

Regardless, I tend to agree with your assessment "the excitation circuit breaker is doing its job" which leads more towards the Voltage Regulator as perhaps the problem ??? Just FYI in case you don't already know, the higher the rotors magnetic field strength (by more current) the greater the genset produces and even with no excitation current the residual magnetism can produce the 7 to 12 volts, but if the VR pumps more current into the rotor then you can get that 120 volts out........

14 hours ago, Tcwndsr said:

So the regulator is either not sensing the high voltage or malfunctioning and sending the high voltage along the line anyway.

 Don't you wish you had a magic wand to test the Voltage Regulator ??? Perhaps try to tweak and adjust it to see if that makes a difference??? an adjustment pot can get dirty, corroded or open circuit.... Still I like to keep it simple and don't overlook bad or loose resistive connections. If the wiring and circuit and connections that sense voltage and sends it to the VR isn't in place or faulty or loose or resistive, the VR may respond by pumping more current into the Rotor thereby raising voltage and perhaps opening the excitation circuit breaker ??? or maybe the VR is just bad ??? darn if I know what your problem is...…..

 

23 hours ago, Tcwndsr said:

The other problem may be finding a service tech, i do know that Generac doesn’t support their old RV generators anymore and won’t offer even the simplest help over the phone. 

I cant speak to any dealers in your area HOWEVER having been to a ton of dealer over years in scattered locations over the USA, many RV dealers have a "generator tech" onboard who can service RV gensets be they Onan or Cummins or Kohler or Generac even if there's no sign saying "X Brand of Generator Service here"      

NOTE I haven't studied the manual as far as other troubleshooting is concerned, you're there not me so I will leave that up to you. 

Sorry, best I have to offer not being there and likely not much more even if I were lol 

 John T  Too long retired n rusty electrical engineer

Edited by oldjohnt

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21 hours ago, Tcwndsr said:

It was pouring rain when I got home this afternoon  so couldn’t really do anything.

Take your time and follow the guide carefully as one doesn't need a bunch of degrees to troubleshoot and be good at it. From what you have told us you seem to be doing well with what you have done so far so just take your time and go as far as you are comfortable. It has been my experience that many RV service folks are very weak in electrical troubleshooting so it will be good to know as much as possible before you visit any service shop. 

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13 hours ago, Kirk W said:

Take your time and follow the guide carefully as one doesn't need a bunch of degrees to troubleshoot and be good at it. From what you have told us you seem to be doing well with what you have done so far so just take your time and go as far as you are comfortable. It has been my experience that many RV service folks are very weak in electrical troubleshooting so it will be good to know as much as possible before you visit any service shop. 

A big AMEN to that, its knowledge coupled with practical experience that makes a good RV service technician (that don't come overnight either). In over 49 years of RV ownership and dealership I've observed competent electrical troubleshooters as well as totally incompetent grrrrrrrrrrrrrrrr

 Best wishes yall n God Bless    

John T

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All is back to normal, at least for now. I was on the verge of ordering the new voltage regulator but went out to check wires, test the excitation circuit breaker and blow some air through the rotor area to clean it a bit. I was also thinking there might be a bit of moisture in there from driving in the rain last week, which we rarely do.

I also checked with a mobile RV tech while here at the SKP Park in Hondo, TX in case I needed him and he said they don’t work on generators at all. Maybe some do.

I don’t know what did the trick but I started it up and got normal voltage. It threw one quick hi voltage error on 1 leg again but soon settled in at 120v. I ran it for almost an hour, ran microwave, AC and oven without an issue.

Hopefully I am good to go from here. This shows the value and importance of just getting in there and wiggling wires, cleaning connections, doing some simple troubleshooting before starting to throw expensive parts at the problem.

Thanks again for the help and encouragement. I learned a bunch trying to figure this out.

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Symptoms may have gone away but causes, be it root or probability  , typically don't resolve themselves 

Edited by palmeris

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