Portable generator questions, really confused

Status
Not open for further replies.
D

driver444

New Member
Just stumbled upon this site. Hope someone knows what's wrong...

I have a GENERAC GP5500 generator, (5500 watts running, 6875 watts surge)

I wired a 6 position manual transfer switch (Reliant) in my home. I'll be as detailed as I can.

switch A downstairs bathroom (15a)
switch B T.V, and internet (15a)
switch C Refrigerator (20a)
switch D Furnace (gas hot air) (20a) I used one of the 20a circuits for this, but the breaker for it is only 15A
switch E microwave (15a)
switch F upstairs bed/bathroom (15a)

These loads are pretty well balanced between the "ABC" and "DEF" side. And even if I run everything at the same time, I'm only around 2000-2500 watts. (way less than what the generator is rated at)

I hooked the White neutral wire and the bare ground wire from the transfer switch to the ground bar in the main panel, and installed all the other wires to the corresponding breakers, as per directions.
I ran about 15 feet of 10/2 romex from the transfer switch to my garage, installed an L-14-30 plug on it.
From there, I have a 15 foot extension cable to my generator, just to get it further from the house.

Here's the problem... The transfer switch works properly, in that the generator powers all the circuits I want when switched, but the furnace blower fan, the other small exhaust fan, and both bathroom fans only run at about HALF-SPEED. The furnace IS working. The control unit works, gas ignites, fan comes on, just like normal, and it will heat the house, but not full power. I don't want to burn these motors up.

Here's what I checked... I checked the voltage at the receptacles on the generator, at the extension cord connections, (both legs of the L14-30 plug), at the plastic plugs inside the furnace that go to the blower fan, and all lights, and outlets that the generator is hooked to. THEY ALL READ 121 VOLTS.

Two things that may help...
1. The generator has a ground lug on it's frame, but I did not ground it to anything yet. Would that make a difference???
2. Although all of the things I mentioned that I checked for voltage, all were 121 volts, EXCEPT, when I checked the voltage on the circuits running on "generator" in the panel, I touched one probe on the ground bar, and one on the screw on the breaker itself, (only on the generator powered circuits) and got 153 volts! Why would that be?

Any help would be greatly appreciated. I'm totally lost on this one.
Thanks in advance
 
Last edited:
Grounding shouldn't make any difference. Sounds like it might be running at too low a speed and/or has the incorrect frequency output. Is the rated frequency output of the generator the same as your appliances (50Hz or 60Hz)?
 
Does your refrigerator seem to work correctly? Is it cooling down like you expect it too?
... Suspect that you have some distributed inductive reactance in your romex and extension cord.
Consequently, the motors, which are basically inductive loads, add to the total inductive load. and consume almost all of the apparent power, produced by the generator.

The other items on your list do not seem to be particularly inductive, more of a resistive nature, and are not critically affected.
 
Last edited:
The refrigerator "seems" to work ok. It is cooling/staying cool. I can't say for sure that it's running full speed though, because it's so quiet to begin with. It's possible that it's not running 100%.

The generator states in the spec sheet that it's 60HZ, and runs at constant 3600RPM. I thought most appliances were 60HZ. I have not checked the actual RPM, but I can get a tachometer and check it.

I'm only somewhat versed in electricity. I know basically what Hertz is, but how can I check that? Do I need a special meter for that? are they really expensive?

So it's a possibility that the generator is too far from the transfer switch, ie, too long of a cable?

I'll try tomorrow and see if eliminating the extension cord to the romex does anything.

Thank you both for the replies. we'll figure this thing out yet.
 
Last edited:
From what you are saying, the most likely problem is that the generator is running at 'half speed'
My first inclintion would be to measure the generator speed with a tacho. It MUST BE 3600 RPM; if not your fans will run at a different speed.
 
OK, so here's what I found...

My house's line power is 124 volts, and 59-62 Hertz.
ALL appliances in the house, furnace included, are 60HZ.
My generator is working at 3600 rpm (correct), and putting out 121-123 volts at the duplex receptacles, and around 245 at the twist-lock connecter (also correct).

The Hertz measurement at the generator is all over the place, probably from the vibration or me not getting a good contact, but I also checked it "at the furnace blower connections" and in a light socket that's powered from the generator. In BOTH places, I got 49-51 Hertz. I also checked it at the connections inside the furnace, on the control board, same thing. So that's low. The generator is rated at 60HZ, but that's not happening.

Also, I noticed when the furnace is running on line power, and I switch to generator power, I hear a click (like a relay or something) coming from inside the furnace, when it slows down. The reverse is true when I go from generator back to line power. Is this from not enough steady power to trick the control board into shifting into "high range" so to speak?

In your opinions...Is this lower HERTZ measurement the cause of this? Can the generator be brought up to the 60HZ?, or do I have to upgrade that?
Thanks to all in advance... I can't believe the knowledge on this site.
 
Looks as though you've got a 50Hz gen then . Wrongly labelled at the factory?
 
A place I worked at a few years ago sold lots of Generac generators and what you have sounds rather typical of their quality control. They are very good at fine details but the obvious like making sure all of the wiring is actually in the connectors or that they have the right voltage and speed regulator boards is their weak point.

I am going to guess that yours most likely uses the Kohler Command engine with if I am remembering right has a simple mechanical governor adjustment screw on top of the engine just under the fuel tank.

Page 52 should help you identify what you need to adjust.

**broken link removed**
 
Actually, it's not a kohler. I have one of those too, an older one. But this one is a "GENERAC" 389cc engine. Basically a Chinese version of the legendary Honda GX390. I only wish it was a Honda.
 
My generator is working at 3600 rpm...

In BOTH places, I got 49-51 Hertz.
Click to expand...

For a simple generator, the frequency is proportional to the speed and the number of "poles" in the generator.

If the generator is running at 3600 rpm, the frequency will be 60Hz

To get 50Hz, the generator must run at 3000 rpm.

UNLESS... the generator just runs and an inverter is used to provide the required voltage and frequency.
I cannot see that being the case unless it is an expensive up-market generator.

JimB
 
If it's the Chonda engine it too will have a simple set screw type governor adjustment someplace.

Just follow the throttle linkage backward from he carburetor to a lever attached to a shaft coming out of the engine.

That level will have a spring attached to it towards the middle with some sort of set screw adjustment at the opposite end. That's your RPM adjustment.
 
something wrong here.
If the generator is a 2 pole machine, it WILL produce 60 Hz at 3600 rpm and 50 Hz at 3000 rpm.
The output waveform should be sinusoidal.
If this is not happening, then there may be a problem with the excitation. My next move would be to check the output waveform with an oscilloscope.
Any 'adjustments' or 'adjustment boards' are likely to be speed controllers operating on the throttle position with a preset or two to refine the actual running speed /frequency.
I'm sort of curious as to how you measured 'speed' and how you measured 'frequency' and came up with the 49 to 51 Hz and 59 to 62 Hz.
Jim B is saying t something similar.
 
I used a multimeter with a HZ setting for the Hertz measurement, and I have a tachometer that run off the spark plug wire for engine RPM
 



Please hire an electrician .... .... before you cause some problems !

This should NOT be a D I Y project .
 
OK, there are a lot of furnace issues that show up because of the flame proving circuit. What does this mean. The ground is EXTREMELY important and it needs to be done correctly.

The problem:
Generators made for stand-alone use have different wiring requirements than a backup generator.

For a generator to work stand-alone:
A ground-neutral bond needs to exist at the generator. Connecting the frame to a ground rod is Optional.
Usually as shipped.

For a generator to work as a home back-up:
The neutral-ground bond at the generator needs to be broken.

The neutral from the generator has to go back to the panel.
The ground from the generator has to go back to the HOUSE ground rod ideally.

==

Frequency stability may play a role, but I suspect not. You already have differences in potentials that should not be.

So, I would bet that if you connected the generator direct to the furnace and nothing else as it's normally wired.
Ground/neutral bonded at the generator, it will work.

Hopefully, you installed a generator input connector to your house.
 

Yes, the ground is bonded to the generator. but is not grounded to anything. Transfer switch, and main panel both grounded to water copper pipe.
You're saying if I ground the generator to that copper pipe directly, it may solve the problem?

I've done a ton of these transfer switches... never had a problem til now. That's what leads me to believe it's the generator. And yes, the generator to transfer switch connection is an L14-30amp twist-lock plug.
 
Status
Not open for further replies.

Similar threads

  • Question
ADF4252 confused
Replies
7
Views
967
baxterdmutt
Y
  • Question
Really basic electeonics
Replies
5
Views
1K
Yugguy
Y
D
  • Question
Finding pressure sensor specifications of Portable device for Integrity Test (Bea Technologies – italy)
Replies
6
Views
2K
Tony Stewart
A
  • Question
A couple resistor and transistor questions
2
Replies
39
Views
5K
ZipZapOuch
D
  • Question
TDA2004 amp questions
Replies
6
Views
1K
Doomguy42
D
Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…