Journey with Confidence RV GPS App RV Trip Planner RV LIFE Campground Reviews RV Maintenance Take a Speed Test Free 7 Day Trial ×
 

Go Back   Keystone RV Forums > Keystone Tech Forums > Technical Corner
Click Here to Login

Reply
 
Thread Tools Display Modes
 
Old 08-03-2020, 04:15 PM   #1
skids
Senior Member
 
skids's Avatar
 
Join Date: Sep 2019
Location: Florissant
Posts: 687
Microwave makes voltage low?

I fired up the AC. With the igen 2500. It ran the AC fine for a few cycles At 124 volts. Then I fired-up the microwave oven while the compressor of the AC was not running. The output showing on the igen2500 generator showed a consistent 97 volts output. Question, why would the voltage output on the display only 97 volts? Is it only showing the real component of voltage when there is a strong imaginary voltage component? It has been too long since my EE classes.
__________________
Skids
2019 Bullet 248RKS
skids is offline   Reply With Quote
Old 08-03-2020, 05:25 PM   #2
Canonman
Senior Member
 
Canonman's Avatar
 
Join Date: May 2016
Location: South Jordan, Utah
Posts: 2,221
Let's say your M/W is running at 1,000 watts. The generator is putting out 97vac. That's about 10 amps that the M/W is using. The A/C is simply pulling more amps therefor the generator has to run at full power to keep up with the demand. 2200 running watts divided by 124 volts equals about 17 amps. That's about what most A/C units draw while running. I can't say what the "imaginary" voltage might be since I can't "imagine" what the amp draw is.
Attached Thumbnails
Click image for larger version

Name:	_MGL1577.jpg
Views:	148
Size:	116.4 KB
ID:	29008  
__________________
2017 Cougar 279RKSWE
2007.5 Dodge Ram 2500 6.7 Cummins
Retirement Training Completed
I think the little voices in my head have started a chat group.
Canonman is offline   Reply With Quote
Old 08-03-2020, 05:50 PM   #3
chuckster57
Site Team
 
chuckster57's Avatar
 
Join Date: Jul 2014
Location: Modesto
Posts: 20,238
Funny, because I just did an amp test on a Coleman Mach 15K unit in a fifth wheel today as part of the diagnosis:
Fan started-3 amps
Compressor started- 13.45 to 13.78 so I would say 14 Amps is a good number to use.
__________________

2012 Copper Canyon 273FWRET being towed by a 1994 Ford F350 CC,LB,Dually diesel.
Airlift 5000 bags, Prodigy brake control, 5 gauges on the pillar.Used to tow a '97 Jayco 323RKS.

Now an RVIA registered tech. Retired from Law enforcement in 2008 after 25+ yrs.
chuckster57 is offline   Reply With Quote
Old 08-03-2020, 05:53 PM   #4
skids
Senior Member
 
skids's Avatar
 
Join Date: Sep 2019
Location: Florissant
Posts: 687
Well, the AC with the compressor going and the converter was showing 1400 watts at 124 volts. Once the compressor was off and only the fan running, the power was way down. Turn on the microwave oven (and only the fan from the AC is running) and the output voltage drops down to 97 volts. This is what has me baffled. The Generator is in economy mode and does not throttle up to max. I always thought the generators compensate to maintain voltage ...
__________________
Skids
2019 Bullet 248RKS
skids is offline   Reply With Quote
Old 08-03-2020, 06:20 PM   #5
Canonman
Senior Member
 
Canonman's Avatar
 
Join Date: May 2016
Location: South Jordan, Utah
Posts: 2,221
Chuck,
Did the Coleman you tested have the soft start cap in it??

Skids,
My 3kw generator does not have a display and I've never used the VOM to check voltage except in the garage before trips. always 110 to 115vac with no load. I think you're right about the generator should provide fairly constant/consistent voltage. May have something to do with it sensing load??
__________________
2017 Cougar 279RKSWE
2007.5 Dodge Ram 2500 6.7 Cummins
Retirement Training Completed
I think the little voices in my head have started a chat group.
Canonman is offline   Reply With Quote
Old 08-03-2020, 06:23 PM   #6
JRTJH
Site Team
 
JRTJH's Avatar
 
Join Date: Mar 2011
Location: Gaylord
Posts: 26,846
There may be a voltage monitor circuit in the generator that is not working properly. At any rate, this situation identifies a "potential weakness" when operating a generator without an ground plug (neutral/ground connection) and putting the EMS in bypass mode so it will allow the generator power into the trailer.... It also identifies a weakness if no EMS is connected and the operator is relying on the generator to "protect the RV electrical system"...

This situation, 97VAC on the trailer input power, will cause damage to the Air Conditioner, the TV, microwave and any electric motors or possibly other A/C powered equipment in the trailer.... It may also do damage to the generator winding if the amperage goes too high and the monitor circuits don't shut down the generator.....
__________________
John



2015 F250 6.7l 4x4
2014 Cougar X Lite 27RKS
JRTJH is offline   Reply With Quote
Old 08-03-2020, 06:49 PM   #7
chuckster57
Site Team
 
chuckster57's Avatar
 
Join Date: Jul 2014
Location: Modesto
Posts: 20,238
Quote:
Originally Posted by Canonman View Post
Chuck,
Did the Coleman you tested have the soft start cap in it??

Skids,
My 3kw generator does not have a display and I've never used the VOM to check voltage except in the garage before trips. always 110 to 115vac with no load. I think you're right about the generator should provide fairly constant/consistent voltage. May have something to do with it sensing load??
Not that I am aware of.
__________________

2012 Copper Canyon 273FWRET being towed by a 1994 Ford F350 CC,LB,Dually diesel.
Airlift 5000 bags, Prodigy brake control, 5 gauges on the pillar.Used to tow a '97 Jayco 323RKS.

Now an RVIA registered tech. Retired from Law enforcement in 2008 after 25+ yrs.
chuckster57 is offline   Reply With Quote
Old 08-03-2020, 07:23 PM   #8
flybouy
Site Team
 
Join Date: Oct 2011
Location: Joppa, MD
Posts: 11,714
Quote:
Originally Posted by skids View Post
Well, the AC with the compressor going and the converter was showing 1400 watts at 124 volts. Once the compressor was off and only the fan running, the power was way down. Turn on the microwave oven (and only the fan from the AC is running) and the output voltage drops down to 97 volts. This is what has me baffled. The Generator is in economy mode and does not throttle up to max. I always thought the generators compensate to maintain voltage ...
There is an issue with the generator. The econo mode is supposed to throttle down under light load and throttle up when the demand increases. I would not use it until you get it fixed or replaced as running the camper at 97 volts will damage systems. Most EMS systems disconnect at 105 volts to prevent damage for good reason.
__________________
Marshall
2012 Laredo 303 TG
2010 F250 LT Super Cab, long bed, 4X4, 6.4 Turbo Diesel
flybouy is online now   Reply With Quote
Old 08-04-2020, 05:40 AM   #9
skids
Senior Member
 
skids's Avatar
 
Join Date: Sep 2019
Location: Florissant
Posts: 687
Quote:
Originally Posted by flybouy View Post
There is an issue with the generator. The econo mode is supposed to throttle down under light load and throttle up when the demand increases. I would not use it until you get it fixed or replaced as running the camper at 97 volts will damage systems. Most EMS systems disconnect at 105 volts to prevent damage for good reason.
It does throttle up and down in eco mode depending on loads. At least it does for every electrical device accept for the microwave. After I installed the MicroAir easy start, I watched the output carefully when the AC is on. It throttles up a bit when the compressor kicks on but maintains voltage. The microwave does cause the eco mode to throttle up, but voltage is not properly maintained. I am going to try a neutral/ground bonding plug.
__________________
Skids
2019 Bullet 248RKS
skids is offline   Reply With Quote
Old 08-04-2020, 06:13 AM   #10
flybouy
Site Team
 
Join Date: Oct 2011
Location: Joppa, MD
Posts: 11,714
Quote:
Originally Posted by skids View Post
It does throttle up and down in eco mode depending on loads. At least it does for every electrical device accept for the microwave. After I installed the MicroAir easy start, I watched the output carefully when the AC is on. It throttles up a bit when the compressor kicks on but maintains voltage. The microwave does cause the eco mode to throttle up, but voltage is not properly maintained. I am going to try a neutral/ground bonding plug.
So it does throttle up, just not to max. I was confused by the wording. Can't imagine it's a ground issue or I would think it would be consistent with any load.
__________________
Marshall
2012 Laredo 303 TG
2010 F250 LT Super Cab, long bed, 4X4, 6.4 Turbo Diesel
flybouy is online now   Reply With Quote
Old 08-04-2020, 07:17 AM   #11
skids
Senior Member
 
skids's Avatar
 
Join Date: Sep 2019
Location: Florissant
Posts: 687
Thanks. I have been doing some research for the use of a floating neutral generator vs. a bonded ground/neutral. Apparently, if you have an EMS installed, the bonded system is needed and if you don’t use an EMS then the bond plug is not beneficial. At least that is what I gleaned from it.

I also looked at a typical power factor for a microwave oven, 0.9. I know that power companies penalize when the power factor is significant because actual power is more than the “real” component. What that means with the meter on the generator is unknown to me. I will avoid using the microwave oven until I figure this apparent malfunction out...
__________________
Skids
2019 Bullet 248RKS
skids is offline   Reply With Quote
Old 08-04-2020, 08:54 AM   #12
ChuckS
Senior Member
 
ChuckS's Avatar
 
Join Date: Mar 2014
Location: Mountain Home, Idaho
Posts: 2,978
Id also be looking at the MW 120VAC outlet for poor connection on backside of plug and the 120 VAC bus bar breaker and lead coming off that breaker for the MW
__________________


2007 GMC Classic club cab 4x4 Duramax LBZ
2014 Alpine 3010 RE. 34 foot fifth wheel
ChuckS is offline   Reply With Quote
Old 08-05-2020, 04:46 AM   #13
skids
Senior Member
 
skids's Avatar
 
Join Date: Sep 2019
Location: Florissant
Posts: 687
OK Folks, thank you for all of your comments and suggestions. This generator used to run the AC just fine but recently I rejetted the carb (OEM jet kit) for higher altitude since I live at 8800 feet and sometimes camp at near 10000 feet. I suspect the smaller jet size limits Hp to throttle-up to the necessary rpm and torque to maintain voltage.

I took the generator to the garage and hooked a 1500 watt heater. And it maintained 124 volts. Then I switched off the space heater and powered-up a Hilti circular saw and it maintained 124 volts. Then I powered-up both devices where the generator showed something like 1800+ Watts and the voltage dropped to 105. I just think that the generator was not keeping up, as if it had a “governor.” I suspect the voltage regulator can truncate the voltage if it is available but not increase voltage if it is not.

So, I will rejet the carb again to get some of that power back. I realize that an EMS would be a good thing (and using a ground/neutral bonding plug) and that undervoltage protection could save the AC from damage, but DAMN those things are expensive...
__________________
Skids
2019 Bullet 248RKS
skids is offline   Reply With Quote
Old 08-05-2020, 06:41 AM   #14
flybouy
Site Team
 
Join Date: Oct 2011
Location: Joppa, MD
Posts: 11,714
Quote:
Originally Posted by skids View Post
OK Folks, thank you for all of your comments and suggestions. This generator used to run the AC just fine but recently I rejetted the carb (OEM jet kit) for higher altitude since I live at 8800 feet and sometimes camp at near 10000 feet. I suspect the smaller jet size limits Hp to throttle-up to the necessary rpm and torque to maintain voltage.

I took the generator to the garage and hooked a 1500 watt heater. And it maintained 124 volts. Then I switched off the space heater and powered-up a Hilti circular saw and it maintained 124 volts. Then I powered-up both devices where the generator showed something like 1800+ Watts and the voltage dropped to 105. I just think that the generator was not keeping up, as if it had a “governor.” I suspect the voltage regulator can truncate the voltage if it is available but not increase voltage if it is not.

So, I will rejet the carb again to get some of that power back. I realize that an EMS would be a good thing (and using a ground/neutral bonding plug) and that undervoltage protection could save the AC from damage, but DAMN those things are expensive...
AN EMS is expensive but they also are less expensive than replacing an air conditioner, a fridge control board, a converter, a television, and any other appliance that gets fried from low voltage.
By rejetting the carb you have reduced the power output of the generator. As long as it's jetted for high altitude at lower altitudes it will have a lower output. At high altitudes it will also have less power even if rejetted. Bottom line, you are not going to be using the MW with that generator.
__________________
Marshall
2012 Laredo 303 TG
2010 F250 LT Super Cab, long bed, 4X4, 6.4 Turbo Diesel
flybouy is online now   Reply With Quote
Old 08-13-2020, 07:29 AM   #15
WDPatterson
Senior Member
 
WDPatterson's Avatar
 
Join Date: Jun 2019
Location: Pipe Creek
Posts: 344
Quote:
Originally Posted by skids View Post
Well, the AC with the compressor going and the converter was showing 1400 watts at 124 volts. Once the compressor was off and only the fan running, the power was way down. Turn on the microwave oven (and only the fan from the AC is running) and the output voltage drops down to 97 volts. This is what has me baffled. The Generator is in economy mode and does not throttle up to max. I always thought the generators compensate to maintain voltage ...
Don't use the generator in economy mode when you have to run the microwave in the air conditioner at the same time. 2500 watts is barely enough for both.
WDPatterson is offline   Reply With Quote
Old 08-13-2020, 07:31 AM   #16
WDPatterson
Senior Member
 
WDPatterson's Avatar
 
Join Date: Jun 2019
Location: Pipe Creek
Posts: 344
Quote:
Originally Posted by chuckster57 View Post
Funny, because I just did an amp test on a Coleman Mach 15K unit in a fifth wheel today as part of the diagnosis:
Fan started-3 amps
Compressor started- 13.45 to 13.78 so I would say 14 Amps is a good number to use.
15000 BTU air conditioner will Spike 52 amps at startup. It's instantaneous, it's brief, but it's significant. After that, it will run between 10.5 and 11.5 amps, constant.
Count on the microwave to consume anywhere between 1100 and 1500 watts.

You'll need between 2400 and 3000 watts to run both.
WDPatterson is offline   Reply With Quote
Old 08-13-2020, 07:36 AM   #17
WDPatterson
Senior Member
 
WDPatterson's Avatar
 
Join Date: Jun 2019
Location: Pipe Creek
Posts: 344
Quote:
Originally Posted by skids View Post
I fired up the AC. With the igen 2500. It ran the AC fine for a few cycles At 124 volts. Then I fired-up the microwave oven while the compressor of the AC was not running. The output showing on the igen2500 generator showed a consistent 97 volts output. Question, why would the voltage output on the display only 97 volts? Is it only showing the real component of voltage when there is a strong imaginary voltage component? It has been too long since my EE classes.
The I gen 2500 is 2500 watts, Peak. It runs at 2200 Watts constant. You're looking at about 2400-3000 Watts, between your air conditioner and your microwave.
This is most apparent during the summer months, when weather is the hottest.
WDPatterson is offline   Reply With Quote
Old 08-13-2020, 07:52 AM   #18
blubuckaroo
Gone Traveling
 
Join Date: May 2019
Location: Ridgefield WA
Posts: 190
As JRTJH already stated, starting or running anything with an inductive load on marginal power is risky. It's really hard on the windings, and will shorten its life.

The same power limitation can be caused by using an extension cord that has too low an ampacity, or is too long.

It may be inconvenient, but If I were using a small generator like that, I'd use only one appliance at a time.
blubuckaroo is offline   Reply With Quote
Old 08-13-2020, 08:11 AM   #19
cdotson
Junior Member
 
Join Date: Jun 2016
Location: Chesterfield
Posts: 17
skids, you got pretty close with the "imaginary" power. Microwaves are just about the worst items for power factor, which is the phase shift of the alternating current between the mains. As you probably do recall the superposition of a sinusoidal voltage wave onto another wave that is phase-shifted produces a peak and average voltage that is less than the non-shifted voltage wave.

Microwaves have a power factor of about 0.3, meaning the voltage wave is shifted 30%. Running a microwave without voltage decay requires significantly more wattage than the rated power of the microwave.

Your generator's engine loses power with altitude. At 10k ft elevation you're down up to 30% from sea level. Between your generator putting out 30% less and your microwave drawing around 30% more, your generator isn't big enough.
cdotson is offline   Reply With Quote
Old 08-13-2020, 08:25 AM   #20
blubuckaroo
Gone Traveling
 
Join Date: May 2019
Location: Ridgefield WA
Posts: 190
Quote:
Originally Posted by cdotson View Post
Your generator's engine loses power with altitude. At 10k ft elevation you're down up to 30% from sea level. Between your generator putting out 30% less and your microwave drawing around 30% more, your generator isn't big enough.
You bring up a good point. Even when you re-jet for higher elevation, you still loose power. There is just less oxygen.

Also, at higher elevation, the boiling point of the fuel lowers, and an engine acts like it has less compression. That's the same reason that there is different instructions, on a cake mix, for higher elevation.
blubuckaroo is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

» Featured Campgrounds

Reviews provided by

Powered by vBadvanced CMPS v3.2.3
Disclaimer:

This website is not affiliated with or endorsed by the Keystone RV Company or any of its affiliates in any way. Keystone RV® is a registered trademark of the Keystone RV Company.


All times are GMT -8. The time now is 06:09 AM.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2024, vBulletin Solutions, Inc.