Good Sam Club Open Roads Forum: AC voltage and line loss
Open Roads Forum Already a member? Login here.   If not, Register Today!  |  Help

Newest  |  Active  |  Popular  |  RVing FAQ Forum Rules  |  Forum Posting Help and Support  |  Contact  

Search:   Advanced Search

Search only in Class A Motorhomes

Open Roads Forum  >  Class A Motorhomes  >  All

 > AC voltage and line loss

Reply to Topic  |  Subscribe  |  Print Topic  |  Post New Topic  | 
Page of 4  
Prev  |  Next
cm2785

So Cal

Full Member

Joined: 10/07/2017

View Profile


Offline
Posted: 07/07/18 07:32am Link  |  Quote  |  Print  |  Notify Moderator

rgatijnet1 wrote:

There are several things happening that you do not show with your meter readings. What you do not show is the increase in amperage, and voltage drop, when one of your AC units is first starting the compressor. This can add several more amps as well as drop the voltage 2-5 volts for a short period of time until the compressor is up and running.
Another things is that as the voltage drops, your amps used will increase for all electrical items in your coach.
If you hear your AC compressors struggling to come on, that is the best indication that the voltage is too low. This is especially true if the AC compressor cannot get started and drops back in to a fan only mode.
Volt meters are fine but they only give you an instantaneous voltage reading on a power supply that is constantly changing.


Thank you for the info, I also have a killawat I can use which gives me more stats. What would you recommend? It seems like 90% is the places I go to here in SoCal, even plugging into my house has not so great power. Even with the Autoformer I’m struggling but I need to be able to run both of these AC units continuously and safely. This rig was designed to do just that so I am not sure what I need to do. I understand what you mean about turning the AC’s on.. I accidentally turned my new AC off yesterday and turned it back on about 15 seconds later and the compressor seemed to struggle so it went back to fan mode and about 20 seconds later it kicked back in just fine.. I think that was without my Autoformer though. Also I don’t really notice a big drop when turning them on that then goes away, only about a 4v line loss per unit.

cm2785

So Cal

Full Member

Joined: 10/07/2017

View Profile


Offline
Posted: 07/07/18 07:39am Link  |  Quote  |  Print  |  Notify Moderator

pianotuna wrote:

Does the Intelligec do "load shedding"? If so, go ahead and use both air conditioners, but DO monitor the voltage and manually shut down one air conditioner if voltage sags below 107.

Does the Intelligec allow you to preset incoming amps? I do this using my Magnum hybrid inverter charger, so on a 15 amp shore power I "dial it down" to 12 amps. On 30 amps shore power, I dial to 24 amps, and on 50 amp shore power, I dial to 30 amps.

If there is a 50 amp outlet, get a 50 to 30 adapter and use that for the shore power. Since a 50 amp can be run flat out at 40 amps, that leaves more for your RV to work with, and voltage drop may be less (I still often use my autoformer).


The intellitec has load shedding, but I can’t program anything. Yesterday it ran both units without shedding with the bad power and Autoformer but it was pulling 29 amps according to the Surge Guard. I do have a 50 amp for shore and I already have all the adapters to make 50 or 30 amp anything else (visa versa, male or female, 20amp, etc). I was wondering if using the 50 and dropping it down to 30 would help... if the power gets real bad today I’ll unplug and fire up the generator.. with the generator putting out I think 41 amps am I still at a limit of 30? Thanks!

pianotuna

Regina, SK, Canada

Senior Member

Joined: 12/18/2004

View Profile


Offline
Posted: 07/07/18 07:47am Link  |  Quote  |  Print  |  Notify Moderator

You are limited to what ever the main breaker in the RV is rated at.

In my case that is 30 amps. I have gotten around that limitation by adding auxiliary shore power cords. One is used to run the electric water heater (the heater doesn't care about low voltage--it just takes a little longer to get the water hot).

I have a "break out box" for a 50 amp service which has 2 20 amp circuits on one leg (with breakers) and 1 30 amp circuit on the other leg (with a 30 amp breaker).

Or if there is a shore power pedestal that has 30 and 15 amp outlets, I can run two cords.

The other auxiliary shore power cord is used for electric heating in the winter. That lets me get to a peak wattage of about 7200 during the worst of the cold.

I do monitor voltage and total wattage being used. The hybrid inverter does load support which means no more over loads when there is only 15 amp shore power. Load support is NOT voltage support--hence the autoformer.


Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp hours of AGM in two battery banks 12 volt batteries, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

CA Traveler

The Western States

Senior Member

Joined: 01/03/2004

View Profile


Offline
Posted: 07/07/18 07:58am Link  |  Quote  |  Print  |  Notify Moderator

First confirm that both meters are accurate or at least the same. Measure on a inside plug that is on a lightly loaded circuit with the A/Cs running. Essentially you will be measuring the panel voltage which should be reasonably close to the the actual A/C voltage.

The recommended sustained load is 80% or 24A. A/Cs represent sustained loads. Therefore only one A/C or turn off other equipment. The US standard is 120V +- 10%. a little below 108V may be OK but check your equipment specs. Otherwise expect to have overheated plugs and/or shorter equipment life. And overheated plugs often means more loss at the plug and hence more voltage loss at the plugs.

Are the 30A male plugs bright and shinny? And if not sure about the female plugs then replace them.

And if the 29A is after the autoformer then the pedestal amps are higher, maybe even above 30A.

Plus RVs bounce and vibrate down the road and connections become loose. Recommend you check EVERY connection be be sure it's bright, shinny and tight which should be a periodic maintenance item.


2009 Holiday Rambler 42 Scepter with ISL 400 Cummins
750 Watts Solar Morningstar MPPT 60 Controller
2004 CR-V and 2014 Grand Cherokee Overland

Bob


Rick Jay

Greater Springfield area, MA

Senior Member

Joined: 02/02/2003

View Profile


Offline
Posted: 07/07/18 08:25am Link  |  Quote  |  Print  |  Notify Moderator

cm2785 wrote:

...I accidentally turned my new AC off yesterday and turned it back on about 15 seconds later and the compressor seemed to struggle so it went back to fan mode and about 20 seconds later it kicked back in just fine...


I believe this is normal. Most A/C's require a short "off period" before the compressor kicks back on. This time is needed to equalize the pressures between the low side & high side of the compressor. If you try to turn on the compressor too soon after it shuts down, there is still a very high pressure which the compressor pistons have to work against, which puts a very high strain on the motor. Giving it some relaxation time is the solution. In fact, I think a lot of A/C's actually have a timer built into the starter circuit to ensure that the compressor does not engage until a certain time after it has shut down.

~Rick


2005 Georgie Boy Cruise Master 3625 DS on a Workhorse W-22
Rick, Gail, 1 girl (21-Angel, Lexi96.org), 1 girl (16), 2 boys (18 & 15). Two Chinook dogs, 14 & 12.
2001 Honda Odyssey, Demco Aluminator tow bar & tow plate, SMI Silent Partner brake controller.


MrWizard

Traveling

Moderator

Joined: 06/27/2004

View Profile



Posted: 07/07/18 09:11am Link  |  Quote  |  Print  |  Notify Moderator

I bought this Bounder 36S, last Sept, moved from the DP to the Bounder in Dec
I have not yet plugged in anywhere
Strickly on generator and Add on inverter
This RV has 30 amp shore cord
I have the intellitec load control also
The rear A/C is on a breaker in the panel
It appears the front A/C is on the 20 amp circuit breaker of the Onan 5000 and goes thru the inteltec but not thru the breaker panel
No breaker in the panel turns the front A/C off

Because it was 116F yesterday, and 95F at 2am this morning
The generator has been on for 26 hours, since Friday morning 7am
Today the prediction is 111F

* This post was last edited 07/07/18 11:38am by MrWizard *   View edit history


Radiate The Happy
....

Connected using Verizon and AT&T
1997 F53 Bounder 36s


wa8yxm

Wherever I happen to park

Senior Member

Joined: 07/04/2006

View Profile


Offline
Posted: 07/07/18 09:53am Link  |  Quote  |  Print  |  Notify Moderator

30 amps you are doing well if you can run both A/C.

If you are seeing that much voltage drop between your Surge Guard and your INdoor Voltmeter.. Let me make an assumption

Park---Hughes autoformer---Surge guard---RV

IF that is how you are set up then do the following

First with the RV not plugged into the surge guard compare the surge voltage reading to the volt meter's reading. You may find a difference. if so you need to figure out which one is right.. Though I DO know how to calibrate a volt meter or check calibration.. Too detailed to describe here. Plus you need a calibrated source I have one but.. Well.

Now if the meters agree Take a look at your power plug. are the blades Bright and shiny or black as knight? (this is mostly the 30 amp plug) Not so much 50s) Dirty/tarnished plugs drop voltage. they also tend to MELT at full power load.

But that is way too much loss between Surge Guard and inside outlet.


Home is where I park it.
Kenwood TS-2000 housed in a 2005 Damon Intruder 377


RLS7201

Beautyful Downtown Gladstone, MO

Senior Member

Joined: 10/26/2002

View Profile


Offline
Posted: 07/07/18 10:43am Link  |  Quote  |  Print  |  Notify Moderator

pianotuna wrote:

A 30 amp service should only be used at 24 continuous.

If the autoformer is raising the voltage 10%, then on the input side of the autoformer the current would be much higher than 29 amps.

Anything above 107 volts is safe for the air conditioners. How are you checking the voltage inside the RV?


Don, I have seen this 24 amp limit for 30 amp breakers mentioned before. Where does it come from? It looks like Fleetwood didn't adhere to that limit with 2 A/Cs on 30 amps.
While looking at trip curves, I find a circuit breaker, as designed, will maintain approximately 1.13 x its rating for over 60 minutes with out tripping.

Richard

* This post was edited 07/07/18 10:56am by RLS7201 *


95 Bounder 32H F53
460/528 stroker
Web Master
MWPSchooners.com

time2roll

Southern California

Senior Member

Joined: 03/21/2005

View Profile



Good Sam RV Club Member


Posted: 07/07/18 11:54am Link  |  Quote  |  Print  |  Notify Moderator

(copied from link below): Section 210.20(A) of the code basically says that a circuit breaker for a branch circuit must be rated such that it can handle the noncontinuous load plus 125% of the continuous load. (A continous load is one where the maximum current is expected to continue for 3 hours or more.) In other words, the breaker needs an extra 25% capacity of the continuous load for headroom. That, of course, means you need a larger, more expensive breaker.

https://blog.schneider-electric.com/data........fusion-80-vs-100-rated-circuit-breakers/

No one actually applies this rule as it is not required for an RV because all items are short term or thermostatically controlled so by definition an RV is not a continuous load. However as you have experienced it is easy to have the air conditioners run continuous for 10+ hours and the EMS will hold the RV very close to 30 amps for well over the 3 hour requirement. Then you have the booster that will draw more amps to get the voltage corrected.

IMO this can put you in the continuous service definition. Ever wonder why so many 30 amp connectors and adapters are burn, worn, and heat damaged? OK not just this but I believe it contributes significantly.

This is part of the reason I suggested all breakers off if running 2x A/Cs. Yes you will be running on battery power for the 12 volt systems while the 120 volt system is under stress. That last 4 amps can make a difference. Turn the rest back on an hour or so after sunset when the system is less stressed. Otherwise make do with one A/C or find 50 amp power.

JMHO


2001 F150 SuperCrew
2006 Keystone Springdale 249FWBHLS
675w Solar pictures back up

cm2785

So Cal

Full Member

Joined: 10/07/2017

View Profile


Offline
Posted: 07/07/18 11:56am Link  |  Quote  |  Print  |  Notify Moderator

wa8yxm wrote:

30 amps you are doing well if you can run both A/C.

If you are seeing that much voltage drop between your Surge Guard and your INdoor Voltmeter.. Let me make an assumption

Park---Hughes autoformer---Surge guard---RV

IF that is how you are set up then do the following

First with the RV not plugged into the surge guard compare the surge voltage reading to the volt meter's reading. You may find a difference. if so you need to figure out which one is right.. Though I DO know how to calibrate a volt meter or check calibration.. Too detailed to describe here. Plus you need a calibrated source I have one but.. Well.

Now if the meters agree Take a look at your power plug. are the blades Bright and shiny or black as knight? (this is mostly the 30 amp plug) Not so much 50s) Dirty/tarnished plugs drop voltage. they also tend to MELT at full power load.

But that is way too much loss between Surge Guard and inside outlet.


Thanks everyone for the help!! I am seeing about a 4v line loss on the internal volt meter per AC running. It’s been 118 here for the last couple days so it’s been a while since I’ve checked it without them running but it should be pretty close to the surge guard when they are off. Is that normal line loss per AC? Thanks

Reply to Topic  |  Subscribe  |  Print Topic  |  Post New Topic  | 
Page of 4  
Prev  |  Next

Open Roads Forum  >  Class A Motorhomes  >  All

 > AC voltage and line loss
Search:   Advanced Search

Search only in Class A Motorhomes


New posts No new posts
Closed, new posts Closed, no new posts
Moved, new posts Moved, no new posts

Adjust text size:

© 2018 CWI, Inc. © 2018 Good Sam Enterprises, LLC. All Rights Reserved. | Terms of Use | PRIVACY POLICY | YOUR PRIVACY RIGHTS