AC voltage and line loss

[cm2785]

Hey guys, I have a 96 Bounder 34j with two brand new Coleman 13,500BTU AC units.. the weather is extremely hot right now and everyone is running their AC’s... even with my Hughes Autoformer I’m running on the low side. With one AC on I’m running at about 113-115v on my Surge Guard outside (inside I’ll see around 110v after line loss). If I kick on my second AC Surge Guard goes down to around 110v and 29 amps (30 amp service) with an inside reading of 105-101... I’ve turned the second AC off for now until I can get correct info but my question is, which reading do I go off of? Are my AC units getting the full 110v like the Surge Guard reads and the inside reading is line loss AFTER the units? I don’t want to burn anything up. Yesterday without the Autoformer my Surge Guard cut off the RV for the first time at the 102v low safety cut off so the Autoformer is on 24/7 now... thanks guys!

[MrWizard]

no you cannot just replace the main breaker with a 50amp breaker

yes you could be rewired to 50 amp service

put that means a new breaker panel and new transfer switch and new wire from TS to breaker panel, plus the new shore cord (which would be the least costly part)

would cost you quite bit to do it

yes the intellitec climate control would still work
but would not be needed when on 50amp shore power

[cm2785]

MrWizard wrote:
yes i'm in SoCal
i'm sure the generator is running near max
but at these temps the A/Cs are hot and pulling full power
the Onan gets hot and gets to point where it is difficult for it to do compressor restarts
put the A/C's on auto, select a low enough temp on the stat, that the A/C comes on and stays on, does not cycle the compressors
makes it a bit cool in the morning, but that helps combat the heat penetration
ran the generator and one A/C all night last night, right now 105 here

I’m in Burbank and it’s 105 here too.. my AC’s are brand new 13.5k units so the one in the bedroom will freeze me out at night, even last night. My sensors on the Inteli seem to be **** so I run on low AC always. Is the Onan really only putting 20 amps into the RV? That doesn’t seem right.

[MrWizard]

yes i'm in SoCal
i'm sure the generator is running near max
but at these temps the A/Cs are hot and pulling full power
the Onan gets hot and gets to point where it is difficult for it to do compressor restarts
put the A/C's on auto, select a low enough temp on the stat, that the A/C comes on and stays on, does not cycle the compressors
makes it a bit cool in the morning, but that helps combat the heat penetration
did 20hrs on batteries for the 12v systems (led lights, water pump, fridge and thermostat controls) aka parasitic loads
did battery charging this morning 3hrs this morning before turning off converter circuit breaker
ran the generator and one A/C all night last night, right now 105 here

[cm2785]

time2roll wrote:
(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/datacenter/power-and-cooling/2014/06/12/clearing-confusion-80-vs...

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

Thanks for the info, are you saying I can put a better breaker on the main that can handle the continuous load? I have 50 amp power available and the dogbone to use it, but obviously I’m not a 50 amp rig... I would gladly pay an electrician to make me 50amp but I can’t get a clear answer on whether my Intellitec will still function. Believe it or not i like the stupid thing (I would ditch it faster than I could click check out if there was a newer digital replacement!)

[cm2785]

MrWizard wrote:
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

Are you in SoCal too by chance?

Is the Onan only putting 20 amps into the RV when running? I thought the Onan put out 41 amps or something so I was under the impression the power was better on the Generator than shore power. Am I wrong?

[cm2785]

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

[time2roll]

(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/datacenter/power-and-cooling/2014/06/12/clearing-confusion-80-vs...

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

[RLS7201]

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

[wa8yxm]

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.

[MrWizard]

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

[Rick_Jay]

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

[CA_Traveler]

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.

[pianotuna]

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.

[cm2785]

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!

[cm2785]

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.