Good Sam Club Open Roads Forum: AC voltage and line loss
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 > AC voltage and line loss

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cm2785

So Cal

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Posted: 07/06/18 08:13pm Link  |  Quote  |  Print  |  Notify Moderator

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!

akrv

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Posted: 07/06/18 08:38pm Link  |  Quote  |  Print  |  Notify Moderator

You want you voltage to 110 or higher. Kept the sun off the power cord if you can heat drops voltage. Pick the part of motor home that has the smallest area to cool and use that AC.


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cm2785

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Posted: 07/06/18 08:54pm Link  |  Quote  |  Print  |  Notify Moderator

Thanks! But I’m wondering which voltage is correct for the AC units? Are they getting the voltage the surge guard is reading or the voltage the voltmeter inside the rig is reading after line loss? Thanks!

time2roll

Southern California

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Posted: 07/06/18 09:00pm Link  |  Quote  |  Print  |  Notify Moderator

Can you get a reading to compare the voltmeters in the same place?
Otherwise I would trust the SG and let it run. Although 29 amps is a bit high for continuous service on 30 amps. I would have all breakers off except the mains and A/C. Put the converter back on to charge the battery when the voltage rises or in the morning.


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pianotuna

Regina, SK, Canada

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Posted: 07/06/18 09:48pm Link  |  Quote  |  Print  |  Notify Moderator

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?


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Full Time in 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.

MrWizard

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Posted: 07/06/18 10:10pm Link  |  Quote  |  Print  |  Notify Moderator

want to know what volatge the A/C unit is seeing

remove the covers from the circuit breaker panel
use a multimeter set on AC volts 200vac or higher (usually something like 600vac on the meter )
read from the neutral bar (the white wires buss) to the A/C breaker

probably safer if you get somebody else to do it


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cm2785

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Posted: 07/06/18 10:13pm 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?


Thanks guys! Good to know about the amp thing, but if that’s the case how do they expect you to run both AC’s? With the Intelligec system running two AC’s at the same time is supposed to be it’s feature. Other than that the converter, fridge, and a bunch of smaller electronics are running. When AC is off completely all my toys run at 4 amps.

I have the Autoformer plugged into the shore power, the surge guard into the Autoformer and the RV into the surge guard... the surge guard was showing 29amp when both AC’s were on earlier. I have the little digital voltmeter from Hughes that came with the Autoformer plugged into an outlet over my couch.. the AC units seem to drop the internal voltmeter by about 3 or 4 volts per AC. I would consider upgrading to a 50 amp service if my Intellitec would still work for my heating and cooling but I don’t know if that’s the case... With the heat we are having here I need to run both AC’s here for a few days.. these units are now about two months old and the main unit has ran about 12 hours today for the first time ever.

cm2785

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Posted: 07/06/18 10:15pm Link  |  Quote  |  Print  |  Notify Moderator

MrWizard wrote:

want to know what volatge the A/C unit is seeing

remove the covers from the circuit breaker panel
use a multimeter set on AC volts 200vac or higher (usually something like 600vac on the meter )
read from the neutral bar (the white wires buss) to the A/C breaker

probably safer if you get somebody else to do it


Thanks for the info! So there is no set info on whether the AC’s are getting the voltage coming into the rig or getting the voltage after the line drop on the internal VM?

I see you have near the same rig.. my rig is a 1997 F53 chassis too.. how do you run your AC’s together on 30 amps? Thanks!

rgatijnet1

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Posted: 07/07/18 04:49am Link  |  Quote  |  Print  |  Notify Moderator

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.

pianotuna

Regina, SK, Canada

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

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).

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