15K BTU Dometic A/C tripping breaker

[Barry2952]

Yes, if you tear off 10% from the formula using 110-volts our answers come very close together. Do you concur?

[firefly007]

Yup, I agree. Sorry for tryin to show off. Just tring to stretch my brain a little. The best answer was your idea on low voltage. Usually when someone ask me about this situation I will find about 105 volts. It makes ac motors mad and draws more current.

steve

[john hd]

Originally Posted by Barry2952

That would be true, if you were not an electrician, which I am. The rule of thumb is that you should never load a circuit in excess of 80% of its capacity. I like to use 75%, but then I'm a cautious person.

In addition, should voltage be 110 volts there is a proportional decrease in the capacity of the circuit. Your formula does not allow for voltage fluctuations, which I'm sure we've all experienced.

hey barry, don't you suppose the capacitors in the airconditioner would bring the power factor to unity?

or are they just for starting the unit?

it would be interesting to put a var meter on a running unit and see what ya get!

i certainly do not disagree about the 80% rule. at the power company we have tried to run lines in emergencies at 110% with bad results!

john

[Barry2952]

Originally Posted by firefly007

Yup, I agree. Sorry for tryin to show off.

steve

No problem, I was just trying to help. I reread my post and I guess I sounded a little snotty.

I'm just concerned when people believe they can put full wattage on a residential electrical circuit. Yes, the wire can take the full wattage but the devices can't, especially with the inherent vibration of a motor home or trailer. Couple that with typical overloading from use of all the appliances available today and it gets pretty scary.

[lewster]

What power utility do you guys use? I haven't seen 110 VAC for years. The last time I plugged in my Fluke RMS multimeter, it read between 119-121 VAC .

[john hd]

when i hook up a new residential customer i like to see 125volts at the transformer.

when you calculate line loss in the service you should be 120/123v at the meter.

tip of the day: buy 130v light bulbs! they last longer!

john

ps, lew fluke meters are iffy at best, my shop meter is a good old simpson!

[firefly007]

Originally Posted by lewster

What power utility do you guys use? I haven't seen 110 VAC for years. The last time I plugged in my Fluke RMS multimeter, it read between 119-121 VAC .

Most of my experiance is at marinas. Poor grounding and moisture damage along with overloading is probably worse there

[silverback]

Back home again and catching up on posts. We lost WiFi access so I wasn't able to report on the campground voltage. It stayed a steady 110 VAC everytime I measured it. Are you guys saying that is marginal? I was beginning to think we may have a bad breaker. If I tried Auto fan while the outside temps were high (even after the humidity dropped) it would consistently trip after a while (hour?). It worked fine in the evening. So it was High fan and high noise levels during the day. Once we moved up to 7k feet and the SW monsoon kicked in the AC was no longer an issue (lighting strikes and flooding took over). And I am happy to say the Safari SE remained leak proof.
Thanks,
Ken

[Barry2952]

Originally Posted by lewster

What power utility do you guys use? I haven't seen 110 VAC for years. The last time I plugged in my Fluke RMS multimeter, it read between 119-121 VAC .

So, Lewster, what have you to say about the previous post?

[mickleton]

This morning I am having an electrician install a 30 amp outlet to plug my trailer into without using the adaptor. It will have its own circuit breaker in the basement of our house. Want to plug in from the driveway when not in campground. Costing me $400. About 20 feet of line from the box to the new outlet. Is this a worthwhile thing to do? Or am I wasting money?

Larry

[crowbar68]

Originally Posted by Barry2952

That would be true, if you were not an electrician, which I am. The rule of thumb is that you should never load a circuit in excess of 80% of its capacity. I like to use 75%, but then I'm a cautious person.

In addition, should voltage be 110 volts there is a proportional decrease in the capacity of the circuit. Your formula does not allow for voltage fluctuations, which I'm sure we've all experienced.

don't forget when calculating motor loads you would use a multiplier of 125% of full load current (FLA) for the inrush start up of an inductive load such as a motor when considering your wire sizes!
ampacities for 14ga thhn is25a, 12ga is30a and 10ga is40a @86deg fahrn.

crowbar

[Barry2952]

Originally Posted by mickleton

This morning I am having an electrician install a 30 amp outlet to plug my trailer into without using the adaptor. It will have its own circuit breaker in the basement of our house. Want to plug in from the driveway when not in campground. Costing me $400. About 20 feet of line from the box to the new outlet. Is this a worthwhile thing to do? Or am I wasting money?

Larry

If that includes trenching and pipe work installation, its a fair price. If it's just a cord plugged into an outlet on the house, it's a rip-off.

What benefit do you get from going to a 30-amp from a 20-amp if it's just parked? I can see the expense if someone were living in it and wanted to run multiple appliances.

[mickleton]

I thought it would be a safe thing to do, having a dedicated outlet for the trailer, and spending some time in the driveway with Air Conditioning. A newbie here, so we spend time hanging out in it. No trench or piping. Just adding a circuit breaker and line to an outlet.

Thanks for input
Larry

[Barry2952]

Originally Posted by crowbar68

don't forget when calculating motor loads you would use a multiplier of 125% of full load current (FLA) for the inrush start up of an inductive load such as a motor when considering your wire sizes!
ampacities for 14ga thhn is25a, 12ga is30a and 10ga is40a @86deg fahrn.

crowbar

Your information is very misleading. MOHOs must comply with NECA. 14 gauge is 15-amp, 12 gauge is 20-amp and 10 gauge is 30-amps. Your disinformation could burn up a MOHO.

Once again. The wire may be able to handle the amperage you stated but the outlets are not. Your calculations go right out the window on a 100° day when the temperature behind the aluminum skin reaches 140°.

[Barry2952]

Originally Posted by mickleton

I thought it would be a safe thing to do, having a dedicated outlet for the trailer, and spending some time in the driveway with Air Conditioning. A newbie here, so we spend time hanging out in it. No trench or piping. Just adding a circuit breaker and line to an outlet.

Thanks for input
Larry

A single pole 30-amp breaker, outdoor oulet box and cover comes to about $50.00 in parts. If you think $350.00 in labor to drill a hole in your house, run some romex and hook up an outlet is fair, go for it.

[crowbar68]

Originally Posted by Barry2952

Your information is very misleading. MOHOs must comply with NECA. 14 gauge is 15-amp, 12 gauge is 20-amp and 10 gauge is 30-amps. Your disinformation could burn up a MOHO.

Once again. The wire may be able to handle the amperage you stated but the outlets are not. Your calculations go right out the window on a 100° day when the temperature behind the aluminum skin reaches 140°.

i was hoping you would bite on that info. i'm mearly pointing out that the wire sizes used for the breakers are more than AMPle to handle the load (125%). you should not upsize your breaker. but you knew that! and don't forget to derate. that's neca

[mickleton]

Wow, thanks for the info. I will ask him to break down the cost. I remember him saying that the wire alone would cost $100. Hate getting ripped off. He has not showed up yet. So you that a dedicated service is not really needed.

Larry

[crowbar68]

a dedicated circuit is nice. it just depends how much you use it in your driveway. i have a 20a single pole for mine w/ no trouble. i just run my ac and a few lights. it is not a dedicated circuit but i'm not running anything substantial off of it out of my garage. there are similiar threads that talk about this. if you run microwave, blow dryer and ac w/ other things who knows! $400 does seem pricey,but it is east coast.

crowbar

[jcanavera]

Originally Posted by silverback

Back home again and catching up on posts. We lost WiFi access so I wasn't able to report on the campground voltage. It stayed a steady 110 VAC everytime I measured it. Ken

Just a thought, take a look at the device you used to measure the voltage with. Some of the low cost devices have a variance factor of up to 10%. Consider that into the equation as to what your real voltage was at that site.

Also be aware that obviously running on auto will increase the run time since the A/C unit is not running at its peak effeciency. That means depending upon the line and its connections, you will be building more heat that could cause a weak breaker to trip.

In my days with my SOB I used to plug into my 20 amp service in the garage at home. I used one of those adapter plugs to mate the 30 amp trailer plug into the outlet. Normally I ran the A/C on high but for some reason this time I ran it on low speed. The A/C unit had some long run times and coming out into the garage I found that the adapter had begun to melt down from the heat generated though that adapter.

Jack

[dwightdi]

Melting adapters mean you are way over the limit for that device. You really need to put in a 30 amp RV plug box so you do not have to use a cheap adapter. If the lines feeding the outlet are the proper size and not servicing anything else you might be able to get away with just replacing the box without putting in a dedicated line and a new breaker down stairs. To do it per code, you would need to do the whole thing right. Unless you know what you are doing, it is good to hire a professional. That said, there are alot of home repair rip of artists out there. Hard to tell the difference unless you check the better business bureau or can get some personal references.