Shore Power: Am I doing something wrong?

Topic: Shore Power: Am I doing something wrong? (Read 1286 times) previous topic - next topic

Shore Power: Am I doing something wrong?

April 17, 2011, 11:40:42 am

When I put my MH into temporary covered storage I plug into a 20Amp receptacle to provide power for the MH to maintain the batteries and provide heat on the few exceptionally cold days during the winter. Naturally I have to convert my 50Amp plug down to a 120V 3-Prong grounded plug in order to plug in. For the second time over the past four years I have observed excessive heat damage at the 30 Amp conversion point. This time the damage was so severe as to "weld" the plugs together (see pic) and prevent an electrical hookup. Thanks to my Progressive Industries EMS-HW-50C, no damage to my internal systems has been observed.

Am I doing something wrong??

Re: Shore Power: Am I doing something wrong?

Reply #1 – April 17, 2011, 12:09:43 pm

If you are relying on that set up for electric heat, you are pulling to many amps for that small 120 v line !!!! It could cause a fire from the heat build up... Only use electric resistance heat when plug into full 220 v / 30 or 50 amp service....

Re: Shore Power: Am I doing something wrong?

Reply #2 – April 17, 2011, 12:23:30 pm

Thanks Gerry for your reply... I guess it means that I'm going to only use Diesel heat for those cold days and make sure that I'm only heating to about 45⁰ to save $$ on fuel costs.

Re: Shore Power: Am I doing something wrong?

Reply #3 – April 17, 2011, 12:26:27 pm

Yup, too many amps is the likely culprit.

A "hidden" big draw is the larger inverter/chargers. Unless you put them to power share, which minimizes the amps of 120 that can be used to charge the batteries, often that load alone can draw 20 amps. Pull out your inverter owners manual and set the amps used to charge the batteries to minimum. That is also easier on the batteries-- slow charge is easier on them than to slam them with 150-200 amps.

Make sure the electric water heater element is off.

And lastly, even with a draw well less than 20 amps, a loose or corroded connection will cause resistance, which yields HEAT when a current flows through it.

Brett

Re: Shore Power: Am I doing something wrong?

Reply #4 – April 17, 2011, 12:58:20 pm

A poor connection could be at issue too - lightly sand your prongs to remove corrosion.
You could also build your own 'connection box that adapts the 50A connection directly to 110 single phase.
I bought a heavy duty 10 guage 20 amp extension cord and replaced the ends with 15a plugs. Made a huge difference in voltage drop. For long runs I bought romex and put a 30 amp receptacle on the end.

Re: Shore Power: Am I doing something wrong?

Reply #5 – April 17, 2011, 03:17:14 pm

Quote from: wolfe10 – April 17, 2011, 12:26:27 pm

Yup, too many amps is the likely culprit.

A "hidden" big draw is the larger inverter/chargers. Unless you put them to power share, which minimizes the amps of 120 that can be used to charge the batteries, often that load alone can draw 20 amps. Pull out your inverter owners manual and set the amps used to charge the batteries to minimum. That is also easier on the batteries-- slow charge is easier on them than to slam them with 150-200 amps.

Make sure the electric water heater element is off.

Brett

I guess it didn't help that the property commercial electrician changed out the 20 Amp breaker on the line for a 30 Amp breaker, huh.

Re: Shore Power: Am I doing something wrong?

Reply #6 – April 17, 2011, 03:29:24 pm

Quote from: Ron Sedgley – April 17, 2011, 03:17:14 pm

I guess it didn't help that the property commercial electrician changed out the 20 Amp breaker on the line for a 30 Amp breaker, huh.

Hopefully they're correct the "mistake" before there are other problems beyond a tenant's melted adapter.

Re: Shore Power: Am I doing something wrong?

Reply #7 – April 17, 2011, 03:35:08 pm

Quote from: Dave Head – April 17, 2011, 12:58:20 pm

You could also build your own 'connection box that adapts the 50A connection directly to 110 single phase.
I bought a heavy duty 10 gauge 20 amp extension cord and replaced the ends with 15a plugs. Made a huge difference in voltage drop. For long runs I bought romex and put a 30 amp receptacle on the end.

I'm trying to visualize the solution you describe above. Is this a 50 Amp receptacle box with two 15 amp plugs coming out to plug into one 115v receptacle?

Re: Shore Power: Am I doing something wrong?

Reply #8 – April 17, 2011, 04:03:17 pm

The 'dogbone' 50A to 30A adapters just 'drop' an incoming line to convert to 30A. They are generally very poorly built with substandard cabling and connections (to me, at least).
The 30A to 15A adapters (especially the triangular ones) are even worse. I've blown up a couple of them - one spectacularly.

Take a connection box, a 50A female connection, some romex or good cable and a 15A female end (hospital grade). Build your own 50A to 15A adapter/reducer. It will be far better than anything on the market.

My comment about the 15A ends on the 20A extension cord was for the 'rest of the run'.
People forget that the are connecting a 10KW load with a 15A extension cord (likely 14 guage wire, at that). The owner of the coach, and the upstream facility circuit breaker are the only factors preventing that extension cord from being severely overloaded.

Re: Shore Power: Am I doing something wrong?

Reply #9 – April 17, 2011, 04:56:35 pm

Maybe if people realized the actual rating of such outlets might be helpful.
15 amp outlet is good for 12 amp load
20 amp 16 amp load
30 amp 24 amp load
50 amp 40 amp load
Now I know some folks are not fully aware of the electric code etc, but these devices are only rated at 80% of what they are marked. Has to do with momentary load vs continuous loading.
Same with the wire gauge sizing.
This becomes clear when a 20 amp breaker will trip with a 16 amp load.
Breakers trip due to either over amps or over temp. Thermal-Magnetic type
If interested, maybe you could check out the NEC National Electric Code Manual.
Just food for thought

Re: Shore Power: Am I doing something wrong?

Reply #10 – April 17, 2011, 06:54:36 pm

Quote from: Dave Head – April 17, 2011, 04:03:17 pm

Take a connection box, a 50A female connection, some romex or good cable and a 15A female end (hospital grade). Build your own 50A to 15A adapter/reducer. It will be far better than anything on the market.

My comment about the 15A ends on the 20A extension cord was for the 'rest of the run'.
People forget that the are connecting a 10KW load with a 15A extension cord (likely 14 guage wire, at that). The owner of the coach, and the upstream facility circuit breaker are the only factors preventing that extension cord from being severely overloaded.

Dave Head, why not draw up a simple sketch or photo of what you have done so that us "boneheads" can make one too-safely???
John

Re: Shore Power: Am I doing something wrong?

Reply #11 – April 17, 2011, 11:06:07 pm

I'll jump back in... If the facility only provides a single 120 v 15 amp or 20 amp duplex outlet to supply your coach during storage and you are attempting to heat your coach and run battery maintenance, the amp draw will heat even a 12 ga wire. If the supply to the facility is feed by a 240 v split into two (2) different 120 v lines in different areas of the building you could combine the two legs to get more usable amps... you must test to make sure that you are on different 120 v supply line areas .. (There should be a slight voltage difference between the 120 v legs...) I have done this in several campgrounds by running two 120 v extension cords from different legs and combining them at the coach to supply each side of the 240 v plug. thus dividing the load.

Re: Shore Power: Am I doing something wrong?

Reply #12 – April 18, 2011, 01:58:56 am

How are you providing HEAT?

Regards,
Jon Twork

Re: Shore Power: Am I doing something wrong?

Reply #13 – April 18, 2011, 08:48:38 am

Quote from: Jon Twork – April 18, 2011, 01:58:56 am

How are you providing HEAT?

Jon - If you were asking me... I use the MH Aquahot system; electric and diesel if the temps are forcasted to be below 35⁰.

Re: Shore Power: Am I doing something wrong?

Reply #14 – April 18, 2011, 08:54:25 am

Quote from: Steve & Michelle – April 17, 2011, 03:29:24 pm

Quote from: Ron Sedgley – April 17, 2011, 03:17:14 pm

I guess it didn't help that the property commercial electrician changed out the 20 Amp breaker on the line for a 30 Amp breaker, huh.

Hopefully they're correct the "mistake" before there are other problems beyond a tenant's melted adapter.

I really have no control over that. Looking at the panel at this Public Storage property there are several 30 Amp breakers spread among the 20 Amp breakers. Each "protecting" to individual receptacles via metal conduit in the storage area.

Re: Shore Power: Am I doing something wrong?

Reply #15 – April 18, 2011, 01:59:31 pm

I suggest that you check to see what the amperage is on the electric requirement of the Aquahot and any other electric that might be activated during storage. It is possible that your plugs were ruined previously by multiple air conditioners running at low voltage over time. High loads create a LOT of heat at any shore power connection including the box receptacle.

Regards,
Jon Twork
Retired, Unemployed, Homeless, Transient
1996 Foretravel U270-36 w/24' Timberwolf Trailer

Re: Shore Power: Am I doing something wrong?

Reply #16 – April 18, 2011, 06:48:02 pm

While knowing the theoretical current load is great, actual numbers are much better. Get a clamp-on ammeter, create a male/female plug extension cord about a foot long with separate wires of at least 12 ga and measure actual draw. If all the draw is resistance then that will be enough. If there are any motors involved then you need to measure startup current also. We never trusted the current labels on equipment, we always measured to make sure we had enough capacity.

Re: Shore Power: Am I doing something wrong?

Reply #17 – April 19, 2011, 08:44:35 am

Thanx all! This had been a good discussion. I appreciate all the help.

Re: Shore Power: Am I doing something wrong?

Reply #18 – April 19, 2011, 11:26:57 am

While it might not help if you are drawing too much, but there are 20 Amp male / 50 Amp female adapters. The adapter is rated for 20 Amps, but uses a plug like a 15 Amp male plug
I use one when connected to 15 or 20 Amps (and am careful with what I try to run)
That way you only have one connection rather than several connections.
Eric

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Shore Power: Am I doing something wrong?

April 17, 2011, 11:40:42 am

Re: Shore Power: Am I doing something wrong?

Reply #1 – April 17, 2011, 12:09:43 pm

Re: Shore Power: Am I doing something wrong?

Reply #2 – April 17, 2011, 12:23:30 pm

Re: Shore Power: Am I doing something wrong?

Reply #3 – April 17, 2011, 12:26:27 pm

Re: Shore Power: Am I doing something wrong?

Reply #4 – April 17, 2011, 12:58:20 pm

Re: Shore Power: Am I doing something wrong?

Reply #5 – April 17, 2011, 03:17:14 pm

Re: Shore Power: Am I doing something wrong?

Reply #6 – April 17, 2011, 03:29:24 pm

Re: Shore Power: Am I doing something wrong?

Reply #7 – April 17, 2011, 03:35:08 pm

Re: Shore Power: Am I doing something wrong?

Reply #8 – April 17, 2011, 04:03:17 pm

Re: Shore Power: Am I doing something wrong?

Reply #9 – April 17, 2011, 04:56:35 pm

Re: Shore Power: Am I doing something wrong?

Reply #10 – April 17, 2011, 06:54:36 pm

Re: Shore Power: Am I doing something wrong?

Reply #11 – April 17, 2011, 11:06:07 pm

Re: Shore Power: Am I doing something wrong?

Reply #12 – April 18, 2011, 01:58:56 am

Re: Shore Power: Am I doing something wrong?

Reply #13 – April 18, 2011, 08:48:38 am

Re: Shore Power: Am I doing something wrong?

Reply #14 – April 18, 2011, 08:54:25 am

Re: Shore Power: Am I doing something wrong?

Reply #15 – April 18, 2011, 01:59:31 pm

Re: Shore Power: Am I doing something wrong?

Reply #16 – April 18, 2011, 06:48:02 pm

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Reply #17 – April 19, 2011, 08:44:35 am

Re: Shore Power: Am I doing something wrong?

Reply #18 – April 19, 2011, 11:26:57 am

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