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07-27-2015, 05:53 AM
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#1
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Member
City: Mt Pearl
Join Date: May 2015
Posts: 21
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Hot power cord
Looking for electrical coaching SVP !
I have just noticed an electrical issue that I am quite concerned about. My 30 amp shore power cord has scorched one of the three prongs while at the same time, I have two on-board electrical heaters (new) and both cords are quite hot after being plugged in for a short period of time. I have since stopped using them until I get to the bottom of this.
Any ideas would be most welcome
Thanks in advance
Zoom
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07-27-2015, 05:59 AM
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#2
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Guru
City: Ft Pierce
Vessel Name: Sold
Vessel Model: Was an Albin/PSN 40
Join Date: Oct 2011
Posts: 28,148
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If cheapo heaters....their cords are barely adequate to begin with and will get hot no matter what you do, except rewire with heavier wire as I have done occasionally.
A 30 Amp circuit will not usually handle 2 - 1500 watt heaters on full and much of any other load like a hot water heater. All 3 at one time will usually trip the breaker.
Once a plug is scorched, and the dockside receptacle should be replaced as both may be compromised enough that it will always be a higher resistance connection now.
That's why I upgraded to a 50 amp setup...I think the 30 amp plugs are almost dangerous in design and having spare juice is better than not enough.
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07-27-2015, 06:06 AM
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#3
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Member
City: Mt Pearl
Join Date: May 2015
Posts: 21
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Thanks for the quick reply sir. I have considered going to the 50amp side, however, I need to understand the problem before making that move. Concur with your heater comment, nonetheless, this does not answer the hot power cord issue. Thanks again.
Zoom
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07-27-2015, 06:22 AM
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#4
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Senior Member
City: Ft Myers, Florida
Vessel Name: Homegrown
Vessel Model: Roberts TY 43
Join Date: Apr 2014
Posts: 209
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Smart plug is a good way to go on shore power cords. Twist lock receptacles are old technology, and by design will cause failures.
Conall
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07-27-2015, 06:37 AM
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#5
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Guru
City: Sarasota/Ft. Lauderdale
Join Date: Apr 2014
Posts: 5,438
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Quote:
Originally Posted by zoomie
Thanks for the quick reply sir. I have considered going to the 50amp side, however, I need to understand the problem before making that move. Concur with your heater comment, nonetheless, this does not answer the hot power cord issue. Thanks again.
Zoom
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Take the heaters home and plug them in and see if the cords get hot.
If not then the issue is that they are on the verge of over loading the circuit on the boat. And you may have other resistance issues with the wiring on your boat.
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07-27-2015, 06:43 AM
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#6
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Guru
City: Galveston, Texas
Vessel Model: 24" El Pescador
Join Date: Nov 2014
Posts: 744
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07-27-2015, 06:51 AM
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#7
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Member
City: Mt Pearl
Join Date: May 2015
Posts: 21
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Cold at home, suspect you are on the right track with your analysis. Not sure where to start. Someone mentioned outlets are old and need replacing. I might swap one out and see what results yield.
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07-27-2015, 07:34 AM
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#8
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Guru
City: gulf coast
Join Date: Jun 2014
Posts: 3,440
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Low voltage will cause excessive current on the fan motor causing hot cords. Bad connections are one of many reasons .
You could try a different dock connection and measure the voltage
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07-27-2015, 07:37 AM
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#9
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Guru
City: Punta Gorda, FL
Vessel Name: Aweigh
Vessel Model: Nordic Tug 42
Join Date: Jun 2014
Posts: 628
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First unplug the boat from dock power. Next pull the receptacle out of the boat and look for scorch marks on the wires, It is usually the white on that burns. If burned, get a new receptacle. It is looks OK tighten each screw. What normally causes hot plugs is loose wires in the plugs, especially the one on the boat. The heating and cooling as heaters and A/C's go on and off cause the connections to expand and contract which over time will cause the screws to work loose and get hot as they arc.
Best is to replace both the boat receptacle and the cord plug and then check the tightness of the screws every few months.
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07-27-2015, 11:13 AM
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#10
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TF Site Team
City: California Delta
Vessel Name: FlyWright
Vessel Model: 1977 Marshall Californian 34 LRC
Join Date: Apr 2008
Posts: 13,728
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Quote:
Originally Posted by bayview
Low voltage will cause excessive current on the fan motor causing hot cords. Bad connections are one of many reasons .
You could try a different dock connection and measure the voltage
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Quote:
Originally Posted by seasalt007
First unplug the boat from dock power. Next pull the receptacle out of the boat and look for scorch marks on the wires, It is usually the white on that burns. If burned, get a new receptacle. It is looks OK tighten each screw. What normally causes hot plugs is loose wires in the plugs, especially the one on the boat. The heating and cooling as heaters and A/C's go on and off cause the connections to expand and contract which over time will cause the screws to work loose and get hot as they arc.
Best is to replace both the boat receptacle and the cord plug and then check the tightness of the screws every few months.
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Great advice! If the dock receptacle is scorched, replace it. If the boat receptacle is scorched, replace it. Replace the scorched plug end and be sure to cut back into the good wire on the cord if replacing the end only.
High resistance from a bad or corroded connection can cause a drop in voltage. A voltage drop will result in more amps being drawn which can cause overheating. Fix your resistance problem and you'll more than likely fix your overheating problem.
I recently noticed that my shore power cord was a bit warm near the dock box. The prongs were just starting to show signs of corrosion. I sanded the prongs, cleaned them with an electrical contact cleaner and reconnected. All is well.
I run electric ceramic heaters but only operate them on the low setting which is 600W. The higher setting (1200 or 1500W) is too high for my 30A service.
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07-27-2015, 01:43 PM
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#11
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Member
City: Mt Pearl
Join Date: May 2015
Posts: 21
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Thanks, sage advice. I will try that
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07-27-2015, 04:25 PM
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#12
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Guru
City: Pender Harbour, BC
Vessel Name: Gwaii Haanas
Vessel Model: Custom Aluminum 52
Join Date: Sep 2013
Posts: 3,791
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All good advice. I would also add: do you have a fridge? Do you have a battery charger? Hot water tank? All of these will overload your 30 amp service. When you have the boat plugged in AFTER you repair the plug, an easy test is to plug your multimeter into a 120 boat socket. I'll bet your voltage is down under 100 volts, which is an easy way to test for overloading. If you do not have 120 volts, you are looking for trouble beyond burnt connections.
Sadly, 30 amps is very small.
Heater 1500
Water heater 1500
Battery charger 1500
Fridge 500
Toaster?
Water pump?
Kettle?
Lights?
Cell phone charger?
USB sockets?
5000/12=42 amps plus. Altogether it would blow the breaker. Unfortunately, as you've seen, the breaker does not blow at precisely 30 amps and there is a lot of room for overloading before it does.
The Smart Plug is great for the boat connection but it is only useful for the dock connection if the marina will allow you to have it installed in their equipment. Visiting many marinas, you will have to use a conventional cord.
__________________
Don't believe everything that you think.
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07-27-2015, 07:20 PM
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#13
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Guru
City: Punta Gorda, FL
Vessel Name: Aweigh
Vessel Model: Nordic Tug 42
Join Date: Jun 2014
Posts: 628
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The problem with a Smart Plug is that it connected to the boat exactly the same way as a regular boat inlet plug. It is better at the cord/boat connection point but the wires from inside the boat attach to the Smart Plug the same way they attach to a regular plug and thus are subject the same arcing caused by a loose connection at that point.
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07-28-2015, 05:19 AM
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#14
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Guru
Join Date: Oct 2007
Posts: 22,553
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Resistance from any part of the circuit causes heat and voltage loss.
Chop the ends of the power hose and use Hubbel ends to replace the molded on cheap junk.
Use a VOM ( $ 7.00 in Wallmart) to measure the Volts at the power post , then measure the V at each heater. A big drop is a problem.
Use a temp sensing lazer gun to see if any connections you can find are hot.
To live well on 15 or 30A of 120 can be easily done , but a load shedding system will need to be installed.
Heating with electric is only worthwhile if the dock does not charge for electric.
Full 30A draw could cost 75c to a buck an hour , 24 hours a day!
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07-28-2015, 09:09 PM
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#15
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Senior Member
City: Maumelle, AR
Vessel Name: Missing Link
Vessel Model: 1986 Albin 34 Family Cruiser
Join Date: Jan 2013
Posts: 112
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With all this heating, have you asked yourself why you are not blowing breakers? Think about it.
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07-29-2015, 07:15 AM
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#16
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Member
City: Mt Pearl
Join Date: May 2015
Posts: 21
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Great note. Thank you for your input
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07-29-2015, 07:20 AM
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#17
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Member
City: Mt Pearl
Join Date: May 2015
Posts: 21
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Thanks for all of the input.
I have narrowed it down to a poor connection on the 30amp house side and have now switched over to the 50 amp side with clean and stable power.
As for the heaters, we have determined cheep heaters with cheep wiring. No more too it than that. Reworded one with a bit heavier cord, and it works very well.
Thanks for all of the replies.
Best regards
Zoomie
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07-29-2015, 07:52 AM
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#18
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Guru
City: SF Bay Area
Vessel Model: Tollycraft 34' Tri Cabin
Join Date: Feb 2011
Posts: 12,569
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Many great mentions here.
With our 30 amp system that has amp and volt meters on electric panel we simply make sure to keep it down to 20 amps max for a very short period (usually we have it under 15 amps) on meter by alternating boat items on/off while utilizing electric features... whether on dock plug or running gen set.
Wally World cheap electric heaters should never be placed on high heat setting - IMO, because they are actually not designed to well-handle that amperage for long periods.
Stay appraised of the amp draw, keep it at least 33% below boat's max, and make sure electric connections are clean/tight. That's how I play it!
Happpy Boat-Amp Daze! - Art
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07-29-2015, 08:00 AM
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#19
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Guru
City: Ft Pierce
Vessel Name: Sold
Vessel Model: Was an Albin/PSN 40
Join Date: Oct 2011
Posts: 28,148
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Cannot agree that you need a safety margin on power cords, it is already built in...just keep them clean, corrosion free and snug.
That's from over a decade of living aboard and a lot of it in Mid Atlantic winters.
Depending what heater from Walmart or any box store.... have been using them for decades on high without fire or more than slightly warm cords. Again, it may be another reason...but not the heater themselves.
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07-29-2015, 08:22 AM
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#20
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Guru
City: SF Bay Area
Vessel Model: Tollycraft 34' Tri Cabin
Join Date: Feb 2011
Posts: 12,569
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Quote:
Originally Posted by psneeld
Cannot agree that you need a safety margin on power cords, it is already built in...just keep them clean, corrosion free and snug.
That's from over a decade of living aboard and a lot of it in Mid Atlantic winters.
Depending what heater from Walmart or any box store.... have been using them for decades on high without fire or more than slightly warm cords. Again, it may be another reason...but not the heater themselves.
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