shore power wire run/hvac circuit breakers running hot

[Pettigrewr]

Good afternoon all;
My hvac circuit (50amp, 125volt. not 240v) has begun consuming 40amps instead of the usual 22amps. also the main and individual breakers get hot, not warm. The panel ammeter reads 20 amps with either hvac on and 40 amps with both on.
The hvac master breaker feeds two 20 amp breakers and each breaker has one 12btu self contained unit.
I have changed out the starboard inlet receptacle, swapped power cords, switched over to the port inlet, changed out the port inlet, changed the individual hvac breakers, changed out the 50amp master breaker. still - each hvac unt pulls 20 amps. I know it's not the hvac units themselves as I have disconnected each one while the other was connected and still the ammeter shows 20amps. Crazy because a clamp ammeter tester on each hvac cable shows about 11amps being consumed by the individual units. also, at the shore power pedestal, shows 11amps consumed by each unit and about 22amps when both are turned on. I'm now thinking maybe the cables running from the inlets to the circuit breaker is bad somewhere. the port and starboard inlets must be joined in a junction somewhere because each inlet has one cable and the breaker box only has one cable entering it.
yes, voltage tested everywhere and about 117 volts beginning at pedestal and ending at each hvac circuit.
Any ideas and any idea where the two inlets could be junctioned?
1965 50' hatteras motoryacht.
Thanks for any and all ideas and suggestions.

 

[Pascal]

If your clamp amp meter shows 10amps, are you sure the panel meter is accurate? I would start there. If original to the boat, I wouldn’t be surprised it a acting up

I m a big fan of the digital Blue Seas multimeters which you can mount remotely like at the helm, and display amp, volts and freq.

On one thing to keep in mind, is that as air con coils get dirty the units will pull more amps. I converted my 53 to chillers a few years ago, each 36k btu chiller pulls about 14/15 amps when clean or in winter. These days with warmer water and faster growth, they pull almost 20 amps. Now, double the amps would be huge but you may want to check the temp of your coils and compressor.

That said I bet on a faulty panel meter

You only have 2 units on a 50 MY?

 

[Pettigrewr]

on lower deck, one unit handles aft and vip, forward unit handles forward and galley.
Salon unit is just a portable freestanding on the house circuit with no issues, not connected to hvac side.
with either lower deck unit on, either 20amp circuit breaker gets very hot.
yet a clamp meter on the hot wires running from the breakers to either unit, reads 11amps not 20amps so I don't understand why breakers are getting so hot and that leads me to believe the panel meter is showing correct and something I am missing. By the way, with master on and hvac breakers off, panel ammeter reads zero as it should. I have tested impedance (ohms/resistance) on breakers and isn't any, reads zero ohms when breakers are closed.
Could this issue be some sort of grounding issue with current backfeeding
or
were the two shore power inlets cables are joined together, bad connections?
like I said port and starboard each have a single cable but only one cable enters the breaker panel.
I have the original schematics and it shows the two inlets coming together and then one cable leading to breaker in panel.

Been working on this for four days now and no closer to finding cause. I'm at a lose for further ideas, at this point will grasp any straws and try anything.

 

[Pascal]

Mine is an early 53 and the early 53s carried over some things from the 50 including the electrical panel in the port ER.

When I redid the entire electrical system a few years ago and set up a new panel in the salon right by the stairs, I was shocked by some of the electrical wiring I ripped out. I also had a port and starboard power cords. The stbd wires ran along the aft gen room Bulkhead where the port wires connected in the middle. How were they connected? The stbd wires were striped, and the port wires crimped on top with a split piece of copper pipe! And probably a roll of electrical tape… I cant believe it worked for almost 50 years!

So anything is possible.

That said, it seems to me that if you had a connection issue, a problem with the wiring, or the breaker, the increase in amp would be matched by a drop in voltage. Have you checked the voltage at the units?

I am still wondering if the problem isn’t your amp meter. Hot breaker? Are they original? Do they move freely? Have you checked the wiring inside the panel? The wiring in my 1970 panel was not in great shape as back then wires were not tinned and would corrode. This is what prompted me to re wire the entire boat… new panel, new wires thru out the boat

 

[Pettigrewr]

so here is what i'm seeing:
At the power pedestal 118 volts, with each unit 11.5 amps, with both 22 amps.
before shore power breaker (70amp breaker) reads 117-118 volts with loads at 11.5 or 22 amps.
At 50amp master breaker for HVAC side of panel reads 117-118 volts.
each of the two 20 amp hvac breakers reads 117 volts with 11.5 to 12 amps.
At each unit reads 117 volts at 11.5 to 12 amps.

with just one unit running, panel ammeter reads 20amps and master breaker hot and unit breaker really hot. if I turn on the second breaker that one gets really hot also and panel meter jumps to 40 amps.

I will definitely check out the cable run behind the generator and if suspect at all, will run new cables from panel to shore power inlets.
Is the wiring secured inside the gunnel near the inlet or is it free to pull from inside the boat close to the inlet?
I checked for access to the inlets and the engine room overheads will need to be cut if I can't simply pull the cables.

My other thought was maybe something is wrong with the breaker buss bar. As i replaced each breaker, nothing appeared wrong with the buss bar but if I pull all the breakers, I may find something. will do that too.

 

[Pascal]

If voltage remains the same all the way to each air con unit, I really doubt you have an issue with the wiring between the shore inlet and the panel. You could use an IR gun to look for hot spots along the way especially where port and stbd connect

How hot do the breakers get? I d still replace the panel meter first.