AC on a 30 amp powr cord

[34Hatt]

Pete thats well stated.

Ill second that!

And for Scott saying his needs attention now that makes sense for a little $$ and time you upgrade.
All a long I been thinking I have two units just one is a little smaller and never have these problems even with a low voltage at dock. But everything is new, ac has been flushed just last year and even all my 15 amp circuits are wired with # 12 well everything was over sized for 0-3 percent drop through out the boat.

 

[SKYCHENEY]

Even though I can get by with running one 50a 240v cord, I like to run two. For the same reasons stated above, I don't have to worry about managing loads and I don't stress the cord or connections if I run two cords. Obviously, this is not always possible, but it sure is nice to be able to run anything on the boat at any time without tripping a breaker somewhere or heating some wire or connection that you cannot see.

 

[Boatsb]

Ill second that!

And for Scott saying his needs attention now that makes sense for a little $$ and time you upgrade.
All a long I been thinking I have two units just one is a little smaller and never have these problems even with a low voltage at dock. But everything is new, ac has been flushed just last year and even all my 15 amp circuits are wired with # 12 well everything was over sized for 0-3 percent drop through out the boat.

Every 2 years or so I have to change out the inlets and power cord ends from the boat end because it gets warm and starts to make the plastic brittle and the connectors are suspect. I have only had one burn up a conductor but the cost of this preventive maintenance would have paid for the upgrade after 2 cycles.

 

[SeaEric]

My AC guy was on my boat yesterday and in the context of back flushing the raw water lines found that the antique start/run knob switch on the salon unit 3 knob control was toast. Replaced that. Related wiring harness can stand replacement, this will happen next week.

My electrical guy was on the boat today. He tested amp draw on the AC units at the condensers individually, then at the shore inlet with both units running full blast. Total draw - condensers, air handlers and pump is 23 amps. Voltage holds and 110v. with all running. He states "you're good".
Both AC units are working perfectly and pumping out plenty of cold air. He further states "run them til they break!"

When they do break, there are some very good options for modern replacements.

We are going to install digital volt/amp meters for both 30 amp panels so I can see whats happening at a glance. This per Pascal's very sound suggestion.

So, for now I am back up and running.

 

[jim rosenthal]

23 amps is more like it. I think with one 12,000 and one 6,000 mine draws about ten or twelve with both running. Glad it was no worse.

 

[spcoolin]

My AC guy was on my boat yesterday and in the context of back flushing the raw water lines found that the antique start/run knob switch on the salon unit 3 knob control was toast. Replaced that. Related wiring harness can stand replacement, this will happen next week.

My electrical guy was on the boat today. He tested amp draw on the AC units at the condensers individually, then at the shore inlet with both units running full blast. Total draw - condensers, air handlers and pump is 23 amps. Voltage holds and 110v. with all running. He states "you're good".
Both AC units are working perfectly and pumping out plenty of cold air. He further states "run them til they break!"

When they do break, there are some very good options for modern replacements.

We are going to install digital volt/amp meters for both 30 amp panels so I can see whats happening at a glance. This per Pascal's very sound suggestion.

So, for now I am back up and running.

Eric~

Not knowing your system sizes...23 amps seems a bit low to me for two 115 volt systems...Well...As I say...Depending on system size...
The way we always figured it for installations, was the amp draw for the systems pretty closely matches the system BTU...

For instance we would figure a 16K system at 16 amps average...The condensing unit was rated at 12 amps cool & 15 amps in heat...Then add the blower & pump to that total...blower maybe as much as 3 amps for a EBS-16 (which was common on Hatt's) & pump as much as 5 amps (if a single large pump for multiple systems)

Blower & pump average stay pretty much the same...But condensing unit (compressor) amperage can change quite a bit with water & cabin temps & the condition of the water system & condenser coil...
That 16K condensing unit in 90 degree seawater & a 100 degree cabin with a dirty scaled up condenser coil might draw as much as 18-19 amps by itself...This is why I mentioned ACID flush earlier...Not just a back flush...A simple back flush will not remove scale from that seawater condenser that may be preventing good heat transfer to the water...

Normal system head pressure under those conditions should be between say 260 to maybe 300 psi....Pressure rises with heat...So if water flow is reduced, or the condenser is scaled up (which makes it hotter)...Then that pressure is much higher...Yes the system will continue to run because the high pressure switch does not cut it off until 425 psi...But as you see, you have quite a way to go between normal & cut out (at least 125 psi)...The compressor pumping against that higher pressure is working much harder & therefore drawing much more than normal amperage.

This method of sizing usually produced spot on predictions for overall amp draw of older 115 volt split systems, with just a bit of fudge factor....The newer systems negate this method somewhat because they are more efficient...

So going by my old method...A 16K & a 12K 115 volt system is about 28 amps average...The comfortable (close) limit of a 30 amp service...Yes there are dual 16K systems on 30 amp cords/services but they must be squeaky clean in warmer climates & they do have the most cord/receptacle troubles...

Steve~

 

[spcoolin]

23 amps is more like it. I think with one 12,000 and one 6,000 mine draws about ten or twelve with both running. Glad it was no worse.

Jim~

You should be drawing around 18 amps in cooling with everything as it "should be" with a hot cabin & warm (80-85 degree) seawater...

If not...You may not be picking up enough heat, and thus your system performance will be reduced...

I should mention for all...That as cabin temp lowers...So will the amp draw because there is less heat load....Lower heat = lower pressure = lower amperage.

Steve~

 

[SeaEric]

Relative to descaling, my boat has really never been in salt water. My electrical guy who was aboard yesterday has the equipment to do the descaling job properly, but based upon his inspection thinks it doesn't need it. As far as testing the amp draw, he pulled the 30 amp power inlet and put his meter right on the incoming wires. We sat around talking for half an hour with the meter attached and the air running full blast. The draw reduced slightly as the cabin got cooler. He promises me that I'm good to go.

I never hesitate to do any maintenance, repair or upgrade on my boat that makes sense. I am good, prompt pay. My vendors all know this. I give these guys a lot of work. I prefer to think that they sincerely look out for my best interest.

 

[spcoolin]

Relative to descaling, my boat has really never been in salt water. My electrical guy who was aboard yesterday has the equipment to do the descaling job properly, but based upon his inspection thinks it doesn't need it. As far as testing the amp draw, he pulled the 30 amp power inlet and put his meter right on the incoming wires. We sat around talking for half an hour with the meter attached and the air running full blast. The draw reduced slightly as the cabin got cooler. He promises me that I'm good to go.

I never hesitate to do any maintenance, repair or upgrade on my boat that makes sense. I am good, prompt pay. My vendors all know this. I give these guys a lot of work. I prefer to think that they sincerely look out for my best interest.

I'm sure they do Eric...Didn't mean to imply that, or that you do not keep up with things....

But...As I try to help all learn.... Scaling is not just a seawater problem...It happens in car radiators, boilers & cooling towers in big chillers on big buildings too...Basically heat exchangers of every kind...It is a known maintenance factor that is dealt with around the world, but for some reason some folks seem to think only happens to marine A/C in seawater...

We in seawater have the same scale issues...But we also have marine growth to deal with...Two separate issues...However marine growth will not usually grow inside Marine A/C condensers (usually too hot in there) but will grow in the hoses & plumbing to & from our units reducing overall flow...Not heat transfer ratio from the insulating affect of scale inside that condenser...

I did say that 23 amps seemed a bit low...But then also said I did not know the size of your system/s and went on to explain the effects of water/cabin temp on the pressures & amperage too...If your system BTU totals around that 23 amps....Then I guess you are within spec...If it's more than 23 K then you are either have nice cool water pumping thru your system/s, or you could be a bit low on refrigerant...Not knowing that info, system pressures, cabin temps at those temps (Cabin air & water) I would have to differ to your tech's experience, and agree that you are "Good to Go"

Again...Most of this & my last post was for everyone's info that owns older 115 volt split systems.

Steve~

 

[SeaEric]

Just before Irene hit, my AC guy was in and re-wired my main salon unit. We eliminated the plug at the unit in the engineroom which was burned and scary looking. Its now wired direct, no plug. The amp draw has dropped a bit as that connection was obviously creating some resistance.

I had both units running today and all is well. Still waiting for my electrical guy to install the Blue Seas digital meters. I want them in the system so I can keep a good accurate eye on what's happening with voltage and amperage. I guess he's tied up with post-hurricane mayhem.

Have I mentioned how happy I am with my old antique 41 TC? Well I am. I like this boat more each day. It's quite remarkable how well Hatteras had their $h*t together in 1966. This boat is quite simple, but well thought out and very well built. No sizzle here, just USA prime steak. It's a way better boat than my 1970 Matthews 46 in a lot of meaningful ways.

With as inexpensive as these old Hatt MY's are these days, they truly represent the most AMAZING yachting value.

 

[SeaEric]

Yesterday my electrical guy installed a pair of http://bluesea.com/products/8247 which display voltage, amps, watts and hertz. One for Ship's service and one for AC service. These are way more accurate than the antique OEM analog meters on the panels. I haven't seen the bill yet (the meters aren't cheap) but I'm very happy with the result.

Both AC units, a 16k and a 12k running full blast are consuming 24 amps total.

 

[jim rosenthal]

As to quality? damn right. DAMN right.

 

[REBrueckner]

"Is there any reasonable way to increase the integrity of the wire connection of the 3 supply wires to the back of the 30a inlet?"

If the wire strands are clean and the connecting screws are down tight about the only additional thing you can usually do is use moisture dispersant/ electrical spray.

Anytime you can eliminate plugs and receptacles in heavy power situations and use fixed screwed connections or single wire installations you eliminate some resistance and potential heat sources.

A related precaution is to be sure fuses and fuse holders are rotated regularly to scrape both clean and shiny for good electrical contact. Otherwise, enough heat can be generated to melt fuses even when current is within proper limits.

Oxidation in a moist high humidity environment is common and this creates enough resistance to begin heating things up, blowing fuses, and or melting electrical cord plugs/receptacles.