16k BTU AC and Water Heater on 30 amp Service

[Tia Bu]

Do any of you currently have both a 16,000 btu air conditioner and a water heater running on the same 30 amp service?

I've got an older 16,000 btu Marine Aire unit. Thinking of adding a water heater, but think the locked rotor startup loads on the compressor would probably blow the main breaker when the water heater is also on. Is there a way to test this out without buying and installing the water heater first?

Would a hard-start capacitor or SmartStart kit help? Is there an incremental way to go about testing these solutions?

Any advice appreciated.

[ranger58sb]

We have one 16K BTU unit and raw water pump, plus water heater, plus two-burner electric stovetop, plus one small fridge on one 110V leg of our 50-amp service, with no overload problems, if that helps.

-Chris

[Tia Bu]

Well, thanks, that kind of helps, but if you're just using one leg of the 50 amp service, does that mean you have 50 amp, 110 volt service?

[ranger58sb]

I have roughly the same amount of stuff running on the other leg, too.

Just thought that first leg's worth, so to speak, would be roughly equivalent to one of your 30-amp supplies.

-Chris

[a64pilot]

My boat has only a single 30 amp service, I run a 16K ac and a 5K ac as well as battery charger, water heater TV's, multiple cell chargers, toaster, whatever. I can easily run the 16K AC and everything except the 5K AC, if I have the water heater on, 11 amp draw, I have the small AC off 5 amp draw.
With everything running including the water heater and 16K AC, but not the 5k ac I have a 26 amp draw, so far no problems.

On edit, the water heater only needs to be on for an hour or so a day it seems to keep water hot pretty well.

My 16K Ac is ancient and it's start up load is pretty big, but on shore power no problems

I keep thinking of things, sorry. If you install a 220V heater element in a water heater running off of 110V you will decrease it's current draw and of course it's heat output greatly, if I had a 220V heating element I could run everything including both AC's, just barely, but as the heater needs to be on only for so short a period I haven't bothered

[Tia Bu]

Tell me more about installing a 220 volt heating element. I'm not sure I follow.

[travellerw]

Not sure if it is available for marine AC units, but in RV ACs you can install a "soft start" kit to help with startup load. Its basically a big capacitor that supplies some of the current for the start up.

I know there are universal kits that might work for a marine AC.

[a64pilot]

A 220 resistance heating unit run off of 110V will I think pull about half the power of a 110V one, it will produce only about half as much heat of course meaning it will take twice as long to get the water to the same temp, but it would keep me just under 30 amps. if I ran both AC's and the water heater.
My old Marine Air 16K AC does have a large start up current, but on shore power it's no problem, I don't believe you need a soft start kit on shore power even with the hot water heater on.

[Tia Bu]

Thanks, guys, for the input. I think I see the way through, now.