Boat Wiring and Onboard Heaters

[Sidclark]

So, on my last boat if I ran a heater over 1000 watts, the heater plug would seriously overheat and threaten to melt. The boat was French built and the wiring was to EU standards. I've put in an offer on a 1987 Marine Trader and my question is; have you guys and gals run electric space heaters on your boat? Shore power or generator. Was the wiring up to it? If all goes well, I'll have to move the boat from Maryland to South Carolina in December. I'd like to have some heat if possible. Any thoughts?

 

[Comodave]

We have a 1987 President 41’. The wiring will support a 1500 watt heater. A 15 amp 14 gauge circuit should work with a 1500 watt heater.

 

[psneeld]

On my last liveaboard, a Silverton (US made) no issues....

My Albin 40 didn't have anyi issues but I wound up rewiring the whole boat. I made sure a couple outlets were heavy duty wired, but remember the outlet itself may be the issue so replace it with a 20A outlet if still getting hot.

 

[gsholz]

Good catch. Heaters are one of the major sources of boat fires. I wonder whether your old boat's wiring was sized for European 220V vs US 120V. A 120V heater pulls about twice the amps at the same wattage. One cannot just reuse 220V wiring for 120V devices. The other way is OK.

I do use oil filled electric heaters but only on 600W when unattended. I would not want to use a fan-type electric heater unattended. You are betting on the over-temp protection to work when the fan bearing locks up.

 

[Pau Hana]

So, on my last boat if I ran a heater over 1000 watts, the heater plug would seriously overheat and threaten to melt. The boat was French built and the wiring was to EU standards. I've put in an offer on a 1987 Marine Trader and my question is; have you guys and gals run electric space heaters on your boat? Shore power or generator. Was the wiring up to it? If all goes well, I'll have to move the boat from Maryland to South Carolina in December. I'd like to have some heat if possible. Any thoughts?

Your questions opens up a Pandora's box:

• Is the boat 30A, dual 30A, or 50A?
• What else is on the circuit that the heater plugs into?
• What else could come on when the heater is running and cause a potential overload?
• Are there any alternative sources of heat?

You may want to consider a diesel furnace (air to air) as a viable option.

 

[DavidM]

Your Marine Trader although built in Taiwan was built to US wiring standards: 14 gauge wire for a 15A outlet. It should handle a 1,500 watt heater as well as one in your home.


David

 

[Sidclark]

Good catch. Heaters are one of the major sources of boat fires. I wonder whether your old boat's wiring was sized for European 220V vs US 120V. A 120V heater pulls about twice the amps at the same wattage. One cannot just reuse 220V wiring for 120V devices. The other way is OK.

I do use oil filled electric heaters but only on 600W when unattended. I would not want to use a fan-type electric heater unattended. You are betting on the over-temp protection to work when the fan bearing locks up.

Yep, it was 220v wiring with 110v type outlets.

Your questions opens up a Pandora's box:

• Is the boat 30A, dual 30A, or 50A?
• What else is on the circuit that the heater plugs into?
• What else could come on when the heater is running and cause a potential overload?
• Are there any alternative sources of heat?

You may want to consider a diesel furnace (air to air) as a viable option.

It's a duel 30 amp shorepower. I would try to find a dedicated circuit to plug into if possible. The other heat source would be reverse cycle heat from a/c units, but have never had good success with those. I only need heat for the trip down, so no need for a furnace. Plan are to leave in November with the migration and return in March, so no need for heat in those months..

Your Marine Trader although built in Taiwan was built to US wiring standards: 14 gauge wire for a 15A outlet. It should handle a 1,500 watt heater as well as one in your home.


David

That's what I was hoping!

 

[syjos]

remember the outlet itself may be the issue so replace it with a 20A outlet if still getting hot.

You would need to upgrade to 12 gauge wiring and 20 A circuit breaker for a 20 amp outlet.

I have several 20 A circuit's on the boat for microwave and outlets dedicated to portable heaters.

I also use an oil filled heater at 1/2 power unattended. It warms the air around the dehumidifier to keep it from freezing during winter.

 

[rslifkin]

You would need to upgrade to 12 gauge wiring and 20 A circuit breaker for a 20 amp outlet

It's not technically correct to put a 20A outlet on a 15A circuit, but it's also perfectly safe. You'd just have an outlet that can safely handle more power than the breaker (and wiring) will allow you to pull.

 

[psneeld]

I didn't make it clear that I was suggesting 20 A outlets on heavier duty circuits.... but I agree that if you keep a 15A CB in the circuit all should be well.


If the outlets are getting hot with 14 ga wire, 15 A CB and standard 15A outlets...something is wrong and dangerous anyhow.

 

[Gordon J]

Was your boat wired originally fir 220volts?

So, on my last boat if I ran a heater over 1000 watts, the heater plug would seriously overheat and threaten to melt. The boat was French built and the wiring was to EU standards. I've put in an offer on a 1987 Marine Trader and my question is; have you guys and gals run electric space heaters on your boat? Shore power or generator. Was the wiring up to it? If all goes well, I'll have to move the boat from Maryland to South Carolina in December. I'd like to have some heat if possible. Any thoughts?

You Say your boat was wired to EU standards. If it was also wired for 220 V, you may have smaller wires that may not be appropriate for 110 V. That may be the source of your problem. Because of the higher voltage, 220 wires are often smaller than 11o, depending on the expected load.

 

[tiltrider1]

I feel it’s unsafe to plug a 1500 watt heater into an outlet as a primary heat source. Most of my issues are with the unsecured heater. Installing a King Picawatt heater on a 20 amp breaker would be my recommendation. 1500w is 13.6 amps which is to close to the limit of a 15 amp circuit for continuous duty. on a boat corrosion is a real issue, adding this extra resistance to an already maxed out circuit is risky.

 

[FF]

"It's not technically correct to put a 20A outlet on a 15A circuit, but it's also perfectly safe. You'd just have an outlet that can safely handle more power than the breaker (and wiring) will allow you to pull."


Its safe and a very easy upgrade, as both 20A plugs and 20A sockets are at at any big box store.
They handle the 1500W heater well.

The genuine 240V plugs and sockets work great with 12V , far better than a cigar lighter socket. No 240V users should be on board.

 

[OldDan1943]

The American Tug has 2 resistance heaters. Turn them both on and that's it, no more..... but, I like them. I just have to remember to make sure I have hot coffee before I turn on the heaters.

 

[diver dave]

Replace the receptacles every 20 years. Don't use the backstab feature. And, if you don't have a good feel for torque, use an instrument. I just finished replacing all the 1988 recepts in my house, and saw a number of issues. A boat doesn't have that many recepts to be a $ issue, and the ones that do exist may get heavy use along with salted atmosphere.
I don't know if this is a rule, but I would not put any stranded wire directly under a screw head. Use devices that clamp the wire end. Also, use devices that are "marine" rated, or at least "WR" (weather resistant). The yokes will be made of a corrosion resistant material.

 

[O C Diver]

Unless you're going to be in water colder than 35 degrees, it makes a lot more sense to run the air conditioning in reverse cycle for cabin heat. It will produce a lot more BTUs with a lot less amps.

Ted

 

[sunchaser]

Unless you're going to be in water colder than 35 degrees, it makes a lot more sense to run the air conditioning in reverse cycle for cabin heat. It will produce a lot more BTUs with a lot less amps.

Ted

But, does one want a raw water pump running on an untended vessel?

 

[rslifkin]

But, does one want a raw water pump running on an untended vessel?

I do it with one of my A/Cs during the hot, humid parts of the summer. The A/C pumps don't flow all that much, relatively speaking. So assuming it won't be unattended for long periods of time, the bilge pumps should be able to handle any A/C related issue for long enough to notice it and fix it.

 

[O C Diver]

But, does one want a raw water pump running on an untended vessel?

Plumbed properly with a magnetic drive centerfusial pump, I would say the risk factor is far lower than either an electric heater or fuel burning heat stove. Millions of boats are left unattended with air conditioners running. From the below article, air conditioning systems failures doesn't even make the list for boats sinking at the dock. Now if we're talking about a Jack leg installation, well they're making more determined idiots all the time.

https://www.boatus.com/magazine/2014/june/why-boats-sink.asp

Ted

 

[Sidclark]

But, does one want a raw water pump running on an untended vessel?

No plans to leave the heater on when no one is onboard. Just need the heat for the trip down from Maryland. There are 7000, 10000 and 16000BTU ac units onboard, so maybe reverse cycle will suffice, just not sure.

 

[rslifkin]

There's a good chance you'll be fine with reverse cycle in that case. A 1500W space heater is only good for 5100 btu.

 

[psneeld]

No plans to leave the heater on when no one is onboard. Just need the heat for the trip down from Maryland. There are 7000, 10000 and 16000BTU ac units onboard, so maybe reverse cycle will suffice, just not sure.

That's about the equivalent of 6 space heaters and way less amp draw.

 

[Carolena]

Those should work just fine for you. We use ours in northern Virginia until the water gets below 40 degrees, which is usually around mid to late December. Below 40 the units will freeze up and stop heating. As others have noted, they reverse cycle heat pumps will throw a lot more heat using much less power than electric units. When the water is warm enough to run ours, the cabin stays plenty warm down into 20 degree air temps. Once we have to switch to electric, we generally are only able to heat the saloon without over taxing our electrical system. In fact, if we stay on the boat in the dead of winter we usually sleep in the saloon pull out as it is difficult to heat the entire boat with just electric. We consider diesel very year, but the really cold weather only lasts a couple of months.

 

[catalinajack]

My reverse cycle heat quits at a water temp of about 45 degrees.

Unless you're going to be in water colder than 35 degrees, it makes a lot more sense to run the air conditioning in reverse cycle for cabin heat. It will produce a lot more BTUs with a lot less amps.

Ted

 

[catalinajack]

We live aboard in Maryland having spent two past winters. When even really cold (single digits overnight) we are still able to keep the boat to 72 degrees using four resistance heaters, all on separate circuits. We just need to shut one off when using the toaster, microwave, or coffemaker. None of the four cause an outlet to become warm. It costs about $5/day to run one heater for 24 hours. Fortunately, the temps are not single-digit cold very often such that we need to run all four. More often it is just two, perhaps three during the day. We sleep cold, 50 degrees in the owners' cabin warm and cozy with just a down comforter.

Those should work just fine for you. We use ours in northern Virginia until the water gets below 40 degrees, which is usually around mid to late December. Below 40 the units will freeze up and stop heating. As others have noted, they reverse cycle heat pumps will throw a lot more heat using much less power than electric units. When the water is warm enough to run ours, the cabin stays plenty warm down into 20 degree air temps. Once we have to switch to electric, we generally are only able to heat the saloon without over taxing our electrical system. In fact, if we stay on the boat in the dead of winter we usually sleep in the saloon pull out as it is difficult to heat the entire boat with just electric. We consider diesel very year, but the really cold weather only lasts a couple of months.

 

[O C Diver]

My reverse cycle heat quits at a water temp of about 45 degrees.

What do you mean exactly by quits? Does the system freeze up or is there a temperature sensor in the raw water line that shuts the system down?

My Webasto units worked down to around 35 degrees (with reduced BTU output). Down around 33 degrees they started to freeze up, but that is a function of insufficient raw water flow. With the new raw water pump in brackish water, I could probably get down to 32 degrees, but BTU output probably makes it unrealistic.

Ted

 

[HiDHo]

Best money I ever spent and peace of mind was for two 450 watt Extreme Bilge Heaters. Light weight, long heavy duty plug in cords. I can winterize in 30 minutes including engine room vent blocks, gravity drain Fresh water system, and plug engine exhaust. I run rv anti-freeze thru both my ac/h units only as a over kill precaution in case electric power goes off. ?

 

[syjos]

We lived aboard Sandpiper for two winters while building our current house.

Sandpiper has no built in heat.

Our marina at the time had unmetered AC !!!!!!!!!!

I installed a second shore power inlet, split the AC panel and ran two 30 amp cords to shore. Bought 5 Caframo True North heaters and ran them at 600 watts. Installed 20 amp dedicated heater outlets with 12 ga wiring and a 20 amp breaker

Kept the boat real warm. Opened windows for temperature control.

Comes in handy now when we boat in winter and a second shore power outlet is available.

 

[catalinajack]

By "quits" I mean that the units stop producing any useful amount of heat.

What do you mean exactly by quits? Does the system freeze up or is there a temperature sensor in the raw water line that shuts the system down?

My Webasto units worked down to around 35 degrees (with reduced BTU output). Down around 33 degrees they started to freeze up, but that is a function of insufficient raw water flow. With the new raw water pump in brackish water, I could probably get down to 32 degrees, but BTU output probably makes it unrealistic.

Ted

 

[O C Diver]

By "quits" I mean that the units stop producing any useful amount of heat.

That may be a function of water flow or design of the unit. My Webasto produces near full output with 40 degree water temperatures. Most reverse cycle home heat pumps and split units produce good heat at or below 40 degrees. My home geothermal will work well down to 20 degrees (antifreeze in loop) although it's never been below 45 yet.

Also there is a noticeable improvement in heating and air conditioning BTU output when I changed water pumps. The output is now about 7 gallons per minute (measured at hull discharge) for each unit (12,000 BTU).

Ted