Heating thoughts.....

[Oldlaxer1]

I installed an 8kw (27000 BTU) diesel forced hot air heater in the port engine room. Ran a duct to a register just aft of the port pilot house door (just forward of our sofa), another duct to the galley floor just to the right of the stove cabinetry, and a third one to the aft stateroom. It keeps us plenty toasty. Because my onboard fuel is getting old I put a 12 gallon tank outside on the port walkway and ran the fuel line in thru the engine room vent. I fill it with jerry jugs. that part is a little bit of a PITA but these heaters really like clean fuel. In the aft stateroom I only brought the heat duct to the space where the air handler is. I just run the fan for the a/c unit and the heat comes out the vent. If I feel ambitious before it gets cold I may bring the ducting to an actual register. I turn the diesel heater down at night to about 60 degrees. We run two small 750 watt heaters in the master and have a heated mattress pad so we're quite toasty at night. When I get up I raise the temp on the diesel heater and in less than 10 minutes the boat is up to 68-70 degrees so my bride is comfy when she gets up. Here is a pic of a partially completed install. All the ducting wasn't complete at this point. Heater install.jpg

[gondolaguy]

Because my onboard fuel is getting old I put a 12 gallon tank outside on the port walkway and ran the fuel line in thru the engine room vent. I fill it with jerry jugs. that part is a little bit of a PITA but these heaters really like clean fuel.

Hi John. I'm in a quandary about the whole fuel supply aspect. I like the idea of tapping into the existing fuel system, but there are several issues with that:

1. Fuel quality - as you mentioned
2. The vertical distance from the fuel tank to where I've mounted the heater (above the water heater) which might require a stronger fuel pump than the one that comes stock
3. Making a change to a functioning system that could result in fuel delivery problems for the engines

I don't want to use the stock fuel tank mounted in the engine room because it would be too problematic to fill.

Is this a recent install, or have you been through a winter with it yet? How often have you have to fill up your 12 G tank?

Also, it looks like the exhaust has an uphill run in it. Water vapor in the exhaust could condense in it and pool in the low spot and cause more back pressure than the unit is designed for. It's recommended to keep it running downhill to prevent that. I assume you have a through-hull where it terminates that is lower than the unit.

Another suggestion I'd make is to run a return duct to the conditioned space like the hallway instead of using the air from the engine room. This will dramatically improve the efficiency of the unit and prevent carbon monoxide from getting into your living space.

Look forward to comparing notes.

Thanks for posting.

[Oldlaxer1]

I checked with the distributor/mfg rep showing him this exact picture and he said the slight uphill run for the exhaust was fine. We ran it all winter last year (after the water got too cold for reverse cycle). I would say I filled the two 5 gallon jerry jugs on average 1 1/2 times per week. So basically I'm guessing I was using maybe 15 gallons per week at the coldest part of the winter. Last year was a relatively mild year in Baltimore. If you choose to do what I did I'd highly recommend paying a little extra for one of these diesel jerry jugs. They make refilling simple. The ones from Home Depot (I have one of them too) are a royal pain.
https://www.amazon.com/gp/product/B014VAGV70/ref=ppx_yo_dt_b_search_asin_image?ie=UTF8&psc=1
Attachment 44162diesel can.jpg

[Oldlaxer1]

BTW, I discussed the return line with my mechanical contractor when he was making up a distribution duct and he recommended just propping the engine room door open slightly instead of putting holes in the hallway wall. He thought the engine room walls may be fire rated. I never bothered to look into if they are or not.

[gondolaguy]

BTW, I discussed the return line with my mechanical contractor when he was making up a distribution duct and he recommended just propping the engine room door open slightly instead of putting holes in the hallway wall. He thought the engine room walls may be fire rated. I never bothered to look into if they are or not.

I'm sure he's a fine mechanical contractor. My training is in energy efficiency and health & safety. I'm concerned about the open return on that unit and its proximity to the exhaust. It doesn't take much for these units to start putting out very high amounts of carbon monoxide. Under the wrong wind conditions your bride might not wake up. You'll also get a lot more heat from the unit if it is drawing from a conditioned space as opposed to an unintentionally conditioned space. I'm not trying to sound like a know-it-all, but I do know about these things. At the very least, please be sure to have a CO alarm in the bedroom and salon.
BTW, I have plenty of extra flex duct and an extra termination for it I'll give you if you want to drop by sometime and pick it up.

[gondolaguy]

I just looked up the specs on your heater and did some calculations on the energy output and the cost per KWH, based on average diesel prices from last winter ($3.25). The unit is about 71% efficient at converting the fuel into hot air when it is at it's peak performance (serviced regularly). If you had no distribution losses in your ducts you would be spending $0.11/KWH to use the diesel heater. Typically, when you have uninsulated, unsealed ducts running through unconditioned spaces you're going to have significant distribution losses. You also have an open return right next to a large opening to the outside. For every cubic foot of cold air it draws through that opening, there is a cubic foot of hot air getting pushed out of the boat through vents and around doors, windows and hatches. You're distribution losses are probably around 25%, meaning that only 75% of the heat that the unit produces ends up heating the living space, so you are actually spending closer to $0.16/KWH (when you also include the electric consumption of the heater) which is probably more than you spend for heating with electric space heaters. I'm not sure if the diesel heater is worth all of the effort in your case. For me, I have to spend $0.25/KWH for electric, and I have well insulated and sealed ducts, so it is definitely worth it in my case. Diesel prices have come down, but they will go back up.

[jim rosenthal]

Oscar, a friend of mine did that a few years ago on an 85' Feadship that was kept in Baltimore Harbor at the Anchorage Marina. He used swimming pool heaters and built a closed system which recirculated the water into the reverse-cycle system as you said. Actually the reverse-cycle systems will work more or less okay down to abotu 45-50 degrees water temperature- lower than that, there just isn't enough heat energy in the water to make it practical- they run all the time and the supply air never gets warm enough.

I lived in the same marina through a few winters, as the Feadship. I had outlets installed in my boat which come off the AC circuit and just ran cube ceramic heaters or oil-filled radiator heaters. Those two are generally reliable, but I did have a friend who had a Delonghi oil-filled radiator heater explode on his boat and make quite a mess. I believe the makers of the heater paid for the repairs, though.

I was on the Feadship while he had the pool-heater system operating. It was VERY warm in there. The pool heaters put out quite a bit of heat into the water and are evidently very robust, because I think once the system was in place it operated fine without much maintenance.

[Oldlaxer1]

I just looked up the specs on your heater and did some calculations on the energy output and the cost per KWH, based on average diesel prices from last winter ($3.25). The unit is about 71% efficient at converting the fuel into hot air when it is at it's peak performance (serviced regularly). If you had no distribution losses in your ducts you would be spending $0.11/KWH to use the diesel heater. Typically, when you have uninsulated, unsealed ducts running through unconditioned spaces you're going to have significant distribution losses. You also have an open return right next to a large opening to the outside. For every cubic foot of cold air it draws through that opening, there is a cubic foot of hot air getting pushed out of the boat through vents and around doors, windows and hatches. You're distribution losses are probably around 25%, meaning that only 75% of the heat that the unit produces ends up heating the living space, so you are actually spending closer to $0.16/KWH (when you also include the electric consumption of the heater) which is probably more than you spend for heating with electric space heaters. I'm not sure if the diesel heater is worth all of the effort in your case. For me, I have to spend $0.25/KWH for electric, and I have well insulated and sealed ducts, so it is definitely worth it in my case. Diesel prices have come down, but they will go back up.

I appreciate the thoughts. In my case we only have one 50 amp circuit available from the dock. It is pretty hard to manage the electric heaters and everything else on the boat with that limitation. I will take your advice and run the return into the conditioned space. The engine room vent is plugged with foam and an insulating blanket except for a small portion allowing fresh air in. I do have three CO detectors on board btw. I didn't know they were allowing liveaboards at Harborview. Is that a new policy?

[Photolomy]

Oscar, a friend of mine did that a few years ago on an 85' Feadship that was kept in Baltimore Harbor at the Anchorage Marina. He used swimming pool heaters and built a closed system which recirculated the water into the reverse-cycle system as you said. Actually the reverse-cycle systems will work more or less okay down to abotu 45-50 degrees water temperature- lower than that, there just isn't enough heat energy in the water to make it practical- they run all the time and the supply air never gets warm enough.

I lived in the same marina through a few winters, as the Feadship. I had outlets installed in my boat which come off the AC circuit and just ran cube ceramic heaters or oil-filled radiator heaters. Those two are generally reliable, but I did have a friend who had a Delonghi oil-filled radiator heater explode on his boat and make quite a mess. I believe the makers of the heater paid for the repairs, though.

I was on the Feadship while he had the pool-heater system operating. It was VERY warm in there. The pool heaters put out quite a bit of heat into the water and are evidently very robust, because I think once the system was in place it operated fine without much maintenance.

How many space heaters did you run? And was it warm, or just livable? I have used space heaters before on the boat, but I found them to be of no comparison to the heat pump, and likewise, I doubt any comparison to a diesel solution. A 1500 watt space heater produces 5000 BTU. There are a total of 4 tons of AC on a 53 MY, which is 48,000 BTU. Obviously, it would take many space heaters to get there, and that was my experience. I am in Florida and don't have the issue of the water being too cold for the heat pumps, but I tried a couple space heaters as a way of preserving the 40+ year old AC units. In mild conditions, they were ok, but during the coldest times, the heat pumps came on and warmed the boat right. I would think in Baltimore, if you used space heaters, you would have to adjust your idea of "warm", unless you used many space heaters.

[oscarvan]

Interesting to see my idea confirmed. However pool heaters are gas/natural gas or electric. And as also accurately pointed out the amount of energy required would push the electrical supply from a 50A shore power supply to the limit, if not beyond.

So, it appears that diesel, of which there is plenty below the floor, is the answer.

Research continues.