Question Replacing Espar Diesel Forced Air Heater with Reverse Cycle AC Unit

[Mark P]

As our boat search continues, I am running into a lot of nice of boats on the West Coast with diesel furnaces, but I need air conditioning to use it in the Southeast. So, one particular boat checks all of the "needs" we have except it has no air conditioning, it has an Espar forced air diesel furnace. The listing mentions that boat has full duct-work for air delivery around boat. It has a 6KW genny.

Is it possible to replace the furnace with a reverse cycle air conditioner/heater? I assume I'd have to load manage with the genny if the a/c unit takes more power than the diesel furnace, but is it doable or am I going to run into a bunch of issues?? Any thoughts would be appreciated.

Thank you.

 

[DavidM]

Well, starting from the bottom and working up:

The A/C will draw much, much more power than the Espar heater and it will be 120V AC not the DC that the Espar uses. Generally Espar heaters use 12V for the controls and blower, roughly 5-10 amps.

Trying to reuse the existing Espar ducting is possible but not likely as is. The Espar heater generates heat at 100 or so degrees or 30 degrees more than ambient. Air conditioners typically lower the air temperature about 15 degrees while cooling and increase the air temp about 10 degrees while heating so they need more air flow, at least double. That will be difficult to push through the existing small ducting.

And finally and this is no big deal, you may want to use a split A/C system with the raw water condenser and compressor in one unit which sends freon to a separate evaparator/fan near where the Espar was. That lets you put the former in a more convenient location. This may not be necessary depending on how it is layed out.

So I would talk to a good marine A/C guy. I suspect he can reuse most of the ductwork but may want to increase the duct size where possible. Or maybe put a booster fan to push more air through the existing ducts, but that might be noisy.

And are you thinking about buying on the West Coast and shipping to the SE. Figure at least $20,000 for that

David

 

[Taras]

Having a diesel furnace is an awesome feature. I wouldn't pull it out. If you don't use it, the next guy will and it will be a selling feature. Instead, just add the AC's as needed. Lots of different set ups for the AC so pull in a marine AC professional and get some estimates on the varying different ways to do it including the potential load on the 6KW genny. Reverse cycle AC's don't heat the boat very well when you're in very cold water. (I'm thinking about resale, of course).

 

[Mark P]

Great comments on the air flow and resale, thanks. Yes, I fear that pushing heavier colder air through the existing ductwork may be a challenge - reworking the ducts may likely be too expensive. Moving the boat some 3K miles will also be expensive, but these are interesting times in boat search. My preference would be to move it on its bottom, but hard to find East Coast boats. On keeping the furnace, that makes sense for a resale. On this particular boat, the older ones with air conditioning have the units under the pilot house bench seats. I'd have to figure out if putting AC units on pilot house roof would make sense or workable. I appreciate the comments, will keep hunting.

 

[catalinajack]

Well, starting from the bottom and working up:

The A/C will draw much, much more power than the Espar heater and it will be 120V AC not the DC that the Espar uses. Generally Espar heaters use 12V for the controls and blower, roughly 5-10 amps.

Trying to reuse the existing Espar ducting is possible but not likely as is. The Espar heater generates heat at 100 or so degrees or 30 degrees more than ambient. Air conditioners typically lower the air temperature about 15 degrees while cooling and increase the air temp about 10 degrees while heating so they need more air flow, at least double.

David

I know you said typically with respect to heating and cooling but here is my experience. I have two reverse cycle units aboard. They cool to 20 and 25 degrees below room temp but the heat side is a lot more than 10 degrees. One unit gives us 30 degrees above room temp, the other 35 degrees and with the water temp at 40 degrees. With higher water temps the heat output goes even higher. I have measured temps as high as 120 degrees.

 

[Porgy]

If it were me, I’d keep the furnace as is and install conventional marine A/C and not rooftop RV or mini-split home A/C. Depending on the size of the boat, the self-contained units fit under seats, berths or in lockers in the cooled/heated space to keep ducting short and facilitate return air via louvered vents. It seems boats around the mid-40’ and up may have split systems as mentioned with the compressors in the laz and air handlers throughout the boat. From friends’ experiences retro-fitting a split system isn’t always easy with self-contained units being easier to install.

 

[FF]

There are split units that use many different size and shape internal units , as well as ones designed with heat exchangers for duct work..Check with a larger seller.

Today there are many new 3rd world mfg , purchase a unit from someone that has a past.

The RV units work fine for AC but only can use a hot wire in real cold (under 40F ) so keeping the diesel package might be worthwhile.
When it gets cold you will meet many of the other folks on the dock who will stop by to visit.


Since the diesel works on 12V you may have the only warm boat when the power is out.

 

[Mark P]

On this particular boat, I think keeping the furnace for heat makes sense, then I'd have to put one of those RV units over the pilot house that would cool the salon as well, and probably another one over sleeping area upfront. Just have to figure cost of units, install expense, electrical work, and then where to drain condensate.

 

[koliver]

Espar furnaces on boats in BC and in the PNW are very common. In older boats they are often the old D7L, or a smaller unit using the same technology. My own boat came with a D7L. I jettisoned that unit after installing a galley diesel stove (Fab-All, by Sigmar) that provides dry heat, free of the problems with the Espar. The most telling failure is the difficulty starting when the fuel is as cold as the water in which the boat is floating.
I would not rely on an old Espar to get you any more $ at resale, especially if it hasn't been used for a few years or longer.
Mine consumed more maintenance $ in my first 5 years of owing this boat than did the twin main engines and genset combined.

 

[Datenight]

Espar furnaces on boats in BC and in the PNW are very common. In older boats they are often the old D7L, or a smaller unit using the same technology. My own boat came with a D7L. I jettisoned that unit after installing a galley diesel stove (Fab-All, by Sigmar) that provides dry heat, free of the problems with the Espar. The most telling failure is the difficulty starting when the fuel is as cold as the water in which the boat is floating.
I would not rely on an old Espar to get you any more $ at resale, especially if it hasn't been used for a few years or longer.
Mine consumed more maintenance $ in my first 5 years of owing this boat than did the twin main engines and genset combined.

+1

Rob

 

[FF]

"and probably another one over sleeping area upfront."

Cold air sinks , and the deck is not in sunshine at usual sleep time.

You might wait a month to see of natural circulation, perhaps with the help of a floor fan , cools the fwd area at night.

A quick evening hose down with sea water helps cool the hull at sunset.