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Old 01-27-2022, 11:44 PM   #1
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Hyrodrnic heat?

Yeah. I mean HYDRONIC. Howdy. 10 year live aboard in San Diego, which is a great place to live, but not a tropical paradise. It's chilly down here on the waterfront. Tired of electric forced air space heaters. Considered diesel, but that is still forced air... I like radiant/convective heat. Can anyone think of a reason I should not install another 120 volt hot water heater and pipe it to a couple of heating elements? I have to heat about 125 square feet in 45-55 degree night temps. Any DIYers or HVAC guys have any interesting thoughts on the issue? Simple system. Water heater, circ pump, two heating elements, PEX pipe.
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Old 01-28-2022, 12:10 AM   #2
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Haven't done it and I am not a HVAC guy. Your existing AC hot water heater is just sitting there waiting for you to use some hot water which on a 24 hour clock doesn't add up to very many hours if even 1 hour. All the other hours could easily be used for heating the boat. Maybe you could make it work with your existing hot water heater. Might need to turn off the cabin heater before showering or washing the dishes. It's only a theory, let's see if someone has some practical experience either way.
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Old 01-28-2022, 06:22 AM   #3
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How many watts of electric heat does it take currently to keep your boat warm? That's what you will need from a HW heater to get the same amount of heat. A 120V HW heater will be limited, and will also be slow to come up to temp. You would want the smallest tank size, but biggest heating element And you will need an expansion tank. Not a big one, but something. And most "radiators" are forced over a heating coil anyway.



Since it's the forced air that you don't like (I think), what about one of the commonly available oil-filled electric heaters? They end up being a quiet convection radiator, and would be much easier to install vs a HW system, pex, accumulator, circulator pump, and radiators.
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Old 01-28-2022, 06:56 AM   #4
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Have had the Webasto hydronic on the last boat and espar on this one. Really like hydronic and the easy way to setup up multiple thermostats and zones. Also like the furnace isn’t in the living spaces and the small radiators with fans behind them are so quiet. Things to know
Any of them are real fussy about any air in the system. Know how to bleed them. If not used for awhile may need to bleed. Sometimes at each station.
They are real sensitive to the condition of the nozzle. Think the nozzle goes bad from moisture and salt entering from the exhaust when not in use. We plugged the exhaust during the summer or other times of prolonged non use. Also carry extras. You will use them. With a good nozzle there’s no soot, a clean total burn and much less maintenance.
Still compared to forced hot air or radiant stove it’s a great improvement. Even dry heat and unobtrusive
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Old 01-28-2022, 07:17 AM   #5
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Yes, the oil filled electric heaters would be an inexpensive easy to try solution.

The other consideration is humidity. Forced hot air can dramatically lower humity, even on a boat. It might be worth experimenting with an ultrasonic humidifier with a humidistat to offset some of the dryness.

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Old 01-28-2022, 07:44 AM   #6
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In Atlanta I have a heat pump.... it works but I never feel warm soooo, I have a passive oil filled radiator on wheels. I guess I could aim a fan at the radiator to spread the heat around.
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Old 01-28-2022, 09:11 AM   #7
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Quote:
Originally Posted by Hippocampus View Post
Have had the Webasto hydronic on the last boat and espar on this one. Really like hydronic and the easy way to setup up multiple thermostats and zones. Also like the furnace isn’t in the living spaces and the small radiators with fans behind them are so quiet. Things to know
Any of them are real fussy about any air in the system. Know how to bleed them. If not used for awhile may need to bleed. Sometimes at each station.
They are real sensitive to the condition of the nozzle. Think the nozzle goes bad from moisture and salt entering from the exhaust when not in use. We plugged the exhaust during the summer or other times of prolonged non use. Also carry extras. You will use them. With a good nozzle there’s no soot, a clean total burn and much less maintenance.
Still compared to forced hot air or radiant stove it’s a great improvement. Even dry heat and unobtrusive
Thanks for that input. I am coming to the end (hopefully) of a year long quest to re-activate the Espar Hydronic furnace on my boat. I can't wait. The story and the misadventures along the way will have to wait until hindsight makes it all seem amusing! ~A
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Old 01-28-2022, 11:00 AM   #8
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Quote:
Originally Posted by dcolman View Post
Yeah. I mean HYDRONIC. Howdy. 10 year live aboard in San Diego, which is a great place to live, but not a tropical paradise. It's chilly down here on the waterfront. Tired of electric forced air space heaters. Considered diesel, but that is still forced air... I like radiant/convective heat. Can anyone think of a reason I should not install another 120 volt hot water heater and pipe it to a couple of heating elements? I have to heat about 125 square feet in 45-55 degree night temps. Any DIYers or HVAC guys have any interesting thoughts on the issue? Simple system. Water heater, circ pump, two heating elements, PEX pipe.

Your question got me to search R/V radiant floor heat. R/Vs are in some respects technically ahead of boats. Have a look at this Gold Heat.
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Old 01-28-2022, 11:15 AM   #9
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One of the beauties of diesel fired hydronic heat is that you don't need a lot of electrical energy when not plugged in. You didn't mention if you regularly cruise in cooler weather or not. If you boat is a floating apartment, and rarely leaves the doc, and you have sufficient electrical supply (like 50 amp, or 30 on a small boat) electric heat is just fine, and probably cheaper than using diesel fuel for heat.

If you are underway a lot when heat is needed, and don't have engine cooling water assist, or don't have a decent sized generator running, electric heat is not really practical. More info is needed to provide answers germane to your situation.
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Old 01-28-2022, 12:28 PM   #10
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Here's another option to look into... I added block heaters to my twin CAT 3208's this last spring. The main reason was for cold starts and the plume of smoke that came with them... First pic shows a cold start. Right side you can see the smoke, left side almost nothing!!!
The added surprise/benefit was a MUCH warmer boat interior!!! As you can see from one of the pics, external temps were 24° !!! Still kept the boat at 53°...
At 48° it was at a comfortable 67°...

The block heaters were easy to add, screw right into existing unused ports on the engines. If you need to do a coolant flush, great time to add them to the engines...

I also added temp control sensors. When either the exterior temps or the engine temps (from running) get to a certain point, they shut off (big fan of "automatic" when it comes to boat stuff) Switches even come with an app so I can see/control them even when not on the boat (I have internal wifi network on boat).

https://katsblockheater.com/
Attached Thumbnails
heater on starboard.jpg   Temp difference.jpg   Temp Dif 24 degrees.jpg   temp switch.jpg   temp switch controller.jpg  

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Old 01-28-2022, 01:17 PM   #11
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It's hard to beat the plug in oil filled radiators.

My hydronic system runs on diesel and also has two 1500w heating elements in the boiler so I can get limited heat on shore power only. But I've found that plugging in two portable radiators is much more effective in heating living spaces than using the hydronic in electric mode.
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Old 01-28-2022, 04:21 PM   #12
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Worked through that as first option; good thought. At present I'm looking at a separate heater cuz they're not all that expensive, I have room and that save's the complexity of valves/plumbing to dual purpose the existing heater. Thanks.
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Old 01-28-2022, 04:26 PM   #13
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I agree 100%... But I'm the kind of guy that sometimes goes looking for trouble when I need a project to work on. Only downside to oil filled or baseboard convection is physical space. Currently using 700 watt 120 volt baseboard convection. It is so much more comfortable than coil and fan heaters. Don't need an air mover. Its generally about 60 degrees when I got home in winter
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Old 01-28-2022, 04:31 PM   #14
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Furnace or propane stove is overkill for me and I dont want to have to install a flue or vent pipe. Thanks.
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Old 01-28-2022, 06:42 PM   #15
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Humidity is generally not a concern in the southwest... I'm definitely keeping oil filled radiant as a full back position if I come to my senses and decide not too do this
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Old 01-28-2022, 06:50 PM   #16
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Simple system. Water heater, circ pump, two heating elements, PEX pipe.

No, it is a bad idea for many reasons. The most important one is it wont heat the boat well. If you have reverse cycle AC that works great. So does any diesel- both hydronic and forced air diesel heat crank out BTU's.
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Old 01-28-2022, 06:51 PM   #17
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Yes, I have an electrical hot water heater plumbed into my Hydronic system and yes it works, BUT!

First, it is the most inefficient and expensive way to heat a boat. It is a very quiet way to heat a boat.

Second, it takes two 1500 watt elements to make it work. This is a challenge with any typical hot water heater. Plus, that’s 25 amps. Now I have a 50a 120/250v, this gives me 100 amps to play with but if you only have 50 amps or 30 amps, you will probably be popping breakers.

I had a tank made for this project, it is about 2 gallons in size with two 1500 watt elements.

I also have built in King Pic a watt residence heaters. While not as efficient as my heat pumps, they do a great job with out being too noisy.
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Old 01-28-2022, 07:02 PM   #18
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Why would anyone need to heat hot water?
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Old 01-28-2022, 07:40 PM   #19
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If you’re at anchor .

No genet set running. Minimal electric draw. Nearly unlimited hot water. On both current (espar) and prior (wesbasto) have a loop from furnace heat domestic hot water. A complete pleasure. Unless it’s clement solar sufficient to keep everything going even with short winter days. Hot water available from engine loop, furnace loop or electrical. Very common set up on cruising boats both power and sail. No use of electrical water heating at anchor or when underway if a powerboat. Only use that coil if in a slip and plugged in.
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Old 01-28-2022, 09:46 PM   #20
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If you’re at anchor .

No genet set running. Minimal electric draw. Nearly unlimited hot water. On both current (espar) and prior (wesbasto) have a loop from furnace heat domestic hot water. A complete pleasure. Unless it’s clement solar sufficient to keep everything going even with short winter days. Hot water available from engine loop, furnace loop or electrical. Very common set up on cruising boats both power and sail. No use of electrical water heating at anchor or when underway if a powerboat. Only use that coil if in a slip and plugged in.
Think you missed his point. You don't need to heat hot water as it's already hot. It's like when people say a hot water heater, it's a water heater.

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