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Old 25-12-2013, 17:05   #1
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Air Versus Hydronic Heater

I'd like to start with the following - please do not post a reply to this unless you actually have experience. I do not need hypothetical information, and I don't need uninformed opinion.

My wife and I normally live aboard a 1978 Morgan 452. We have been living on board since 2008 and we live in the southern Chesapeake Bay area. Up until now, we have been able to keep warm in the winter using standalone propane heaters and electric heaters. However, by next winter, we are headed off and we don't want to be restricted to 110 volt sources.

I originally did my research and decided that the best bet was a Webasto DBW 2010 hydronic heater. I then found one on eBay for about half the price of a new one. I bid on it, didn't get it and then the seller contacted me and told me he had one "just like the first one" that he would sell me for the same price.

It was presented to me as "new, but it had been on the shelf for a while." It wasn't "new" - it had soot in the combustion chamber. It had been "on the shelf" for quite a while - it was the 1980 version. I thought about returning it, but I figured it would be "good enough."

I have started to try to install it and I have discovered that I do not have an installation manual for the unit I have. I can't figure out which connections go to which connections, nor do the operating instruction I have refer to the control panel I have. So, I am thinking that no matter what I do, I will never get this right.

So, I am returning to square 1. However, in figuring out how to install the original unit, I realized that running hydronic hose from a central location throughout the boat is not going to be fun. In addition, mounting coils is tricky in the spaces I have is really difficult. In both of these cases, it can be done, but...

Now, for those of you not familiar with the Morgan 452, it is a center cockpit ketch, with a full owner's cabin aft, separated from the main cabin by an engine room and passageway.

Now, I know that trying to heat that entire space with a single air heater is considered next to impossible. That's why I went to the hydronic heater. But, given the difficulties with the hydronic installation, i am considering installing not one, but two air heaters, one for the forward spaces and one for the aft cabin.

This is, by the way, the current set up for my HVAC units. I have a 16,000 BTU unit forward, which cools (and can heat) the v-berth, main salon and galley/nav station area. I have a 12,000 BTU unit aft, which cools (and can heat) the aft cabin and aft head. So, installing a similar arrangement for 12 volt diesel heaters would seem to make sense. It would allow me to heat only those portions of the boat I was actually using, and would not require me to run air ducting any further than necessary. I could install "diesel day tanks" for the individual units, rather than having to tap off the main tank.

So, for those who have experience with either or both of these systems, would I do better going with two air heaters or one hydronic heater?
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Old 25-12-2013, 17:48   #2
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Re: Air Versus Hydronic Heater

I have had both hydronic and hot air units.

My preference would always be for a hydronic unit on even ness of heat and the ability to make hot water.

However with your central cockpit air might work especially if you can add it on to the existing heat pump set up.

I have never found the plumbing particularly difficult to fit in for a hydronic system.

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Old 25-12-2013, 18:11   #3
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Re: Air Versus Hydronic Heater

I would go hands down hydronic. Air heaters are great for a quick warm up, not very efficient always cycling, which leads to more annual maintenance glow plugs.

The Webasto DBW 2010 is a great unit, older units can suffer from a cracked heat exchanger, which allows carbon monoxide poisoning. The heat ex's should be tested at a minimum of every 3-5 years.

Sure Marine has all the manuals on line, and is well setup to ship parts.

Lloyd

Here is my system.
http://photos.imageevent.com/studio4.../Hydronics.jpg
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Old 25-12-2013, 18:55   #4
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Re: Air Versus Hydronic Heater

Is this the manual you have?
http://www.google.ca/url?sa=t&rct=j&...58187178,d.b2I
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Old 25-12-2013, 19:43   #5
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Re: Air Versus Hydronic Heater

This will be my second install with the hydronic setup. the last time I did the hose around the boat with heater cores in every cabin , worked fine but the unit was noisy . The biggest drawback was with moisture buildup in the boat , this ruins wood around the port-lights , heater cores just recycle the air in the boat, if you don't know what I mean switch to recycle heat in your car and see how much moisture builds up , then go to fresh, bam! it's all gone .
This install I will have my 2010 which will stay in the aft lazerate,plumbed into one large single heater core with 40000 btu with a single centrifugal fan blowing just over 300 cfm located in the engigine room amidships. . These are made by Hunter, they are used to heat heavy equipment. Then some very simple 4 inch ducting forward and aft from the center engine room. I will have the abilty to draw all fresh air or a percentage of it with a lockable baffle on the intake which will draw air from a clamshell vent in the cockpit.
My Bristol has amazing cabinetry in it and I really don't want any moisture problems ruining it , also say goodbye to any mold associated with moisture . You have to keep the air dry when there are cold surfaces involved, boats are not insulated like homes . There are millions of cold spots that mold loves to grow. This experience I have had . Darn cold up here in Canada.

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Old 25-12-2013, 19:44   #6
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I have both a webasto diesel hydronic system and three separate HVAC/heater units on my Hylas 47, which is also a center cockpit with a full aft stateroom. I love being able to make hot water when we're on the hook, without having to run the generator. We can also turn off the fans on the individual heat exchangers so as not to waste energy heating areas we aren't using. We only have 30 amp service right now, so to turn on the electric heat, I have to go top sides, disconnect the 30 amp shorepower cord and connect it to the HVAC inlet. I like having both types of heat. And air conditioning can come in handy, but if I needed heat more, and I had to choose one type, I'd go with the webasto.
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Old 25-12-2013, 20:18   #7
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We have both a reverse cycle AC/heater for when plugged into shore power and above 30f. When it gets really cold and/or at anchor we use our 12v hydronic system. It definitely makes the boat more comfortable with more even heating. We have fan units in the master cabin, salon and aft cabin. You can see my installation article at the following link.

http://tkronaboat.com/heater-installation.html
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Old 25-12-2013, 20:59   #8
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If I stay on the boat another two winters like I am planning; then this next summer I will be installing the webasto 2015 and running 4 heater heads. I like the diesel heaters because I can use the fuel already on the boat. I thought about installing 4 individual Dickson diesel room heaters but I don't like the idea of having to cut four vent holes through the roof. Price seems cheaper and fewer moving parts and greater redundancy. I'm still debating it though.
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Old 25-12-2013, 21:34   #9
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Re: Air Versus Hydronic Heater

As others have said: hydronic has a lot of advantages, and the relatively thin hoses are pretty easy to run. The air-type heaters are great for smaller boats which don't need much air distribution, but I think it would be madness to install two (!) of them in place of one hydronic. That means two fuel supplies, two exhausts, etc., etc. Two combustion chambers to decoke, two glow plugs to futz with.

The only thing I don't like about my hydronic system is the noisy fan coils with constant running fans. Passive radiators would be great on a boat with room for them. I don't have room for passive radiators, so I guess I'll be looking for better fan coils, when I get around to it.

As far as moisture is concerned -- this is a question of ventilation. I have six big dorade vents on my boat and don't have too much of a problem with moisture (however, this is a double-edged sword -- I also lose a lot of heat out the dorades, and have constant cold drafts inside). Neither the air-type heaters nor the hydronic ones will dehumidify, and a boat which is heated in cold weather will have condensation in the hatches and ports, and on any uninsulated inner hull surfaces, unless it is well-ventilated.
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Old 25-12-2013, 23:14   #10
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Re: Air Versus Hydronic Heater

We used actual heaters from school bus's that we got from a couple of wreaking yards. These had very quite fans on the low speed which was way more then we needed to heat the compartments they were in ! We had 5 of them in a 45 ft boat. We heated the water in coils in the diesel heater ! it flowed into a 40 gal insulated tank mounted higer then the heater! We used pumps to move the water to the heaters from the hot water tank ! Worked for us in Anchorage Alaska Hot water makes for good heat for cheap if your useing a dickerson style diesel heater with coils!!
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Old 26-12-2013, 01:58   #11
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Re: Air Versus Hydronic Heater

Hydronic hands down, we managed to find small off the shelf passive radiotors, installed one on the end of the bunk in aft cabin and one under seat in pilothouse, we put a fan matrix in for'd saloon for fast heating and i made a towel rail/radiator for galley, nice and quiet and warm. I also siamesed a
small hot water cylinder and a circulating pump into system so when on shorepower we used same system
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Old 26-12-2013, 05:13   #12
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OK, OK - I surrender

I officially bow to the collective wisdom and will continue on my original path!

Seriously, thank you all for your input. I appreciate the help and advice. I'll take a look at the links; hopefully, I'll get some good ideas about how to place some of my cores.

However, I have to warn you all - when I am armpit deep in this project and can't remember why the heck I am doing it, I'm coming back here for moral support, so you guys better still be here!!!



Thanks again, Frank
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Old 26-12-2013, 06:35   #13
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Re: Air Versus Hydronic Heater

Yes, I have this one, but the circuit diagrams don't seem to match what I have. For example, using the DBW 2010 Preset NA Version diagram, the B wiring harness is supposed to have a Black and a Violet wire connected to pin 1, a Brown wire connected to pin 2, a Green and a Yellow wire connected to pin 3, a Red/Black wire connected to pin 4 and a Brown wire connected to pin 6. What I have for that harness is a Green wire on pin 1, a Black wire on pin 2, a White wire on pin 3, a Green wire on pin 4 and a Red wire on pin 5. So, if nothing else, I am short two wires. The samething is true about all of the other diagrams - I can't find a match to what I have. What I am unsure of, of course, is do I have the wrong diagram - or the wrong cabling? Did someone put a cable harness from something else in with what I received? Quien sabe?
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Old 26-12-2013, 07:37   #14
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Re: Air Versus Hydronic Heater

We have both , air for quick heat on a cool summer evening( though pretty uncontrolable and constantly cycling as well as noisy, and a newly installed htdronic unit , providing controlable constant background heat and lots of hot water for cold weather cruising


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Old 26-12-2013, 09:08   #15
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Re: Air Versus Hydronic Heater

I am partial to the hydronic heating systems but I'm not sure that they are an owner installable system unless you are familiar with coolant based heating systems. They get quite complicated with heating, hot water, engine pre-heat (if you want), electrical wiring, etc. and the last thing you need is a system that is leaking fluid or is unreliable. I really don't think they are a system that you should be trying to install on the cheap. If you want to save money then a hot air system will be cheaper to install, although I don't think they will be as comfortable. Less expensive yet is something like a diesel stove and a few fans to circulate the air around.
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