Marine Cabin Heaters vs Baseboard Radiators

[daveola]

So, I'm installing a 30 kBTU Proheat, mostly to supply my interior with heat.

I thought about building some radiator fan enclosures, but decided I wanted heat sooner.

I looked at some of the pre-made radiator/fan heaters, I'd need a bunch and they seemed awfully expensive.

I was going to do a bunch of baseboard radiators, they seem to run about $10/ft and 600 BTU/ft, which means I'd need to take up one wall and still not get the full 30 kBTU, not to mention the cost and time of installation (lots of plumbing!)

Of course, I ordered all the radiators when I discovered Marine Cabin Heaters, which are evidently a single radiator/fan that can handle all the BTUs.

So, it seems I can get a Marine Cabin Heater that does 30 kBTU for the same price as the radiators, and it'll be much smaller and much easier to install (running a bunch of air hoses to vents seems much easier than plumbing hot coolant.)

I know the cabin heater will use power, but I can handle using up some electric power, so that's not much of a concern.

Am I on the right track?  I'm tempted to sell off the baseboard radiators and go with a Marine Cabin Heater - anyone have one of these and like it or dislike it?

I'm talking about heaters like this:

  http://great-water.com/zcart/index.php?main_page=product_info&cPath=133&products_id=3743&zenid=c596caf7f99867cea4692426b62e4952
And:
  http://tinyurl.com/ybppn68

[scanzel]

I plan on using some of these in my conversion. Check out www.Suremarine.com and then click on REAL under heating, they have a very large selection and are not as expensive. I thought of baseboard too because of it being quiet but more plumbing etc. Runtal makes a nice Euro design aluminum baseboard but very expensive. Good Luck!

[Jeremy]

Unless I'm missing something these units are simply a heater matrix and electric fan - if so you could build one very cheaply using car parts. I've just looked on UK Ebay and new heater matrixes (sp?) can be had for as little as £20 or so ($30) - or no doubt you could get a used one for next-to-nothing from a junk yard if you're prepared to take a dashboard apart (they are quite tricky to get to).

Build several into boxes with fans and you could could heat the whole bus for much less than the cost of a single marine heater of the type shown in the links.

Jeremy

[JackConrad]

A friend went to a junk yard and purchased several heater cores from pick-up trucks for next to nothing. Built boxes for them out of 1/2" plywood and added some 12 volt muffin fans from a surplus center.  Total cost was about less than $50 for everything.  Jack

[TomC]

If you want immediate heat (within one minute), for a total cost of about $700.00 you can install a 35,000BTU propane furnace.  I have one in my bus now and after 14 years of no maintenance (except for cleaning) had to replace it-only because I left it on for two weeks and burned the blower fan motor out (I replaced it since the new model is quieter).  Just about as reliable a heat source as you can have.

With hydronic, using old heater cores with blowers in a home made enclosure is about as cheap as you can get.  And if you have the water circulating through the heat exchangers all the time with just the blower on a thermostat, it will also create immediate heat.  Good Luck, TomC

[Sean]

I think you will be better off with several smaller fan-coil units than with one large one.  For one, you will get the heat more directly where you need it, and for another, you can control the heat output in "zones" -- no need to heat the back when you are in the front and vice-versa.

Also remember that you will not get all 30,000 BTU/h out of your Proheat, so getting a single 34,000 BTU/h fan-coil unit is overkill.  You need to account for losses in the lines, plus any heat that might be going into your DHWH and/or engine if you have those plumbed into your hydronic loop.  By contrast, if you get smaller individual heaters, a total greater than the boiler capacity is acceptable, since there will be times when not all the units are running at once.

We have five MSR toe-kick heaters, rated 7,000 BTU/h apiece, on our hydronic loop, and our boiler is rated at 45,000 BTU/h.  We also have a small baseboard heater, maybe 1,500 BTU/h, and of course the DHWH plus heat exchangers for the engine and hot tub.  BTW, the five toe-kicks are more than enough to heat our 40' coach in conditions well below freezing, and one of those units is dedicated to the downstairs cockpit -- four units would have been plenty in a more conventional coach configuration.  Even in subfreezing conditions, neither the boiler nor the fan units run full-time.

Having both fan-forced and passive radiators, I will say that the former are much more effective, and, IMO, well worth the small amount of juice they draw.

-Sean
http://OurOdyssey.BlogSpot.com

[Lin]

Sean, did you mean the former (fan heaters) were more effective?

[Sean]

Sean, did you mean the former (fan heaters) were more effective?

Yes, Lin, sorry.  Good catch.  I have fixed it in my post.

This is what comes of typing before the coffee has kicked in  

-Sean
http://OurOdyssey.BlogSpot.com

[daveola]

Check out www.Suremarine.com..

I had seen SureMarine, they are actually more expensive (per BTU) than the heaters I linked to.

The SureMarine 6400 series is 14 kBTU, so to get the same heat output would require two of them, at $600, as opposed to $390 for the West Marine heater.

[daveola]

..you could build one very cheaply using car parts...

Yes, as mentioned, I had considered building some, but my problems with that are:

1) Wanting heat sooner
2) How to match up the heater matrix with the fan size, and how many BTUs that would be.
3) Total cost of building a few of these would likely start climbing up towards $390 if I really wanted 30 kBTU of heat.

[daveola]

..you can control the heat output in "zones" -- no need to heat the back when you are in the front and vice-versa.

My bus doesn't really have zones - the bus floorplan is completely open, the only walls I have in the entire bus is around the toilet.  And if that wasn't bad enough, my bus isn't necessarily insulated very well since I'm not ready to get rid of all the windows.  Add to that the fact that I want to be able to go into freezing climates, and you might be able to see why I want to have lots of BTU/h of heat.

I'm also not worried about DHWH or engine preheat since at most those will only run for a few minutes each day and then shut out of the loop, so most of the time the Proheat will be dedicated to cabin heat (and losses in the line, though they will just contribute to bay heat which will help keep my bays from freezing 

I know my bus design is a bit atypical - I've been through that discussion on bus forums enough times, that's for sure.. 

It's good to hear that your five toe-kicks heat your coach below freezing - presumably that means you can heat all the rooms in your coach at once, since the toe-kicks are easily handled by your boiler.

Even so, you say that fan-forced is much more effective, so my point still stands - considering the fact that the fan-forced heater is *cheaper* and *smaller* and *more effective* and *easier to install* - it sounds like I shouldn't keep the baseboard heaters I purchased (maybe return them or sell them on ebay) and just go with one of the cabin heaters I linked to.

[daveola]

Of course, one issue is that if I hook up the cabin heater to the Proheat directly, I don't really have much coolant in the system, which seems that it would cycle too quickly.  I'm going to have an expansion tank, but as I understand it, the coolant only expands into the tank, and doesn't really flow through it, so it doesn't change the amount of fluid that is in the cycle by much.

If that's the case, should I just get some sort of coolant tank with inlet/outlet on opposite sides?  Or maybe just adapt to a few feet of large PVC pipe?  Is there a good solution for this?  I'm under the impression I want to have 5 gallons or so in my system, but I'm not sure where that idea came from.

[buswarrior]

An inexpensive option is to get the rear heater unit out of a retired school bus.

Often twin fans, controllable for low/high, and some louvers for the discharges.

Same thing as the linked marine cabin heater.

Visit the bus scrapper near you!

happy coaching!
buswarrior

[chuckd]

On the Sure Marine site they have lots of Webasto information and schematics of how to install a bus system.  Also they mention what the minimum amount of fluid that should be circulating and they have capacities of the heater, lines, and heat exchaners.

Chuckd
1979 Prevost shorty
Stillwater MN

[daveola]

On the Sure Marine site they have lots of Webasto information and schematics of how to install a bus system.

That sounds great but where?  I've scanned through their site (including the 'more info' section) and couldn't find anything.