Water Radiator in a bus?

[indigo_k]

The idea occurred to me this morning, as I've been reading a lot of discussion on wood stoves vs diesel heaters, that I don't think I've seen anyone use a reclaimed cast-iron water radiator in a bus, and I started wondering if it would be feasible.

The idea is that the thermostat would activate a water pump, pushing the water through an instant water heater and into the radiator. Then the water gets recirculated back into the fresh water tank. Or possibly even it could be a closed recirc system, so as not to rely on water in the water tank (say, if hooked up to city water).

Obviously a radiator would take up space in the bus, but so does any heater, really.

It's a thought, I guess. Anyone know of a skoolie or house-truck that's done this?

[cadillackid]

why??? if you are heating the water hot enough to make a radiator work then just put a fan coil in.. like a Jegs heater or such..

[PhilipE]

In your building of the buss. Remember this rule. Build as lite as you can.

A 300-to-500-hundred-pound chunk of cast iron isn't needed. There are many lite weight new design copper tube radiant heaters on the market. Also remember you need to secure everything in the bus. You do not need large heavy objects flying around in the event of an accident or hard stop.

A universal automotive heater would give you the radiator and fan in one small package. The fan would be 12 volt also. This is just one example.

https://www.jegs.com/i/JEGS+Performa...CABEgLYivD_BwE

You might want to do some research on the instant hot water heaters. I have seen complaints on other forums when trying to use as a heater source.

[cadillackid]

Originally Posted by PhilipE

In your building of the buss. Remember this rule. Build as lite as you can.

A 300-to-500-hundred-pound chunk of cast iron isn't needed. There are many lite weight new design copper tube radiant heaters on the market. Also remember you need to secure everything in the bus. You do not need large heavy objects flying around in the event of an accident or hard stop.

A universal automotive heater would give you the radiator and fan in one small package. The fan would be 12 volt also. This is just one example.

https://www.jegs.com/i/JEGS+Performa...CABEgLYivD_BwE

You might want to do some research on the instant hot water heaters. I have seen complaints on other forums when trying to use as a heater source.

that jegs heater is the one i replace my rear underseat heater with.. works like a CHAMP!

[indigo_k]

These are great points - I'm definitely hesitant to add such a large, heavy chunk of cast iron to the bus, especially when lighter options are available. It was really a thought experiment - knowing that a water radiator is a closed system, and all that's needed is a source of hot water, it seemed on the surface to be an ideal solution for some dry heat.

BUT! Thinking about it more, I realize that an instant water heater wouldn't be able to produce hot water at a volume needed to make a radiator effective. Also, a water heater, instant or otherwise, isn't designed to heat the water to the boiling temperature that radiant heating requires.

I think for me the allure of the idea really came down to nostalgia. But for that effect, I could easily pick up one of those electric portable radiators and save myself the weight (and water!)

[cadillackid]

Originally Posted by indigo_k

These are great points - I'm definitely hesitant to add such a large, heavy chunk of cast iron to the bus, especially when lighter options are available. It was really a thought experiment - knowing that a water radiator is a closed system, and all that's needed is a source of hot water, it seemed on the surface to be an ideal solution for some dry heat.

BUT! Thinking about it more, I realize that an instant water heater wouldn't be able to produce hot water at a volume needed to make a radiator effective. Also, a water heater, instant or otherwise, isn't designed to heat the water to the boiling temperature that radiant heating requires.

I think for me the allure of the idea really came down to nostalgia. But for that effect, I could easily pick up one of those electric portable radiators and save myself the weight (and water!)

you can get heat out of a radiator starting at about 150 or so absolute minimum.. 180 is the typical temperature used in residential systems.. one of the issues in a small space would be that you would have wild temperature swings.. your radiator would heat up slowly and then stay hot forever.. in a larger home thats perfect because the system is sized properly and can maintain a nice constant temp.. a radiator too big will result in cold then blasted hot conditions..

[indigo_k]

Originally Posted by cadillackid

one of the issues in a small space would be that you would have wild temperature swings.. your radiator would heat up slowly and then stay hot forever.. in a larger home thats perfect because the system is sized properly and can maintain a nice constant temp.. a radiator too big will result in cold then blasted hot conditions..

A thermostat hooked up to the water heater would help alleviate this though, right? Something you could just leave running 24/7 to keep a constant temperature, as opposed to a wood stove that would die out overnight unless you got up to keep feeding it.

[cadillackid]

a thermostat can control the room temperature or the water temperature.. the issue is that unless you have a properly sized radiator where the water temp can remain in a fairly tight band you end up with wild temperature swings.. I dealt with that complaint more than in home heatinfg systems.. "water heat is supposed to be even but its hot then cold then super hot then cold" . id go out to find that either the boiler was too big or there were way too many radiators... sometimes a house went from no insulation to having walls insulated,, metal windows replaced with wood and suddenly the heating system was oversized for all but the coldest days..



radiators are slow.. wit ha big water heater you can warm them up faster but they take forever to cool down.. if you warm the room too fast because the boiler heated the water quickly and the radiator was too big you will well overshoot the room thermostat.. the radiator has so much mass that it takes a long time to stop radiating heat.. or even slow down enough to hold the temp...



the Nicer boilers I installed had enthalpy sensors where the water temperature was lower the warmer it was outside.. which helped.. since outside temperatures swing a lot it would be rather tedious to have a manual thermostat where 5X a day you had to adjust your water temp..



if you are using a fan-coil, when the room temp is reached you simply shut off the fan and the pump.. if your water heater is a tank type, the hot water remains hot and ready to go inside the insulated tank.. so when the pump and fan turn on you have heat pretty quickly.. a variable speed control on the fan allows to to have the fan lower or higher...



just seems better than a big ole ugly clunky iron radiator..

[Ronnie]

Well now lets through a monkey wrench in all this. What about useing a wabasto coolant heater and pump to heat the water/ antifreeze for the iron radiator? I have seriously thought of doing this as I have the Wabasto and pump already. I love the warm but not hot and constant heat of an old radiator.

[cadillackid]

Originally Posted by Ronnie

Well now lets through a monkey wrench in all this. What about useing a wabasto coolant heater and pump to heat the water/ antifreeze for the iron radiator? I have seriously thought of doing this as I have the Wabasto and pump already. I love the warm but not hot and constant heat of an old radiator.

the issue is still the same.. unless its a perfectly sized radiator for your rig you will have wild temperature swings.. it will stay hot too long and overshoot the inside temp.. the webasto will warm it up quick depending on its size.. most room size radiators are going to bake you out of a bus.. if you have one of the small bathroom sized ones maybe. but you need a full on hydronic system to use it.. pressure relief valves.. expansion tank.. air bleeder.. obviously use coolant in it since its in a bus.. that wont hurt an iron radiator.. youd never ever run your domestic water through a cast iron radiator..



youd have better luck wit ha baseboard radiant heater that has much less mass.. the reason they are even heat in a house is because the boiler typically has a tight deadband on max temp in cold weather.. in warmer weather the system shuts down and doesnt heat all the way up to 180..



a *real* webasto like my 5kw TSL-17 does have auto throttling but its going to maintain 170 degree water which is pretty hot for anything but the coldest day.. a chinese diesel heater will cycle on and off .. my 16kw unit has a digital control where i can set the water temp.. but its always a 15C swing from on to off..


carboning up diesel heaters is an issue if you short cycle them.. im convinced thats why the real webasto runs continuously unless it overshoots the 170 by a few degrees. . bit with one heater fan on in that bus and that heater will run on a slow speed forever.. just like the chincese diesel Air heaters do.. im not sure why the water heaters from china dont have the throttle up and down features.. none of the 3 ive tested do..

[Ronnie]

I have been keeping an eye out for a small one like would be used in a bathroom. So far most are way to big. When plugged into shore power I do use an oil filled electric radiator.

[cadillackid]

the electric ones have a much lower BTU rating than a water unit would have so you can get as pretty even heat with them.. esp since the one i have has a 600,900 and 1500 watt setting so you can adjust it accordingly..



my 16kw diesel heater has a digital control to adjust the water temp.. so say if it was 140 instead of 175 or so it would radiate less heat from the radiator.. I havent yet tested what happens if I run that heater extended in lower temp mode.. or if i can get hotter than 75c output temperature from it.. it has a computer datalink that ive cracked a good portion of the comms for .. ill be testing if it carbons up from running at say 35 or 40c for an extended time. one thing I cannot change with it is the fact it has a 15c differential.. so if you set it at 60, its off at 60 on at 45.. if you pump the water slower through it you can short cycle the unit "purposefully" by creating a higher rise through the unit which will put out hot water pretty quick, that water cools down pretty quick also which will trigger a restart..

[Ronnie]

My electric is just as you say, 600 and 900, or both for 1500 watts. Below freezing temps I would need two of them. As it is I use a propane heater for off grid use, or when the electric is not enough.

I think the wasbasto could be set up with different controls to keep a smaller temp spread. Another thing to think about is the radiator and the water in it will hold temp pretty well, so even short hot burns may not be a comfort issue as it takes a bit for the radiator to react.

You know if I had a diesel bus I would be right on this. As it is with a gas bus and propane for hot water and stove, I really do not want a third fuel type, for the sake of convenience.... however if the right radiator drops in my lap so to speak I might just have to try if nothing else then for the fun of experimenting

[cadillackid]

some of the 5kw heaters can run on gasoline.. ive seen them out there..



when it comes to controls diesel heaters asre not just a slap a spark and go.. you need a pretty sophisiticated algorithm to control the glowplug, the fan motor, and the fuel pump to get a good ignition.. they use variable speed drive on the motor and variable output on the glowplug.. and when you shut down there is a sequence as well.. some units shut the pump off straight and then dlow down the fan.. making sure to burn off the rest of the fuel... running the glowplug on shutdown as well. you could build a controller of your own but you'll need safeties and such in there..


you can simply cycle on and off the enable switch wire to the heater which will trigger startup snd dhutdown.. the pumps do shut off after the shutdown and the circuit is monitored for current pull so you can just externally control the pump.. no reason you cant have an externally controlled additional pump (which is what I do).. you just have to also have one or a dummy load on the heater's pump circuit.



the real webasto DBW2010 heater has a much better chance of being short cycled than the clickety-click type as its just like a home heating system.. you could cycle that unit on and off externally fairly quickly without issues.. they go through a 10 second fan-only purge then light off. an external pump solves the pump monitor issue.. those heaters are big though.. 16kw minimum..



for me though? Meh on radiators.. I can make my bus 80+ degrees with warm air from my jegs heater and any number of other heater fans on.. and they blow warm air so I have that nice warm air feeling... no need for a 500 lb hunk of iron..


if my heaters didnt blow Hot air then I could understand wanting a radiator.. like id never heat a bus with a minisplit heat pump.. that air is tepid at best

[Egsbigsister]

Found this on Facebook and looked up weather or not it would work on a bus. Found this thread and thought I would share. I also found more info on the radiator on pinterest.
http://pin.it/6Br4W7W