aftermarket engine cab heater

[mannebk]

i ordered 2 aftermarket under dash coolant based radial fan heaters. the biggest i could finde for reasonable price with radial fans, not the PC fans.

i do not want to run my propane heater while my engine radiator vents off heat from my engine while driving. considering my driving volume its just an incredible wast of energy. besides i like it warm in the winter, i usually have 74-75f set at my thermostat.

I also want to be able to use my engine instead of the genset and harvest the waste heat while charging my battery. the main engine is just so much more quiet than the genset. and with a remote start, its just a switch over to select the main instead of the genset to be started by the inverter on low battery.

where and how would you guys mount these.

how is it done on the factory systems?

one is clearly is going underneath the fridge next to my hot water tank...

but where do i suck the cold air from, and where do i vent the hot air too?

i thought about blowing thr hit air into the propane heater intake and when ever the engine heat is on i also switch on the stock atwood fan to distribute it inside the RV.

the second unit i want to use to head the storage compartment so we dont have so cold floors and the stuff down there does freeze.

my hot water tank does get an engine upgrade while i fix the frost crack its having from me being to stupid to keep it on over night in freezing conditions.

i also want to add 120v heater to it, but i probably just take a block heater and patch it into the loop to make hot water and heat the cab when on shore power.

so what are your thoughts on this?

[SafariBen]

How much experience do you have with hot water heating? all you Germans are born Grundfos engineers, right?



I can't tell you the exact flow or pressure the engine water pump is capable of, but I've seen test procedures, and the pressure was way higher than I was expecting. My safari has a bypass at the heater core, 35' from the engine, to allow coolant to circulate with the valve off, presumably to allow faster response. I'd ordinarily think the bypass would reduce the flow through the heater core, but apparently not enough to matter. That method of using a "diverter Tee" is common in heating systems, or you could run the heater hose in a loop with both heaters and the dash in one series loop. That would be fewer connections than the diverter tees, especially if you added valves to the bypasses.



I would skip the electric block heater. Electric air heater are light and easy to use. If you want the electric for the water heater, maybe. But the plumbing would be much more complex, a block heater is not needed for a gas engine, and you'd waste so much heat circulating through the engine block, without an overly complex plumbing scheme.



As long as you put the heaters low, they'll get cool enough air to be effective.

[mannebk]

not all Germans :-) but i actually own a hydraulic shop. :-)

so yes your mostly right. thing is, each bent in a pipe must be overcome. hence if you give the water an other option besides the stock cab hester with lots if bends and small and thin pipes it usually is happy to take that route too.

mostly cause thr pump delivers a significant pressure drop.

and water is incredible dense regarding energy transportation.

1 quart can hold a out 100w of heat with no state of matter change between freezing and boiling. and if you add just freezing and evaporation, so just below freezing and just above boiling, its 300W.

so to have a coolant based car heater outperform any 1800w space heater you just need to flow like 100 quarts an hour. But a 3/8th pipe can easily do like 900 quarts an hour...

and an engine that uses 5 gal an hour gasolin outputs 66% of that in heat, about 100kw, some through the oil and exhaust, but mostly through water. for a diesel at the same 5 gal per hour its about 85kw, same distribution.

that also makes it clear why heating from your 12v grid doesn't make sense. even if you suck up 100% of your alternator 120ah at 13.4v is about 1600 wats but youd need an awg 5 or so cable (120ah=at lest 16mm² /awg 5 depending on length) and nothing would be left to cover for the other needing of your electrical system. let alone: the alternator delivers 100% of rated power at peak rpm, not at highway or idle rom. (well thats not entirely true but close enough, but that's how the alternators die if you switch to lifepo without charging management)

and heating the hot water tank from coolant is simple, you t into the hot side of the cooling, and make the return go back to the same place so you dont actually have a pressure drop and then add an electric pump and a check valve plumbed into the same coolant loop behind your hot water tank. and wired int the same electrical circuit that starts your propane burner, but when ever D+ is hot (alternator is charging means engine is running) you switch the "heat the darn tank" signal by relay from burner to pump.
it will never overheat, and its fire and forget, as soon as the engine is running you wont wast any propane anymore. and when you stop its back in anti freezing and camping mode.

one can actually use the hot water return coolant line for the cab heater too. one has to stay on the engine side of the check valve and pump to take out hot water. the hot water maker needs max flow with almost no temp drop, so its return is fine for several heaters. but run an own heater core return line to original factory return for the factory heater cores. so its 3 lines you need. one with no pressure drop for hot water and one with significant pressure drop for the heater cores. while the hot water return is fine as a supply line for the heaters. or you add a D+ controled pump and check valve to that heater core too, then you only need two coolant lines.


---------

but my question did aim more towards the motorhome side of installation....

ive never seen a factory version of the coolant based rv heater.

how do they make it get distributed in the RV? where do they mount it?

i think about adding flaps to automatically prevent unwanted back flow or make the air always go though the heater cores, even when the propane burner is active, but then they tend to clog up from the dust in an rv... and that would lead to overheat in the propane burner...

[SafariBen]

You're preaching to the choir regarding the heat available and the relative ease of using it. I'm considering something similar, whether to do a series loop, or Tees, or pumped circuits. I haven't seen many, if any, similar RV conversions.



The closest things I've seen are school bus heaters, just a heater core and fans under a seat, on the coldest day you want that seat, any other day you don't want that seat.
An aquahot is a direct diesel fired hydronic heating system, plumbed into various water to air heat exchanger units in various zones. For just one heating unit to heat the bedroom, bathroom, and living room, I'd still just mount it low and let the air circulate. A cold air return from the other room would help.



Another thing I've considered was a "fin tube" run in the basement for heat, but haven't figure out how to get that low for convection and protected from damage.

[mannebk]

finned tubes work, in floor radiant heat too, but both options require an extensive refitting for an RV. something i don't olan to do.

but adding them to the basement is an outstanding idea

but for fast heat inside leaves me with an heater core and blowers :-)

so whos having a factory engine based rv heater? and would be willing to share a bit about it?