Diesel Coolant heater sizing question

[kbeefy]

Yeah, took me a bit to figure out the differences. The 3 wire version are the ones that don't draw power constantly and don't return home when power is removed. I was originally going to use irrigation valves for sprinklers, but most say not to use with heated water.

I may still use a sprinkler valve for my Grey water dump.

 

[charlieaarons]

I'm building my next campervan and I'm incorporating a diesel coolant heating/hydronic heating system. (van is diesel E350).

I don't have any experience with diesel heaters aside from a toyotomi cabin (air) heater that I had in my last van.

Most Diesel Coolant/water heaters seem to be 5kw heat output. I don't really know what that relates to, or how it would perform in real life. It looks like I can get a 12k heater for not much more money.

Does anyone have any reasons I shouldn't get the bigger version, or how the 5kw would work for heating 15 gallons of coolant and domestic hot water?

Also, anyone have any real life experience with a diesel coolant/parking heater? Any recommendations? I'm not looking to buy a $2000 Webasto or Eberspacher... a knockoff version is OK with me.

Unicat told me that an oversized heater leads to more rapid soot/carbon buildup in the combustion chamber, which can cause premature malfunction (at exactly the wrong time of course), necessitating a rebuild or even replacement.
Because it spends too much time at the lowest heat output; OTOH higher output more of the time “burns the carbon buildup out”. Like an old carbureted spark ignition engine idling too much and fouling spark plugs. Fixed by high speed running.
FWIW, my camper box is ~16’ long. Starting 5kw Webasto at -20F results in thoroughly warm camper in ~4 hours.
Calculations with R values of camper walls/floor/ceiling show it can keep my box warm at Martian polar winter temperatures. Far below where #1 diesel would be solid.
The above potential problems with a 9kw or larger heater for a 12-16’ well insulated box would get much worse at altitude.
If anyone is interested, Unicat sent me a workaround to the altitude issue for non altitude compensating diesel heaters that’s very simple and totally non electronic.
Rather than a bigger heater I’d consider a 5kw hydronic plus a 2kw air heater, for rapid warmup and that thing called “redundancy”.

 

[kbeefy]

Unicat told me that an oversized heater leads to more rapid soot/carbon buildup in the combustion chamber, which can cause premature malfunction (at exactly the wrong time of course), necessitating a rebuild or even replacement.

Rather than a bigger heater I’d consider a 5kw hydronic plus a 2kw air heater, for rapid warmup and that thing called “redundancy”.

Thanks, I had been reminded of that over on the SMB forums.

I have decided to go with the knockoff 5kw heater. The way my system is designed, the main vehicle engine will be my 'redundancy'. If it can't provide enough heat I will also have the 'double redundancy' of being able to drive somewhere warmer. After living 40 years in Alaska I'm not too keen on camping below freezing anymore, anyways.

 

[kbeefy]

Finally getting this all put together.

Still need to install the inlet and exhaust, but its all working.

Thats the hot water heater, cabin heater, and expansion reservoir.
I ditched the electronic valves as I just ran out of space. A couple ball valves that are accessible inside the van will do.

 

[llamalander]

That looks clean and compact--can't hardly tell how much work went into it!
Keep us posted when you find out how it all works together...

 

[kbeefy]

So, I've been thinking. If I run my heater fan while the coolant heater is off and not circulating, it will very quickly cool the coolant in the heater core.
The heater can be configured to maintain a temp window, but if the coolant isn't moving it won't respond to the heater core getting cold.

My original idea was to tap a line from the heater fan control to the coolant circulation pump (diode protected) so that when the heater fan kicks on, the coolant circulation pump will also engage. Then, when the coolant in the heater drops below the turn on threshhold (60*C) the coolant heater will automatically fire up an heat to it's shutoff (80*C).

From my bench testing, I know that straight 12v motors the pump far faster than it usually commands via the coolant heater control board.

So, I'm thinking of using a PWM motor control instead of straight 12v (still diode protected) to regulate the voltage to the circulation pump to the lowest voltage the coolant heater ever commands. Then the coolant heater can command higher flow when desired, and the cabin heater can circulate the coolant to keep it from getting cold.

Any thoughts? Anyone smarter than me paying attention in here? Will it work?