Opinions on Block Heater replacement.. 400watt vs 1000 watt

Fredricksen

Member
I have a 7.3 IDI Diesel with a block heater that danced its last dance.

I am going to switch it out.. but I am considering putting a 400watt replacement in, rather than the 1000watt it comes with.

My rationale:
Since I do not have generator, if I go somewhere without shore power, (say a ski slope parking lot)
I could use the batteries and solar panels to power 400watts and keep things warm. (where 1000W would draw too much power)

I park the van, tilt the panels: run the heater like a trickle charger, preventing the engine from getting too cold, rather than warming a cold engine;
Or if I camp, and it is cold in the morning, just allow extra time to warm it up.. (If i choose not to put a Coleman under the oil pan, as mentioned in another thread)

Is my rationale flawed here? Is the mass of the engine too much for 400 watts? (thermal equilibrium and heat transfer ..etc.?)
Aspects I am missing?
 

Rebuilder

Observer
Is 1000w too much for your inverter or just too many watts to run all the time? If your inverter will handle it how about getting the 1000w and adding a timer to turn it on a few hours (or whenever) before you plan to start the truck? If you time it right you would use the same or less power than running the 400w continuously and you get the benefit of having more heat from the 1000w.
 

Fredricksen

Member
I am thinking it might be too many watts to run..
2000 watt inverter, only 200aH of battery

In my brain, I was thinking; keep a block a 60 degrees as it cooled down from operating temp VS warming a block UP to 60 degrees that had cooled to 20 degrees.
(60 being an arbitrary number)

if I kept the engine 'warm' during the day, while the sun was shining,
At 400 watts, the solar panels would be the primary source for the energy, and the block would not get cold.
Then the block would not need as much heat to warm it from a lower temperature at the end of the day when the sun is lower in the sky providing less solar power.

If I went with the 1000 watt, it would be relying primarily on battery power (late in the day)... and I am thinking margin of error/murphy's law.


I was picturing it as some sort of inertia problem.
1000 watt heater tasked with a warming block which had cooled all day.
vs
a 400 watt unit working to maintain a block temp that was already moderately warm, using solar to drive it.


I have no concept of thermodynamics, so I may be talking out my butt.
 

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Joe917

Explorer
Coolant heater is the best option, just not the cheapest. Is the vehicle a camper or just a truck? the coolant heater would be a great addition to a camper.
We have the Webasto Thermotop C and it is a very good unit. I would avoid the cheap Chinese knock offs, there is a cheaper Russian option from Planar that might be an option.
I think trying to keep the engine warm with battery and limited solar is a lost cause. 20 min of pre heat is a better idea.
 
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alanymarce

Active member
Interesting question. I'm reflecting on some of the comments:

Since I do not have generator, if I go somewhere without shore power, (say a ski slope parking lot)
I could use the batteries and solar panels to power 400watts and keep things warm.
Key questions are "How cold is it going to be?" and "How long are you going to leave the engine without running?"

If you're going to be leaving the vehicle for 8 hours or so above -17 deg C you don't need a block heater; if for 8 hours below -17 deg C you'll may not need a block heater (I used to leave my vehicle (smaller engine) parked outside every day in temperatures down to - 30 deg C or so without plugging it in); if you're leaving it for 8 hours in temperatures below -30 deg C then you'll probably need a block heater which is powered. By the way, if you're in temperatures below - 20 deg C or so, you won't want to be skiing!

So, I'd say that for 8-12 hours 400W would be enough.

If you're planning on a period over 12 hours, in temperatures below - 17 deg C (without running the engine) you don't need to keep the block that warm, so won't need that much power. I recall that we used to plug the block heater in for a couple of hours to warm the engine if we'd left the vehicle for 24 hours or more at temperatures between - 17 and -30 deg C.

Once again, I'd guess that 400W would be enough.

Now all of the above are related to the block heater, not the fuel - that's a different question.

In the Arctic, in winter (temperatures down to -50 deg C or so) we used to leave the engines running all winter - not that that helps you much.
 

Verkstad

Raggarkung
I have no concept of thermodynamics, so I may be talking out my butt.
Even if you did have concept and ignore unpredictable variable of windchill, it will be allota work to gather enough data to make sort of reasonable estimation.
 
I am assuming your latitude is roughly 50 deg (northern US or southern Canada). Remember that solar panel ratings are usually for the sun directly overhead (unless they are tiltable). And the output power rating is for 19-20v (if designed for nominal 12v system, which is down adjusted to ~14.5v by solar regulator). Combining effects of latitude, angle of sun at zenith on Feb 17 (arbitrary choice on my part) and panel actual rating, panels will put out ~33% of rating. A nominally rated 600w array might put out ~1.2 kwh over 1 day under totally optimal conditions.
Enough for the 400w heater for only 3 hours. And remember that your 2.4 kwh batteries (hopefully not also tasked with starting the truck) only are good for 50% = 1.2kwh if lead acid based. Maybe half of that if cold soaked. Resistance heating is a waste of scarce high tech energy, electricity. Use your abundant diesel fuel for heat, a 5kw Thermo Top C or Planar equivalent (I second recommendation against Chinese knockoffs)uses 46w or less to run.
Also remember that camping overnight or outdoors activities aren’t really fun below -17C or so. Even though my vehicle has a second 9kw Webasto just for engine and cab heating, and the 5kw unit with R13 camper insulation and double pane windows etc can keep camper warm in -45C which still occurs occasionally in my state - doesn’t mean that I want to do it!!!
The 5kw Webasto or Planar will be very adequate to heat living space and engine and cab very adequately overnight.
It would help to know where you live (latitude and climate).
 

turbodiesel

Active member
Rather than the diesel air heater, you could use something like Espar Hydronic D5E to heat the coolant directly. That will be very efficient in heating up the block.
 

SquirrelZ

Member
Rather than the diesel air heater, you could use something like Espar Hydronic D5E to heat the coolant directly. That will be very efficient in heating up the block.
That is essentially the same thing as the Webasto Thermotop C. I have owned both Espar and Webasto air heaters and they are both very good products.
 

turbodiesel

Active member
That is essentially the same thing as the Webasto Thermotop C. I have owned both Espar and Webasto air heaters and they are both very good products.
My bad, I knew I should have looked it up before commenting. I have a D2 with high altitude sensor that is fantastic. Also tried two different Chinese knock offs but they both had issues between controllers, pumps and failed seals. Friend has one that works perfectly and adjusts for altitude without issue. Very hit or miss.
 

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CaulkinsCo.

Member
Money aside the hydronic is really the only option but I know a few snow bums where money is the only factor. In that case I wonder the effectiveness of a $100 airtop (hit and miss I'm told but you can return anything to Amazon) running at 100 percent for a few hours with the dog house off and a blanket over the grill. If the cabin air it brought up to 85 then I'm assuming the engine bay temp could be around 40 degrees. If it's a ambulance there's plenty of room to carry a blanket big enough to cover the grill and fender wells.
 

Fredricksen

Member
A high mileage IDI, running 15w40, can be temperamental in the cold. (The only thing worse is the side-eye from wife.)

Maybe I should slap a "12V 100W Pizza Hot Food Delivery Bag Silicone Heating Pad/Mat" from wally world on the bottom of my oil pan, for that all day, slow simmered, goodness


What's the quickie/back of the envelope formula for estimating solar panel output from one's location?
cos(latitude of location + 23.54 (in winter) or -23.45 (in summer)) * power of panel
 
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