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Discussion Starter · #1 ·
We did our first winter excursion in ours, and spent 5 days with ~10 degree lows with a ~0 degree low on the last night. The water pump seems to have taken some cold soak and froze up this morning, but just barely. We still had residual hot water coming out of our Isotherm, but the water pump wouldn't work. You could hear it "try" to work with a click when the switch was pressed. A few hours at ~50 degrees here in Denver, and it started to work again. There was a touch of an icy crunch followd by SUPER cold water out of the tap.

We have a Webasto Airtop 2000ST for the interior and it keeps it super toasty at 70-80 degrees depending on how open our ceiling vents are. The garage, separated by a bulkhead, stays pretty cold though (47 degrees), even when we left the bulkhead open all night. And it's apparently even colder in the water box. Makes sense.

For visual context of what the water box and bulkhead look like: http://instagr.am/p/CXZvv_drgPk/
My last van had these heater pads that I would turn on when the weather was under 32 degrees: https://www.amazon.com/gp/product/B01MUC7XI5/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1 I had one stuck on the water pump and a couple wrapped around the short water run from water tank to pump and from pump to faucet. They run at 0.333 Amps each, so 3 of them do 1 amp, and I've got plenty of power to run them 24/7 along with the heater and everything else. 200Ah Lithium, 30Ah DC-DC charger, and 400w solar.

I was planning on doing the same thing this time around as well, but didn't know if there were any better ideas out there? It's not really feasible to route any heat from the Webasto back there, as it's under the couch, on the opposite side of the van, and the routing of the air would be a giant PITA.

Thanks!
 

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2021 3500 Extended
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How about a computer fan to pull the heated air into the garage? Then again, if you have enough battery to run those heater pads, that might be a better idea since they will be right where they are needed.
 

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Van #2 2021 EXT
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Hi @trhoppe

Love your interior colours & pattern choices BTW - it looks great 👍

I “plumbing terms” a product called “heat tape” is used on plumbing lines but usually 120v. It can also be called “pipe trace”.

Maybe there is something in the RV world that runs 12v? I would try researching those words on google etc, & you might find something.

Another method that would use less electrical would be a “recirc” line that utilizes the Isotherm hot water to heat the cold water lines with a low volume 12v pump. If this interests you let me know & I can help more with this non-vetted idea that really just popped into my head.



 

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How about a computer fan to pull the heated air into the garage? Then again, if you have enough battery to run those heater pads, that might be a better idea since they will be right where they are needed.
I had this same problem on my build and this is what I did to solve it. I also added self regulating heat cable to the plumbing, but it has not been necessary since two computer fans keep the temperature in the garage above freezing. I used an arduino and temperature probe to control the fans and ramp up the speed when the temperature on the water lines gets low, but you could also just run them at fixed speed.
 

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Discussion Starter · #6 ·
Oh man, thanks guys.

That heat tape is WAY better than these stupid pads I have, and I can not only run it along the cold lines, I can run it around the pump. Going to 100% switch to that.

I also really like the fan idea, and not sure why I didn't think of it before. I'll run a computer fan to pull air from the kitchen cabinet (which is in front of the water box) into the water box. The kitchen cabinet stays nice and toasty, because that's where the fridge van blows into. So I'll just blow some of that air into the water box too.

I bet with both of these, any issues will be solved. I'll report back!
 

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I would recommend not cheaping out on the computer fans, especially if you will be running them at higher speed or for long periods. I am using these magnetic bearing fans: https://www.amazon.com/Corsair-Premium-Magnetic-Levitation-CO-9050040-WW/dp/B08DL48YPX?th=1
They are quiet and can move a ton of air for their size.

EDIT: If you use a 4-pin fan like that one and want to control the speed (instead of running at max all the time), you also need a fan speed controller like this https://www.amazon.com/Noctua-NA-FC1-4-pin-PWM-Controller/dp/B072M2HKSN
That will let you connect the power and ground pins directly to your 12v and control the fan speed with the knob.
 

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Discussion Starter · #8 ·
Had a "duh" moment, when I checked out how Tourig does their setups in their $100k+ Sprinter builds. They attach a 2nd fridge fan to the fridge, and put that into the bulkhead. So that way, when the fridge fan comes on, and blows hot air into the cabinet next to it, the 2nd fan also comes on and blows that into the bulkhead :) Also helps keep the fridge coils cooler, which helps. I'll be doing that for sure.

The heater pads worked at -5 this past weekend, so for this season, I'm going to call it done.

For next season, I'm going to install, again, what Tourig did in this van. It's a 12v, 50w little small heater. Pulls 4 amps when running, and it's got a temperature controller to come on at 35 degrees and go off at like 45 degrees. It's only heating a 3 sq ft (just the water pump compartment), so it barely turns on, it's set it for life and forget it, and barely uses any power.
 
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