DIY Tank Heating... (1 Viewer)

phazaar

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Dec 19, 2018
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Well, winter is here and talk is of heading north so winterisation has jumped up my priority list.

I have two underslung tanks, and will be insulating them (of course) probably with some simple foil-based stuff. Independent of that consideration, I'd quite like to put tank heaters on them, even if as a bit of a 'just in case' feature. However looking at the cost of commercial solutions (£100 a tank from the US and £60 a tank from CAK) I'm wondering if I can do a better job myself...

Immitating the CAK solution would be easy, and probably half the cost (cheap DC element in the tank) though I don't feel like this is good for the element, the tank, or the water.

The Ultraheat solution (rebranded over here as something like 'Tank Heater' if I recall correctly) is brilliant, but also potentially really simple. As best as I can see, it's a piece of resistive wire snaked across a butyl panel adhered directly to the tank. What else is a resistive wire snaked across a panel? Underfloor heating, and Electric Blankets.

So the options then are:

1) Make from scratch. Grab a butyl panel, some resistive wire, and go from there... Probably the cheapest option, but lots of waiting on orders from China and more manual work involved.

2) Try to find Underfloor Heating that will run on 12v (there's a few on eBay) AND can be cut small enough to sit on the tank. Probably the most expensive option (looks like about £50 at minimum).

3) Grab a couple of £15 12v electric blankets from Amazon and go to town on it. (Super simple, and cheap, but potential issues in water/mud getting onto the blanket, and potential wastage if it's not possible to trim the blanket down to only cover the bottom. Maybe offset by extra insulating capacity?!)...

So, what does everyone think? Any warnings, other ideas, or experience of doing the same thing?
 
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phazaar

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Oh, fourth option - 'reverse engineer' one of those aftermarket car seat warmer. Has the advantage of including all the controllers etc you need already included, but higher cost than a blanket...
 
May 5, 2015
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Have you got a dog?

No, he/she wont be able to help warm your tanks but if you order their food from Monster pet supplies you'll get some nice big plastic sacks that they put the dog food bags in for delivery, that you could wrap around the tanks and blankets!
 

scotjimland

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Powering by 12v.. will need big batteries.. how will you charge them ?

What I would do..
KISS.. leave grey waste tank valve open. If on a site, use a bucket (not a waste hog) to catch the waste water, dump when full or if frozen, a big lollypop left on site drain .

Fresh tank , just lag it, won't freeze when it's being filled and used constantly.
 

pappajohn

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All these solutions may work if you plan on being on sites with EHU every night to maintain your battery/ies.

Batteries and heat production are not compatible or advisable.

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Lenny HB

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Better to do what Germans do in their vans. Insulate the tank you can make an encloser from poystyrene sheet bonded with glass tape & GRP resin at the edges then coat the all the sides with resin, paint black to look pretty. Leave an air gap around the tank and take a small diamiter feed into the enclosure from your blow air heating. Efficent and no battery drain.
 
Feb 27, 2011
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Best bet is to keep the grey tap open and empty into a container under the van. I am a fulltimer and it is what I do now.
 
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phazaar

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Dec 19, 2018
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Have you got a dog?

No, he/she wont be able to help warm your tanks but if you order their food from Monster pet supplies you'll get some nice big plastic sacks that they put the dog food bags in for delivery, that you could wrap around the tanks and blankets!

That's actually a great idea, and another tick in the 'get a dog' column ;)

Powering by 12v.. will need big batteries.. how will you charge them ?

What I would do..
KISS.. leave grey waste tank valve open. If on a site, use a bucket (not a waste hog) to catch the waste water, dump when full or if frozen, a big lollypop left on site drain .

Fresh tank , just lag it, won't freeze when it's being filled and used constantly.

We're running 800Ah of LFP, soon to be charging off a secondary alternator, but for now the combination of 400W solar, 60A when on EHU, 60A from the primary alternator, and an optional generator ought to see us through, I reckon. We'll likely adapt a fair amount of our DC gear to run direct off an AC-DC Converter whilst on hook-up too.

Your 'adaptations' are what we've previously gone for, but in the interests of building this out as 'all-singing, all-dancing'...

All these solutions may work if you plan on being on sites with EHU every night to maintain your battery/ies.

Batteries and heat production are not compatible or advisable.

The usage of a couple of electric blankets or seat warmers is about 30W each. With minimal insulation on the tank, it'll take over 2 hours to drop from 1C to 0C at -10C outside. With 25mm of insulation this is increased to around 5 hours. If we run 30W for 4 hours, this will give us slightly more heat than was lost in the preceding 5 hours, so let's call it a 50% duty cycle at -10C. This means we'll be using around 30Ah from the battery per day to keep the fresh tank from freezing. Seems alright to me...


Quite keen to avoid anything needing to be inside the tank, though at that price I'll admit I'm tempted!

Better to do what Germans do in their vans. Insulate the tank you can make an encloser from poystyrene sheet bonded with glass tape & GRP resin at the edges then coat the all the sides with resin, paint black to look pretty. Leave an air gap around the tank and take a small diamiter feed into the enclosure from your blow air heating. Efficent and no battery drain.

I'm not sure 'better' is synonymous with 'costing twice as much and taking twice as long' ;) The resin to do that alone would run more than the cost of a couple of blankets unless I'm misunderstanding the construction (got a link?), before even considering the cost of the extra ducting and the foam. It also would involve running our diesel heating (around 30W, and 0.25l diesel per hour!) even when not in the van.
 
Feb 22, 2008
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6008B9A3-3BC1-4E6E-B26F-D2E50C066E75.png
 

Two on Tour

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As it happens I have just been accumulating various bits to winterize our fresh and grey tanks.

Using these as tank heaters. https://www.ebay.co.uk/itm/Self-Adhesive-Thermo-Heating-Pad-12V-15W-35-40degC-S-A-Pad/121744329623?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

Trace heating cable for the grey waste dump pipe.

Digital thermostats for each tank. Amazon product ASIN B01429KIJ2
Tank insulation. Amazon product ASIN B011PJSR22
Pipe insulation for the grey waste dump pipe.

Spray contact adhesive. https://www.toolstation.com/spray-contact-adhesive/p47790

Aluminium tape. https://www.toolstation.com/aluminium-foil-tape/p97723
 

pappajohn

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That's actually a great idea, and another tick in the 'get a dog' column ;)



We're running 800Ah of LFP, soon to be charging off a secondary alternator, but for now the combination of 400W solar, 60A when on EHU, 60A from the primary alternator, and an optional generator ought to see us through, I reckon. We'll likely adapt a fair amount of our DC gear to run direct off an AC-DC Converter whilst on hook-up too.

Your 'adaptations' are what we've previously gone for, but in the interests of building this out as 'all-singing, all-dancing'...



The usage of a couple of electric blankets or seat warmers is about 30W each. With minimal insulation on the tank, it'll take over 2 hours to drop from 1C to 0C at -10C outside. With 25mm of insulation this is increased to around 5 hours. If we run 30W for 4 hours, this will give us slightly more heat than was lost in the preceding 5 hours, so let's call it a 50% duty cycle at -10C. This means we'll be using around 30Ah from the battery per day to keep the fresh tank from freezing. Seems alright to me...



Quite keen to avoid anything needing to be inside the tank, though at that price I'll admit I'm tempted!



I'm not sure 'better' is synonymous with 'costing twice as much and taking twice as long' ;) The resin to do that alone would run more than the cost of a couple of blankets unless I'm misunderstanding the construction (got a link?), before even considering the cost of the extra ducting and the foam. It also would involve running our diesel heating (around 30W, and 0.25l diesel per hour!) even when not in the van.
After spending a small fortune on batteries, solar and a future second alternator your going to buy a couple of cheap blankets off eBay and bodge a tank heating system.

It appears you can afford to spend money on a proper tank heating system and do the job properly.

Good luck.
 
Nov 18, 2011
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The most important thing I have fund is pipe work lagging is the most important thing in very could conditions I have fund that a full thank of water will only freeze on the firs half inch on the top sum times and that when the van is not occupied and allowed to cool down.
Covering the water tank with even a minimal amoun of lagging will work if you intend to have your hating running from time to time consider re rooting one of the hot aire ducts or just tee off a 50mm bit of ducting blowing on the bottom of your tank will stop it freezing I have bean winter motorhoming camping as long as I can remember and have used that method to stop my tank freezing it dose not take a lot of heat to stop it freezing but defrosting is another mater.
You have to think of battery power and what dose it cost to do it my vans a old one so I don't care if I cut a hole in the fore for a fit of ducting.
bill
 
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phazaar

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As it happens I have just been accumulating various bits to winterize our fresh and grey tanks.

Using these as tank heaters. https://www.ebay.co.uk/itm/Self-Adhesive-Thermo-Heating-Pad-12V-15W-35-40degC-S-A-Pad/121744329623?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

Trace heating cable for the grey waste dump pipe.

Digital thermostats for each tank. Amazon product ASIN B01429KIJ2
Tank insulation. Amazon product ASIN B011PJSR22
Pipe insulation for the grey waste dump pipe.

Spray contact adhesive. https://www.toolstation.com/spray-contact-adhesive/p47790

Aluminium tape. https://www.toolstation.com/aluminium-foil-tape/p97723


Great finds - thanks for sharing! Glad to see I've got a lot of the same stuff you've linked in mind :) Have you received/tested the heating pads or trace cable yet?

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phazaar

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After spending a small fortune on batteries, solar and a future second alternator your going to buy a couple of cheap blankets off eBay and bodge a tank heating system.

It appears you can afford to spend money on a proper tank heating system and do the job properly.

Good luck.

A lot of assumptions in this post, so to just run them down a second...

I've neither spent a small fortune on batteries nor on solar, and to put it into perspective, the cost of a second alternator which will be used constantly all year round is slightly less than the cost of two tank heaters which might see use for a few weeks of the year.

I'm not sure where I've suggested I wasn't planning on 'doing the job properly' - I'm just planning on doing it myself. There's an initialism in there somewhere - could have sworn I saw it at the top of the page ;)

There's a difference between cost and value. In some situations, the cost of something is far below its value; take a decent water pump for example. To make yourself one you'd spend 5 times as much just on parts, before all the R&D and mistake-induced misery. When looking at the simplicity of what's on offer for tank heating, at £100 per tank for something that has a parts cost in the pennies and particularly straightforward implementation, it looks like that equation might be reversed, with cost far exceeding value. Throw in the added value of the satisfaction of doing something yourself to boot...
 
May 7, 2016
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These are small but cheap enough to buy in numbers. Can be used flat or bent round pipes.
 

Two on Tour

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These are small but cheap enough to buy in numbers. Can be used flat or bent round pipes.

But they are 15 watts each and as they are only 110mm long you would need a fair few to wrap around the length of a grey waste dump pipe.

The trace heat cable is only 19.6 watts per metre and my pipe run to heat is 800mm long
 

funflair

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Better to do what Germans do in their vans. Insulate the tank you can make an encloser from poystyrene sheet bonded with glass tape & GRP resin at the edges then coat the all the sides with resin, paint black to look pretty. Leave an air gap around the tank and take a small diamiter feed into the enclosure from your blow air heating. Efficent and no battery drain.
If you are going to use Polystyrene foam you can't use normal GRP resin (Polyester) this contains Styrene which will melt the Polystyrene, better to use Epoxy or us a Polyurethane foam and then normal GRP resin is OK.

Martin
 
May 7, 2016
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But they are 15 watts each and as they are only 110mm long you would need a fair few to wrap around the length of a grey waste dump pipe.

The trace heat cable is only 19.6 watts per metre and my pipe run to heat is 800mm long
Fair enough, just a cheap suggestion I have used for other purposes.

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Two on Tour

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I did have a look at the grip warmers as tank heaters when I think it was Richard and Ann pointed them out in another thread but then I found the ones with the larger area with the same wattage so went for them.
 

Two on Tour

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I have posted this somewhere on here a few times.

Had three fully winterised motorhomes (internal tank/double floor etc).

But also, our current Hymer with underslung waste tank, did not freeze even at -17c

Is your current Hymer underslung waste tank winterised (insulated and heated) or just bare.
 

Darcar

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Pipes will freeze first. So lag those.
We’ve been snowed in unable to move for a day or two, but our tanks never froze.

We do have a couple of 5 litre containers inside when we go winter camping. But never needed them because of the cold.

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