CAK Tanks auto defrost element

jonandshell

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Dec 12, 2010
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Hi all

I was wondering if any skiing Funsters had used one of these successfully to stop an underslung GREY tank freezing.
The website quotes a current draw of 2.5 amps which is fine for us because we are well endowed in the battery department!
The website also quotes that this element will also prevent the freezing of 45 litres of water, in an uninsulated tank, at -25, subject to tank shape.
Well, I intend to insulate our tank and bearing in mind nearly all waste water discharges are warm to start with, do CAK's claims stack up?

If any Funsters have any real time experience of these units in Alpine conditions, I would be grateful for your collective opinions. As mentioned previously, the current draw isn't an issue for us, even off grid.

Thanks in advance!
 
Jan 8, 2014
958
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Hi I have a burstner travel van and it has a heater element in the waste tank, never used it though, but it must work as the van was partially designed for winter sports.
 
OP
jonandshell

jonandshell

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Hi I have a burstner travel van and it has a heater element in the waste tank, never used it though, but it must work as the van was partially designed for winter sports.
Hee hee!

NEVER believe a dealer or manufacturer's claims about ANYTHING!!!!!:wink:

My judgement says this element should work, but the cold can penetrate in wierd ways once the temperatures plummet.

Having said that, Burstner are quite good vans for those conditions, although I have known a water pump freeze on a double-floored Elegance!:Eeek:

Thanks for the input though.(y)
 

scotjimland

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Jul 25, 2007
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CAK tank's claim broadly agrees with Tank Blanket .. which draws 5A and protects 121 lt

In the case of TankBlanket, which services a tank up to 121 Litres against a minimum benchmark ambient temperature of -24 degC, and to achieve this using a 12V supply the draw is circa 5A . It is governed by Ohms Law.
The current UK market standard, that is, an in-tank suspended probe has a lower draw, but you have to look at performance. A typical in-tank Frostat probe currently fitted to many Motorhomes uses a 12V supply and only draws circa 2.5A, but it only services a 45 litre tank!
 

icantremember

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Sep 2, 2010
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Hi all

I was wondering if any skiing Funsters had used one of these successfully to stop an underslung GREY tank freezing.
The website quotes a current draw of 2.5 amps which is fine for us because we are well endowed in the battery department!
The website also quotes that this element will also prevent the freezing of 45 litres of water, in an uninsulated tank, at -25, subject to tank shape.
Well, I intend to insulate our tank and bearing in mind nearly all waste water discharges are warm to start with, do CAK's claims stack up?

If any Funsters have any real time experience of these units in Alpine conditions, I would be grateful for your collective opinions. As mentioned previously, the current draw isn't an issue for us, even off grid.

Thanks in advance!
That appears to assume a full tank ... unless the probe is at the bottom of the tank, where it could get covered with gunge, what would happen to a partly full tank?

Anyway, why would you want to keep a tank of grey waste? Surely better to run directly into a tapered bucket and dispose of as a big lollypop!
 
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jonandshell

jonandshell

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That appears to assume a full tank ... unless the probe is at the bottom of the tank, where it could get covered with gunge, what would happen to a partly full tank?

Anyway, why would you want to keep a tank of grey waste? Surely better to run directly into a tapered bucket and dispose of as a big lollypop!
It all depends where we stop!

We might be neighbours of members of the Motorhome Fun Grey Water Police!

We currently use a bucket, but its easy to overflow it and leave a tomato pasta sauce coloured ice rink!

I plan to fit the element over our slide valve, as low as it will go.
 

haganap

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Dec 5, 2007
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Yes i had one on my last van. It helps but even fitted real low won't work for what you want. There is always some amount of water trapped in the pipe outlet which will freeze at harsh vt temps.
The problem is that they do not heat the tank they just stop it from freezing ...There will always be a weak spot in extremes....so do yourself a favour....buy a bigger bucket ;-)
 

canopus

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Nov 27, 2010
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Hi all

I was wondering if any skiing Funsters had used one of these successfully to stop an underslung GREY tank freezing.
The website quotes a current draw of 2.5 amps which is fine for us because we are well endowed in the battery department!
The website also quotes that this element will also prevent the freezing of 45 litres of water, in an uninsulated tank, at -25, subject to tank shape.
Well, I intend to insulate our tank and bearing in mind nearly all waste water discharges are warm to start with, do CAK's claims stack up?

If any Funsters have any real time experience of these units in Alpine conditions, I would be grateful for your collective opinions. As mentioned previously, the current draw isn't an issue for us, even off grid.

Thanks in advance!

If you buy a N+B as you indicated you might do, then you won't need tank heaters.
 
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jonandshell

jonandshell

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If you buy a N+B as you indicated you might do, then you won't need tank heaters.
That was the plan, albeit the expensive option!
Theres nothing we like at the moment so I will persevere with our underslung tank until something comes along we like and can do a deal on.
We arent in a hurry! Fools rush in as they say!
 
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jonandshell

jonandshell

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Dont
Yes i had one on my last van. It helps but even fitted real low won't work for what you want. There is always some amount of water trapped in the pipe outlet which will freeze at harsh vt temps.
The problem is that they do not heat the tank they just stop it from freezing ...There will always be a weak spot in extremes....so do yourself a favour....buy a bigger bucket ;-)
Don't have a discharge pipe, just a slide valve straight out the bottom!

You can get 300 or 600 watt 12v elements for about 18 quid. I wonder if I could fit one for emergency defrosting with the engine running?
 
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jonandshell

jonandshell

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The purpose of the modification wouldnt be so much to store huge quantities of grey water but to give time to make emptying a planned rather than emergency operation!
 
Jun 30, 2013
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I fitted them to my Fresh and waste tanks. I also have the tanks insulated, as well as all the pipework including the drain outlets.
Nothings frozen yet in temperatures down to -10.
I'll let you know next year how they perform this winter...
Allan
 

haganap

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Yes but there's -10 Alan and skiing in VT....;-) they do work i fitted one in my fresh and never frozen since....seems like a lot of hassle jon get two buckets you lazy git
 
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jonandshell

jonandshell

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We used a three bucket system last year!

The two thawing in the garage created a cold area which made our batteries inefficient!
I just want to buy a little time between bucket emptying! It would be nice to do it at a leisurely pace, perhaps whilst emptying the cassette! Instead, I'm out there during every shower making sure the bucket doesn't overflow!

Besides, I've committed to the project now! There's a roll of Screwfix foil bubblewrap loft insulation sitting in the garage ready to stick onto the tank! As good as 55mm of polystyrene it says!

We shall see............!
 
May 23, 2012
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Spoilt it now, I was thinking that you built a big pile of frozen blocks of ice with the waste from your buckets that did not melt till the spring.
 
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jonandshell

jonandshell

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Spoilt it now, I was thinking that you built a big pile of frozen blocks of ice with the waste from your buckets that did not melt till the spring.
At the end of most Aires, there's a pile of bulldozed snow left by the loading shovels they use for snow clearance.
That's where you chuck the great water igloo building blocks!!!
 
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jonandshell

jonandshell

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Good News!

I am now able to conduct a cold chamber test at a constant -22 courtesy of one of my customers!
Hopefully I should have the element and insulation fitted in a few days. I am then able to place the tank in a coldstore and leave it connected to a battery for a day or so.
I am able to keep the battery at ambient temperature and run a cable into the coldstore. This will mean my battery wont be killed off in the process!
I will post the results good or bad!
 
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jonandshell

jonandshell

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OK, so the tank has been in the cold store for 9 hours now.
This morning a 0700, I half filled the tank with 50 litres of cold tap water, connected the defrost element to one of my traction batteries and went and did some work!
The ambient temperature is -22, the tank is still liquid and the slide valve is still free to move.
The battery is rather annoyingly still showing 12.8 volts! Which means the insulation must be very efficient because the element has drawn next to no power so far. The element did come on for a short time during the afternoon, during a routine check.

I am back to site at 0900 tomorrow, so I will issue a further update then!
 
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