‘Faking’ an EHU Hookup? (Override EC700)

[Heebson]

Strange one this, but I’ve just discovered that the heat mats on my water tanks will only kick in if temp is less than 2°C; there is at least 25% liquid in the tank AND we’re on hookup. This is controlled by the SARGENT EC700.

I’m guessing this was to prevent folks super quickly draining their leisure batteries, but there’s many ways to do that! With higher capacity lithium setups nowadays, this could be managed for the rare time it’s needed - e.g. parking for the day somewhere between hookups. Like my skiing plans!

So, is there a way to override my EC700 here? Completely faking an EHU connection may have unintended consequences I guess (switching fridge to electric?).

Cheers,
Heeb

 

[chaser]

Why would you want them to kick in at a higher temperature?
They are only to stop it freezing aren't they,
Don't really understand the rest of the post.

 

[yorkiebar]

Why would you want them to kick in at a higher temperature?
They are only to stop it freezing aren't they,
Don't really understand the rest of the post.

Heeb wants the heater to work when the temp goes below 2 degC regardless of whether the van is on EHU or not.
Currently the heater only comes on at temps below 2 degC when on EHU.

Perhaps the heat mats are 240v ? Unlikely though. I think you need to look into a bypass circuit for the heater rather than faking a EHU (due to unintended consequences as you mention). Make sure you have a big indicator light when you switch on the bypass !

 

[bladerunner]

are there not 12v tropical fish tank heaters you could drop in?

 

[chaser]

So presumably if you have an ecoflo or similar power pack you could plug that into your ehu.

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[Pausim]

Even lithium batteries are not bottomless so you need to take care if you bypass the built in protection. I am guessing that the heater mats are at least 30W each so 60W for 2 tanks which at 12V would be at least 5A. I don’t have heated tanks and if faced with a similar dilemma I would leave the gas heating on, that would keep the fresh water tank warm and mean the van was nice and warm when I got back. It should use less battery power too. My grey tank is a bit more vulnerable but well lagged with an inboard drain valve but if I was worried I would drain it down before parking up.

If you have an exposed grey water drain off tap on the end of a pipe then no matter how much you heat the tank the pipe and tap will freeze.

 

[CAB96]

Inverter, and run a lead outside to the hookup.

Turn fridge manually to gas.

Turn off mains battery charging.

 

[Heebson]

Thanks for the replies! For hopefully more clarity:

1. Yes, the challenge is that it will be sub-zero (the Alps in Feb), but if I go park at a ski lift to ski for a few hours, then I risk coming back to a 100 litre ice cube. Alternatively, I just can’t find an Aire with hookup to overnight and would like to mitigate a bit.

2. I would be leaving the heating on gas at a low peep during this time, so internals would be warm - and no frost valve triggered

3. Unfortunately my tanks are both under slung and exposed. The heating mat (will work whilst driving apparently) is Auto-Sleeper’s “winterisation” solution

4. I’m not worried about the waste. Will be draining that straight to a bucket to avoid frozen pipes (no heating element in those of course!).

5. I’ve a 106Ah Lithium leisure battery. At 5A draw (they are 12v, this is just EC700 overdesign IMHO), I’d be willing to sacrifice a fair chunk to this purpose if I knew I was going to be driving a distance or getting onto hookup soon.

I guess I could just disconnect the mats from the EC700 and run via a switch to the battery (as was the setup in pre EC700 apparently!) if I can trace the wires back.

 

[Heebson]

Inverter, and run a lead outside to the hookup.

Turn fridge manually to gas.

Turn off mains battery charging.

This has me thinking!

Not sure how I’d get the lead outside without opening a window - which is likely a bad idea in sub-zero conditions!

I do have an external 3-pin socket. If I could get that connected to the inverter….

Will need to experiment to see if switching off the mains charger (a button on the EC700) would trigger it’s infuriating programming to disable the mats anyway!

 

[Lenny HB]

Rewire them to a 12v temperature controller.

Amazon.co.uk

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[CA]

Not exactly helping your original request here (sorry!) but some ski stations have aires close by and have hookup.

My thoughts on heat mats - had a Wildax van conversion some years ago; and took it to the alps 2-3 times a year to ski. Both fresh and waste tanks were underslung and had heat mats - they worked on 12v. These may vary completely to yours however! I alway ran the gas heating full time (on low when out the van all day). It was on 24/7. Never cold inside, always toasty. But the tanks froze despite running the mats.

At temps down to about minus 7/8 degrees were fine. Anything colder than that, then the matts couldn't cope I suppose. Only solution was move the van into a sunny location in the daytime (as it was always at night the real super low freezing temperature happened) and almost always they defrosted by early afternoon.