12v tank heater

May I please check something? Having put fresh water in the tank, I switched on the tank heater last night because frost was forecast. (I had a heater in the van to ensure that the dump valve didn't operate.) When I switched on the tank heater (above the hab door) its light came on. I assumed that the tank heater was therefore on.

However, when I looked at the current display on the panel, and switched off and on the tank heater, there was no change in current. That suggests that the heater wasn't using current. There was no change whether I had mains on or off.

So the possibilities are that either the tank heater doesn't work, or that it is thermostatically controlled and so it hadn't come on because the temperature wasn't at or very near zero. Does the tank heater have such a thermostat?

Thanks.

Cymro wrote:Does the tank heater have such a thermostat?

Some do and some don't! CAK do one that switches on at 5°C and off at 10°C

Interesting question, how do you know whether you even have the tank heater fitted, our 2005 (2006 model with the newer curved cupboard doors) Exec has the illuminated switch to the left of the hab door step on the fridge panel. The light comes on but we don't have a current monitor on the EC200.

I'd assumed that any tank heater would be 230V anyway, what wattage is the 12V heater likely to be?

12v 30W from CAK. Only way to know if you've got one and where the switch is, is to look at the tank and follow the wiring if there is one there.

Hi, mine [water &waste] were factory fitted by A/S at the build stage ,but I could never get a definite answer on whether they were controlled by a thermostat and/or had some sort of level switching, other than the notorious tank studs which to say the least are fairly unreliable. So quite frankly I have never been brave enough to chance turning them on!!  My switch for them both is like yours by the habitation door with a red light above, taped to off! I will watch this post with interest ,hopefully to find out if I can "flick the switch" with confidence       Kind regards         Paul

The outside temp is showing 6C here at the moment.

Although our tanks are empty, I'm tempted to go out and check the battery current with a meter while switching the heater on and off. The van is in shade on the North side of the house, so it may well be a couple of degrees down from where our Weather station sensor is sited.

Can I be bothered though? 


EDIT: Actually, I have an idea. The EC200's PSU fan starts up whenever the load on the system is increased, even when we switch a few LED lights on, maybe I don't need the ammeter.
"I'm just going outside, and may be some time". 

Well, that was quick.

We have a 110W solar panel which is currently delivering 2A into the engine battery, having fully charged the hab battery, both batteries showing 13.9V off load on the EC200.

I tried switching on some LED lights first, the hab volts dropped to 13.7V, some more lights and they dropped to 13.5V, switched all off and the battery instantly rose back to 13.9V.

Tried the tank heater switch - no change.

So either:

1. There's a wiring fault.
2. It's not cold enough to operate the heater, (which would mean that it DOES have a thermostat)
3. There's no heater element or wiring.

I'll have to wait until it's much colder and try again.

Thanks to you all for your prompt replies. Your description, Meanchris, corresponds to mine.
How odd that AS cannot confirm whether or not it's thermostatically controlled. Because the heater isn't very powerful, it would be best if it came on before the air. \ water temp nears zero.

I'll leave it on tonight and, if it's below zero, I'll see if it draws current.

Meanwhile thanks again to you all.

Cymro

On my Bourton besides the switch on the control panel near the habitation door there is also a switch under the offside bench seat above where the sergeant main unit is located next to the access hole for the auto dump valve, it is a small black circular rocker switch which the dealer told me was for the tank heaters and had to be switched on as well as the one on the control panel.
Don

Thanks Padraig. I have a switch under the o/s bench, but it's labeled isolation switch for waste heater. It's off because waste tank is empty. I suppose I could try that and see whether it causes current change. But I a assumed each heater was separately wired.

Thanks to Peter's info, I found this:

Let's hope we have the DF02, with integrated thermostat.

Ah.  I thought that on mine (2015 Nuevo with "winter pack") the heater is a pad, fitted beneath the base of the tank - rather like a heated pad which our cattery uses in the winter to keep feline backsides warm.

Whatever I've got, it doesn't seem to draw current!

https://www.autosleeper-ownersforum.com/t9552-premium-and-winter-packs?highlight=winter

A lot in the thread linked above re tank blankets including a link from Paul to the supplier and thence the spec. 12v 4A and come on at 7°C so you would definitely notice the current.

Very many thanks, Peter, and to Paul for his earlier research. It's clear now that mine should have cut in, but didn't. Another for the warranty list......
Cymro

Just a quick update. The heating pad sure draws current!  Last night it dropped to 12.5C here; I'd left the water tank heater pad switched on (plus low space heating in the van). I'd left the Sargent panel on the setting to charge both batteries from EHU. Both batteries showed just above 13v.

Early this morning I checked. The leisure battery showed "2.5v (poor)".  And the current was -5 amps.

I changed the Segent setting to charge leisure battery only. It drew a frightening 22 amps as it began to replenish that battery. The charge rate is now dropping as the battery recovers.

From this I deduce that if you leave the heater pad on overnight, it will totally drain the leisure battery if not on EHU; and will draw high current if on EHU and Sergent set to charge leisure only.

Frankly, it's a poor system, which isn't worth the money. I shall in due course insulate the water tank and pipes, as recommended on an ealier thread on this Forum, and not bother with the pad. Unless it's truly Arctic!

My thanks to all contributors. It's been interesting!

Cymro

Thanks for the report Cymro.

Out with the sticky tape when it warms up a bit. Sounds like those switches are potentially disastrous, so mine will be taped "off" to ensure no accidental switch-ons.

May make little covers for them instead, if I can think of a good way to attach them??

Dave

"2.5V" 

I went out and switched our tank heater switch on this morning, with the temperature in the van at approx 1.5C, no change in battery volts, so I presume that there's either no heater or a connection/wiring fault.

Ah well, I'll have another look, under the van, when it's warmer.

Cymro, you say "I'd left the Sargent panel on the setting to charge both batteries from EHU. Both batteries showed just above 13v."

Which Sargent unit do you have? Mine (EC325) and I think the EC328, only charges either vehicle or Hab battery, not both. 2.5v seems low?

PLOUGHLIN wrote:Cymro, you say "I'd left the Sargent panel on the setting to charge both batteries from EHU. Both batteries showed just above 13v."

Which Sargent unit do you have? Mine (EC325) and I think the EC328, only charges either vehicle or Hab battery, not both. 2.5v seems low?

Further to the above, yes I did query with Sargent about the battery charging as my vehicle battery had gone flat while on hook up.
They tell me that on the EC325 and 328 the default charge is to the leisure battery (for instance when you first turn the panel on etc). If you want to charge the vehicle battery you have to ensure the panel is on and the blue light and switch next to the  main panel switch is on and the display should show vehicle battery and the voltage. Mines been OK while on hookup and not used. I charge the leisure battery occasionally during the winter.
Dave

Cymro has the EC500 that can be set to charge both at once both from mains and from the solar panel.

Peter Brown wrote:Cymro has the EC500 that can be set to charge both at once both from mains and from the solar panel.

Sorry, must be missing something in the posts. I could not see where he said he had an EC500
apologies if I have missed it.

Sorry for delayed response. Am in no wifi part of mid Wales. Please see Chudders' post above: that's what I've got ( I checked with Sargent). The pad drained the battery notwithstandingg that I was on ehu.
I shall not use it again. Shall do as Gromit says. Shall also insulate tank when weather permits.

Enjoying posh hotel tonight courtesy of daughter. Nuevo outside. Minus 3 already. So gas heating on to prevent dump valve activating. Can't I just tie it up to stop it opening?

This isn't progress!!! Shall post again when home at cweekednd. Meanwhile, I really appreciate all above contributions.
Cymro

Cymro wrote:The pad drained the battery notwithstandingg that I was on ehu.

There must be a fault somewhere. The spec for the EC500 shows that it can supply up to 25A, split between battery charging and habitation load. The heating pads only take 4Amps (according to a post above) so there is no way that the charger/power supply will not keep up with that. Also, the EC500 is set to cut off all habitation load when the leisure batter drops to 9V so, provided the power to the heater is supplied via the EC500, there is no way it should have dropped to 2.5V. I cannot see this as anything other than a fault in the system.

Thanks Mojo - but mine is the 328S system. Should that sustain a similar drain when on mains and using the heating pad?

Incidentally, just been to see van having left gas heating on low overnitght - snug inside so dump valve didn't open. Fascinated to see icicles below the outside flue!

Leisure battery coped fine with overnight heating - shows 12.3v this morning.

Pretty cold here in mid-Wales!

Hope to find a signal so as to post this.

Cymro wrote:Thanks Mojo - but mine is the 328S system. Should that sustain a similar drain when on mains and using the heating pad?

Incidentally, just been to see van having left gas heating on low overnitght - snug inside so dump valve didn't open. Fascinated to see icicles below the outside flue!

Leisure battery coped fine with overnight heating - shows 12.3v this morning.

Pretty cold here in mid-Wales!

Hope to find a signal so as to post this.

According to Sargent the EC325/328 has a 25amp 3 stage intelligent charge routine which presumably means it will supply up to 25 amp of charging and reduce as it sees fit as battery voltage rises. (battery management so that it can be left on charge all the time and monitor itself) You just need to select which battery. When the van is laid up for a while I leave it on vehicle battery and just give the leisure battery a bit of charge occasionally. If I'm using the van I let it default to the leisure battery as it takes weeks for my vehicle battery to drop significantly
Not sure what type of dump valve you have. I have the Webasto system so is probably different from yours. But when I had a Truma system, I like many others put a clothes peg on the red knob of the dump valve to stop it dumping too soon. I think it dumps at about 4 degrees but cant be reset until the temperature surrounding the valve is about 8 degrees.
However you may have a different system and if you use this method you need to be sure that its not cold enough to freeze as of course the dump valve protects the heater from freezing.
Dave