12 Volt Tank Heaters

[moosetags]

While watching the Colonial Airstream video featuring the new Flying Cloud 20C Bambi, I became aware that Airstream is now offering 12 volt tank heaters for winter camping.

That is an interesting concept that seems like it would be a major plus for winter Airstream use.

Brian

[Al - K4GLU]

The 20 has always had 12V tank heaters due to the fact it does not have ducted heat which can be directed over the tanks.

[AWCHIEF]

My 2006 Safari 23 also has 12 volt DC tank heaters. I thought they were common for modern Airstreams without ducted air. I have used them while plugged in to 120 AC. I feel a feeling that they would suck a battery down quickly using 12 volt DC only.

[Antique Pedaler]

Our '05 Bambi had them.

[idroba]

On my 20' FC there are two 12 volt tank heaters, one for the fresh water, the other for the gray water. The black water tank is above the floor so it needs no heater.

Each heater takes about 3 amps and are thermostatically controlled, but at what temperature is unknown.

Yes, they will draw the batteries down pretty quickly if boondocking.

[369goose]

How would I know if my 2014 FC has this heat option on the tanks?

[Al - K4GLU]

Originally Posted by 369goose

How would I know if my 2014 FC has this heat option on the tanks?

This is not a option. It is standard in the smaller trailers without ducted heat and the switches are in the bathroom - at least they are in the 20.

[TurboDog]

Has anybody actually used the tank heaters? We are getting ready to head out in our '08 20' Safari. The manual was a little ambiguous, saying all but the 22 and 23 had ducted heat, but then mentioned tank heater pads for 22-23 only. This series of posts above confirm what I suspected, the 20 is also unducted. So has anybody used the electric tank heaters while boondocking? I have solar to charge quickly in the morning, but don't want to lose cabin heat in the middle of the night. Thanks for any info!

[idroba]

I was just looking at my measurements of 12 volt power used in my 20' and see I don't have the numbers for the tank heaters. However I did measure them at one time, but my memory is my only record. I think they took about 3 amps for each one.

So, a 6 amp load for the two (gray water and fresh water, the black water tank is above the floor under the toilet).

In cold weather they would be running constantly. So, lets say a 10 hour use.

6 amps x 10 hours = 60 amp hours. Your battery capacity assuming the original batteries is about 75 to 80 amp hours each, or 150 to 160 total, and you really don't want to run them down below about 40% of capacity, so really you have about 60% of 150 = 90 amp hours useable.

So, the tank heaters plus some furnace load plus lights etc would most likely pretty much drain your batteries overnight. You would need a pretty substantial solar system to recharge that kind of a load during the day.

In addition, the exposed drain pipes underneath, gray and black water, have liquid in them and are not protected at all by the tank heaters and can easily freeze, so the tanks cannot be drained.

The idea sounds good, but in actuality the tank heaters are pretty much a bust in my opinion, for boondocking at least.

[TurboDog]

Thanks, Idroba, exactly what I was looking for and good point about the drain pipes themselves. My panel charges at maybe 7 amps max, so I'd probably get a little farther behind each day. I suspect I will spend today winterizing instead...

[BoldAdventure]

Originally Posted by idroba

I was just looking at my measurements of 12 volt power used in my 20' and see I don't have the numbers for the tank heaters. However I did measure them at one time, but my memory is my only record. I think they took about 3 amps for each one.

So, a 6 amp load for the two (gray water and fresh water, the black water tank is above the floor under the toilet).

In cold weather they would be running constantly. So, lets say a 10 hour use.

6 amps x 10 hours = 60 amp hours. Your battery capacity assuming the original batteries is about 75 to 80 amp hours each, or 150 to 160 total, and you really don't want to run them down below about 40% of capacity, so really you have about 60% of 150 = 90 amp hours useable.

So, the tank heaters plus some furnace load plus lights etc would most likely pretty much drain your batteries overnight. You would need a pretty substantial solar system to recharge that kind of a load during the day.

In addition, the exposed drain pipes underneath, gray and black water, have liquid in them and are not protected at all by the tank heaters and can easily freeze, so the tanks cannot be drained.

The idea sounds good, but in actuality the tank heaters are pretty much a bust in my opinion, for boondocking at least.

Sounds that way for sure.

But depending on how full they are, and if the temp only drops at night below freezing, then they shouldn't freeze based on size and thermal mass. The larger the volume of water, the longer it takes it to freeze. So if it's just dropping below freezing at night and say coming up to 40 in the day, you shouldn't have a problem and would only need to run it a bit perhaps.

[TurboDog]

Thanks for the input folks. We cancelled, but I just went out to get some current numbers. I'm running a Morningstar Pro-Star solar controller that shows load amps. Flipped on the tank heaters and with both heaters on they settled to 10 amps after an initial slightly higher surge, which is to be expected. I did discover they must be two different sizes (or maybe blk/gray each have a pad, but going to same switch?), as fresh tank by itself is about 3.7 amps, bk/gy around 6.5 amps.
Either way, without dropping below 40% on the batteries, not going to make it through the night. I wonder how critical that 40% number is for the life of the battery?
On a related note, I highly recommend the ProStar. It not only works well, but when we rolled our truck and Bambi a few years ago the faceplate on the solar controller got scratched up. I emailed Morningstar, told them I'd like to buy a faceplate and they swapped out a brand new unit at their expense. Way above and beyond for customer service.
BTW, I don't recommend rolling your rig as a way to upgrade.