Small scale heat tape project -- is this possible?

[profdant139]

We just spent a week in the Sierra, with single digit temps at night -- I was able to avoid frozen pipes by getting up every couple of hours at night to run my DIY crude-but-effective hot water recirculating device.

We figured out that the problem area is where the fresh water hose emerges from the tank, under the trailer, and runs to the interior of the trailer. As a stopgap, I used an old electric heating pad wrapped around the pipe, powered by an inverter hooked to my spare battery. It worked, but this is not a permanent solution.

So here is my plan: first, I am going to enclose and insulate the underside, of course.

Second, we need to warm just that particular pipe. It is only about three feet long. I want to put some heat tape on that pipe and then insulate the pipe and the tape. I will power the tape with my spare battery.

Is that doable? Is there a way to have a low wattage heat tape on a particular pipe? If the wattage is low enough, the battery can handle the load just fine. I don't want to heat the pipe up to room temperature -- keeping it just above freezing will be enough.

I think I don't really need a thermostat -- I can start it and stop it manually.

I understand that this solution will not work below zero, or where the daytime temps never get above 20 degrees. Under those conditions, the whole fresh water tank will freeze.

I don't care much if the gray water and the black water tanks freeze. The waste water dumps into them just fine. When we need to dump, we are almost always in a much warmer place at a lower elevation.

Thanks in advance for your advice!!

[SteveAE]

Don, Good catch. Thanks for keeping me honest (written early in the morning when I was worried about my dog in surgery)

pianotuna wrote:
power goes down by the square of the voltage.

120 x 120= 14400
12 X 12 = 144

So heat output at 12 volts is 1/100, not 1/10.

SteveAE wrote:
Here's another thought.
I have never tried this, but I see no reason why it shouldn't work for the temps you experienced as long as you insulate the pipe.

Wrap the shortest Home Depot heat tape around the pipe (they are intended to be laid on the pipe, not wrapped) and power it with 12 volts. No, it won't get as warm (it will get about 1/10th as warm....maybe a little warmer since you wrapped it), but if you leave it on all night and your pipe is insulated, I suspect that you will be fine for temps into the single digits. And, if it doesn't work, then simply just power it with your inverter (120 volts) and use a timer to cycle it on/off.

[grizzzman]

I bought 3 meters of heat wire that responds to outside temps. The risistance changes
With temp so no thermostat and it’s 12 volt. I found it on eBay . Cost under 7.00
From China .

[profdant139]

piano, that is a good point -- I will have to monitor the temp to make sure it is just high enough to prevent freezing. I have a remote sensor thermometer -- I use it for my barbecue and smoker -- so I will stick the probe in under the heat tape and look at the remote readout to verify that I am getting enough heat.

It looks like the Annod line of products may be the way to go -- they have plug and play heat tapes, if I am reading their website correctly.

If I get this work-around set up properly, it will mean (ultimately) that I have a 3.5 season trailer -- not a true 4 season unit that would be good enough for Canada in mid-winter, but good enough for (say) the Eastern Sierra in late autumn and early spring.

[pianotuna]

power goes down by the square of the voltage.

120 x 120= 14400
12 X 12 = 144

So heat output at 12 volts is 1/100, not 1/10.

SteveAE wrote:
Here's another thought.
I have never tried this, but I see no reason why it shouldn't work for the temps you experienced as long as you insulate the pipe.

Wrap the shortest Home Depot heat tape around the pipe (they are intended to be laid on the pipe, not wrapped) and power it with 12 volts. No, it won't get as warm (it will get about 1/10th as warm....maybe a little warmer since you wrapped it), but if you leave it on all night and your pipe is insulated, I suspect that you will be fine for temps into the single digits. And, if it doesn't work, then simply just power it with your inverter (120 volts) and use a timer to cycle it on/off.

[profdant139]

Excellent suggestions -- thanks!

And yes, we do like it cold -- it is a refreshing change from Southern Calif. This time it got a little too refreshing -- the temp inside the trailer was 28 degrees on our first morning! We were comfortable -- two down comforters and three blankets. We slept for nine hours -- unheard-of.

We turned the heat on before breakfast, also a rarity.

The rest of the week, the temp inside was in the mid 30s in the morning -- positively balmy.

The campsite was at 7500 feet, not far from Tioga Pass. The canyon funneled the cold air off the mountains and down into the valley below us.

For some reason, we were the only boondockers for miles around . . . . 😉

[SteveAE]

Here's another thought.
I have never tried this, but I see no reason why it shouldn't work for the temps you experienced as long as you insulate the pipe.

Wrap the shortest Home Depot heat tape around the pipe (they are intended to be laid on the pipe, not wrapped) and power it with 12 volts. No, it won't get as warm (it will get about 1/10th as warm....maybe a little warmer since you wrapped it), but if you leave it on all night and your pipe is insulated, I suspect that you will be fine for temps into the single digits. And, if it doesn't work, then simply just power it with your inverter (120 volts) and use a timer to cycle it on/off.

[SteveAE]

Dan,
I understand. Just looking for other options that might help.

Yes, heat tape will work. Heck, just get a short length of 120 v tape at Home Depot, cut the thermostat off, and run it from your inverter. Losses really won't be that much, especially if your inverter is controlled by a timer so it is only on for a couple times a night, for an hour or so at a time. Don't forget to insulate the pipe or all this will be a waste. My experience is that it doesn't get too hot for fex type plumbing.....even when then that plumbing is insulated.

As to your recirculating system, am guessing you just have a valve that you open and close by hand. If so, you could replace that manual valve with one that is controlled by a solenoid (~15.00). Then just use a timer (unknown price as I built my own) to activate it.

Another thought. If I remember correctly, you prefer to save battery power by keeping the inside of your trailer cool (er, cold) at night. Perhaps if you heated the inside of the trailer, maybe even directed some heat into the problem area with a fan, and insulated the pipe, the problem would go away. Yea, I know, the darn furnace draws a lot of power.....much more than heat tape does. So just install a Wave Heater (and an second CO detector). Not only "might" your freezing problem go away, but no more cold noses and toes too.

You can use the thermostat you cut off the heat tape to control a fan (it's just a switch).

[Tiger4x4RV]

Another silent option is to use chemical handwarmer packs at critical places. They last all night. They've gotten the Tiger's plumbing through several very cold Eastern Sierra nights.

[profdant139]

Thanks for all of those links -- lots to think about! Steve, yes, the area in question is within my recirculation zone, but I do not want to have to get up every two hours at night and run the hot water. It is no fun to stand in the freezing cold and dark for five minutes, hoping I do not wake DW. I want the tape to do the job silently, and then I will recharge the battery in the morning.

[pianotuna]

Hi,

You do need a thermostat, or the self regulating tape type which is cut by the foot.

[SteveAE]

Is the trouble area included in your recirculation loop?

[Chris_Bryant]

Lots of 12 volt choices- I like ptc (positive temperature coefficient) type self regulating, like this by the foot heat tape. 5 watts per foot, cut to fit.

[time2roll]

Instead of inverter sapping power just put the 12v right on the pipe.

https://www.annodindustries.com/shop/ultraheat-am-ph-513-rv-pipe-heater.html

Just 2 amps, maybe 4 if you have two of them.

Themostat:
http://senasys.com/product/12-thermostat-switch-430-301a985-l

Insulate for more efficiency.