Question on UltraHeat tank heater systems

Question

Greetings.I have a 2011 Carri Lite 37' fifth wheel with double walled black/grey tanks heated by a 4" duct from a 40,000 btu LP furnace. I'm outfitting the trailer for 15-25 degree winters in the mid and north west. While in parks at a 50 amp pedestal, I want to cut back on running LP to heat the tanks, especially since the T-stat is inside and the tanks are outside. I like to use electric heat a lot while in parks. I've reviewed UltraHeat's webside and have a couple questions for those who use these tank heating systems. 1. Should I get the one that runs DC and AC? If it's 20 out the DC would seem to make sense traveling. I wouldn't use it while dry camping, because it looks like it would kill the batts fast. 2. Does this system work with double walled tanks? I'd be sticking the pad to the outside cover, not the tank. 3. I'd leave the 4" LP heat duct to the tanks in place and have that LP heat alternative available if I loose electrical power in the night. I'd set the T-stat on say 50, while using ceramic space heaters and my fireplace inside. I have a heat pump in the living room, but it would be too cold for that. Does my thinking make sense or is there a better strategy to coordinate LP, electrical and UltraHeat systems? 4. Does anyone know if he DC heater kicks on if the electrical power goes out? I ask because this would be good to keep the pipe pads and elbows warm. As long as the power didn't stay off long, I guess the batts could hold out. 5. I'd buy this today and install it soon for next winter. Any thoughts on where the on/off switch should be located would be great. I assume it goes in the coach maybe on the bulkhead wall adjacent to the furnace. 6. I'd get the pipe/elbow pieces. I already let one of my electric valves freeze, so want to avoid that. I wonder if buying a pipe or elbow piece and putting that on the water pump makes sense. My pump is above the underbelly insulation just behind the shower in the service compartment where the cable comes in from outside. I've already had the shower freeze, so I figured I'd just disconnect/plug it off during winter.  Thanks for any thoughts. From what I read, this is a tried and true product. For me, quality/ dependability trump price.  OWB

dave17352 · Answer

I assume there is a air space between the double wall on your tanks. That could be a major problem using heating pads. You are suppose to have a third of a tank of fluid to run the heat pads for them to operate properly the way I understand it. I have heat pads that run on dc in my 5th wheel. I think the pads would heat up way to quick and shut down. Not sure if it could also cause a melting problem. I would check into that first. If you could put a aux fan on the duct running to the holding tank area which would circulate the warm area from the cabin to the tanks that would be the easiest. JMHO

One other thing I leave my final gate valve open in freezing temps just to incase a small amount of fluid leaks from the upline valves. I use a cap with the hose connection on the end. I leave it open. Now if people think that small amount of potential fluid is a problem you could always leave a bucket under it while parked.

boogie_4wheel · Answer

The heat pads cannot be used on a double wall. As Dave said, the tanks are supposed to be partially full to help absorb the amount of heat that they give off.

I have twin 40g holding tanks and bought the 120VAC pads. They did a great job on my exposed tanks in -20*F (trailer was skirted with OSB). If you were to travel, then the combo AC/DC pads could be a benefit, but heating elements work via electrical current and would have the ability to pull the battery(s) down quickly.

They would be powered separately, you would turn on/plug in the AC plug or flip on the DC switch; they will not automatically switch over.

dave17352 · Answer

I was also thinking you may also have problems with water lines by not running your furnace in freezing temps.  These four season units count on the furnace being run. JMHO

outwestbound · Answer

Great info. I saw two points:

1. Yes, my tanks have an exterior wall (shell) that allows fiberglass insulation in about a 7" space around the entire inner tank. A 4" duct from the furnace blows into this insulated space from directly above where the suburban 40K btu furnace is.

A preclusion from using utltraheat would be unfortunate due to double walls, but I can see they wont' work as I'd planned. What if I had the double wall removed, which can be lowered by taking a billion screws out (which I've done to replace a valve), then I could pull down the insulation and stick the heat pads right onto the inner tanks? Then, I'd repack the insulation and screw the outer shell back on. I wonder if this would work or whether the pads would overheat?

2. My Carriage trailer has about 14" between the finished carpeted floor and the insulation below in the underbelly. Under the insulation, there is a typical mesh nylon membrane of some kind. Last winter, I left a 1,500 watt space heater in my basement, which seemed to warm everything above the belly insulation. The cold spot is in the rear living room. Thus, I planned to put a "Y" on the duct going to the tanks and two valves, where I can run an alternate hard 4" duct and push it through the sub-floor back under the living room and I'd lust leave that open on the end. A mechanical contractor who full times suggested this to me and he's seen it done. If I ran the space heater and this living room subfloor 4" open duct, I "assume" that using the electric heaters on the tanks would not result in freezing pipes, as someone mentioned, but I'm not sure.

outwestbound · Answer

Just spoke with Eric at UltraHeat - very helpful person. He said the pads may be installed on the double walled tanks, but I have to remove the outer shell and stick then right on the inner tank. He said they actually are more efficient in this set up. He confirmed that if the electricity goes off, then won't switch over to DC, assuming they were on AC when I go to bed. I remedy this in places were power is suspect, he said just switch it over to DC and go to bed. Worst case, I wake up with dead batteries, but then I could start my generator if the electricity was still out. These sound like great units, so I'm buying 3 AM-M3600 units and some other parts for the lines around the valves.

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