2021B Micro Minnie - heating the tanks info

[backtrack15]

I had to diagnose a furnace issue yesterday. While I was in there looking around, I noticed that there was not a duct to heat the underbelly (tanks) on my trailer. The 2021B trailers (built 8/2020 or later) have electric heating pads on the tanks. I was told that the electric heaters were "in addition to" the standard furnace duct, but that is obviously not the case on my 2100BH.

The electric heaters are fine if you have outside electricity (something I have most of the time), but at ~15 amps (three at ~5 amps each when running) they are an unwelcome burden for folks who go boondocking in cold weather.

I asked Winnebago about this and the response was that the "larger" trailers still had the duct into the underbelly. I'm not sure what that really means, so... if you plan to boondock in cold weather, please confirm your Micro Minnie trailer actually has a furnace duct into the underbelly.

Winnebago appreciated the feedback and the engineer said he would look into getting a duct plumbed into the underbelly on future builds.

[creativepart]

Originally Posted by backtrack15

Just to add to this thought: I recently discovered that (in contrast to what I was told) my specific trailer does not have a furnace duct into the underbelly to heat the tanks.

As an FYI- in most cases they don't actually put air ducts into the underbelly. They route the RV's regular heater ducting that is under the floor around the tanks to indirectly warm the area.

The Winnebago website for your TT says it offers:

Heated and enclosed tanks

No doubt this is proven true by the routing of heating ducts around your tanks and the electric pads on your tanks, as well.

On some RVs with fully enclosed underbellies the ducting is provided by routing hot air from the heater between the floor and the solid sealed underbelly. Winnebago does not do this. Some models of Arctic Fox TTs do or did at one time.

Some motorhomes with basement compartments do have one or two ducts on each side that lets warm air from inside the coach circulate down to the compartments.

Heating pads do use a lot of power - any electric item that produces heat uses a lot of power.

Both ducting the runs around the tanks and heating pads, can only do so much and do not make a RV 4-seasons livable/usable.

[creativepart]

Originally Posted by backtrack15

Winnebago appreciated the feedback and the engineer said he would look into getting a duct plumbed into the underbelly on future builds.

I wonder why they said this to you? I don't think they directly heat tanks via any dedicated ducting servicing the tanks on any TTs or most motorhomes.

I've have seen people comment that they do this on some of their Class B Vans. But in some cases all of the plumbing and the much smaller tanks are all located inside the conditioned interior. Certainly not all of their Class Bs, but a couple mention directly heated tanks.

A Micro Minnie only has an 18,000btu heater I can't see how that could heat the interior and directly heat the tanks. Especially since it's not a sealed underbelly.

[backtrack15]

I don't have direct knowledge of the heating situation for the pre-2021B models (have not opened the access panels on them myself), but I have a friend with a 2020 2108TB that tells me there is a furnace duct that heads down through the floor (I think it is below the bathroom sink). There is no other purpose for this duct, as it does not "reappear" anywhere else in the camper. I've also seen a post or two here somewhere reporting a similar duct on prior models.

The Micro Minnie tanks are covered on the bottom side with chloroplast, so there is a small volume into which they could (and I think they previously did, based on the above) throw heated air.

But, maybe they never had a duct to the underbelly... My old fifth-wheel had one. I thought my friend's older 2108 had one. I asked the Winnebago support lady if it had one and she said yes... so I was just surprised to see that it didn't.

Regarding the furnace, these trailers are so small that even our little electric space heater (electric hookups are common in TX) has been able to keep the interior at 70F overnight (low of 32F outside).

[tinglett]

Yep, the access panel under the bathroom sink on the 2019 2108DS for sure has this duct. From the left (through the bathroom wall to the furnace that's under the fridge) are two ducts. One duct goes into the floor, and the other duct is attached to the access panel door which is the vent that heats the bathroom. The water heater bypass valves are also in this space.

Here's a photo, but the duct coming forward into the access panel is obscuring the one going into the floor. Next time I get in there I'll take a better shot of this.

[creativepart]

Let me try to understand. The duct terminates with an outlet into the space between the floor and the underbelly OR does the ducting just run through that space to some other floor register inside the livable space?

[backtrack15]

There are no floor registers in the MM. I expect it terminates just inside the underbelly. They probably count on the few large holes in the floor for the drain pipes etc to act as pathway for displaced air to get back into the trailer.

[creativepart]

Originally Posted by backtrack15

There are no floor registers in the MM. I expect it terminates just inside the underbelly. They probably count on the few large holes in the floor for the drain pipes etc to act as pathway for displaced air to get back into the trailer.

I don't follow this. As I described the way "heated tanks" usually, almost always, work inside an RV is the ducting that delivers heated air from the furnace directly into the interior of the RV is routed around and near the tanks. The radiant heat from the ducting passing through the area heats the tanks - not via open ducts or "registers" on those ducts leading into and through the underbelly.

Feel free to correct me if you've got heating supply ducts from your heater running directly into the underbelly that are open to directly deliver heated air to the tanks. It would be the first time I've heard about this and it would be helpful for me to know about.

[tinglett]

I haven't done anything to open mine up from underneath so I can only say so much as to where this duct goes. But the tanks are directly under, and as backtrack15 says, there are no other ducts coming up from the floor.

The furnace ducting on my unit is super simple. The furnace is under the refrigerator and has a duct directly out the front. Then it has a duct out the right side going into the bathroom that divides into the floor and out the access panel to heat the bathroom. There aren't any other divided spaces that would need heat. As far as I know there is no duct that joins in with the A/C ducts that run above the ceiling. Perhaps that's a shame, but then again it would need a lot more fan to move the air, I'd think.

[SonofBert]

Originally Posted by creativepart

I don't follow this. As I described the way "heated tanks" usually, almost always, work inside an RV is the ducting that delivers heated air from the furnace directly into the interior of the RV is routed around and near the tanks. The radiant heat from the ducting passing through the area heats the tanks - not via open ducts or "registers" on those ducts leading into and through the underbelly.

Feel free to correct me if you've got heating supply ducts from your heater running directly into the underbelly that are open to directly deliver heated air to the tanks. It would be the first time I've heard about this and it would be helpful for me to know about.

My 1706fb (with "Offroad Package" and "Heated Enclosed Tanks") the furnace ducted into the bathroom probably has a T-fitting under the sink that dumps heat into the underbelly. Probably a dead end heat dump into the underbelly and I'm not gonna pull the access panel under the sink to view it, don't want to risk detaching the bathroom furnace duct.

The furnace probably shunts some hot air around the tanks along with the bathroom heat but I think 12v heating pads are more effective. 12v heating drains batteries but in the rare times camping below freezing for extended times heating pads seem better. The big deal is the enclosed insulated underbelly. We've wintered in AZ and NV for years offroad in the desert, open desert December through February overnight temps often are in the 15F-20F range. Just having enclosed foam insulated underbelly is the big deal.

[backtrack15]

At the end of the day, I believe there was a philosophical shift made for the 2021B Micro Minnie models. If you have a Micro Minnie with electric tank heaters, please don't assume you'll get any heating of the tanks from the furnace like the pre-8/2020 models. Please confirm the existence of the appropriate duct first.

[Old Navy]

Originally Posted by backtrack15

at ~15 amps (three at ~5 amps each when running) they are an unwelcome burden for folks who go boondocking in cold weather.

Not sure how effective the heaters are, but if you can budget 15-30 amp hours, that's 1-2 hours of running. I would hope that would be enough. Is there any timer or thermostat control or is it just an on/off switch? With this and the 12V fridge, maybe Winnebago should start offering a lithium/solar option on these new trailers.

[backtrack15]

Originally Posted by Old Navy

Not sure how effective the heaters are, but if you can budget 15-30 amp hours, that's 1-2 hours of running. I would hope that would be enough. Is there any timer or thermostat control or is it just an on/off switch? With this and the 12V fridge, maybe Winnebago should start offering a lithium/solar option on these new trailers.

It’s a simple switch that sends power to all three. They each regulate their own temperature, turning on at 45F and off at 68F. So theoretically they are only on intermittently. It’s probably a good idea to ensure you have a few gallons of water in all three tanks while using them.

[tinglett]

We have a bit of a heat wave today (high 40's) so I got into the camper. Here's a photo of the heat ducting into the floor. As you can see, it's a pretty small duct. I tried to get down in there further to see how the duct splits from the other duct you see, but it's a tight space in the bathroom to get a camera in there . Note that the panel you see to the left is the access panel cover that closes this space off. I found that this tiny duct really ends right there at the floor. That is, you can lift it out, and there is a fiberglass-like meshy stuff there that it's blowing into.

If I was really planning to use water out in cold weather for long periods of time, I think I'd also want temp sensors in the tanks so I could know where I was at. At this point, I don't think I'd trust this setup other than to get through cold nights and reasonably warm days.

[creativepart]

OK, thanks so much for that. I learn something new every day.

[backtrack15]

Originally Posted by tinglett

... I found that this tiny duct really ends right there at the floor. That is, you can lift it out, and there is a fiberglass-like meshy stuff there that it's blowing into.

Thank you for investigating this. It looks like something I could replicate on my 2100BH since the furnace has additional output ports available and there is quite a bit of room to work forward of the furnace. I just need to "pick my spot" carefully.

[Rick 99037]

An interesting discussion. If my motorhome had a heated area around the tanks from the furnace, I'd expect a very limited increase in protection from cold. I'd also point out a weakness in this concept. Unless there was a temperature sensor down by the tanks, that could activate the furnace, and there won't be; the furnace would only activate when the living space needs more heat. So heating the tanks is almost an afterthought, and unregulated for temperature at all. Assuming this tank area is sealed from the outside, a fan that pulled air from the living compartment, through this tank zone, so then helping to equalize the temperatures, might be helpful, and such could be triggered by a well placed temperature sensor too. It would require both an inlet from, and exit bake into the living area. For those w/o a heat duct to this area, this could be an answer for them as well. (If the furnace was on, and set, that is.)

For me, this is all academic, for on my unit, the tanks are quite visible in their plastic glory underneath, so I know if mine got cold, if they didn't rupture, I'd be waiting till spring to empty them.

[NV_Camper]

Since I used this post as a reference when researching I figured I would update with my experience. I just picked up a 2022 2100BH with heated tank pads and the heater vent hole under the shower is just a cover panel now and behind it there is a duct going into the underbelly.