Foretravel Owners' Forum For owners and Fans of Foretravel Motorcoaches September 13, 2025 ...

PLENUM IN WATER BAY, WINTERIZING

September 03, 2017, 06:04:22 pm

I put two fans in the water bay to spread warm air around, but does anyone know if this is necessary?

Did Foretravel install a warm-air hose from the furnace to inside the hidden regions of the water/utility bay? I assumed not, so I installed two 120VAC fans that are energized by a thermostat in the water bay, as follows:

- Left side:
Behind the utility wall, at the sealed bulkhead area of the black and gray tanks.
  Foretravel put a passive vent there but I believe this is not sufficient in very cold weather, so I installed a fan that forces air into the area.

- Right side:
  Below the manabloc and black / gray water tank:
  See attached photo of my cigar box plenum (I don't smoke), which moves warm air from the front side of the bulkhead to the rear side, since I can only see a furnace duct pointed at the water pump. That warm air needs to be pumped past the bulkhead into the rear manabloc area.

In any case, I share a few photos of the right side. Not pretty, but my water bay smells like cedar.

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Re: PLENUM IN WATER BAY, WINTERIZING

Reply #1 – September 03, 2017, 06:14:10 pm

My 1993 U300 has heating ducts going into the wet bay in several places. I have a very small electric heater set to the lowest setting plugged in whenever we're in areas where it is possible for the temperature to drop to below 40*F. Don't know if it actually comes on or not, but so far we've never had a problem with anything freezing.

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Re: PLENUM IN WATER BAY, WINTERIZING

Reply #2 – September 03, 2017, 08:32:27 pm

I have heat ducts in mine. But in the winter I add 1 ceramic 1000watt heater in each side. I am always connected to 50amp service.

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Re: PLENUM IN WATER BAY, WINTERIZING

Reply #3 – September 03, 2017, 09:19:06 pm

We use small heaters in bays.  Lots written on Forum with members using Lasco 200 watt Personal Heaters.  We have four of them down in bays with a manual switch to turn them all on at one time.  We do have remote wireless thermometers to know what is going on without opening bay doors.  In real cold weather big pieces of Reflectix seal in the heat behind water compartment bay doors.
Yes our propane furnace has small diameter ducts that reach selected areas, but only when furnace runs.

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Re: PLENUM IN WATER BAY, WINTERIZING

Reply #4 – September 03, 2017, 10:46:55 pm

Our 99' U270 has three heater ducts in the utility compartment, two on the street side and one on the curb side that comes down over the top of the fresh tank part way down the side and blows in the general direction of the pump. On the street side there is one duct with a vent in the utility wall, and the other one that is just a length of 2" duct that blow into the area behind the utility wall where the waste piping is.
Don

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Re: PLENUM IN WATER BAY, WINTERIZING

Reply #5 – September 04, 2017, 07:17:24 am

We have outlets similar to Dons in our 270.

With your battery capacity and solar array take a close look at Barry's solution.  We use three Lasko 200w with thermo cubes.  One on each side of the wet bay and one in the electrical bay (lithium).  Each area has its own remote thermometers.  We haven't gotten close to freezing to date so it is little more than backup. Set the charge alarm for the level you are comfortable with as you can still charge your lithium bank with the genset. The bay temperature will be above freezing.  But 18 has been our low in the desert or anywhere else.

I was also considering a 12v tank warmer under the battery's but hasn't been necessary
We use our heater with no workarounds, i.e. propane catalytic, when boondocking. 

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Re: PLENUM IN WATER BAY, WINTERIZING

Reply #6 – September 04, 2017, 06:11:30 pm

Problem of relying on heat ducts to keep water bays from freezing is that the furnace only comes on when the inside of the coach needs more heat.  Bays get colder than inside of coach and need heat before inside needs heat.  And what does one do if furnace fails to start.

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Re: PLENUM IN WATER BAY, WINTERIZING

Reply #7 – September 04, 2017, 09:03:46 pm

Agreed. Thanks for your replies. If the furnace fails, I have installed two thermostatically controlled, 200 watt 25 ft, 115VAC heat tapes, one on each side of the bay. The 115VAC fans distribute heat around the wet bay.  The cigar box fan plenum helps distribute the heat since the convection currents created by the heat tapes would cause stratification and likely allow the lower pipes to freeze.

The lithium battery bay is sealed and insulated. This bay has a 115VAC fan supplying warm air from the coach.

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