Air circulation in Scamp 19 Deluxe

[Paul O.]

I am trying to solve the problem of getting warm air to the loft of my 19' Deluxe. We just came back from a four week trip from VT to AZ. A few nights were below freezing, one down to 10F, and the loft was COLD!. When the heater is on, the natural air circulation is insufficient. I now have two 12V, 3 inch dia. blowers (from old PC power suppplies that I saved years ago) mounted inside the large storage compartment, above the shower. They move plenty of air which exits through the open doors of the compartment. I plan to cut one more 3 in. hole to distribute the air via the side compartments as well. My question is this:
How can I wire the blowers so they only operate when the Suburban furnace blower runs?
The two blowers together draw about .35Amps.
Has anyone done something like it? TIA
Paul

[Paul O.]

Well, I found a way that seems to work quite well. I did not want to touch any of the furnace wiring for fear of causing problems in operation, and I don't want to become a self-taught RV furnace tech and have my life depend on it!
The key part is a "make on temperature rise" switch, like those that turn on blowers in kick-space heaters or fireplaces. The one I happened to have turns on at 130F, off at 110F. It is mounted with a spring and wire on the end of the furnace vent pipe, near the outside wall. When the furnace warms up, the fans turn on. It takes about 1 - 2 minutes after the furnace started. When the thermostat turns the furnace off, it takes about 5-6 minutes for the vent pipe to cool enough for the fans to turn off. The wiring goes through the cabinetry on the port side of the Scamp. I can post pictures of the setup if anybody is interested. I tested it a few times yesterday and today and I hope my DW likes it if we go camping in "spring" again.