Converting an A/C Unit to a Vent Fan

[Colonel Monk]

Howdy all:

So I have a non-working A/C unit on my old 32-foot class A which is equipped with two A/C units, one fore and one aft.

I don't really need that kind of cooling power where I live and I want to replace the non-functional unit with a Fantastic Fan.

The rub is that the A/C unit is 120v AC and the vent fan is 12v DC. I have an inverter so my 120AC circuits are always hot.

I'm wondering: is there a commercially available "converter" that is of small size that can be mounted at point of use to provide the 12V and 4 amps of power required by the fan?

If not, a slim-line "wall-wart" adapter could be used to provide the 12V. It just wouldn't look as nice....

I do realize that 12v DC power could be run to this vent opening, but I don't relish the thought of fishing wire through the roof of this RV.

Has anyone done this?

Regards,

CM

[RV Mech Tech]

CM: any type of 'converter' would be a type of step down transformer and would give off heat, so you would not want to conceal it in the roof. Another alternative and one that I have used when doing other similar jobs is to tap into an available 12 volt circuit nearby (being careful not to overload that circuit), and run the wire through or under some type of molding and direct it to the fan. This would be mounted on the surface. Residential electricians use 'Wire Mold' for 110 volt circuits when they cannot go through walls to install wiring such as in a condominium (concrete walls). This molding is approved for use for high voltage wiring and it's expensive, but you can use another type of molding or cover. In all cases, protecting the wiring for any voltage is important as fires can be started by low voltage wiring as well. This would be a simple and less expensive alternative to going through the ceiling in an RV. Also your A/C unit will have a 12 volt supply wire to the control board, but the gauge may be too small to supply power for the fan (this would be part of the thermostat wires going to the control board in the A/C).

[Colonel Monk]

RVMT:

Right, I had not thought of that! The wire mold would be an easy way to bring 12V there without drilling and fishing.

I'm going to look into that.

CM

[RV Mech Tech]

CM: also you will have that high voltage wire there for the A/C. If you just want to cap that circuit off and the wire is not in a junction box, then thin plastic electrical boxes are available at Home Depot or an electrical supply store. All high voltage wires have to be capped off and in a junction box to prevent shorting out. These are about half the width of a regular house electrical junction box and I have used these in RVs especially in the walls where you have almost no room. These boxes are made for electrical work in houses built in the 50s and 60s where there is very little room between the outside brick and the inside of the interior wall. In some cases, a regular metal junction box will touch the wall and these thinner plastic boxes are perfect for those and RV applications.

[Colonel Monk]

Thanks for the tips!

I'm gonna check out the breaker box and see if by some miracle the circuit has its own breaker. If so, I could also just pop out the breaker and de-energize it. Who knows? At some point someone might want to use it again.

Regards,

CM

[RV Mech Tech]

CM - it does - usually 20 or 30 amp and if you have two A/C's it may be a tied breaker for both A/C's - if one A/C is a lower BTU (bedroom) then you may have one 20 amp and one 30 amp breaker (usually front A/C) and the wiring will be a 12/2 12 gage wiring- 20 amp or 10/2 10 gauge wiring ( you have two A/C units so this is more than likely what you have) - you cannot use that wiring for a standard circuit (14/2 15 amp) as it will be overrated for any standard appliance - for example - a standard microwave can use a 15 amp 14/2 gage wiring but a combination convection/microwave will need at least a 12/2 gage 20 amp circuit - best to cap it off if you can - if you do not have the room at the ceiling location to install a junction box the electrical supply shops will have a smaller version that electricians use for confind areas such as alarm system panels or electrical house entrance panels -check this out if you need one.