Installing a Fantastic vent with proper sealant

For what it's worth, i have a Hong knockoff of a FantasticFan in our unit. It came with only one speed and direction. I found a 6 ohm wirewound resistor rated or 25 watts- a big honker. I replaced the old single pole switch with a SPDT switch. One side runs straight voltage for high and the other side goes through the resistor for low. Since the resistor does get warm (but not hot), i attached it inside a small steel pancake fixture box which not only protects the RV from the heat but also acts as a heatsink for the component. Just like that, I have a two speed fartfan. It consumes nearly half the current on low too (about .7A) - despite the resistor warmth. Perfect for remote boondocking. But I wasn't done! I also added a DPDT switch which i cross-wired to enable instant fan reversal. Why reverse an RV fartfan to blow in? Because when you flush the can with the fan sucking air out, much of the air it sucks up is drawn out of the biffy and brings with it that wonderful black tank aroma. That's why! I also didn't want to use an oscillator circuit which was suggested here as that tends to cause radio interference.

Well, I just had a new rubber roof installed on my camper and I purchased a 4000R FF. I've always loved them. They installed it for me and did use the gasket with Dicor on the screws and around the edges. I'll keep a close watch on it! I was going to do all the vents myself but when I went to pick up the camper yesterday they had installed all new vents and tank vent caps! Love it, but unless I do something like this myself I'll always worry that they may not have sealed them just the right way or the way I do!

So, that said, If in fact it does leak I can at least go back to them to fix it... Hope that doesn't happen! I HATE leaks!!

As I said before HMS Beagle, GREAT work. That's the kind of work I would like to have seen on my roof, but alas.... :)

Dak

Sorry guys, but the day I replace an Air Conditioner with a vent fan is the day I quit camping. I've had to sleep with power outages in the middle of summer. Never again!!!!
These tiny boxes with four wheels get real hot in the sun. I'm so glad God invented Air Conditioning... :):R:B:C
Happy trails,

Will you marry my husband? It seems the two of you were made for each other ... :B

OVERSIZE LOAD wrote:
I personally would not have used the 3m fast cure adhesive sealant. that is pretty much permanent. if that fan quites in a few years then it is going to be very difficult to remove. but that's just my opinion. what you did was a very clean install.

The 3M products come in a range of strengths. 5200 is very tenacious (700 psi), 4200 less so (300 psi), and 4000UV about the same. With some diligence and debonding products, even 5200 can be removed, but it takes a lot of patience.

Also, the Fantastic fans seem to last much longer than a few years, and the fan is replaceable without removing the flange if that is ever necessary.

I would not use it on a TPO roof though until I had determined that it is compatible with that material. Removal from any sheet type roofing might be difficult, since the polyurethane may be stronger than the sheet.

installing mine i put eternabond around where the fan would sit, screwed it down, then used dicor to secondary seal it over the screws and edge.

HMS Beagle wrote:
Thanks.

I did not use the foam gasket. I would not use any gasket in this application and the one provided is polyethylene foam which it seems to me is particularly unsuitable. If the roof was crowned enough to require something other than sealant it should be filled with something solid and shaped to the crown, then wet sealed without a gasket.

Gaskets generally work if the flange and the surface are stiff enough to retain some clamping pressure between the fasteners over the long term. The flange is certainly not stiff enough, and the roof is suspect!

John I'm so glad I found this thread. Love the detail and your description is fantastic ( no pun intended ).

Six months ago I removed my rooftop air conditioner and replaced with another Fantastic vent also. I followed the instructions and used the foam gasket and used Sikaflex 11 PU around the outer joint, which is the only seal apart from the foam under the flange.

Sure enough, it has leaked, but not real bad. No staining on the lining of the ceiling. My fiver is a small Okanagan with grey carpet on the ceiling, and a polystyrene & ply roof with TPO on the top.

I have managed to get the vent out, not real hard, but the difficult part was removing the Eternabond which I placed after I found the leak ! It's all back to square one now and I have installed new spacer timbers as the hole was a little large for the Fantastic vent. I have secured these well and they are screwed and sealed with PU adhesive.

Because the TPO roof does not cover the top of the timber spacers, I intend to place Eternabond over the TPO and timber. Strips of about 50mm should do. Then I intend to mount the Fantastic vent directly on the Eternabond, I hope that makes sense. I will use the scourer supplied with the Eternabond to roughen up the surface of the tape before I mount the vent with the PU adhesive and screws.

Can anyone see any issues that may arise before I finally fit the vent in a few days ?

Best wishes

Pat

I personally would not have used the 3m fast cure adhesive sealant. that is pretty much permanent. if that fan quites in a few years then it is going to be very difficult to remove. but that's just my opinion. what you did was a very clean install.

Mice job! I did the bathroom fan with a fantastic fan but I opted for the foam gasket and just siliconed with dicor like crazy... The old vent has the putty tape and that was a real pain to clean.... If I have any problems I will definately go with what you did....

Mike

Well that got me thinking: it must be looking for a high current (or low voltage) on the motor circuit. I could install a power resistor in series with a diode, paralleled with the motor, so that UP it would stop but DOWN (current reversed) it would run and shut for the rain sense. But I would still have to pull the knob out then push it back in every time I adjust. I guess I ought to just buy one "take it out of the box" and see what I could do with it.