A thought on protecting outdoor HVAC units

[cornutt]

Here's another idea, one that I haven't tried yet but I'm toying with the notion. In my area, we've had a rash of thieves who steal outdoor HVAC units from houses. Especially in mild weather, they figure that they can go to a house that's unoccupied during the daytime disguised as HVAC repairmen, and with bolt cutters they can have the outdoor unit freed on and their truck in seconds. If the weather is mild enough and the system isn't being used, the owners might not notice for a couple of days that their outdoor unit is missing.

Well... I had one of mine open a couple of weeks ago (fan motor bearings were shot), and I noticed that there are two conductors on the LV cable that aren't used. And I thought: "Hey, I can make a red-wire sensor with those." Loop them internally through some piece of metal that has a hole (putting in a grommet first), solder the ends together with an EOL resistor. The corresponding furnace units are in the same utility room with the OPII, so I can find the other ends of those conductors there, extend them over to the controller, and connect them to zones which will be defined as tamper zones. Then, if the bad guys either cut the LV cable or rip it loose from the unit, the alarm goes off. Surprise!

(Of course, I have to remember to bypass this if I call for service... )

 

[BraveSirRobbin]

You man also consider a well placed "pull tab" sensor (I think that is what they are called).

 

[signal15]

You could also epoxy a strong magnet to the concrete pad under it, and mount a wireless reed sensor in the bottom of the unit. If it was picked up or moved, it would alert.

I have a microwave/PIR above my AC unit outside. It's not to prevent AC theft, I just want to know if someone is wandering around in my backyard. Or know if there is a coyote back there.

 

[fabriziojoe]

GRI makes an HVAC Kit just for this purpose.

GRI HVAC KIT

 

[sic0048]

GRI makes an HVAC Kit just for this purpose.

GRI HVAC KIT

Looks pretty cool. Basically the same idea that we have been throwing out here (a wire that if cut will set an alarm condition) but with the extra addition of a tilt sensor. So if the unit is tilted it will also set the alarm off.

 

[fabriziojoe]

GRI makes an HVAC Kit just for this purpose.

GRI HVAC KIT

Looks pretty cool. Basically the same idea that we have been throwing out here (a wire that if cut will set an alarm condition) but with the extra addition of a tilt sensor. So if the unit is tilted it will also set the alarm off.

All of this outdoor detection has me thinking-what about lightning strikes?
The number one item that is burned up in a lightning storm is the AC compressor. So the lightning hits the compressor and then flows back into your alarm panel and there goes everything. How is everyone protecting their panels when using outdoor contacts or is this not an issue?

 

[signal15]

GRI makes an HVAC Kit just for this purpose.

GRI HVAC KIT

Looks pretty cool. Basically the same idea that we have been throwing out here (a wire that if cut will set an alarm condition) but with the extra addition of a tilt sensor. So if the unit is tilted it will also set the alarm off.

All of this outdoor detection has me thinking-what about lightning strikes?
The number one item that is burned up in a lightning storm is the AC compressor. So the lightning hits the compressor and then flows back into your alarm panel and there goes everything. How is everyone protecting their panels when using outdoor contacts or is this not an issue?

Wireless would be the only reliable way to do it.

 

[drvnbysound]

Looks pretty cool. Basically the same idea that we have been throwing out here (a wire that if cut will set an alarm condition) but with the extra addition of a tilt sensor. So if the unit is tilted it will also set the alarm off.

Speaking of a tilt sensor - there are some really inexpensive mercury tilt sensors I know of that are originally designed for automotive alarm uses (trunk lid opening, etc):

http://www.mongoose.co.nz/media/10663/MS00...mercurytilt.jpg

If desired, that should be pretty easy to integrate since its simply a NC connection.

 

[cornutt]

All of this outdoor detection has me thinking-what about lightning strikes?
The number one item that is burned up in a lightning storm is the AC compressor. So the lightning hits the compressor and then flows back into your alarm panel and there goes everything. How is everyone protecting their panels when using outdoor contacts or is this not an issue?

Mine are underneath a deck that is supported by steel framing, so they are unlikely to take a direct hit. I have experienced compressors being burned out by lightning or surges coming in through the service (I don't know why, but compressors seem to be particularly sensitive to that), but I don't think such surges would couple back to the low voltage since there is no direct connection.