300mA @ 24VDC & 22Ga wiring, bad idea?


Staff member
So I finally 'have to' run my wiring for the sprinkler head so I can automate the garden watering, but would like to know how big of a hole I have to drill in my siding. Since this setup might only be temporary (2 years maybe), I don't want to create a big hole since vinyl siding is hard to patch. The powersupply is good for 24VDC and 300mA, so can I use my 22Ga alarm wiring and avoid a large hole. The total distance will be about 40-50ft. Thoughts?
A 22ga pair has a voltage drop of 0.32 volts per hundred feet. If you draw the entire 300ma then your voltage drop is 0.96 volts per hundred feet or 0.48 volts for your 50 foot run. Losing half a volt shouldn't cause you too much trouble.
I think you are fine. You and I and BSR discussed this one night and did the math a couple ways. As I recall, 22 ga was fine.
Try this link for more conservative calculations. Treat your cat-5 scenario as a power transmission parameter and you will still be fine by a wide margin.
And drill through the siding at the seam under a lip and at an upward angle from the outside, which will make the hole easy to fill and almost invisible when no wire is there.
I don't have much 'height' to work with (the spigot runs in between the joists in the basement), but that's a very good idea gordon, thanks!

Thanks everyone else for confirming!