Can you drill holes in a box to mount relays?
- Thread starter aharreld
- Start date
ptonsparky
Tom
- Occupation
- EC - retired
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Yes. 3R does not technically mean water will not get in, only that it will not build up inside the box to live electrical parts. Most have some sort of “weep hole” or gap in the bottom to allow water or condensation to leak out. There is a corrosion resistance issue as well, and drilling through the enclosure wall exposes the metal to rusting. Put something on it to give it some protection. I use a dollop of RTV (silicone seal).
The biggest problem I have seen is that people use the weep hole as a pilot hole for
punching a conduit entry, then use a sealing nut, so liquid builds up inside (if the door is gasketed).
The biggest problem I have seen is that people use the weep hole as a pilot hole for
punching a conduit entry, then use a sealing nut, so liquid builds up inside (if the door is gasketed).
qcroanoke
Sometimes I don't know if I'm the boxer or the bag
- Location
- Roanoke, VA.
- Occupation
- Sorta retired........
Yes, and if you told me I was voiding the UL listing I'd punch you dead in the face...... 
gadfly56
Senior Member
- Location
- New Jersey
- Occupation
- Professional Engineer, Fire & Life Safety
Use the backplates anyway. If the box is exposed to the elements and you snug up the relay to the box wall, when the sun is beating down on the metal the relay is going to get much toastier than if you have that relay on a backplate with an air gap to the box wall.
ptonsparky
Tom
- Occupation
- EC - retired
If warranted.
Many of mine were one or two contactors used for a few days at harvest or after. Heat was never an issue.