Small enclosure for a relay - Page 1
Forum section: electronics / general

author: delicado
author_rank: Contributor
timestamp: August 05, 2020, 04:17:44 am
content: HiI've recently added a remote switch to a mains-powered exhaust fan and I'm currently using just a Tupperware to house the switch and wiring. Is it a good idea to 'upgrade' to a junction box? Are junction boxes more fire-retardant than Tupperwares? How about lining the inside with aluminium foil?Thanks

author: Zero999
author_rank: Super Contributor
timestamp: August 05, 2020, 08:00:41 am
content: Quote from: delicado on August 05, 2020, 04:17:44 amYes. A Tupperware container is a bad idea, because it's flammable and any idiot can open it. A proper enclusure will be fire retardant and require a tool to open.Lining it with aluminium foil is a bad idea. It will need to be eathed, which is just about impossible to do reliably and foill can easilly flake, causing short circuits and an increased fire hazard.You haven't posted enough information for anyone to suggest a specific product.My advice would be to ask an electrician.

author: ChristofferB
author_rank: Frequent Contributor
timestamp: August 05, 2020, 08:05:14 am
content: My philosophy with regards to this is that cludges and bodge solutions belong to low energy low voltage stuff. Once dealing with mains voltage, either do it right or dont do it at all.Yes plastic junction boxes are usually flame retardant, and more sturdy. Also of no small importance, they signal to other people that "here is a mains installation".I agree with zero999, if you need to ask this question you should probably consult an electrician

author: TimFox
author_rank: Super Contributor
timestamp: August 05, 2020, 03:48:51 pm
content: Tupperware is made from LDPE (low-density polyethylene) and has a low melting point. It is fine for its intended purposes of food storage.I totally agree with those who posted that "real" junction boxes (easily found at hardware stores at reasonable prices) are required for mains voltages.Depending on your jurisdiction's regulations, they may be metal or good plastic.

author: duckduck
author_rank: Frequent Contributor
timestamp: August 05, 2020, 07:35:32 pm
content: Quote from: delicado on August 05, 2020, 04:17:44 amPlastics are thermoset (won't melt) or thermoplastic (melt when they get hot enough). Plastic mains enclosures usethermosetplastic or they use metal. If you use a metal enclosure it must be connected to the ground wire of your home. Mains electrical connections must be crimped or screwed, not soldered (because solder can melt). Mains enclosures should not be able to be opened without tools (because kids and humans). The live wire of a mains device should be fused where it enters the device (to prevent a fire). There are many many other rules that must be followed for the sake of safety, and this is why many jurisdictions require an electrical inspection for significant modifications to home wiring and why responsible manufacturers submit their mains-powered devices to UL or similar testing companies.If you feel uncomfortable at all working with mains, you should pay an electrician. If a device that you built and connected to mains starts a fire that burns down your house, the insurance company could use that as an excuse to not reimburse you for the loss of the insured property. If a child touches a live mains wire in a device you created and is injured or dies as a result you could face severe criminal and civil penalties. This is not the place to play and learn and save money because the results of a small mistake due to ignorance or oversight can be tragic for you and your loved ones.EDIT:Re-read and realized I sound like a jerk. I'm just trying to say "Yes, and please take this stuff very seriously."EDIT EDIT:...and I got the thermoset thing wrong.

author: Ranayna
author_rank: Super Contributor
timestamp: August 06, 2020, 07:02:55 am
content: Also consider the price of real Tupperware. That stuff is expensive, you can buy *a lot* of junction boxes for the price of a Tupperware box :p

author: AlbertL
author_rank: Regular Contributor
timestamp: August 06, 2020, 02:26:28 pm
content: Yes, absolutely - for safety you must use a proper electrical enclosure approved by the applicable authorities. Without knowing the details of your project, in general my preference for this type of installation is a steel enclosure with a removable interior panel for mounting the components. These are commonly used in industrial control installations, and are made in a wide variety of sizes, for both indoor and outdoor use.

author: Red Squirrel
author_rank: Super Contributor
timestamp: August 06, 2020, 11:48:36 pm
content: Yeah I would use a junction box, maybe one that is for an oven or dryer plug, and with a cover. (should give you plenty of room).From my understanding even the low voltage wire going to it should be rated for high voltage because it's in the same box. Ex: if the relay is switching 120v, the wire that powers the relay should also be rated for at least 120v (I think 600v rating is standard) even if it's only carrying 12v. Ideally try to keep the wires as separate as possible so they don't mix as well. You'd have to double check, but I would imagine thermostat wire would probably fit that rating.I'm not a professional so don't take this as professional advice, it's just the way I would do it.

author: Back2Volts
author_rank: Unknown
timestamp: August 11, 2020, 02:37:20 am
content: I am working on the electrical wiring for my garage/workshop and there will be a current sensor on the table saw power line, driving a relay to turn on the dust vac. Both sensor, relay and a couple of switches will be in a 2-1/8" deep, 4-11/16" square steel box, 2-1/8" deep plus a 2-1/8 ring extension and raised cover. Since you only have the relay, you could probably do with a 4"x4"x2-1/8 with raised cover which gives an extra 1/2" space. See the attached pictures. You may want to look for comparable items in the UK.

author: TimFox
author_rank: Super Contributor
timestamp: August 11, 2020, 01:23:24 pm
content: I believe that the safety requirement on wire insulation assumes that the wire insulation touches other insulated wire, and each insulating layer (by itself) should be capable of holding the maximum voltage between the two wires (even if one voltage is much higher than the other), should the other insulation fail.

author: NiHaoMike
author_rank: Super Contributor
timestamp: August 11, 2020, 01:56:11 pm
content: Quote from: TimFox on August 11, 2020, 01:23:24 pmIt's more complex than just that since the wiring in a CRT TV set doesn't have to be all rated for 30kV just because there's a 30kV wire for the CRT supply.

author: Monkeh
author_rank: Super Contributor
timestamp: August 11, 2020, 01:56:56 pm
content: Quote from: duckduck on August 05, 2020, 07:35:32 pmPVC, ABS, PP, nylon.. can I find some more extremely common thermoplastics used for electrical enclosures? Oh, PC..https://www.homedepot.com/p/Legrand-Pass-Seymour-Slater-Old-Work-Plastic-1-Gang-Swing-Bracket-Switch-and-Outlet-Box-P116W/304234113Thermoplastic.https://www.homedepot.com/p/Carlon-1-Gang-18-cu-in-Old-Work-PVC-Heavy-Wall-Electrical-Switch-and-Outlet-Box-BH118R/100154882Thermoplastic..https://www.homedepot.com/p/Serpac-11-8-in-L-x-10-2-in-W-x-5-5-in-H-Polycarbonate-Gray-Hinged-Top-Cabinet-Enclosure-with-Gray-Bottom-I342HL-TGBG/303702897Thermoplastic...https://www.homedepot.com/p/Carlon-3-4-in-PVC-Type-X-Round-Junction-Box-with-Cover-E970CDE-CTN/100404094Thermoplastic....Quote from: NiHaoMike on August 11, 2020, 01:56:11 pmThe wiring in a CRT TV is not covered under the same standards.

author: Monkeh
author_rank: Super Contributor
timestamp: August 11, 2020, 02:10:54 pm
content: So to answer the question, yes, you should absolutely replace the tupperware with something suited. For example:https://cpc.farnell.com/spelsberg/33341601/ip55-grey-junction-box-with-terminal/dp/EN85181There are many sizes, work out what will fit your needs.

author: TimFox
author_rank: Super Contributor
timestamp: August 11, 2020, 02:55:06 pm
content: Quote from: NiHaoMike on August 11, 2020, 01:56:11 pmCRT HV wires should not touch other wires ever. Wires in an electrical box can touch each other.