# Hedge relay current capacity with additional wiring

I ordered several OMRON “ice cube” 110 VAC relays, contacts rated for 10A (LY2NJ). When I inspected them under a microscope I noticed the contact wires are AWG 24. The rest of my setup uses AWG 18. My gut instinct was to open the relays and solder in some short runs of the AWG 18 patch wire. Was this overkill or prudent? I do require switching 10 A.

The left relay is the original. The right relay with the red wire is the modified relay.

• Do you think that OMRON engineers were cheating the university? Aug 17 '19 at 20:41
• Purchased from AliExpress. Who knows what to expect. Aug 17 '19 at 20:41
• OMRON, he don't make no junk! IF they are genuine OMRON, then if the spec sheet says that they are 10A rated then they are. After you have modified them they MAY still be. r not. Aug 18 '19 at 5:40
• It turns out they are knock-off ONROM relays, not OMRON. Aug 19 '19 at 3:41

## 3 Answers

You have about 30 mm of wire there. A quick check on a couple of online calculators shows that 30 mm of 24 AWG will have a resistance of about 3 mΩ.

From $$\ P = I^2R \$$ we get power dissipation will be $$\ 10^2 \times 0.003 = 300\ \text {mW} \$$. I don't think you'll have a problem there. (The 12 V DV version has 160 Ω coil which will dissipate 900 mW.)

Voltage drop will be $$\ V = IR = 10 \times 0.003 = 30 \ \text {mV} \$$.

• Transistor, you seem to answer all my questions like a wise guardian angel. Thank you. Aug 17 '19 at 20:43
• Happy to help. Keep asking easy to answer questions! I forgot to mention that soldering may soften the plastic enough disturb the contact alignment and could cause you further difficulty. Aug 17 '19 at 20:47

This page comes up second in a search for fake OMRON relays marked "ONROM" (a brand name clearly meant to deceive).

The weak point in these relays is not the wire gauge - as noted in the accepted answer - but in the cheap alloy used to make the contacts.

My experience with a sample size of 10 (tricked into buying, like OP) is that contacts will endure perhaps several hundred cycles as long as they carry only control-level current (~100mA or less).

Contacts that carry load current of even just a few amps will fail in less than 200 cycles. My lot also included one with a bad coil (10% failure rate, but not conclusive due to small sample size).

@Drakes, please post your failure modes and stats.

• You typically get what you pay for.
– Gil
Jun 28 at 20:04
• @Gil, what was 'paid for' were authentic OMRON relays at market price from a reputable supplier. The counterfeits so closely resemble the real product, they are hard to detect unless carefully checking for them. Markings use the same fonts, font sizes, character placement, etc. Fraud at its finest.
– u2n
Jun 29 at 19:15
• Is that what you got? If not complain to the OEM, they take great pains to keep counterfeit items away from their customers, there reputation is based on happy customers. They have ways to deal with distribution outlets that substitute counterfeit items for there's. Why do you assume they are counterfeit, have you compared what you got with there specification or did you assume?
– Gil
Jun 30 at 20:08

Those wires are connected to the coil, not the contacts. The coil doesn't require 10A.

• Rightmost contacts are the coil contacts. All the rest, including my patch wire, are non-coil contacts. Aug 17 '19 at 19:38
• The coil will be connected to mains. I’m switching 10 A on the other contacts which is my concern. Aug 17 '19 at 19:52