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24 volt AC wiring in same conduit as 220 volt single phase and in same outdoor enclosure as 220 v silgle phase and 3 phase

I have an electricall contractor that ran my 24 volt controll wires for AC systems in the same conduit as 220 volt power. I understand that if they are the same insulation its ok but it is not the best practice more over they ram two sources of 220 single phase one source of 3 phase and 3 sources of 24 volt control in the same junction box outside.
Whan my Heat pump goes into defrost it fries the defrost board this has happened atlest 4 times with some transformers aswell.
I keep requesting they separate my 24 volt control wiring from all high volt and they keep saying it sok to do this.
We even ran a temporary thermostat wire outside of conduits and systems ran fine. They removed my t stat wire and hooked their wires back in and we started to fry boerds again
We even contacted the manufacturer and they said they do not want 24 volt controll wires in the same conduit and high voltage but the Electrical contractor will not bugde its been over a year and a half
What can I do
 

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Super Moderator
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You might have to bite the bullet and get someone to pull the wires out.
Who has been paying for the boards and labor?
 

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Idiot Emeritus
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I've run tons of 24 in the same conduit as 480.

n my experience, if the 24 goes to electromechanical devices (like relays) it'll be ok. If it goes to electronic devices, it might be ok, but a lot of cheap boards (like most HVAC) will have trouble.

One possibility is to pull shielded cable for the 24 in the same conduit as the higher voltage stuff.

Rob

P.S. Ground the shield at one end only, never both ends.
 

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Master Electrician
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generally it's a dumb idea, legally you can do it but all boxes need to be identified as having two voltages in them. As the previous poster says running a shielded cable will probably solve your problem but it's still a sketchy install.
 

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andrew79 said:
generally it's a dumb idea, legally you can do it but all boxes need to be identified as having two voltages in them. As the previous poster says running a shielded cable will probably solve your problem but it's still a sketchy install.
It is legal but once you commingle LV with 120v don't you have to use 600v insulation? That seems to push you to more expensive bulkier wire and undermines the benefit.
 

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Idiot Emeritus
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It is legal but once you commingle LV with 120v don't you have to use 600v insulation? That seems to push you to more expensive bulkier wire and undermines the benefit.
All conductors need to be rated for the highest voltage in the conduit.

If there's 24, 120 and 240, nothing can be rated less than 240.

There's plenty of 300 volt wire available that's less bulky than 600.
 
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