Situation;
mid 1980s house, 220 volt 3 ton central air. The A/C Disconnect box ( on outside side of house) is wired as follows:
– feed wire coming from the house breaker panel, in the outside disconnect box, has 3 wires. black (a hot), red (a hot) , white.
– line from A/C unit (in the “whip” rubber cable) has 4 wires- black, red, white, and a bare ground wire
-the A/C unit”s black and red wires connect thru the disconnect “pull out” piece to the similar feed black and red wires from the house .
-the two white wires are connected to each other in a metal piece that is screwed on or part of the metal disconnect box housing.
-the bare ground wire is not connected.
question 1 -Should the bare ground be connected to the two white wires which are screwed onto the box housing? Sorta like electric dryers of the same vintage?
question 2 if i buy a new central a/c will I have to run a new 4 wire from the disconnect box back to the inside house breaker panel? or just keep using the same set up?
Thanks
Thanks
Replies
The white wire should not be used at all. The bare wire is supposed to be your ground. The reality is it really doesn't make that much difference to the electricity and since it appears they cut the bare wire out of the cable feeding the disconnect I would just tape the white feeding the disco with green tape (or strip it all the way back) and get on with my life.
AC disconnects don't usually have any neutral load (supposed to be the white) so ideally you would not use the white wire at all.
just hook the bare to a ground rod driven by the a/c unit
My take on your current situation:
>>- feed wire coming from the house breaker panel, in the outside disconnect box, has 3 wires. black (a hot), red (a hot) , white.<<
Odd, open disconnect box and look very closely at where the cable enters the disconnect box -- is there a clipped off bare wire visible?
If yes, open breaker panel, locate #xx-3 entrance to the breaker panel - where do the white and bare wires from that cable go? To the ground/neutral buss? I thought so. Bare clipped off at breaker panel also?
If yes, the white wire has been utilized as the ground - except for re-coding issues, it is fine and safe.
>>- line from A/C unit (in the "whip" rubber cable) has 4 wires- black, red, white, and a bare ground wire<<
This is unusual - generally done with loose conductors in Carflex or similar flexible conduit here. "Rubber whip cable" may or may not be legal/safe due to weather/UV resistance (read insulation jacket).
>>-the A/C unit"s black and red wires connect thru the disconnect "pull out" piece to the similar feed black and red wires from the house .<<
Sounds good.
>>-the two white wires are connected to each other in a metal piece that is screwed on or part of the metal disconnect box housing.<<
The "metal piece" is a buss bar which connects the two wires AND grounds the disconnect box enclosure.
>>-the bare ground wire is not connected.<<
Open connection box at A/C, bare wire not connected there either, right? Whoever wired this was just barely competent, and used the white as the ground.
>>question 1 -Should the bare ground be connected to the two white wires which are screwed onto the box housing?<<
Only if connected at the A/C unit, otherwise it does nothing. Redundant to connect.
>>Sorta like electric dryers of the same vintage?<<
Usually, those dryers were fed by black, white and bare.
>>question 2 if i buy a new central a/c will I have to run a new 4 wire from the disconnect box back to the inside house breaker panel?
No. ---- 3 wires is all you will need for 240v. 4-wire required only if there is a 120v component on the circuit - like a clock in a stove, or a timer in a dryer.
>>or just keep using the same set up?<<
Assuming black & red are the hots and the white has been used as a ground at all the panel and at the disconnect it will be fine (though not perfectly code compliant). You will help avoid future confusion by stripping the insulation off of the white wire at the disconnect box and at the panel box.
When the new A/C is installed, change to an approved method for the disconnect to unit wire run. UV resistant, weather tight conduit - not a "rubber whip" - unless there is something out there which I have not seen, possible...
WORST CASE SCENARIO:
Installer used xx-3 Romex from the panel to the disconnect and then clipped the white off at the panel, and then clipped the bare off at the disconnect box. This would leave you with an ungrounded disconnect box and A/C.
Mind you the A/C would still run fine..........but it is ungrounded and potentially very dangerous.
Check for ground path by measuring voltage with a volt meter between red / disconnect box and black / disconnect box. Should read 120v both places. Red to black should be 240v.
Jim
"Usually, those dryers were fed by black, white and bare."Not exactly.For stoves and dryers you can use non-metallic cable (romex) and SE (service entrance) amount other wiring methods.Now for ones that are not grounded you run the 2 hots and NEUTRAL.For romex that would be black and red hots and white NEUTRAL. Now for an installation between when grounded wiring was common and 96 NEC where 4 wire circuits where required it is technically not legal to run 10-2 and use the bare wire as the "neutral". I know that it was done, but the wording of the code does not allow it.And safety wise it makes not difference as the neutral is also used as the ground in those installations.Now to confuse things more SE cable is also allowed. 3 conductor SE cable is 2 hots (either black and red or two blacks) and the those inturn are wrapped with a stranded bare NEUTRAL. Now that is common on stoves, but I don't think that it is made in the smaller sizes for use on a dryer..
William the Geezer, the sequel to Billy the Kid - Shoe
I see lots of seemingly wierd stuff here in houses from the late 70's to the late 80's. Inspectors must not have been too fussy about this.
For dryers, Cu 10-2 Romex is fairly common, also see lots of AL #8 SE. More AL SE than Cu Romex. Only occasionally see Cu 10-3 Romex with one wire not connected or clipped off.
4 wire conversions go really easy with a Cu 10-3 with one wire not connected and not clipped off too short.
It's nice to live and hope......
Jim
Never underestimate the value of a sharp pencil or good light.
Edited 11/11/2009 1:25 pm ET by JTC1
will do!
Thanks
I will check inside the inside house breaker box and will use my VOM (an OLD big black Simpson meter from the 70s) to do the checks you said to do at the disconnect box.I think I have the right whip- its a semi rubber semi hard / soft plastic tube with three "loose" wires in it red, black, white and a bare ground wire.
I will look and if the bare wire is grounded in the A/C unit, I will then ground it to the disconnect box white wires/box frame connection, after checking that that is really a ground.Thanks
>>....semi rubber semi hard / soft plastic tube....loose wires....<<
Gray, helical coil like pattern around it? Sounds like Carflex - check printing on exterior anyhow.
Good luck.
Jim Never underestimate the value of a sharp pencil or good light.
I did the voltage checks youu suggested. In disconnect bx- feed s from house to white ground (in the disconnect box) were 120 v each, between each feed lead , 220.And the bare wire from the a/c unit when checked on the r x 1 scale shows connectivity with the white wires in the disconnect box, which tells me they are connected together in the a/c unit,
and that I should/could connect the bare wire to them in the disconnect box too. But connecting the bare wire really doesnt do much as the white wire is the main ground (right??)
Correct!
My guess would be the bare wire is just in contact with the junction box wall inside of the A/C unit.
JimNever underestimate the value of a sharp pencil or good light.
It might be easier and more reassuring if you looked in the panel to be sure what is connected there. Testing is still a good idea.
I did (just) look in the inside house panel. looks like 3 wire, 10-3 without ground.
I think from the inside breaker to the outside disconnect box they ran a 10/3 with no ground. (I looked in the breaker box- no bare 4th wire, and the white goes to the grounded buss bar). I can crawl under my house and read the wire printing also.
I'm having a little trouble picturing who, in the 80's (and not the 1880s) would have installed anything without a ground. Was this presumably professionally installed, or a DIY hack?
Check the feed from the house to see if it's in conduit or armored cable. If so, the cable jacket is the ground.
Tying the ground to the neutral is probably a bad idea.
Not clear why the AC should need a neutral at all.
In a 220 v , 3 wire circuit black, red, white is the white the ground,
and is it only the ground?
or is it a "grounded neutral also.
White is the "groundED conductor", which is to say the neutral. The bare copper is the "groundING conductor", which is to say the ground. They serve different purposes.
A strong nation, like a strong person, can afford to be gentle, firm, thoughtful, and restrained. It can afford to extend a helping hand to others. It's a weak nation, like a weak person, that must behave with bluster and boasting and rashness and other signs of insecurity. --Jimmy Carter
"rubber whip" - unless there is something out there which I have not seen, possible...
Called Sealtight.
http://www.anacondasealtite.com/products.htm#Sealtite¯%20Metallic%20Flexible%20Conduit
or liquidtight.
Used all the time for motor connections. Provide vibration isolation and moisture/liquid protection.
It could also be a non-metallic flex such as Carlon Liquidtight.http://www.carlon.com/Product_CarflexLiquidtightFlexibleNonmetallicConduit.html.
William the Geezer, the sequel to Billy the Kid - Shoe
This product appears to be the competition to Carflex which BillHartmann linked in ####.18.
Carflex is the our local "standard".
I just would not describe either one as a "rubber whip". I had visions of a chunk of #10 flexible appliance cord.....
As it turned out, the unit was connected with a flexible conduit by some manufacturer.
JimNever underestimate the value of a sharp pencil or good light.
> As it turned out, the unit was connected with a flexible conduit by some manufacturer.
That's what I assumed when I saw "rubber whip". If nothing else because any regular factory cable would have come with a ground wire.
A strong nation, like a strong person, can afford to be gentle, firm, thoughtful, and restrained. It can afford to extend a helping hand to others. It's a weak nation, like a weak person, that must behave with bluster and boasting and rashness and other signs of insecurity. --Jimmy Carter
Edited 11/23/2009 8:28 am by DanH
sorry about the mis info- its (to me ) a legit electrica item, not a "water hose" etc with wires run thru it
Is the feed plastic sheathed, greenfield, or metal pipe back to panel. If its greenfield or metal pipe the metal carries the ground. Just ground the a/c to the disconnect housing.
Richie
Edited 11/21/2009 11:06 pm ET by Richie921
That is a good way to kill someone, a overcurrent device (fuse/circuit breaker) will never open to clear a fault & the NEC does not allow that practice.
"Was this presumably professionally installed, or a DIY hack?"
Hackdom is not confined to DIY. From what I have seen and dealt with, there a lot more hacks hiding in the professional ranks.