Installed a dishwasher over the new year's break. If you plug it in to the same three prong wall socket as the disposal is does not work, but the disposal works fine. If you plug the three prong dishwasher plug into a two prong extension cord and plug it into the same three prong wall socket as the disposal it still does not work.....but if I plug it into another two prong socket it works fine. I switched the wires on the dishwasher plug, leaving the ground the same and there was no difference in the behavior. What don't I understand and how can I fix this?
Is there an electrician in the house?
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JHZR2
Staff member
stupid question... shouldnt dishwashers be hardwired?
JMH
JMH
First let's make sure you have the plug on the dishwasher end wired correctly.
White to the silver screw. Black to the brass screw. Green/bare to the green/ground screw.
Then check the wiring of the outlet that the disposal is plugged into. It should be the same. You might want to get an outlet tester for $3 that can do this too.
What I'm afraid of being the case here is that someone mis-wired that disposal outlet and mis-wired the plug on the disposal to match.
The hot wire should have 120V on it and should light up a test light connected between either hot and neutral or hot and ground. A test light is about $1.99 if you don't already have one.
White to the silver screw. Black to the brass screw. Green/bare to the green/ground screw.
Then check the wiring of the outlet that the disposal is plugged into. It should be the same. You might want to get an outlet tester for $3 that can do this too.
What I'm afraid of being the case here is that someone mis-wired that disposal outlet and mis-wired the plug on the disposal to match.
The hot wire should have 120V on it and should light up a test light connected between either hot and neutral or hot and ground. A test light is about $1.99 if you don't already have one.
They do make a kit to make them portable..I have no idea if this is what we're talking about here.
Now that I think about it what I suspect is the case is that someone installed a three-prong outlet, there were only two wires, hot and neutral (which is likely to be the case if your houses has two-prong outlets in it still!) and they connected the hot wire to the hot terminal but connected the neutral wire to the ground terminal. Then they wired the neutral from the disposal to the ground on the plug. "Afer all, dem dum wires do dey same ting anywayz!"
You need to check that the outlet is wired correctly, and make sure that there is a ground connection. If there is no ground connection due to the useage of knob and tube wiring or 2-wire cable, the electrical code allows you to install a GFCI outlet without a ground connection and that will provide protection against an electrical shock. That outlet must be labled "no equipment ground" but neither the dishwasher nor the garbage disposal needs one to function.
I would NOT leave the three-prong outlet in there if it has no ground connection. That is a safety hazard and a violation of the electric code.
You need to check that the outlet is wired correctly, and make sure that there is a ground connection. If there is no ground connection due to the useage of knob and tube wiring or 2-wire cable, the electrical code allows you to install a GFCI outlet without a ground connection and that will provide protection against an electrical shock. That outlet must be labled "no equipment ground" but neither the dishwasher nor the garbage disposal needs one to function.
I would NOT leave the three-prong outlet in there if it has no ground connection. That is a safety hazard and a violation of the electric code.
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Actually, either way of wiring is acceptable. The plug in pig tail allows the unit to be removed from the kitchen cabinetry and run for troubleshooting, and disconnected easily for service. Could be that the electrician broke the connecting tabs between the upper and lower sockets so that only one device can be used on that outlet. Odd, but I've seen it before. Use a simple three prong circuit tester (Sears) to check the outlet.
First get a $3.00 electrical tester to test the outlet to see what is and isn't working (and what is miswired).
Would you hard-wire your refrigerator? Electric stove? Disposal? Microwave?
I believe some few codes require hardwired DW's.
I too suspect a miswire or plug problem and honestly if this can't be figured out yourself, well get someone in there.
I too suspect a miswire or plug problem and honestly if this can't be figured out yourself, well get someone in there.
Disposals and dishwashers are always hardwired around here. I suspect that has less to do with codes and more to do with cost.
JHZR2
Staff member
I have some knob and tube in my late 1920s house... I have some ungrounded outlets. It is more than simple enough for most any first story outlets to become grounded (the receptacle/switch and/or the box itself) to water pipes for next to no dollars and very little effort. Ive done it multiple times, and even grounded my water pipe to a deep-driven rod outside for an extra-good ground.
IMO there is no excuse for ungrounded outlets, particularly in a place like a kitchen... of course someone might care to enlighten me to my lack of knowledge
JMH
I don't believe it's acceptable to ground an outlet to the water pipe anymore. IIRC it used to be acceptable to ground a service to a nearby waterpipe--now the ground has to be connected to the waterpipe where it comes out of the foundation.
The reason why is that you can't rely on the pipe being copper all the way back to the foundation. Back in the days when copper pipe was all that existed you could..but that's no longer the case.
The reason why is that you can't rely on the pipe being copper all the way back to the foundation. Back in the days when copper pipe was all that existed you could..but that's no longer the case.
"Would you hard-wire your refrigerator? Electric stove? Disposal? Microwave?"
My disposal and dishwasher are hard wired, they are "installed" and not just sitting like the fridge, etc.
John
My disposal and dishwasher are hard wired, they are "installed" and not just sitting like the fridge, etc.
John
JHZR2
Staff member
aah, yes, I see what youre saying. I know for sure that my house has copper all over. Plus, it has a ground that goes from the pipe into a rod in the ground, so it has a double ground.
What you stated makes a lot of sense - Ive seen PVC water pipe in use in various places, including my parent's weekend house - between the foundation wall and the diaphragm bladder - but that house is well grounded at each outlet, through the box, through an 8' rod in the ground.
I assume if I use one of those 3-prong outlet testers, and it tells me that all is well, then I know that there is continuity on the ground via the water pipe, right? As I said, I know that mine is continuous, but just for conversation - a waterpipe ground that goes to a pipe that is not continuous copper through the foundation would NOT check out as a correctly wired outlet via one of those $3 outlet testers, right?
Thanks again!
JMH
What you stated makes a lot of sense - Ive seen PVC water pipe in use in various places, including my parent's weekend house - between the foundation wall and the diaphragm bladder - but that house is well grounded at each outlet, through the box, through an 8' rod in the ground.
I assume if I use one of those 3-prong outlet testers, and it tells me that all is well, then I know that there is continuity on the ground via the water pipe, right? As I said, I know that mine is continuous, but just for conversation - a waterpipe ground that goes to a pipe that is not continuous copper through the foundation would NOT check out as a correctly wired outlet via one of those $3 outlet testers, right?
Thanks again!
JMH
I agree with Brain. The outlet is probably miswired. Open it and check to see if neutral and hot are connected properly. If you don't want to do that or buy a cheap tester you can check it with a voltmeter or test light. The small slot is hot, the large is neutral. Although you'll have power between the small and large slot if it's wired right you'll also have power between the small slot and ground. if not something is wrong.
If there was nothing else that you were connected to, then it's got to be static.
Otherwise you need a circuit...
like the guy that I used to work with who remodelled his bathroom himself. Wifey complained of "tingling" when she went to get out of the shower, or washed the screen with the shower running. Turned out he'd run a screw into the lead for the exhaust fan (240V). He was an animal who showered without the fan on, so never experienced it for himslef.
Otherwise you need a circuit...
like the guy that I used to work with who remodelled his bathroom himself. Wifey complained of "tingling" when she went to get out of the shower, or washed the screen with the shower running. Turned out he'd run a screw into the lead for the exhaust fan (240V). He was an animal who showered without the fan on, so never experienced it for himslef.
JHZR2
Staff member
cripes! screw into a 240V lead, in a bathroom?!?
She's lucky!
She's lucky!
The $3 outlet tester uses a neon bulb. Neon bulbs don't require a very good ground to glow. Certainly, a ground that isn't good enough to trip a 15-amp breaker could make one of those testers light up. And you WANT a ground that can make that breaker trip if a fault occurs.
From the electrical-wiring http://www.faqs.org/faqs/electrical-wiring/part1/section-31.html FAQ:
One simple way to perform a "real" test is dead short the hot
to ground and see if the fuse or breaker trips. This is,
unfortunately, _extremely_ dangerous. The fuse might explode.
The breaker may malfunction. You may get sprayed with molten
copper. You may start a fire. You may get electrocuted or
blinded. So don't even think of trying this.
One moderately safe approach is to connect a 100W lightbulb
between hot and the ground you wish to test. The lamp should
light fully. If you have a voltmeter, test the voltage between
the ground and the neutral. You should see less than 2 volts.
If the voltage is much higher, or the lamp dims, disconnect it
quickly - the ground may be overheating somewhere. The ground
should be checked for poor connections.
JHZR2
Staff member
OK, thanks!
Though I know that everything is grounded and my water system is all copper, Ill run these tests one of these days (the multimeter one, not the others!), out of curiosity and becuse I just got a new Fluke multimeter...
Thanks again,
JMH
Though I know that everything is grounded and my water system is all copper, Ill run these tests one of these days (the multimeter one, not the others!), out of curiosity and becuse I just got a new Fluke multimeter...
Thanks again,
JMH
have you tried turning on the garbage disposal then turning on the diswasher at the same time? maybe both recepticles are wired to the switch.
The dishwasher works find when pluged into the three prong socket under the sink. I nite light will not light when plugged into this socket and the dishwasher will not work plugged into the exact same socket. When you plug the dishwasher into an extension cord and plug it into another two prong socket it works fine, as does the nite light. Yikes.
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