Voltage dropping under load

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Fatty

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I went to look at a home that was "flipped" about 2 years ago. all new receptacles, switches, lights, service entrance, and panel. The client has lived in the home the last two years with no washer or dryer. She recently bought a washer and dryer and had a problem creep up with the electrical in her home. Every time she runs the washing machine and it starts the agitation cycle the lights throughout her entire home either dim or brighten depending on which phase of the panel they are on. I opened the panel tested for power, both phases read 124v to ground and neutral and 244v phase to phase with the washing machine off. when the agitation cycle starts the voltage on A phase would jump from 124v to 100 volt on B phase the voltage would jump from 124v to 140v every time the motor moved the agitator. my thought was that there may be a loose connection somwhere in the panel or outside, i was able to check everything inside. I was not equiped to pull the meter for checking connections outside. My other thought was that there could be an indirect short somehwere because the lighting issue happens when the overall current exceeds 10 amps. Any information anyone has to help me lead them to the right solution would be highly appreciated.

Thanks in advance
Fatty
 
Definitely a loose or open connection in the neutral ahead of the panel. The troubleshoot is to find out where upstream the imbalance stops, so you need to check voltages at various points in the supply while it's occurring.
 
Thank you for the quick response guys, do you think i should check everything from the weather head down before i have the customer call the POCO? That way i can avoid looking like a dummy and it ends up being within my scope of work.:dunce:
 
Fatty said:
Thank you for the quick response guys, do you think i should check everything from the weather head down before i have the customer call the POCO? That way i can avoid looking like a dummy and it ends up being within my scope of work.:dunce:
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That will depend on where the meter is. You can check the voltage at the WH, but they will need to remove power before you repair anyway.

Who owns the overhead? Where is the meter? On pole or on house?
 
I would go to the weather head and move the neutral wires around-- have someone inside notice if the condition changes. If you don't feel comfortable with that call the power company but I will warn you that they are terrible about finding loose neutrals. They need to test it with a load and they never do- at least around here.
 
Disconnect all those pesky electronics, load the washer receptacle up with a portable electric space heater or hair dryer then w
hip out your trusty thermal imaging camera and start scanning. You have already done what you needed to do with your voltage checks. We have taken a couple sticks of PVC and bumped the overhead connections to find which one is loose. You already know its the neutral connection. My help found a POCO service drop neutral bad mid span last fall. He could see the failure.​
 
Fatty said:
Thank you for the quick response guys, do you think i should check everything from the weather head down before i have the customer call the POCO? That way i can avoid looking like a dummy and it ends up being within my scope of work.:dunce:
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You really can't do much checking these days because the POCOs don't want you cutting the meter seals.

If it is a bad connection at the weather head then they will have to do a new connection.

Don't worry about looking like a dummy no one thinks we are that smart to start with.
 
First job this morning was existing overhead to underground. When POCO cut the drop loose and it hit the ground, the neutral pulled apart at the weather head. One side was never crimped.
 
chris kennedy said:
First job this morning was existing overhead to underground. When POCO cut the drop loose and it hit the ground, the neutral pulled apart at the weather head. One side was never crimped.
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The first thing I would do is check voltage phase to neutral ahead of the MDP to determine if the problem is in the house or with the service. A faulty neutral in the MDP shouldn't affect the service voltage.
 
growler said:
You really can't do much checking these days because the POCOs don't want you cutting the meter seals.

If it is a bad connection at the weather head then they will have to do a new connection.

Don't worry about looking like a dummy no one thinks we are that smart to start with.
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In Michigan I am responsible from the point of attachment down. So to do my due diligence i would have to check everything from the splices down. and if I find one bad there I will have to splice the connection myself.

Also the comment about not being that smart is the funniest thing i have read today.
 
ggunn said:
The first thing I would do is check voltage phase to neutral ahead of the MDP to determine if the problem is in the house or with the service. A faulty neutral in the MDP shouldn't affect the service voltage.
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If i don't find a any noticeable physical issues i will go this route, i just have to get me hands on enough high wattage stuff to make it happen.
 
180329-1645 EDT

Fatty:

You probably don't need more than a 1500 W space heater. The one I have tends to be about 10 to 12 A when warmed up. When the heater coil is at room temperature resistance is about 10 ohms. As the heater heats the resistance goes up a little, about 10%.

If the pole transformer is close by connect a long test lead (some piece of wire) to the pole ground rod, or next to it with a screwdriver into the earth. This will be your voltage reference. This is a good reference if the grounding wire from the transformer neutral to the pole ground rod is good. This technique requires no ladders.

If the pole is hard to get to, then put a rod (screwdriver) in the earth at a furthest point from the home in the direction of the pole transformer, and use this as your reference.

At my home I get about 0.4 V drop for a 10 A change (0.04 ohms) over my neutral from the transformer to the neutral bus in the main panel.

.
 
I had a situation years ago that the lights would blink once in a while. The power company checked their connection at the weatherhead and pole and thought they were ok. They then called me. I put a recorder on to monitor voltage for a day and at what time working back to the meter and found it to be a bad connection from the weatherhead neutral to the drop. Told them it was their connection. Pays to double check everything. I am lucky in my area they give me seals to replace when I open meter boxes and let me borrow locaters and other equipment. I have been working with them for 43 years and a box of doughnuts for them at morning break always helps.
 
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