K8MHZ
Senior Member
- Occupation
- Electrician
My sister has had problems with the control board in her furnace. The furnace guy told her last time it happened she didn't have a ground. So, I went over there and physically traced the old Romex all the way back to the panel. This involved taking paneling off, moving stuff in the attic, etc. Everything was as I expected from the readings I took before we did the physical tracing. Nothing was wrong.
A couple days ago, she loses another board. Furnace guy says same thing. I reminder her of the above. So I asked her to ask the furnace guy if a bad neutral causing over voltage is known to take out the boards. He said it was possible so I went over there to load things up and check for signs of a bad neutral.
Here are the readings. Voltages are (L1-N) - (L2-N) L readings at the main breaker, N readings at the bare neutral coming into the main panel.
Lightly loaded, 118.3 - 118.4
Moderately loaded 115 - 121
Heavy load 109 - 115
The 109 side is the furnace side. The boards probably don't like low voltage. That I understand.
A call to the POCO gets a linesman out right away.
He pulls the meter and puts this cheesy thing called a 'Super Beast' on the tabs, turns it on and by looking at two crude analog meters he tells me the neutral is almost perfect. Now, this thing is using 12 awg extension cord wire with clamps that look like they belong on a 6 amp charger.
I told him (as nice as I could) what I thought of his Super Beast and told him if I loaded the house up with the range, microwave, etc,. I could get the voltage down to 109. I know he is wrong about the bad neutral, but at least I can show him the sag. So (while the Beast is still connected) he tells me to load the house up.
I told him I would probably need the meter put back in for that to happen. So he puts the meter back in and says he can't connect the Beast at the can because there is no room.
He decides to check some connections at the pole feeding the house. 119 -119 lightly loaded, 114-116 heavily loaded. He did this with his meter, the Beast lay unused in the snow.
While he was doing his thing, I took voltage readings at the meter (there was room for a regular meter probe) and got my loaded voltage down to 109 - 116. (L readings at line side meter tabs, N at bare conductor in can).
The other end of the cable right at the tranny read (we talked via cell phone) 119-119 no load (main off) and almost that loaded.
So he shuts the power down for a couple hours (sister not happy) and replaces the triplex that (to me) read OK. He also replaced a bunch of connectors. He turns the power back on.
I repeat the test and the drop is within a volt of my earlier tests. I showed him, he verified it with his meter and was dumbfounded. So, he changes the connectors at the drop (without testing them). That recovered about a volt, but we were still tilted and low with 116-112. Also our loading gear (the stove) was cycling less as it got hotter. The triplex from the house to the pole was not changed. He said he did change the connections on both ends.
By now my sister has been without steady power for three hours and she is sick of it. I told the linesman that and he said he thought it was the transformer, anyway, and was closing out the ticket. He told me the transformer was a 10kva and it should be a 20. This is for at least four homes. There may be a fifth one, I will check later.
I gave the linesman my card and asked if he would have the area field engineer call me. He said he would.
So, what do you think is going to happen when they heavy up the transformer and don't look for the bad neutral (that is somewhere between the meter can and the pole) ?
If they bring the loaded voltages up, one side may get real high. The most I could get the high side to swing to was 121. But that was with 115 on the low side. If they bring the low side up to 120, that will put the high side at 126. Or worse, as bad neutrals don't ever get better, they just get worse.
But anyway, so much for the 'Super Beast'.
Why would anyone use such a crude instrument for troubleshooting professionally? It looked like it was made from drain pipe and Radio Shack parts.
A couple days ago, she loses another board. Furnace guy says same thing. I reminder her of the above. So I asked her to ask the furnace guy if a bad neutral causing over voltage is known to take out the boards. He said it was possible so I went over there to load things up and check for signs of a bad neutral.
Here are the readings. Voltages are (L1-N) - (L2-N) L readings at the main breaker, N readings at the bare neutral coming into the main panel.
Lightly loaded, 118.3 - 118.4
Moderately loaded 115 - 121
Heavy load 109 - 115
The 109 side is the furnace side. The boards probably don't like low voltage. That I understand.
A call to the POCO gets a linesman out right away.
He pulls the meter and puts this cheesy thing called a 'Super Beast' on the tabs, turns it on and by looking at two crude analog meters he tells me the neutral is almost perfect. Now, this thing is using 12 awg extension cord wire with clamps that look like they belong on a 6 amp charger.
I told him (as nice as I could) what I thought of his Super Beast and told him if I loaded the house up with the range, microwave, etc,. I could get the voltage down to 109. I know he is wrong about the bad neutral, but at least I can show him the sag. So (while the Beast is still connected) he tells me to load the house up.
I told him I would probably need the meter put back in for that to happen. So he puts the meter back in and says he can't connect the Beast at the can because there is no room.
He decides to check some connections at the pole feeding the house. 119 -119 lightly loaded, 114-116 heavily loaded. He did this with his meter, the Beast lay unused in the snow.
While he was doing his thing, I took voltage readings at the meter (there was room for a regular meter probe) and got my loaded voltage down to 109 - 116. (L readings at line side meter tabs, N at bare conductor in can).
The other end of the cable right at the tranny read (we talked via cell phone) 119-119 no load (main off) and almost that loaded.
So he shuts the power down for a couple hours (sister not happy) and replaces the triplex that (to me) read OK. He also replaced a bunch of connectors. He turns the power back on.
I repeat the test and the drop is within a volt of my earlier tests. I showed him, he verified it with his meter and was dumbfounded. So, he changes the connectors at the drop (without testing them). That recovered about a volt, but we were still tilted and low with 116-112. Also our loading gear (the stove) was cycling less as it got hotter. The triplex from the house to the pole was not changed. He said he did change the connections on both ends.
By now my sister has been without steady power for three hours and she is sick of it. I told the linesman that and he said he thought it was the transformer, anyway, and was closing out the ticket. He told me the transformer was a 10kva and it should be a 20. This is for at least four homes. There may be a fifth one, I will check later.
I gave the linesman my card and asked if he would have the area field engineer call me. He said he would.
So, what do you think is going to happen when they heavy up the transformer and don't look for the bad neutral (that is somewhere between the meter can and the pole) ?
If they bring the loaded voltages up, one side may get real high. The most I could get the high side to swing to was 121. But that was with 115 on the low side. If they bring the low side up to 120, that will put the high side at 126. Or worse, as bad neutrals don't ever get better, they just get worse.
But anyway, so much for the 'Super Beast'.
Why would anyone use such a crude instrument for troubleshooting professionally? It looked like it was made from drain pipe and Radio Shack parts.