Timer for Pool - 240v at the panel turned into 360v at the pool timer

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Not Pretenting

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Hi… totally confused and don’t pretend to be an electrician.
My pool timer went out. It’s a T104. I changed it out and checked the volts on it. It’s a head scratcher. There’s a 40 amp double pole breaker in the panel. Each breaker tested out at 120volts for a total of 240v.
At the new timer next to the pump line 1 from the panel tests out at 120v but line 3 tests out at 240v. Totaling 360v on the t104 pool timer. Line 2 matches line 1 at 120v when operating. And line 4 tested and matched line 3 at 240v. I’ve never seen something like this. All I did was change wire for wire. How is it possible to get 120v and 240v when the breakers in the panel are 120v and 120v. And I’m not sure. Is it safe to run it this way or not. In addition will it burn out the pool pump. How did it grow in volts. I’m assuming it’s been this way for the 3 years I’ve owned the house. Last thing. The pool pump used to start hard and was more powerful in the old timer. On the new timer the pump is quieter and doesn’t pump as much water.

Any help would or advice would be greatly appreciated. Thank you.
 
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jadnashua

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Measuring voltage requires a bit of understanding. When I worked on repairing high voltage power supplies used in a radar in the Army, the filaments on one regulator were 5-volts measured one way, but 4995 volts measured another! It's very important to understand what the reference point is. In this case, to keep the filaments from arcing, one side was at 5000-volts, and the other was 4995, giving the required 5-v difference. Thinking you were just going to be measuring 5-vdc could, at least in this case, kill you if you weren't careful, or blow out your meter or both!

In the way a typical US household is supplied with power, it comes in as 240vac. There is no source of native 120vac coming into the house, it is single phase 240vac. To get 120-vac, they put a center tap on the secondary of the transformer, so from either end to the middle, you have 120vac, but across the full width of the transformer, you get 240.

Unless you have commercial power, there's no way you have 360vac supplied, and even then, 360 is not a typical value..

With a 240vac circuit, ideally, you'd break both hot leads when switching it off, but you don't need to to stop current from flowing...all you need to do is break the circuit anywhere, creating an open circuit. But, you'd then measure, potentially, 120-vac on one lead if you measured it to ground, but you could measure 240-vac across the load, depending again on how you did it.
 

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Measuring voltage requires a bit of understanding. When I worked on repairing high voltage power supplies used in a radar in the Army, the filaments on one regulator were 5-volts measured one way, but 4995 volts measured another! It's very important to understand what the reference point is. In this case, to keep the filaments from arcing, one side was at 5000-volts, and the other was 4995, giving the required 5-v difference. Thinking you were just going to be measuring 5-vdc could, at least in this case, kill you if you weren't careful, or blow out your meter or both!

In the way a typical US household is supplied with power, it comes in as 240vac. There is no source of native 120vac coming into the house, it is single phase 240vac. To get 120-vac, they put a center tap on the secondary of the transformer, so from either end to the middle, you have 120vac, but across the full width of the transformer, you get 240.

Unless you have commercial power, there's no way you have 360vac supplied, and even then, 360 is not a typical value..

With a 240vac circuit, ideally, you'd break both hot leads when switching it off, but you don't need to to stop current from flowing...all you need to do is break the circuit anywhere, creating an open circuit. But, you'd then measure, potentially, 120-vac on one lead if you measured it to ground, but you could measure 240-vac across the load, depending again on how you did it.
Thanks for responding. I see what you’re saying. I have residential and no commercial. What would cause the 240v reading on the 3 line. I see it’s impossible and read on multiple meters. Is it a grounding issue inside the timer casing. An arcing issue?
 

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"At the new timer next to the pump line 1 from the panel tests out at 120v but line 3 tests out at 240v. Totaling 360v on the t104 pool timer. Line 2 matches line 1 at 120v when operating. And line 4 tested and matched line 3 at 240v."

Did not follow. Can you get lines 1, 2, and 3 in the same photo?

Also, when you measure voltages, you measure between two things. Such as you might measure from line 2 to line 1. So you need to specify where each probe goes.
 

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"At the new timer next to the pump line 1 from the panel tests out at 120v but line 3 tests out at 240v. Totaling 360v on the t104 pool timer. Line 2 matches line 1 at 120v when operating. And line 4 tested and matched line 3 at 240v."

Did not follow. Can you get lines 1, 2, and 3 in the same photo?

Also, when you measure voltages, you measure between two things. Such as you might measure from line 2 to line 1. So you need to specify where each probe goes.
 

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When I meter I go from green ground screw to screw on line 1. When I measure line 3. Same thing. Green ground screw to line line screw. Line 1 measures 120. Line 3 is 240 Line 2 is ran from green ground screw to line 2 screw while the pool pump is running. Same as line 4. Measured from green ground screw to line 4 (to the right of line 3 in photo) it comes up 240. Same as line 3. In summary when the pool pump is running lines 1 from breaker panel is 120. Line 2 going to the pump is 120. Line 3 is 240 from breaker panel while running and line 4 is 240 into the pool pump. 2 white grounds are on the first screw which is A. There is a wire that runs from A to the green ground screw on the casing inside at the bottom. Thanks for your help.
 

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When I meter I go from green ground screw to screw on line 1. When I measure line 3. Same thing. Green ground screw to line line screw. Line 1 measures 120. Line 3 is 240 Line 2 is ran from green ground screw to line 2 screw while the pool pump is running. Same as line 4. Measured from green ground screw to line 4 (to the right of line 3 in photo) it comes up 240. Same as line 3. In summary when the pool pump is running lines 1 from breaker panel is 120. Line 2 going to the pump is 120. Line 3 is 240 from breaker panel while running and line 4 is 240 into the pool pump. 2 white grounds are on the first screw which is A. There is a wire that runs from A to the green ground screw on the casing inside at the bottom. Thanks for your help.
 

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jadnashua

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To get 240vac, you do not have or use a ground lead or neutral for the current flow...you have two hot leads. If you measure between the two hot leads, you should get 240vac, if you measure from any of the two hot leads to neutral you'd get 120vac. Since ground is tied to neutral back at the panel, you MIGHT get exactly the same readings as if you were going between a hot and neutral.

Since it appears you have a 240vac pump, other than for safety, you do not need the neutral or ground leads as all for the pump to operate. Now, the timer itself MIGHT need the neutral, since it COULD be a 120vac device, controlling your 240vac device.
 

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Ok. So if pull the wire from line 3 (originally the 240vac) and put it into line 1 it will show 240vac on line 1 and line 2 now. And now line 3 has the 120vac show line 3 and line 4 will reflect 120vac. So the line that was in line 3 which is now in line 1 is the neutral? Which I don’t need. Do I cap it? And just use the 120vac.
 
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jadnashua

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I do not know if your timer needs neutral or not. If the timer operation runs on 120vac, it is required to operate.

240vac devices in the USA have L1 and L2, both are 'hot' as opposed to what is used where 220-240vac is the norm, then one of those is neutral//ground.

As I said, everything when measuring voltage needs the appropriate reference, that may not be ground. To get 240vac, you have to be measuring between L1-L2, not L1-ground/neutral or L2-ground/neutral. And, in a perfect world, you'd get zero volts between neutral/ground, but you might see a couple of volts, but it should not be much.

A typical 240vac device in the USA will have a double-pole breaker, where each leg (L1 and L2) are individually connected to a breaker, and the two handles are joined so they both trip together. That's what it looks like you have.
 

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Hmmm. I’ll end up bring out an electrician. I’m just trying to get a better understanding. Wouldn’t the 2 hots be equal. 120vac. With the neutral / ground near zero. Just puzzles me because my mind is trying to understand how one reading is 120vac and the other being 240vac. When I’ve seen videos on YouTube when the guy meters a line 1 reading 120vac and the other hot line in line 3 is 120vac. I think this is where I struggle. Something I thought was a simple plug and play went sideways.
 

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Hmmm. I’ll end up bring out an electrician. I’m just trying to get a better understanding. Wouldn’t the 2 hots be equal. 120vac. With the neutral / ground near zero. Just puzzles me because my mind is trying to understand how one reading is 120vac and the other being 240vac. When I’ve seen videos on YouTube when the guy meters a line 1 reading 120vac and the other hot line in line 3 is 120vac. I think this is where I struggle. Something I thought was a simple plug and play went sideways.
Plus my pool guy made me question everything. He said my pump wasn’t turning on hard enough, it was getting hotter than normal, and was quieter. I had it where it was working and the timer was turning until he said my water was moving less and the pressure on my tank was higher. This is the guy who thought an old school utility scientific Atlantic box next to the filter was my fuse panel. Maybe it’s all right after all.
 

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In this diagram, when the point X1 is high X4 is low, so you'd measure 240vac. This is what's coming into your home. The transformer on the pole has high voltage on it, and the transformer drops the voltage down to residential voltage levels. At your panel, the neutral point is connected to the ground rod to reference it. But neutral is a power carrying conductor, so all of the power that goes out say X1 or X4 for 120vac devices, goes back through the neutral. For 240vac devices, the power goes only through X1 to X4 through the device it's powering.
 
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