Jdoll42
Computer Systems Engineer
Here's some pic's I took tonight. (It was dark out, so I hope they turned out OK!) I'm guessing it's a 25KVA? Would that be sufficient for my current setup?
Power Sags
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Jdoll42
Computer Systems Engineer
The nearest substation is about 2-3 miles from here. Now I'm not 100% sure what route the lines take, but I think it's a straight shot. It's down the same road that our drive is off of. (Then again, maybe the substation I'm coming from is in Timbuktu instead?)
You mean the electric strip heat in the unit? To my knowledge they've never been on since the geothermal loop has been hooked up. I'd have to really crank one of my thermostats to make that turn on. I might do that one day just to see what will happen.....
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Mikey
Aspiring Old Fart, EE, computer & networking geek
How about a time delay relay ahead of one of these loads, so the starting currents are separated?
Bob NH
In the Trades
Here is something you could do but you should do it only if you are completely comfortable and sure that you can do it safely.
If you choose to do this, you are completely on your own.
You should remove all jewelry (such as rings, watch, bracelet, necklace) and get a good pair of heavy rubber or clean and dry leather gloves. Wear some kind of eye protection. There may be others on the forum who will suggest some specific personal protection equipment or procedures.
The measurements are to discover any voltage drops across connections that would indicate bad connections or circuit breaker conditions. You are looking for voltages on the order of tenths of a volt where they should be very close to zero, or differences of tenths of a volt where they should be the same.
1. Remove the cover from your service panel.
2. Turn on significant loads so that you get a lot of current. Since the largest loads are probably 240 Volts you can turn those on for one set of tests on both hot sides and then try to set up an unblanaced load (see step 5) for the neutral test.
3. Measure the voltage drop between the conductors coming in from the utility and the conductors going to the largest loads that are turned on for that phase. Any significant voltage drop indicates a connection problem somewhere along that line, or a bad breaker.
4. Measure the voltage between the load conductors after they leave the breaker, and the utility neutral. The measurement should be the same on both sides of the bus. Any significant difference could indicate a utility transformer problem or a connection problem.
5. Try to turn on 120 Volt loads on one side to produce a large current in the neutral. Then measure the voltage drop between the neutral conductor for the circuit and the neutral conductor from the utility. Anything greater than a few hundredths of a volt indicates a bad connection.
6. With the high neutral current condition of Step 5, measure the voltage between the utility neutral and the ground wire in the panel. Any difference indicates a bad connection in the panel, since both are supposed to be connected in the panel.
When measuring things that should be zero (voltage drops on the same phase or bus), use a low scale on the voltmeter. You are trying to get accurate measurements on the order of hundredths or tenths of a volt.
If you choose to do this, you are completely on your own.
You should remove all jewelry (such as rings, watch, bracelet, necklace) and get a good pair of heavy rubber or clean and dry leather gloves. Wear some kind of eye protection. There may be others on the forum who will suggest some specific personal protection equipment or procedures.
The measurements are to discover any voltage drops across connections that would indicate bad connections or circuit breaker conditions. You are looking for voltages on the order of tenths of a volt where they should be very close to zero, or differences of tenths of a volt where they should be the same.
1. Remove the cover from your service panel.
2. Turn on significant loads so that you get a lot of current. Since the largest loads are probably 240 Volts you can turn those on for one set of tests on both hot sides and then try to set up an unblanaced load (see step 5) for the neutral test.
3. Measure the voltage drop between the conductors coming in from the utility and the conductors going to the largest loads that are turned on for that phase. Any significant voltage drop indicates a connection problem somewhere along that line, or a bad breaker.
4. Measure the voltage between the load conductors after they leave the breaker, and the utility neutral. The measurement should be the same on both sides of the bus. Any significant difference could indicate a utility transformer problem or a connection problem.
5. Try to turn on 120 Volt loads on one side to produce a large current in the neutral. Then measure the voltage drop between the neutral conductor for the circuit and the neutral conductor from the utility. Anything greater than a few hundredths of a volt indicates a bad connection.
6. With the high neutral current condition of Step 5, measure the voltage between the utility neutral and the ground wire in the panel. Any difference indicates a bad connection in the panel, since both are supposed to be connected in the panel.
When measuring things that should be zero (voltage drops on the same phase or bus), use a low scale on the voltmeter. You are trying to get accurate measurements on the order of hundredths or tenths of a volt.
JWelectric
Electrical Contractor/Instructor
If I understand a geothermal heat pump I don’t think that it uses Freon at all but instead compresses the liquid in the thousands of feet of buried pipes until it becomes heated and then releases the heated liquid as a vapor thus heating the air around it. Then the fan in the air handler blows this heated air through out the house. This process is reversed in the summer releasing the cooler liquid to cool the air.
Even if there was a relief valve and I am sure there is, the amount of current needed to move thousands of feet of liquid will be more than the pressure needed to move a little Freon in a conventional heat pump.
I am coming off the top of my head with this so don’t take it very seriously but I think that the geothermal heat pump is rated around 1000 feet of 1 inch pipe per ton of cooling and heat. One thing we must consider is what the volume of a pipe for a 31/2 ton unit. Liquid is about 7.5 gallons per cubit foot. In a pipe that is one inch in diameter and 3500 feet long the motor would have to push a lot of weight just to start the liquid flowing thus a large voltage drop across the entire system.
Lakee911
I&C Engineer (mostly WWTP)
Hey folks,
That is a 25KVA transformer. It's oil filled transformer and it's 12470/7200x240/120. I am not sure if it has any other taps for slightly boosting or bucking the voltage.
FYI, 25KVA Single Phase 240V Amps are 104A.
Jason
That is a 25KVA transformer. It's oil filled transformer and it's 12470/7200x240/120. I am not sure if it has any other taps for slightly boosting or bucking the voltage.
FYI, 25KVA Single Phase 240V Amps are 104A.
Jason
Jadnashua
Retired Defense Industry Engineer xxx
Ground source heat pumps use the circulating water as a heat exchanger...that loop is not refrigerant. The pump on that part is similar to the water pump on a car...it moves the fluid around, the refrigerant extracts or inserts heat, depending on the mode in the coil, similar to a conventional system, but instead of using air blowing over it, the heat is extracted or inserted into the circulating water that goes back into the ground via those pipes and the pump.
Bill Arden
Computer Programmer
A good way to understand Ground source heat pumps is to look at your window air conditioner. It uses freon and a compressor to remove heat from one side and add heat to the other.
Since the compressors are on a different breaker (50A 240V), you should be able to turn it off and have it run just the electric heat.
-
We now know more things
1. It's a 25KVA transformer. (FYI: my house and my neighbors are both connected to one 25KVA transformer)
2. The transformer is a newer "better" unit based on the image.
3. The utility is using twacs. Twacs pulls 90 amp surges near the zero crossings to transmit signals.
It can read "15 minute peak" and total kWh daily.
4. You are not that far into the woods where power line resistance is significant.
Moving on. (process of elimination)
Provided that your wiring is all good and your lights don't dim when using electric, we can move forward by looking back at the heat pump itself.
Since the compressors are on a different breaker (50A 240V), you should be able to turn it off and have it run just the electric heat.
-
We now know more things
1. It's a 25KVA transformer. (FYI: my house and my neighbors are both connected to one 25KVA transformer)
2. The transformer is a newer "better" unit based on the image.
3. The utility is using twacs. Twacs pulls 90 amp surges near the zero crossings to transmit signals.
It can read "15 minute peak" and total kWh daily.
4. You are not that far into the woods where power line resistance is significant.
Moving on. (process of elimination)
Provided that your wiring is all good and your lights don't dim when using electric, we can move forward by looking back at the heat pump itself.
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Jdoll42
Computer Systems Engineer
Bob, thanks for the procedure. Everything you've said makes sense and sounds pretty straight-forward. I will try to run those tests this weekend. Now I just need to figure out ways to get some decent loads on the system (other than the compressor motor). Might have to break out the halogen lights and shop vac and see what kind of draw I can put on that. Heck, I'll get the toaster and iron going too!
Jdoll42
Computer Systems Engineer
Exactly. I have two very small pumps that circulate the water/methanol mixture through all of the buried piping. They probably are no bigger than a small coffee can each. There is also a compressor with freon, but the total length of the freon lines is only a few feet since everything is self-contained in the same cabinet. The big difference is in how it dissipates/collects the heat. A "normal" heat pump uses a fan outside to exchange the heat with the outside air. A geothermal heat pump uses the ground (via the thousands of feet of pipe) instead.
Jdoll42
Computer Systems Engineer
I have no idea how you figured all that out, but you 'da man! I believe they said that the lines feeding it are around 13,000V, so I'm guessing that's the 12470 part?
Also, if the compressor is rated at an LRA of 150A, is the 104A capacity of the transformer sufficient? I'm not sure how it handles surges like that.
Bob NH
In the Trades
Ground Source Heat Pumps and Geothermal
Ground Source Heat Pumps and Geothermal Heating systems are not the same.
A geothermal system is one wherein the source of heat (the geothermal source) is hotter than the place you are trying to heat. You can get heat from it without any phase-change cycle such as a reversed refrigeration system.
Most residential units in the United States don't have access to geothermal sources.
Most "ground source" heating systems require a system to move energy from a cooler source to a warmer destination. That is why they are called "heat pumps".
All heat pumps (except thermoelectric devices which none of you have heating your houses) use some kind of fluid that changes from liquid to vapor when heat is added to it, and gives up heat when it changes from vapor to liquid. The fluid can be water/steam; ammonia as is used in many commercial refrigeration systems, hydrocarbons such as propane or butane, or any of a class of artificial refrigerating fluids some of which have the trade name of Freon. There are a lot of different fluids such as Freon-12 and Freon-22, which are called R-12 and R-22 when the non-trademarked brand is used.
The ground water can be used to heat or to cool. When it is used to heat, the water is used to heat the "Freon" (hereafter called the gas) in a heat exchanger (usually called the evaporator) so that it evaporates, cooling the water and adding energy to the fluid. The gas is compressed, raising its temperature and pressure. At the higher pressure the gas will condense at a temperature higher than the temperature of the place you want to heat. The condensing gas heats water (or other fluid) going through a heat exchanger that is usualled called the condenser. The condensed gas, now a liquid after giving up its heat, is returned to the evaporator to start the cycle again.
It is possible in some cases to cool a house with water from an aquifer without going through a phase-change cycle, but it is not possible to heat your house that way unless you live in Iceland or near a hot spring in Yellowstone Park or a few other places.
Ground Source Heat Pumps and Geothermal Heating systems are not the same.
A geothermal system is one wherein the source of heat (the geothermal source) is hotter than the place you are trying to heat. You can get heat from it without any phase-change cycle such as a reversed refrigeration system.
Most residential units in the United States don't have access to geothermal sources.
Most "ground source" heating systems require a system to move energy from a cooler source to a warmer destination. That is why they are called "heat pumps".
All heat pumps (except thermoelectric devices which none of you have heating your houses) use some kind of fluid that changes from liquid to vapor when heat is added to it, and gives up heat when it changes from vapor to liquid. The fluid can be water/steam; ammonia as is used in many commercial refrigeration systems, hydrocarbons such as propane or butane, or any of a class of artificial refrigerating fluids some of which have the trade name of Freon. There are a lot of different fluids such as Freon-12 and Freon-22, which are called R-12 and R-22 when the non-trademarked brand is used.
The ground water can be used to heat or to cool. When it is used to heat, the water is used to heat the "Freon" (hereafter called the gas) in a heat exchanger (usually called the evaporator) so that it evaporates, cooling the water and adding energy to the fluid. The gas is compressed, raising its temperature and pressure. At the higher pressure the gas will condense at a temperature higher than the temperature of the place you want to heat. The condensing gas heats water (or other fluid) going through a heat exchanger that is usualled called the condenser. The condensed gas, now a liquid after giving up its heat, is returned to the evaporator to start the cycle again.
It is possible in some cases to cool a house with water from an aquifer without going through a phase-change cycle, but it is not possible to heat your house that way unless you live in Iceland or near a hot spring in Yellowstone Park or a few other places.
Bill Arden
Computer Programmer
The transformer will be fine since it's only at a high current for a short time , but the voltage will sag.
Mikey
Aspiring Old Fart, EE, computer & networking geek
Which is the problem, no?
Lakee911
I&C Engineer (mostly WWTP)
I called the manufacturer.
Personally, I think it's undersized for handling the start up plus other running loads.
Jason
Jdoll42
Computer Systems Engineer
I've done some testing/measuring. Hopefully this will help.
House under "normal load" (compressor not running):
Hot Leg "A" to Hot Leg "B" -> 247.6V
Hot Leg "A" to Utility Neutral ("N") -> 123.5V
Hot Leg "B" to Utility Neutral ("N") -> 124.2V
Panel Ground to Utility Neutral -> 0mV
House under "heavier load" (double ovens turned on high broil, compressor not running):
Hot Leg "A" to Hot Leg "B" -> 247.5V
Hot Leg "A" to Utility Neutral ("N") -> 123.4V
Hot Leg "B" to Utility Neutral ("N") -> 124.2V
Voltage drop through Compressor breaker
-Compressor Off Leg "A" -> 16.6mV
-Compressor Off Leg "B" -> 16.7mV
-Compressor On Leg "A" -> 57.6mV
-Compressor On Leg "B" -> 51.8mV
House under "normal load" with compressor running
"A"-"B" at main panel lugs -> 247.2V
"A"-"B" at compressor breaker lugs -> 247.1V
House under "unbalanced load" (shut off breakers on one leg):
"A"-"B" at main panel lugs -> 249.6V
"A"-"N" at main panel lugs -> 124.5V
"B"-"N" at main panel lugs -> 125.1V
Min/Max/Avg during compressor startup at main lugs
232.0V/247.9V/246.9V
I used a clamp on amperage meter on one of the main 3/0 wires while the compressor was starting up hoping to visually catch a max amperage. (The clamp on meter doesn't have min/max/avg.) It was reading about 20-25A until the compressor started, then it just went blank. I guess it was too much for it? It immediately came back and started reporting higher amperages, but by then the compressor was already running.
I can provide pictures of the main panel where I took these measurements if necessary. They are already on my camera.
House under "normal load" (compressor not running):
Hot Leg "A" to Hot Leg "B" -> 247.6V
Hot Leg "A" to Utility Neutral ("N") -> 123.5V
Hot Leg "B" to Utility Neutral ("N") -> 124.2V
Panel Ground to Utility Neutral -> 0mV
House under "heavier load" (double ovens turned on high broil, compressor not running):
Hot Leg "A" to Hot Leg "B" -> 247.5V
Hot Leg "A" to Utility Neutral ("N") -> 123.4V
Hot Leg "B" to Utility Neutral ("N") -> 124.2V
Voltage drop through Compressor breaker
-Compressor Off Leg "A" -> 16.6mV
-Compressor Off Leg "B" -> 16.7mV
-Compressor On Leg "A" -> 57.6mV
-Compressor On Leg "B" -> 51.8mV
House under "normal load" with compressor running
"A"-"B" at main panel lugs -> 247.2V
"A"-"B" at compressor breaker lugs -> 247.1V
House under "unbalanced load" (shut off breakers on one leg):
"A"-"B" at main panel lugs -> 249.6V
"A"-"N" at main panel lugs -> 124.5V
"B"-"N" at main panel lugs -> 125.1V
Min/Max/Avg during compressor startup at main lugs
232.0V/247.9V/246.9V
I used a clamp on amperage meter on one of the main 3/0 wires while the compressor was starting up hoping to visually catch a max amperage. (The clamp on meter doesn't have min/max/avg.) It was reading about 20-25A until the compressor started, then it just went blank. I guess it was too much for it? It immediately came back and started reporting higher amperages, but by then the compressor was already running.
I can provide pictures of the main panel where I took these measurements if necessary. They are already on my camera.
Jdoll42
Computer Systems Engineer
I cracked open the cabinet and was following the wiring around. It looks like there is a decent sized capacitor in the wiring for the compressor. Is this what you were talking about?
View from the front:
View from around the back: (Sorry about the wires. It took me about 15 tries just to get the text in focus and not washed out by the flash.)
If this is a capacitor (can't think of anything else measured in μF) and is assisting the motor in starting, is there a chance that it is bad?
Mikey
Aspiring Old Fart, EE, computer & networking geek
That 232V Min is what you're seeing the effect of, I think. Bill Arden noted previously that the human eye can detect the effects of a 1% sag, as I recall, and you're seeing a 6% drop. Since this occurs at the main lugs, it points to the service -- either the transformer or the feeders. It'd really be instructive to see what the maximum current really is, and what the duration of the sag is. In any case, I think you might be able to talk the utility into a bigger can.
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Bill Arden
Computer Programmer
That is the "start cap". It provides the phase shift needed to drive the "start winding" on the compressor.
A 6% drop is annoying, but technically it's within the requirements power utility has to meet.
At this point I think we have explored all the possibilities and we should look at possible fixes
1. Larger transformer. (unlikely since it's owned by the utility)
2. Continuous Spinning reserve load or 3-phase converter. (would help, but wastes energy)
3. Lights that are less sensitive to voltage fluctuations. (The sag is not a problem if you can't see it)
4. Adding "soft start" or "hard start kit" to reduce the current pulled. (would not prevent other devices from causing detectable sags)
Lakee911
I&C Engineer (mostly WWTP)
It's possible that you could provide a another transformer (at your cost) and parallel the utilities transformer. You might be able to pick up a used surplus transformer for a few hundred bucks, if it's worth that much to you. The utility company would most likely hook it up for you if you installed it next to the existing per their specifications.
The other thing that you could do is tell them you're getting a swimming pool or instantanious electric water heater or something of high load. They will then probably replace it withn a larger unit. You would need to be sure you don't tell them you're getting something that would exceed your existing service, or they would be expecting to upgrade that as well. Once it's replaced, they would most likely not notice if your consumption didn't increase. You might pay a small amount for their upgrade though.
I don't know if a soft start has been suggested, but I'm not sure if they exist for a single phase motor. I know the existing caps would need removed though.
Generally we like to keep voltage drop at 5% or less. 6%, I think I read, seems excessive.
Jason
The other thing that you could do is tell them you're getting a swimming pool or instantanious electric water heater or something of high load. They will then probably replace it withn a larger unit. You would need to be sure you don't tell them you're getting something that would exceed your existing service, or they would be expecting to upgrade that as well. Once it's replaced, they would most likely not notice if your consumption didn't increase. You might pay a small amount for their upgrade though.
I don't know if a soft start has been suggested, but I'm not sure if they exist for a single phase motor. I know the existing caps would need removed though.
Generally we like to keep voltage drop at 5% or less. 6%, I think I read, seems excessive.
Jason
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