electro7
Senior Member
- Location
- Northern CA, US
- Occupation
- Electrician, Solar and Electrical Contractor
Hi,
I have been trouble shooting a solar system that is quite convoluted. It has single phase inverters connected to a three phase system (delta with a high leg). It is residential. The homeowner has not seen a change in his electric bill since putting in the second solar system. The first solar system was installed in 2006 with three single phase inverters, two of which were connected to his three phase system. The other to his single phase system. (He has two meters, one single phase system and the other which is three phase.) He did see about a 50% decrease in his bill after installing the first solar system.
The second solar system was installed in 2013. It has three single phase inverters, two of which are connected to the three phase system. (The biggest concern is the 3-phase system inverters and the true up bill he is getting from that meter.)
I have checked all the read outs on the inverter for "energy total" and everything seems to be working fine. The utility meter tech was there today and found that the meter is working correctly. We even turned off all other loads and checked what the meter was reading vs what was reading on the inverter screens for instantaneous power and it added up pretty close between the four inverters that are connected to that meter. As a matter of fact I think the meter was reading more that what the solar was putting out.
I checked voltage in a lot of configurations- two inverters off, the other two on; the other two invertes off, and the other two on; all inverters on and all inverters off. I am thinking that the inverters are throwing the voltage off so that there is a higher imbalance between phases. Therefore causing the motors to run hotter, harder and more inefficient. I am wondering if somebody could confirm this for me and help me out with a solution? Here are the readings I got:
No Solar On: Readings at the garage sub-panel ("Garage solar")
A-B 246; B-C 243; C-A 243 (Avg 244V, .8% Vmu)
Readings at the solar in field ("Field Solar") (240V to 208V step down transformer, 2-208V single phase
inverters connected)
A-B 212; B-C 213; C-A 215 (Avg 213.33, .78% Vmu)
"Field Solar" On, "Garage Solar" Off: Readings at the garage sub-panel
A-B 247; B-C 243; C-A 244 (Avg 244.67, .95% Vmu)
Readings at solar in field
A-B 213; B-C 215; C-A 217 (Avg 215, .93% Vmu)
"Garage Solar" On, "Field Solar" Off: Readings at the garage sub-panel
A-B 252; B-C 245; C-A 246 (Avg 247.67, 1.75% Vmu)
Readings at solar in field
A-B 211; B-C 215; A-C 216 (Avg 214, 1.4% Vmu)
All Solar on: Readings at the garage sub-panel
A-B 251; B-C 245; C-A 246 (Avg 247.33, 1.48% Vmu)
Readings at field solar
A-B 214; B-C 220; C-A 222 (Avg 218.67, 2.14% Vmu)
I did not take any readings at the service. I tried switching on of the two inverters in the garage sub-panel from phase C-A to B-C phase at it tripped both solar breakers in that sub-panel. Not completely sure why that happened. I tried it to hopefully correct the voltage imbalance.
The two "field solar" inverters are connected to phases C-A and B-C. The two "garage solar" inverters are connected to A-B and B-C.
Can anybody help me??
I have been trouble shooting a solar system that is quite convoluted. It has single phase inverters connected to a three phase system (delta with a high leg). It is residential. The homeowner has not seen a change in his electric bill since putting in the second solar system. The first solar system was installed in 2006 with three single phase inverters, two of which were connected to his three phase system. The other to his single phase system. (He has two meters, one single phase system and the other which is three phase.) He did see about a 50% decrease in his bill after installing the first solar system.
The second solar system was installed in 2013. It has three single phase inverters, two of which are connected to the three phase system. (The biggest concern is the 3-phase system inverters and the true up bill he is getting from that meter.)
I have checked all the read outs on the inverter for "energy total" and everything seems to be working fine. The utility meter tech was there today and found that the meter is working correctly. We even turned off all other loads and checked what the meter was reading vs what was reading on the inverter screens for instantaneous power and it added up pretty close between the four inverters that are connected to that meter. As a matter of fact I think the meter was reading more that what the solar was putting out.
I checked voltage in a lot of configurations- two inverters off, the other two on; the other two invertes off, and the other two on; all inverters on and all inverters off. I am thinking that the inverters are throwing the voltage off so that there is a higher imbalance between phases. Therefore causing the motors to run hotter, harder and more inefficient. I am wondering if somebody could confirm this for me and help me out with a solution? Here are the readings I got:
No Solar On: Readings at the garage sub-panel ("Garage solar")
A-B 246; B-C 243; C-A 243 (Avg 244V, .8% Vmu)
Readings at the solar in field ("Field Solar") (240V to 208V step down transformer, 2-208V single phase
inverters connected)
A-B 212; B-C 213; C-A 215 (Avg 213.33, .78% Vmu)
"Field Solar" On, "Garage Solar" Off: Readings at the garage sub-panel
A-B 247; B-C 243; C-A 244 (Avg 244.67, .95% Vmu)
Readings at solar in field
A-B 213; B-C 215; C-A 217 (Avg 215, .93% Vmu)
"Garage Solar" On, "Field Solar" Off: Readings at the garage sub-panel
A-B 252; B-C 245; C-A 246 (Avg 247.67, 1.75% Vmu)
Readings at solar in field
A-B 211; B-C 215; A-C 216 (Avg 214, 1.4% Vmu)
All Solar on: Readings at the garage sub-panel
A-B 251; B-C 245; C-A 246 (Avg 247.33, 1.48% Vmu)
Readings at field solar
A-B 214; B-C 220; C-A 222 (Avg 218.67, 2.14% Vmu)
I did not take any readings at the service. I tried switching on of the two inverters in the garage sub-panel from phase C-A to B-C phase at it tripped both solar breakers in that sub-panel. Not completely sure why that happened. I tried it to hopefully correct the voltage imbalance.
The two "field solar" inverters are connected to phases C-A and B-C. The two "garage solar" inverters are connected to A-B and B-C.
Can anybody help me??