Starting from nothing, but going big

[TRW]

I've thought the same too about slow starts.
I have a Dayton compressor that now has trouble starting the second time (unloader but tank at 80 psi). I've had it connected across two 120V circuits. I think when one tripped it was experiencing brown out, often stalled and got hot. I think the starting windings could be partially cooked.

An A/C bleeds down pressure fully, unlike an air compressor. So each time it has to fill the condenser with pressurized refrigerant. How long at 3600 RPM does that take? That would say how may turns at reduced speed the soft-start could do.

I don't have anything soft-start. I do have a VFD with default setting of many seconds to ramp up a 3-phase water pump. A single phase motor wouldn't want to be started that slowly. But I would think even 1/4 second ramp up would be a big reduction in current draw.

If anyone does measure reduced running current with an Easy Start, my first suspicion would be the meter isn't true-RMS. When modified sine wave voltage is measured with a cheap meter, I think it inaccurately registers 90V or 100V instead of 120V so would expect similar from a funny current waveform.

It does appear the Easy Start make a big difference for starting an A/C when limited current is available.
If you haven't built yet, an inverter drive compressor would be even better.
I have one experience with a transformerless PV inverter apparently being upset by VFD, which is why I recommend transformer type. Any new inverter meeting latest codes for grid-tie is probably transformerless. I picked up older models.

For off-grid, there are several transformer type battery inverters with good motor starting surge. I have Sunny Island (more of them than I really need) and a small A/C, no trouble running that. Brands like Victron and Schneider have models that should work as well. Most brands will also have lightweight transformerless designs. Certainly for PV inverters, possibly for battery inverters (SMA has Sunny Boy Storage with 400V battery, and Tesla Powerwall is similar, both wimpy surge.) Most older 48V battery inverters would be transformer type, but I think newer and cheaper brands aren't.

Thanks for the input and info! I can tell you, as an expert in refrigeration, that the compressor builds pressure slowly, by that I mean it takes 5 seconds to get a small buildup, and it does not reach max pressure on a normal system for over a minute and much longer under some conditions. You have made some great points here, and I will sort them out later when I have time, but always enjoy your input.

Here is a device that works extremely well, and I have used hundreds of them, for over 40 years. This will help your compressor starting 99 percent.

Amazon.com

 

[TRW]

I've thought the same too about slow starts.
I have a Dayton compressor that now has trouble starting the second time (unloader but tank at 80 psi). I've had it connected across two 120V circuits. I think when one tripped it was experiencing brown out, often stalled and got hot. I think the starting windings could be partially cooked.

An A/C bleeds down pressure fully, unlike an air compressor. So each time it has to fill the condenser with pressurized refrigerant. How long at 3600 RPM does that take? That would say how may turns at reduced speed the soft-start could do.

I don't have anything soft-start. I do have a VFD with default setting of many seconds to ramp up a 3-phase water pump. A single phase motor wouldn't want to be started that slowly. But I would think even 1/4 second ramp up would be a big reduction in current draw.

If anyone does measure reduced running current with an Easy Start, my first suspicion would be the meter isn't true-RMS. When modified sine wave voltage is measured with a cheap meter, I think it inaccurately registers 90V or 100V instead of 120V so would expect similar from a funny current waveform.

It does appear the Easy Start make a big difference for starting an A/C when limited current is available.
If you haven't built yet, an inverter drive compressor would be even better.
I have one experience with a transformerless PV inverter apparently being upset by VFD, which is why I recommend transformer type. Any new inverter meeting latest codes for grid-tie is probably transformerless. I picked up older models.

For off-grid, there are several transformer type battery inverters with good motor starting surge. I have Sunny Island (more of them than I really need) and a small A/C, no trouble running that. Brands like Victron and Schneider have models that should work as well. Most brands will also have lightweight transformerless designs. Certainly for PV inverters, possibly for battery inverters (SMA has Sunny Boy Storage with 400V battery, and Tesla Powerwall is similar, both wimpy surge.) Most older 48V battery inverters would be transformer type, but I think newer and cheaper brands aren't.

I may have misunderstood your starting problem, so I am not sure the spp6 is the answer to your problem, but you can research it.

 

[Hedges]

I may have misunderstood your starting problem, so I am not sure the spp6 is the answer to your problem, but you can research it.

I'm guessing a partially shorted starting winding, due to overheating stalled a number of times.
It always seems to start from zero PSI, often stalls on restart.
I replaced the capacitor with no apparent difference.
I do have it on its own 240V circuit now, good enough wiring. Fed from the grid it has pretty much unlimited current available.

I was looking over the Supco data sheet

Supco

www.supco.com

I could try the 3W1 model, a 3-wire version for 1 to 3 HP.

I'll have to study my motor. Thought it had centrifugal switch for starting windings, but capacitor is "run" type.
The Supco adds a second capacitor in parallel so larger for starting, revert to standard for run.

My compressor does have an unloader, but the short pipe would build pressure quickly if tank had backpressure.
I was thinking if I added a cooling coil that would also delay pressure buildup.

 

[TRW]

I'm guessing a partially shorted starting winding, due to overheating stalled a number of times.
It always seems to start from zero PSI, often stalls on restart.
I replaced the capacitor with no apparent difference.
I do have it on its own 240V circuit now, good enough wiring. Fed from the grid it has pretty much unlimited current available.

I was looking over the Supco data sheet

Supco

www.supco.com

I could try the 3W1 model, a 3-wire version for 1 to 3 HP.

I'll have to study my motor. Thought it had centrifugal switch for starting windings, but capacitor is "run" type.
The Supco adds a second capacitor in parallel so larger for starting, revert to standard for run.

My compressor does have an unloader, but the short pipe would build pressure quickly if tank had backpressure.
I was thinking if I added a cooling coil that would also delay pressure buildup.

If you currently have a run capacitor, not a start capacitor, this should work for you.

 

[TRW]

So, I hope this is an ok question in this thread. There several new all in one units like the , All-in-one MPPT Solar Charger, Growatt SPF5000ES, I assume I could wire this up to an array and not need the micro invertors. I expect to never have any shading at all, and these units can be paralleled to fit as many panels as I have. Does this seem like a good alternative or a good design?

 

[Supervstech]

So, I hope this is an ok question in this thread. There several new all in one units like the , All-in-one MPPT Solar Charger, Growatt SPF5000ES, I assume I could wire this up to an array and not need the micro invertors. I expect to never have any shading at all, and these units can be paralleled to fit as many panels as I have. Does this seem like a good alternative or a good design?

It depends.
Where do you live and nd what power voltage do you need?
Are you planning to use the autotransformer like he did in the video?

 

[TRW]

It depends.
Where do you live and nd what power voltage do you need?
Are you planning to use the autotransformer like he did in the video?

I live in Wisconsin and will have 240 volt 60 cycle and yes I guess I will need the transformer to accomplish the 120 volt. Thanks for the reply and help!

 

[SolarPrep]

Have to consider whether it is on-grid or off-grid, and if on-grid are utility rates time-of-use?

Good net metering is better and cheaper than the best and cheapest battery. Use that if you can.
I wouldn't use lithium polymer, because even UL listed units have caught fire. Or if I did, located in a separate bunkhouse.
DIY LiFePO4 looks attractive (low price and high cycle life), with cells having welded on studs, and a BMS capable of delivering surge current. Or bypassed with a relay.
The AGM I presently use works fine for high surge current. It wouldn't be good for frequent deep cycling.

If time-of-use rates, it would be good to store PV generated power prior to 4:00 PM and spin the meter backwards 4:00 to 9:00 PM when rates are 3x as high.
I don't have experience with any inverters that do peak shifting. My Sunny Island (23kW continuous 44kW surge from 4 inverters) don't support that. Sunny Boy Storage does, but as a back-up inverter (with separate autotransformer and transfer switch) it is only 6kW continuous, 7.7kW maybe 9kW surge.
For peak shifting, I'd have to look over various companies and products, find something which also supports surge loads to start motors.
But when I looked at my cost for GT PV vs my cost for batteries, I think it is better to backfeed the grid with 3x the kW in the morning rather than buying a battery to store 1x the kW to be delivered during peak rates.

Rather than just an array facing South, I would have arrays facing SE and SW, so power production is spread over the day. This reduces peak battery charge current or grid export and gives more hours of production, for about 40% more Wh/day.

I would consider 3-phase. With my present split-phase utility connection, I could have only 6.7kW come from grid or backfeed grid through the 56A relay of one 120V Sunny Island. The other two would create the missing phases. With 3-phase connection 3x as much power could pass through, or off-grid 6x as much PV power could be supported. What I have now is split-phase with four Sunny Island, so 26 kW can pass through.

PV panels - find one known to be reliable. Accelerated stress testing shows high failure rates for some brands, as has field experience. When I added on last year one I considered was SunPower. Nothing I read questioned reliability, only whether it was worth the higher price. There was also that claim that of N-type silicon doped to make a cell vs. P-type, one has lower degradation rate, and that's what SunPower used. I'm not certain about the claims, but went with that brand. There was one model "P17" series I considered but it had some new and unusual aspects to how it was built so I bought more conventional "E20" series instead.

Software/firmware - I don't want anything updated. The boxes should work together as delivered and perform the functions specified in the manual. Shouldn't have to push updates to get the to do what was originally promised. Maybe a manual update to change from UL-1741 to UL-1741SA if desired.

Internet connectivity - Don't want to be a victim of Stuxnet, Sandworm, or the like. Nothing from the outside should be able to change the system unless I authorize it. A method to push data would be OK if there are no vulnerabilities, but I don't trust software, especially networking.

For the functions it does implement, my Sunny Island/Sunny Boy system works fine. I would use older transformer type inverters not the newer transformerless, because I think they're better at filtering out poor power-factor from switching power supplies like a VFD I have.

I have wondered if Sunny Boy Storage would work on a Sunny Island system, responding to frequency-watts and storing/providing power when needed. That would keep AGM batteries on Sunny Island always floating, except when they supply surges. Sunny Boy Storage is transformerless, and at least some of the 400V batteries compatible with it are lithium polymer. REC offers BMS for high cell count batteries; that might work to make a 128s LiFePO4 battery (100 kWh) for Sunny Boy Storage.

I know there are other good brands such as Schneider, Outback, Victron, but I don't have experience with them. I might consider if they had features I needed. I would look for units that could be stacked for higher wattage.

Where to buy - used/overstock vendors like SanTan have good deals on PV panels compared to retail outlets. There are probably other vendors who are good but I have bought from him.
For inverters and batteries, I've used Google to find listings, also eBay. Many retailers use eBay as a platform to advertise and it is the first place I look for everything. (But for LiFePO4 cells, forum members have identified good sources.)
I'm obviously not looking for a lot of support - I'm an EE and a contractor. For the inverters I've used SMA's help system.
Some of the retailers can put together a package and design the series/parallel configuration. AltE store for instance, who is represented on this forum.

Hedges: Reading some old posts...had a question about one part of your comment. How does the 3-phase come into play in an off-grid situation? Do you mean truly off grid? I cannot imagine a cabin or off grid house with 3 phase.

If you are somehow adding phases, I'd certainly like to know the answer to this. One thing I just cannot get out of my mind are the thousands of high quality 3 phase inverters sitting in warehouses from cancelled projects. If it was possible to use them off-grid, I know Amish guys who would love to learn about this to power their shops.

Am I mis-understanding your point?

 

[Hedges]

If someone has an off-grid property with shop tools, a 3-phase system could be considered.
I think 3-phase motors have better starting torque (good phase shift), but still draw a high surge current so inverter needs to supply that (33kW surge capability for a 3-phase Sunny Island setup)

With SMA, that would be three 6kW battery inverters connected 120/208Y. Split phase could be 12kW or 24kW, and 3-phase would be 18kW.
PV can be DC coupled, or some number of GT PV inverters. Up to 18 kW of GT PV could charge battery in 3-phase configuration, and more GT PV could be processed if used immediately for AC.

If used for a grid-backup system, the 3-phase configuration of Sunny Island battery inverters can either take in 3-phase from the grid (at full power), or one of the battery inverters can connect to one phase of 120/240V split-phase. In that case, only about 6kW can come from grid, and the other two inverters will make the missing phases.

Several other brands can do 3-phase too, including Victron and Outback.

What surplus 3-phase inverters do you mean? VFD for motors, 3-phase grid-tie PV, or 3-phase battery inverters?

For PV systems, 3-phase GT PV inverters can be AC coupled to battery inverters if both support frequency shift. SMA makes Sunny TriPower from about 12kW to 50kW which would work. They are 230/400Y so need 3-phase transformer for use with Sunny Island. SMA makes a 70 kW battery inverter for Europe of the same voltage, isn't UL listed but could be set to U.S. 60 Hz frequency. I haven't seen enough documentation to see if it works for an off-grid system. I think it is transformerless and it uses a high-voltage battery.

If VFD, those can take in split-phase (at least for low wattage) and ramp up frequency of 3-phase to start motors. They are better with 3-phase input. But the cheap little ones have diode-capacitor front end which draws a surge of current each time AC input exceeds capacitor voltage, and that has upset my GT PV inverters. A power-factor corrected VFD would be preferred.

It seems to me that VFD have a DC rail which could be fed from a (high voltage) battery, or from PV. Without an MPPT circuit in between, would want to size PV array so Vmp never exceeded capacitor voltage. I've contemplated whether I could feed PV into VFD on my pool pump, with diodes isolating PV from AC input. When PV available, could hold voltage above what AC delivers.

 

[TRW]

If someone has an off-grid property with shop tools, a 3-phase system could be considered.
I think 3-phase motors have better starting torque (good phase shift), but still draw a high surge current so inverter needs to supply that (33kW surge capability for a 3-phase Sunny Island setup)

With SMA, that would be three 6kW battery inverters connected 120/208Y. Split phase could be 12kW or 24kW, and 3-phase would be 18kW.
PV can be DC coupled, or some number of GT PV inverters. Up to 18 kW of GT PV could charge battery in 3-phase configuration, and more GT PV could be processed if used immediately for AC.

If used for a grid-backup system, the 3-phase configuration of Sunny Island battery inverters can either take in 3-phase from the grid (at full power), or one of the battery inverters can connect to one phase of 120/240V split-phase. In that case, only about 6kW can come from grid, and the other two inverters will make the missing phases.

Several other brands can do 3-phase too, including Victron and Outback.

What surplus 3-phase inverters do you mean? VFD for motors, 3-phase grid-tie PV, or 3-phase battery inverters?

For PV systems, 3-phase GT PV inverters can be AC coupled to battery inverters if both support frequency shift. SMA makes Sunny TriPower from about 12kW to 50kW which would work. They are 230/400Y so need 3-phase transformer for use with Sunny Island. SMA makes a 70 kW battery inverter for Europe of the same voltage, isn't UL listed but could be set to U.S. 60 Hz frequency. I haven't seen enough documentation to see if it works for an off-grid system. I think it is transformerless and it uses a high-voltage battery.

If VFD, those can take in split-phase (at least for low wattage) and ramp up frequency of 3-phase to start motors. They are better with 3-phase input. But the cheap little ones have diode-capacitor front end which draws a surge of current each time AC input exceeds capacitor voltage, and that has upset my GT PV inverters. A power-factor corrected VFD would be preferred.

It seems to me that VFD have a DC rail which could be fed from a (high voltage) battery, or from PV. Without an MPPT circuit in between, would want to size PV array so Vmp never exceeded capacitor voltage. I've contemplated whether I could feed PV into VFD on my pool pump, with diodes isolating PV from AC input. When PV available, could hold voltage above what AC delivers.

This reply is to the fist part where Hedges said "If someone has an off-grid property with shop tools, a 3-phase system could be considered. I think 3-phase motors have better starting torque (good phase shift), but still draw a high surge current so inverter needs to supply that (33kW surge capability for a 3-phase Sunny Island setup)"

This is all completely accurate, but it is easy, but not cheap, to soft start three phase motors. And they have remarkable starting torque, that is somewhat diminished when soft started.