480Y or 208Y service from 240 Delta

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solarken

NABCEP PVIP
Location
Hudson, OH, USA
Occupation
Solar Design and Installation Professional
I am working with a commercial customer to solve some problems with their current service as well as lower their energy costs by installing Grid-tied solar. After monitoring their service through numerous adverse events and damaged equipment, I believe we have convinced them that the root of most of their problems is the open delta 240V service and that it needs to be changed. I would like to ask for any opinions on which service to go to, and any thoughts on pros and cons in making the choice. They currently have 400A service for their 3-phase equipment, open Delta 240V, and a separate 200A service for their single-phase loads like outlets,lighting, and office area appliances. The kWh usage is pretty equal across both services. A few of their machines have transformers that can be rewired to work with 208 or 480 Y. Some machines can operate off 208 as is with no changes. A few machines are designed for 480 but have transformers to convert to the existing 240 Delta.
The decisions to be made:
Change 240 Open Delta to 480Y or 208Y?
collapse their single phase service into the new 3-phase service, Yes or No?

Since the customer has been thru hell the last few years with blown SPD's, damaged machine controls, and downtime after voltage excursions and phase loss events, what protective equipment should we plan to included if any for the new service? Obviously cost is a consideration, but also reliability and resolving their power quality/reliability issues is very important.

Any advice, insight, or suggestions about other things I need to consider are appreciated.

480Y would be better for soalr inverter selection but I want to make the best recommendation for the customer.
 
I am not familiar with open delta, is the secondary voltage 120/240 3 phase? Does it have B phase at 208 to ground?
 
solarken said:
I am working with a commercial customer to solve some problems with their current service as well as lower their energy costs by installing Grid-tied solar. After monitoring their service through numerous adverse events and damaged equipment, I believe we have convinced them that the root of most of their problems is the open delta 240V service and that it needs to be changed. I would like to ask for any opinions on which service to go to, and any thoughts on pros and cons in making the choice. They currently have 400A service for their 3-phase equipment, open Delta 240V, and a separate 200A service for their single-phase loads like outlets,lighting, and office area appliances. The kWh usage is pretty equal across both services. A few of their machines have transformers that can be rewired to work with 208 or 480 Y. Some machines can operate off 208 as is with no changes. A few machines are designed for 480 but have transformers to convert to the existing 240 Delta.
The decisions to be made:
Change 240 Open Delta to 480Y or 208Y?
collapse their single phase service into the new 3-phase service, Yes or No?

Since the customer has been thru hell the last few years with blown SPD's, damaged machine controls, and downtime after voltage excursions and phase loss events, what protective equipment should we plan to included if any for the new service? Obviously cost is a consideration, but also reliability and resolving their power quality/reliability issues is very important.

Any advice, insight, or suggestions about other things I need to consider are appreciated.

480Y would be better for soalr inverter selection but I want to make the best recommendation for the customer.
Click to expand...
If solar is important to them and they are considering a large-ish system, say 50kW or more, 480/277V will play more nicely with the PV than 208/120V will. The selection of 208/120V inverters is very limited and they are mostly (all?) less than 30kW or so. There are a lot more 480/277V native inverters and they are available in much larger kW ratings. You can connect them to a 208/120V service but you'd need a step down tran$former and much larger conductor$.
 
What is the input from your power provider ?
It seems questionable that changing to 208 or 480 will help a lot with phase loss and SPD failures.
As to the solar, I rely on ggunn expertise in the above post,
 
hillbilly1 said:
Yes, same as a full delta, but only two transformers used instead of three. Mostly for services that don’t have a heavy concentration of three phase loads.
Click to expand...
Open and closed delta are simply descriptions of how the transformer windings are interconnected, similar to saying a Wye connection. These terms do not indicate what the Line to Line and Line to Neutral voltages are.
 
One thing to check is whether the branch circuits have adequate ampacity for the somewhat larger current that could be drawn by motors at 208V vs. 240V. If some don't have enough margin, then they would need to be changed if you go to 208V.
 
jim dungar said:
Open and closed delta are simply descriptions of how the transformer windings are interconnected, similar to saying a Wye connection. These terms do not indicate what the Line to Line and Line to Neutral voltages are.
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Yet you are not familiar with them? Very common in the US, and never seen it used for any other service voltages. Mostly 400 amp or less services, mainly Stop and Rob’s and light industrial.
 
As hillbilly1 said, it is three-phase derived from two transformers instead of three. Sometimes (usually) an add-on to a single-phase service when a piece of equipment requiring three-phase is added.

It used to be very common on rural REA systems (grew up on the farm) to avoid running two additional wires down the road, when one would suffice...and they got away with it in rural applications for many years as most loads were motor loads only.

The second transformer usually smaller than the single-phase unit, and the voltage on the 'open' leg from the smaller transformer can vary wildly depending on load(s) and power factor of those load(s); phase angle would also vary somewhat.

In my earlier life as a broadcast tech, I would see all kinds of damage in transmitters hooked to open deltas (broadcasters are a tight-fisted bunch, when given the option to save a few bucks by not going to a 'full upgrade' to three-phase, 99% of them chose the open delta (usually without consulting the guy who would be on the pointy end of the stick when it went off the air).

Within the last 20 years or so, broadcast transmitter manufacturers have universally declared 'NO WARRANTY' if a transmitter is connected to an open delta.

Manufacturers of other equipment may have the same clause in their warranty legalese (if not, they should !!)

Sorry to be long-winded and hope this helps.
 
hillbilly1 said:
Yet you are not familiar with them? Very common in the US, and never seen it used for any other service voltages. Mostly 400 amp or less services, mainly Stop and Rob’s and light industrial.
Click to expand...
I am more than familiar with these connections. Over the past decades, I have made lots of money off of contractors that thought these just these terms were sufficient to order equipment or perform troubleshooting.

Have you ever worked with open delta 120V 3phase 3wire? I have.
 
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