Trying to reduce 2 services to 1

S

SforresterBHC

Member
Location
Bullhead City Az
Occupation
Maintenance Electrician
Hello all, I work for a city utilities department, and I have a project I am working on concerning ATS.
I am trying to install ATS at all water distribution sites, all is good, except for 1. The site in question is fed from 2 sources, 1) 480v 400A 3 phase service from overhead powerlines that is used to power transfer pumps and 2 well sites close to the feed site, 2) a 120v/240v single phase 125A service from the street that is used for the main site 120/240v loads(lighting, RTU Cab, 208/230v AC, 120/240V sub panel on chlorine room, and recepts with a 240v welder recept in the work shop). The 2 well sites are no longer in operation and are completely abandoned, the 2 transfer pumps used at feed site are only 30A a piece. I want to set it up to only need 1 generator to power in a black out. My question is: is it more efficient to change the site over to being fed from the 3 phase 480v source with a 3 phase step down 120/208 panel and a couple buck-boost transformers for the 240v loads, or keep the 120/240v source and install a small transformer that only gets power when generator is in use that is also tied to a manual transfer switch to power RTU, Chlorine Room and lights only. First configuration would be simpler and straight forward IMO, but second could be less work and possibly cheaper (which is what I am told is the main factor in making this change).
 
Comments
A 480 TS is more expensive than 240
What is the minimum cost for each meter?
Are the transfer pumps single or 3 phase?
Are there two separate buildings?
 
tom baker said:
Comments
A 480 TS is more expensive than 240
What is the minimum cost for each meter?
Are the transfer pumps single or 3 phase?
Are there two separate buildings?
Click to expand...
Since the op is using a manual transferswitch at the other location, the transformer can be ahead of the switch, so the mts can be 250 volt, unless there is a voltage drop issue.
 
the transfer pumps are 480v 3 phase and the only loads off the 480v meter now, these are the main concern and a ATS for these the primary concern, however if we only power these they would need to be operated in hand and the level indicators, RTU would not be powered since they are fed from the secondary meter of 120/240v.

There is 1 building w/ 2 sub panels, 1 for a metal addition workshop and 1 for the small chlorine shed that feeds the 240v chlorine pump and level transmitters.
 
Install 1 single phase transformer 480V to 120/240V to refeed old equipment. Decommission the old single phase service. Get a transfer switch that picks up the whole board. Install a genset onsite that can carry the whole load or cam locks with a portable generator at a nearby supply yard.

Because of SCADA alarms and other related nuisance callouts I would advise making the transitions automatic to avoid your control center or on call crews coming in just to hook up or manually transfer the pumps. What seems cheaper right now might not be after a couple years of labor for the call outs. Not to mention the loss of SCADA itself during an outage.
 
The pumps are 25 HP so the 400A service feed is a bit overkill now.

I was going to just do a single phase 480 to 120/240v transformer but I would think that unbalance of load on the 3 phase 480v side wouldn’t be ideal in the long run. Is this just overkill thinking with the 480 transfer pumps being so small of a demand?

Short term we would be using a cam lock quick connect set up with the new ASCO ATS until we get a new permanent generator installed.
 
SforresterBHC said:
The pumps are 25 HP so the 400A service feed is a bit overkill now.

I was going to just do a single phase 480 to 120/240v transformer but I would think that unbalance of load on the 3 phase 480v side wouldn’t be ideal in the long run. Is this just overkill thinking with the 480 transfer pumps being so small of a demand?

Short term we would be using a cam lock quick connect set up with the new ASCO ATS until we get a new permanent generator installed.
Click to expand...

The unbalance is fine.

The cam locks are okay for a temporary measure but I would still advise on getting the automatic ATS now and spacing everything out.

Depending on the state regulator, you might be required to have an emergency system that automatically transfers. Or enough pumps on a emergency system to fulfill the systems needs.
 
Yes this is in the works, we will be doing an ATS, but use it as manual in the mean time because the city is short on portable generators at the moment, they had just recently acquired the water company a few years ago.
As for regulation, either no one cares or there isn’t much regulation on immediate emergency back up, some sites have auto switches with fixed generators, others have manual with no generator, and some like this one have neither, but this project I’m doing is going to add 8 ATS. This is the only oddball site with 2 separate feeds.

The only other question I would have, is the efficiency of having the step down transformer for a permanent change significant enough to warrant possibly trying to keep the 120/240v service? And only using the step down transformer for when the generator is hooked up?
 
SforresterBHC said:
The only other question I would have, is the efficiency of having the step down transformer for a permanent change significant enough to warrant possibly trying to keep the 120/240v service? And only using the step down transformer for when the generator is hooked up?
Click to expand...

Efficiency can be seen as two different things.

1) Being conscious of wasteful usage
2) Cost associated with increasing load due to transformer impedance

Efficiency has been getting better and is typically pretty good for dry types. I wouldn't worry too much about it. If your concern is wasteful usage than you would be weighing the utility XFMR and wire against the efficiency of the dry type. That would be negligable.

You will, however, be paying for the transformer losses in KWH and a small amount of KW on the billing. But it is typically a small difference and might be less depending on the electric utility rate schedules.
 
You must log in or register to reply here.
Top