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I went on a service call to a dialysis clinic and found that they were damaging sensative electronic dialysis machines and also learned that they have to hand crank them. The clinic is located in an existing nursing home and the clinic part is fed from a new 75 kva transformer and all new wiring. However, the main that feeds the transformer is fed from the existing switchgear and there is an old hydro elevator motor that is still in use. Whenever the motor kicks on it sags all power in the building and causes all the lights to flicker as well as the new transformer. The dialysis machines as well lose power and are constantly going out. I have never seen surges like this before and was wondering if someone could help me figure out the best way to fix this problem and maybe what could have been done to prevent this before the new construction of the clinic took place.
I looked at the service itself and the feeds from Edison dont look big enough. ALso it is a 240 volt 3 phase with high leg and the transformer is stepped down to 208/120.


Esteemed Member
Re: power

The delta service likely has one small transformer for only 3 phase load. This is causing a voltage sag when the motor starts. Ask the utility company to install a larger transformer.

The other solution is to install a fly wheel motor generator to power the dialysis equipment.
This will have ride through capability during the sag.


Senior Member
Re: power

The electric utility will not just install a larger transformer, they will have to have some test data to indicate that they are the root cause of the problem. My guess is that the load has grown and the electric utility was not informed. The result of no information is that the electric utility will not keep up with the growing needs of its customer.

Call the electric utility and they will send a trouble man out to check for loose connections, and get an ampere reading. If things look border line, they will request a test to be run with a chart for a period of time (usually 3 days). If their reading is really high, they will send a report to their engineering people. At least that is the way most electric utilities do it. :)

Ed MacLaren

Senior Member
Re: power

Does the elevator motor have a soft starter (reduced-voltage starter) installed.
This voltage sag problem is exactly what they were designed to remedy.

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