UPS changeout

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WECC

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We have a small regional 911 call center that also handles state police and EMS commuications networks. There is no alternate site to transfer these systems to at this time for a shutdown.

They are powering the communications equipment through a single phase 208V 16KVA UPS system that is having problems and needs to be replaced. The UPS was not provided with an external bypass but has an internal bypass that takes normal power around the inverter and batteries and sends it through an isolation transformer before it feeds the panel.

The owner has purchased an identical UPS unit to the one that is failing and needs to change it out without an outage. We believe we can take the new UPS place it in bypass and use it to parralell feed the equipment panel then shut down the old ups and remove it from the system.

Basically we will be feeding the same panel with (2) Isolation transformers built into the UPS units for a short period of time while the old one is removed. We beleive it will work as long as we keep the phasing correct and check for voltages between the 2 feeds before energizing the new unit.

If anyone has some thoughts we would like to hear them.
 
At least you won't have far to go to call 911 when things go horribly wrong.
 
Is the existing bypass inside the existing UPS? How do you remove it when you are using the bypass path?

Run a temp from a spare upstream of the UPS to a spare load breaker and parrallel for a short period of time being sure to check to see if the existing isolation xfmr is delta-wye, because then the phases will not be syncronized and you can't do it this way.
 
And does the new installation include a method to do this again in the future without being energized?

Once, to fix an old install can be excused. But there's no excuse for not providing for the future of the system.
 
WECC said:
We have a small regional 911 call center that also handles state police and EMS commuications networks. There is no alternate site to transfer these systems to at this time for a shutdown.

They are powering the communications equipment through a single phase 208V 16KVA UPS system that is having problems and needs to be replaced. The UPS was not provided with an external bypass but has an internal bypass that takes normal power around the inverter and batteries and sends it through an isolation transformer before it feeds the panel.

The owner has purchased an identical UPS unit to the one that is failing and needs to change it out without an outage. We believe we can take the new UPS place it in bypass and use it to parralell feed the equipment panel then shut down the old ups and remove it from the system.

Basically we will be feeding the same panel with (2) Isolation transformers built into the UPS units for a short period of time while the old one is removed. We beleive it will work as long as we keep the phasing correct and check for voltages between the 2 feeds before energizing the new unit.

If anyone has some thoughts we would like to hear them.
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Should NOT be done. UPS output should never be paralleled with another source. You can do it through a static switch.
  • Install the static switch.
  • Connect the 'old' UPS to input A and
  • Connect the load to the static switch output.
  • Connect the 'new' UPS to input B,
  • Force it to select B input,
  • Cut A input.
Doing this energized? Hmmmmm, safety folks will be screaming.

Your Static switch MAY have a problem with the bypass and in that case chunk the whole idea above:roll:

The static switch will be your new external bypass source and can connect input A to anything you like.
 
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