ATS Switching vs Elevator, Motor Operation
ATS Switching vs Elevator, Motor Operation
I am not a code guy but I may shed some light on what I have experienced with
ATS switching and elevator/ motor operation.
If this is the cable (M-G) type (not hydraulic) driven elevator with solid state controls then
the equipment ATS should be equipped with a pre-signal or pre-transfer feature (see attached reply to a previous MH post.) As for the smaller HP motors the switching should not be an issue. Although the older, large, across the line setups presented problems in the past (breakers tripping, motor damage, etc.) Most newer motors are VFD driven and are designed to shut down and restart after transfer.
I had trouble attaching the file so I pasted it:
ATS Elev Pre Signal explained_MH
All of these replies are giving you the correct info but allow me to elaborate on the subject.
Basically, an elevator pre-signal, pre-transfer feature signals the elevator controller prior to a hot-bus hot-bus transfer (both sources energized.) This normally occurs when the ATS transfers back from gen to utility during a power outage or as stated, when the test button is used for initiating the transfer. During a power outage the feature is not activated on transfer to gen since this is a dead-bus hot-bus transfer (no utility power on ATS.) This feature, although can be found on the older relay logic ATSs, was not normally required with the controllers that used relay logic. However, it is extremely critical with the newer solid state controller logic on new installs or when old equipment is upgraded. The point is that the car cannot be moving during the switching of the motor load from one hot source to another with solid state controllers. Equipment damage such as blown circuit boards and components in the elevator controller can and will occur.
Part of my business involves designing and installing this feature on older systems (25 to 35 yrs) that have been upgraded.
Normally what I find is that the elevator vendor requires 2 seperate dry contacts that either NO or NC depending on the particular design/ Manuf. One contact operates 20 sec (adjustable) prior to transfer of the ATS. This signal sends the car to the nearest floor and the doors open. After transfer occurs, the contact resets and the car continues as normal. The second set of dry contacts operates after the ATS is in the emer position. Usually this signal puts the controller in emer mode and only allows for 1 car to operate on gen since they are not designed to power the whole bank of cars. We call
this the Switch Position contact. When norm power is restored, the sequence repeats in the retransfer to utility and both
contacts reset for normal elevator operation.
So depending on how the spec is written I usually see (4) #12 or #14 gauge (THHN, 600V building wire) field wires pulled between ATS and elevator room. I always recommend pulling spare wires for future use: wire is cheap compared to labor
PS: forgot to mention, on the older ATSs these field wires connect to a TB block and use plugin timers/relays. On the newer ATSs with microprocessors the connections are at the back of the processor and time delay is programmed in from the HMI touch pad.
hope this helps
