ATS or Relay...

[mbrooke]

https://m.youtube.com/watch?v=ycaW6Wbl5UY

think this is the one I mean

Very simple and elegant- however I would add two things:


1. A time delay relay set to about 5 minutes on the normal supply contractor coil. This will prevent immediate transfer if the utility source comes back briefly and drops back out again, plus time for the POCO system to stabilize after an extended outage.

2. A voltage frequency relay on the generator contractor. As the generator is speeding up its not uncommon for the voltage to rise faster than the frequency. High voltage low frequency can cause motors, solenoids, transformers, and other equipment to saturate thus overheating and ruining them. If you can't find a VF relay, time delay relay set at 5-10 seconds while not ideal will usually get you buy.

 

[mbrooke]

This is not my idea. A contractor wants to submit a proposal for using 100A relays instead of a normal ATS; I asked him for documentation which hasn't send. So, I'm researching about the hardware and it's possibilities, particularly, when it's being used somewhere else...says him.

Let me provide another path... Microgrid systems, even though inverters have internal switching, need a disconnecting device at the service entrance. Manufacturers and installers will use relay controlled switches, but also mention the use of relays themselves as the disconnecting means. So, there seems to be some hardware that qualifies.

Regulation for microgrids in Puerto Rico is still developing, but constructions are being authorized; soon I will see one of those.

If done correctly it will work fine- but will violate the NEC. IEC not so much if within a DIN enclosure.

 

[Julio Trujillo]

If done correctly it will work fine- but will violate the NEC. IEC not so much if within a DIN enclosure.

So, adequate hardware is manufactured? Could you point me to a brand that I can read about?

I saw a couple of videos related to Adamjamma's youtube link; they use contactors arranged to work as an ATS. Interesting, I didn't know about those configurations. That could be a solution for the generator issue, maybe it's what used for the custom cabinets made for this purpose. Still, relays should take less space.

 

[drktmplr12]

Very simple and elegant- however I would add two things:


1. A time delay relay set to about 5 minutes on the normal supply contractor coil. This will prevent immediate transfer if the utility source comes back briefly and drops back out again, plus time for the POCO system to stabilize after an extended outage.

2. A voltage frequency relay on the generator contractor. As the generator is speeding up its not uncommon for the voltage to rise faster than the frequency. High voltage low frequency can cause motors, solenoids, transformers, and other equipment to saturate thus overheating and ruining them. If you can't find a VF relay, time delay relay set at 5-10 seconds while not ideal will usually get you buy.

3. 2 phase monitors in each transfer enclosure: (1) to ensure all legs are within thresholds before transferring load to the generator and (2) check utility power. alternatively you could take a signal from the generator system that indicates it is ready to be loaded. but would require multiplying the signal so a dry contact is available for each transfer switch assembly and ensuring the mechanism multiplying the signals has power during utility outage.

i think this will cost more, require more space, and be less reliable than traditional ATS.

consider staggering the closing of the transfer switches. can't imagine the gen is rated for all air compressors starting at the same time.

edit:

would there be a SCCR rating issue with using stand alone contactors?

 

[mbrooke]

So, adequate hardware is manufactured? Could you point me to a brand that I can read about?

I saw a couple of videos related to Adamjamma's youtube link; they use contactors arranged to work as an ATS. Interesting, I didn't know about those configurations. That could be a solution for the generator issue, maybe it's what used for the custom cabinets made for this purpose. Still, relays should take less space.

It is- Google things like time delay relays, phase loss relay, voltage relay, ect. Check out grainger- though I would imagine you can order them cheaper elsewhere.

3. 2 phase monitors in each transfer enclosure: (1) to ensure all legs are within thresholds before transferring load to the generator and (2) check utility power. alternatively you could take a signal from the generator system that indicates it is ready to be loaded. but would require multiplying the signal so a dry contact is available for each transfer switch assembly and ensuring the mechanism multiplying the signals has power during utility outage.

i think this will cost more, require more space, and be less reliable than traditional ATS.

consider staggering the closing of the transfer switches. can't imagine the gen is rated for all air compressors starting at the same time.

edit:

would there be a SCCR rating issue with using stand alone contactors?

Your load is indeed something to take into consideration- look at the inductive and restive switching ratings of the contractor.

 

[Adamjamma]

Since siemans makes a load of the stuff sold in Hong Kong, India and Europe that are shown in the videos, have you considered talking to their engineers? Could be they have something that is actually approved but not normally sold in USA... but is already type approved for USA...

 

[Russs57]

I’d wager interrupting current ratings would be a problem if used on the service conductors. Given the growing number of homeowners with ATS’s in the 100 to 200 amp range I doubt you could make something approved any cheaper.

 

[jeremy.zinkofsky]

So, adequate hardware is manufactured? Could you point me to a brand that I can read about?

I saw a couple of videos related to Adamjamma's youtube link; they use contactors arranged to work as an ATS. Interesting, I didn't know about those configurations. That could be a solution for the generator issue, maybe it's what used for the custom cabinets made for this purpose. Still, relays should take less space.

What mbrooke is saying and what i think you may be missing the point of, is that the NEC requires installations to be UL listed and listed for their use. No one is necessarily questioning whether relays or contactors will work or not. It is whether they are AHJ approved methods for automatic generator transfer. Please note that what may be acceptable in other countries is most often not acceptable to America or American Territories.

If you start searching for products that are listed to be used as an automatic generator transfer device, you probably will find that the only offerings are circuit breakers or automatic transfer switches.

I would get the AHJ to sign off on your approach before you keep spinning your wheels on this design.

 

[mbrooke]

What mbrooke is saying and what i think you may be missing the point of, is that the NEC requires installations to be UL listed and listed for their use. No one is necessarily questioning whether relays or contactors will work or not. It is whether they are AHJ approved methods for automatic generator transfer. Please note that what may be acceptable in other countries is most often not acceptable to America or American Territories.

If you start searching for products that are listed to be used as an automatic generator transfer device, you probably will find that the only offerings are circuit breakers or automatic transfer switches.

I would get the AHJ to sign off on your approach before you keep spinning your wheels on this design.

Yup, said it better than I could

 

[jumper]

And I thought I was a mad scientist...

 

[mbrooke]

Are you referring to what we call a "walking beam mechanism" that is connected to the handles of both breakers such that moving one handle On moves the other one Off? That would be a MANUAL Transformer Switch (MTS). The "Automatic" in the ATS means it needs no intervention or action by a human whatsoever once it is set up.

Is this what you are referring to by chance?

Here are the pros and cons of each ATS type. Yes contractors are the cheapest- but first run it by the AHJ.

https://electrical-engineering-portal.com/contactor-circuit-breaker-transfer-switch

 

[mbrooke]

And I thought I was a mad scientist...

 

[romex jockey]

And then there's the 'farmer' methods i see out in God's country..... ~RJ~