Trying to add a load to Back-up Generator

[JOHNEO99]

Hello,

I have been looking at a job where the facilities manager wants to add the 5-AHU's to the back-up generator. Here is the scenario as I see it. There is a 175K Gen Set feeding a 400 and 200 ATS both 208/120v. From the 200 AMP ATS it goes to a 200 amp 42 circuit panel board for life safety circuits and there are three breaker spaces unused. The 400 AMP ATS goes to a 400 amp emergency equipment distribution panel with 42 circuits and there are also three breaker spaces unused. It also has two sub-feeds: 100AMP breaker for telecommunication room panel, 200 AMP breaker for a disco feeding a boiler switch board. The gen set is running at 28-30% on their monthly checks.

I am trying to get the 100 AMP panel for 5- AHU's (which draws about 40 AMPS) that is fed from a switchboard to be fed from the back up generator but everything is filled up on the existing emergency equipment and life safety panel boards minus the three breaker spaces left over which I don't think I can use as they are not rated for a sub feed? Plus I would think I would need a visible disconnect for the AHU panel.

Ive gone through a number of situations in my head to try and figure out how to make this work by code and don't feel comfortable with one yet. I think the generator can handle it but need to find a way to include the new load.

Any suggestions would be helpful.

 

[Len]

genset

genset

1st you cannot tie into life saftey.
2nd you need to do load calc to make sure genset is big enough.
3rd you need to find out if AHU would be optional. If it is then you must add another ats.

 

[JOHNEO99]

I'm not sure what an optional AHU is. I am thinking of coming off the 400 amp panel to a small 100 amp panel and feeding them that way. I didnt do a load calc but the 400 amp panel is drawing 60-120 amps within the sample half hour I did.

 

[ceb58]

1st you cannot tie into life saftey.
2nd you need to do load calc to make sure genset is big enough.
3rd you need to find out if AHU would be optional. If it is then you must add another ats.

I'm not sure what an optional AHU is. I am thinking of coming off the 400 amp panel to a small 100 amp panel and feeding them that way. I didnt do a load calc but the 400 amp panel is drawing 60-120 amps within the sample half hour I did.

Would the air handlers be deemed emergency or optional? If it is optional you cannot tie into the emergency system and must add another ATS.
Your load calculations must be done per article 220. A 30 min. sample wont cut it.

 

[hillbilly1]

I'm not sure what an optional AHU is. I am thinking of coming off the 400 amp panel to a small 100 amp panel and feeding them that way. I didnt do a load calc but the 400 amp panel is drawing 60-120 amps within the sample half hour I did.

Since you do have a seperate T-switch for the life safety, and as long as the load calc comes up good, there should be no problem adding a 100 amp sub off of the 400 amp panel, if you can come up with the space. A common practice is if a panel is full, with no space to add a breaker for a sub panel, move two or three of the circuits out of that panel into your new panel in order to free up space for the new sub panel feed.

 

[JOHNEO99]

Since you do have a seperate T-switch for the life safety, and as long as the load calc comes up good, there should be no problem adding a 100 amp sub off of the 400 amp panel, if you can come up with the space. A common practice is if a panel is full, with no space to add a breaker for a sub panel, move two or three of the circuits out of that panel into your new panel in order to free up space for the new sub panel feed.

After going back and thinking about it after my original post and hearing your post I have come to the conclusion that this is the most practical installation.

 

[JOHNEO99]

Would the air handlers be deemed emergency or optional? If it is optional you cannot tie into the emergency system and must add another ATS.
Your load calculations must be done per article 220. A 30 min. sample wont cut it.

I cant say but I know the boilers are running off the EM panel and these air handlers run in conjunction with them on a standard basis and so they want the air moving in order to move the heat in the hallways and paient rooms. I can do the load calc for you.

 

[hillbilly1]

Did not know this was a healthcare facility, there may be some other requirements you may have to meet, but in an ordinary occupancy you would be ok.

 

[JOHNEO99]

Did not know this was a healthcare facility, there may be some other requirements you may have to meet, but in an ordinary occupancy you would be ok.

Its an assisted living type 1 facility.

 

[kwired]

Its an assisted living type 1 facility.

Assisted living generally is not a health care facility. It could have limited health care areas, but those would be about the same thing as exam rooms in a clinic. Equipment, life safety, and critical branches apply to health care facilities. Even after reading 517.25 the NEC does not really determine whether these separate systems are required, it tells how they are to be installed when required. The FPN after 517.25 refers us to NFPA-99 to determine if the system is required.

If it is not required you could still have a Art. 701 legally required standby system - it will not have the three branches required in a hospital though.

If the boilers are on the standby power but the air handlers are needed to distribute the heat there was likely an error at the inital install.