Another harmonics question

[Dave_PE]

Existing elementary school. Plans are to add 180 plus computers, approximately 6 per classroom. Normal practice on the 277/480V schools would be to use a k-13 rated transformers and 200% neutrals to "deal" with the harmonics. However this school is served at 120/208V.

Plan is to add three 150A/3P CBs to the MDP with each feeding an 150A MLO panel with 200% neutrals for the feeders. Each panel would in turn feed about 60 computers, 3 per circuit with each circuit having a dedicated neutral.

Anything else needed? Harmonic Filters, Zig-zag transformers, Snake Oil?

 

[frenchelectrican]

Existing elementary school. Plans are to add 180 plus computers, approximately 6 per classroom. Normal practice on the 277/480V schools would be to use a k-13 rated transformers and 200% neutrals to "deal" with the harmonics. However this school is served at 120/208V.

Plan is to add three 150A/3P CBs to the MDP with each feeding an 150A MLO panel with 200% neutrals for the feeders. Each panel would in turn feed about 60 computers, 3 per circuit with each circuit having a dedicated neutral.

Anything else needed? Harmonic Filters, Zig-zag transformers, Snake Oil?

Harmonic filter will work nice if it do feed back to the POCO system or in the school electrical system .

Zig-Zag transformer humm ,,:roll: IMO not really pratical to use that at all

Snake oil :-? naw i am not crazy with it

but really you should check out with harmoic filter and find out what it will suit your need.

but i want to head up with ya for real quick senice you mention school watch out with the lighting system as well due most will use electronic ballast for their lumaires so it might compound it to some degree but check out with the tms ampmeter than the standard plain jane ampmeter on main supply so this way you can find out how much haromic it is loaded up that time

Merci , Marc

 

[robbietan]

Existing elementary school. Plans are to add 180 plus computers, approximately 6 per classroom. Normal practice on the 277/480V schools would be to use a k-13 rated transformers and 200% neutrals to "deal" with the harmonics. However this school is served at 120/208V.

Plan is to add three 150A/3P CBs to the MDP with each feeding an 150A MLO panel with 200% neutrals for the feeders. Each panel would in turn feed about 60 computers, 3 per circuit with each circuit having a dedicated neutral.

Anything else needed? Harmonic Filters, Zig-zag transformers, Snake Oil?

harmonic filters if you do have harmonic problems. how much of the load will be electronic? how much of the load are motors (aircon, pumps, fans, etc)? even if the loads are mostly electronic, still have to measure the level before doing anything. so that you will know the exact problem (if there is) and the right solution can be applied.

zig zag for ungrounded delta supplies. at 120/208, I believe that the supply is wye, no zigzag transformers needed.