120/208Y Cheaper?

[mbrooke]

Good point on motors, I had not thought of that despite being obvious (at least it should have been for me).

Does anyone have the losses for typical dry type 50-112.5kva step down transformers?

 

[kwired]

All the loads can be 120/208, or the HVAC and lighting can be 277/4

Which gets us to why some were asking, how much KVA would be needed for 208/120 loads after you put as much HVAC and lighting or other major loads on the 480/277? Maybe instead of needing 5000 amp @ 208/120 you got it down to only needing 400 or 600 amps at that voltage.

 

[mbrooke]

Which gets us to why some were asking, how much KVA would be needed for 208/120 loads after you put as much HVAC and lighting or other major loads on the 480/277? Maybe instead of needing 5000 amp @ 208/120 you got it down to only needing 400 or 600 amps at that voltage.

I'm getting roughly 800 amps at 480 volts for 120/208 volt loads, mostly cooking appliances.

 

[petersonra]

It seems to me that this situation meets one of the exceptions where you could have two services entering the building. So why not have the POCO give you both and hook up whatever you can to the 480/277 V service and what you have to to the 208/120 V service.

 

[kwired]

I'm getting roughly 800 amps at 480 volts for 120/208 volt loads, mostly cooking appliances.

Is this going to be bigger load than HVAC and lighting? If so then maybe having service @ 208/120 is fairly justified, unless you have 480 volt options on said cooking appliances.

 

[petersonra]

Alot of chain retail and restaurants are 208v 3phase in the 400A to 1200amp range, if 480v makes the service smaller and cheaper they would be all over it to save money.

It might also be that they perceive that the systems can be maintained by someone who costs less. There are a fair number of people including a fair number of electricians who think there is something special about 480 V that precludes just anyone working on it, as opposed to 120 V systems.

The reality is that there is not all that much difference.

 

[kwired]

Is this going to be bigger load than HVAC and lighting? If so then maybe having service @ 208/120 is fairly justified, unless you have 480 volt options on said cooking appliances.

Or depending on circumstances you have 480 feeders to certain areas of the building and multiple 208/120 systems covering smaller areas? Still can depend on certain factors as to which is best. Save on copper now vs more losses over time? Client maybe not expecting a long stay in leased space and rather spend less upfront instead of worrying about long time losses?

 

[kwired]

It might also be that they perceive that the systems can be maintained by someone who costs less. There are a fair number of people including a fair number of electricians who think there is something special about 480 V that precludes just anyone working on it, as opposed to 120 V systems.

The reality is that there is not all that much difference.

I see that applying to anything that is not 120/240 single phase more so than just to 480 volt systems where I have been.

Even more so the guy that can wire anything, as long as it is only 120 volts (one grounded and one ungrounded) is pretty common as well, but don't let them run into an existing multiwire circuit or they get themselves into trouble.

 

[mbrooke]

Is this going to be bigger load than HVAC and lighting? If so then maybe having service @ 208/120 is fairly justified, unless you have 480 volt options on said cooking appliances.

HVAC and lighting combined will be a bigger load.

 

[mbrooke]

It seems to me that this situation meets one of the exceptions where you could have two services entering the building. So why not have the POCO give you both and hook up whatever you can to the 480/277 V service and what you have to to the 208/120 V service.

Honestly, I think this would be the most ideal.

Though for some reason not all POCOs allow it?

 

[mbrooke]

Or depending on circumstances you have 480 feeders to certain areas of the building and multiple 208/120 systems covering smaller areas? Still can depend on certain factors as to which is best. Save on copper now vs more losses over time? Client maybe not expecting a long stay in leased space and rather spend less upfront instead of worrying about long time losses?

As it is now the building is expected to be used by the same client for 40-60 years. Not just capitol, but long term bills are being considered.

 

[petersonra]

As it is now the building is expected to be used by the same client for 40-60 years. Not just capitol, but long term bills are being considered.

Someone will need to run an analysis of how much electricity will be used one way versus the other. Unfortunately, it is very hard to get numbers that reflect reality because most of the equipment has a low duty cycle. It is pretty easy if you assume everything runs 100% of the time, but when your real load is 20-50% of the maximum load most of the time, getting real numbers is tough.

Years ago I became aware of a project to replace some old motors with new high efficiency motors. This was supposed to save money on electricity. There was some kind of subsidy involved paid for by the POCO (so really the other rate payers) to provide "free" motors.

Most of the motors that were proposed to be replaced were for pumps that were rarely used (like sump pumps). You could never economically justify replacing a motor that is used a few minutes at a time a half dozen times a day. But their calculations based on 100% duty cycle showed how much money would be saved. So they got a bunch of free motors that effectively became spares.

 

[Russs57]

I would think it easy to find 480 volt cooking equipment.

What I can say is it is becoming harder/more costly to find 208 volts motors (unless you are willing to except a 240 volt motor running at 208 with a 1.00 service factor).

 

[kwired]

It seems to me that this situation meets one of the exceptions where you could have two services entering the building. So why not have the POCO give you both and hook up whatever you can to the 480/277 V service and what you have to to the 208/120 V service.

Honestly, I think this would be the most ideal.

Though for some reason not all POCOs allow it?

Even if they do, what is long term cost for an additional service vs losses you will have if you separately derive one system? sounds like you are somewhat 50-50 with the load on each system, but that probably per NEC? if a lot of cooking equipment, as already mentioned POCO very well puts in a smaller transformer on the 208 system than you possibly do if you separately derive it.