240 volts 1-phase, 3-phase 1-line

[vaaoc1425]

On customer request I have a design for 240 voltsa 1-p,3-p system 1-line with CT connection to provide power for 4 tenents.

Can some one direct me to a link for a typical 1-line to refresh my memory.
I do not do 240 vots system on regular bases.
I need to have 120 v, 240 volt 1-p and 240 v -3p loads. I know a Y-Delta transfor will take care of this but I like to review a typical 1-line for such system

Thank you in advance

 

[waross]

First check with your utility. Some utilities will not supply four wire delta services. Consider open delta. It avoids a few issues with wye:delta transformers and transformer banks. Cheaper also.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[dpc]

Google "high leg delta".

I agree with Bill - many utilities will no longer provide this service.

The spilt between three phase and single phase loads and between 120V and 240V loads is also a factor.



David Castor

http://www.cvoes.com

 

[jraef]

Start with the utility before you worry about the one-line diagram. If they will do a "high leg delta" service it's only when there is a small percentage of 1 phase loads compared to 3 phase loads, and I have never heard of a utility supplying it to a multi-tenant service. Most likely they will want to drop a 480/277V 3 phase 4 wire service and let you deal with what happens after that, or maybe a 208/120V 3 phase 4 wire service.

"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
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[waross]

Hi jraef.
In other areas open delta may be used to power a relatively small three phase load and a large single phase load.
One particular application was a small machine shop in a residential area. There was a 100 KVA single phase transformer serving a couple of blocks of residences as well as the machine shop. There was a teaser transformer of about 25 KVA to supply open delta 240 Volts to the three phase machinery in the machine shop.
Open delta was also used for large residential loads back when large single phase air conditioning units were not available.
I don't think that many new installations are going in but I have seen the remnants of the three phase residential services a few times. As well as the normal 120:240 Volt single phase service there would be a teaser transformer to supply open delta three phase for the air conditioner.
And in agreement with you, I have seen a number of full delta three phase services for factories where the lighting was fed from one of the three transformers in the transformer bank.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Miguel Villarroel]

How large line is? Does it has lateral connection or only tenants at the end (thinking in future demand)? How many and how much needs 120vac-1p 240vac-1p and 240vac-3p?

If there was no electricity there would be no internet. Good point, don´t you?

 

[vaaoc1425]

This is an existing system [strip Mall] the user has roof top HVAC system and other equipment at 240V. He does not want change it more actable . This is 800 amp systems and the user wants it to be designed for four clients and meter them separately. In short the designer has no choice except to give him what he wants.

 

[dpc]

In short the designer has no choice except to give him what he wants.

The utility has a choice.

David Castor

http://www.cvoes.com

 

[Miguel Villarroel]

I think you are right with wye neutral grounded, e.g. you can serve each tenant with one leg supplying two lines and neutral, they´ll can connect 120vac or 240vac one phase loads only, and keeps three legs to move HVAC system and other 3p loads

If there was no electricity there would be no internet. Good point, don´t you?

 

[waross]

It will be cheaper to put in four single phase services and meters and then one three phase service and meter for the HVAC. But, what the customer wants and What the utility will provide.
At 800 Amps the utility may demand a three phase wye service. It depends. Some utilities will meter up to 400 Amps single phase directly without CTs.

Bill
--------------------
"Why not the best?"
Jimmy Carter