Single to 3 Phase converter for HVAC Equipment

[crazedengineer]

Has anyone here used solid state (Static) Phase converters for HVAC units before? I have only seen them used in industrial applications before (Hydrolic Shears, Press Brakes, etc.). I was hoping to get some real world experiences before recommending them as a possible solution to a client.

 

[Jraef]

Has anyone here used solid state (Static) Phase converters for HVAC units before? I have only seen them used in industrial applications before (Hydrolic Shears, Press Brakes, etc.). I was hoping to get some real world experiences before recommending them as a possible solution to a client.

No matter what you use, there are losses, so there is a loss of efficiency in converting electrically and that loss of efficiency translates DIRECTLY to higher utility bills. On machines, that loss is often offset by some other benefit to using 3 phase, or there simply is no single phase motor available for that machine, or if there is, it is too difficult to get at to swap it. On HVAC systems, there is zero benefit to using 3phase and in general, it is usually a simple task to swap out a 3phase motor for a single phase version, because they are usually off-the-shelf motors anyway.

Lets start there first. Why is your client wanting 3phase? Did someone sell him on that old chestnut of it being more efficient? Not true (let the "3phase is more efficient" wars commence).

 

[StarCat]

HVAC Systems

HVAC Systems

Speaking as a Jouurneyman HVACR Shop Foreman, there is every benefit in the world with 3PH vs 1PH for HVAC and refrigeration systems with respect to the major load which is the compressor. They are definitely more efficient, especially with respect to starting inrush, and without the need for single phase start components. Single phase start components also add a large extra layer of complexity to service which is totally absent when dealing with 3 phase machines. IN commercial-industrial properties such as the one I currently oversee, HVACR loads are the biggest in many cases. 3 Phase distribution and 3 phase HVACR gear is the obvious choice when it is possible. Any HVAC man worth his salt will tell you that he would rather work on 3 phase gear all day long than single phase.
For the job in question, without knowing the specifics I will say this.
It would most likely be better to convert the system in question to single phase internally if 3 phase is not available, or otherwise replace the unit with equivalent single phase machines. IF we were talking about one unit which only needed a compressor replaced to make it go, the price vs. and entire unit could be looked at. A savvy HVACR Tech can easily make this conversion.
Having run motor driven phase converters in the past on some Milnor commercial laundry machine, they can be very problematic and require time consuming machine retrofits to allow everything in the chain to " get along " and run without incident. I cannot say I advise them ever for large inductive loads with electronic controls, and especially not 3PH VFDs.


Sincerely