Mike Dolt Enterprises
Mike Dolt Enterprises
User: jbrown, Location: Chapel Hill, NC
Asked on: Friday, April 29, 2011 at 7:12 pm EDT
Answered on: Tuesday, May 14, 2024 at 4:48 am EDT
Question: Hi gang,I have a potential project that seems to skirt the edges for standard feeder calculations. What I'm finding keeps referring me back to branch circuits, which is not my issue at the moment, and I'm wondering if someone would double check my thinking process on this. And yes, Connecticut still uses the '05 code.Here's the fundamentals-The project proposes a new separate 120/208Y 3Ph~4w equipment panel to supply the following equipment:5) Taylor 794 twin soft-serve ice cream machines. ( 2) 3P ckts/machine; 19.0 MCA ckt-1; 15.0 MCA ckt-2 per spec cut sheet, or 34.0A per phase)4) Frigidaire FCRS201LF commercial refrigerators. (6.6A@120V/unit per call to Frigidaire, no tech info available online)1) Turbo Air MUR-48 undercounter refrigerator. (6.5A@120V/unit per spec cut sheet)Here's how I've been working to size the panel feeder and panel. Does this make sense or am I missing something obvious...?1. Largest units are the Taylors. I'm using the Min Ckt Amps as permitted in 440.35 and the 1st unit at 125% per 430.24.34.0A x 1.25 = 42.5A for 1st unit2. I then added the remaining 4 identical Taylors.34.0A x 4 units = 136.0A3. I totaled the Taylors,42.5 + 136.0 = 178.5A4. As long as these Taylors are not HVAC units, I believe 220.56 lets me apply a demand factor, 70% for 5 units.178.5A x .70 = 124.95A5. I added two Frigidaire's each on the A & B phases, the Turbo Air was added to the C phase. I didn't apply any demand factors to the fridge's because, well really, its a minor load.124.95A + 6.6A + 6.6A = 138.15A Total LoadI believe I should be able to use a 150A (min), 200A (preferred) feeder for this panel.Anybody have any thoughts, yea or nae on my feeder calc's? Any input would be appreciated.
Your feeder calculation method is generally correct, but there are a few points that could be clarified or adjusted:1. Circuit Amperage for Taylor Machines
Instead of using the minimum circuit amps (MCA) for the first unit, you should consider the maximum circuit amps (MCA) instead, as per Article 430.24. The MCA for the Taylor machines is given as 19.0A and 15.0A, so you should use these values for your calculation.
2.
Demand Factor
You have correctly applied the demand factor of 70% for five units of non-HVAC equipment. However, you have not accounted for the diversity between the ice cream machines and the refrigerators. In practice, it is unlikely that all of the ice cream machines and refrigerators will be operating at their maximum load simultaneously. You could consider applying a further diversity factor to account for this.3.
Refrigerator Load
While the load from the refrigerators is relatively minor, it is still good practice to include it in your calculations. Using the provided values, the total load from the four Frigidaire refrigerators and one Turbo Air refrigerator is 6.6A + 6.6A + 6.5A = 19.7A.
4.
Feeder Ampacity
Based on the adjusted calculations, your total load would be approximately:(19.0A + 15.0A) x 5 units x 0.70 + 19.7A ≈
130.3A
Considering this adjusted load, a 150A feeder would be insufficient. A 200A feeder would be appropriate for this application.Here is an updated summary of the calculations:1. Taylor Machines: (19.0A + 15.0A) x 5 units x 0.70 = 119.0A2. Refrigerators: 6.6A + 6.6A + 6.5A = 19.7A3. Total Load: 119.0A + 19.7A = 138.7A4. Feeder Ampacity: 200AConclusion:
Based on the revised calculations, a 200A feeder would be appropriate for supplying the proposed equipment panel. It is important to note that these calculations are based on the provided information, and actual field conditions should always be verified before finalizing the design. Flag for review