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| Subject - oh well, ask a stupid question..., | |
| doug | I have a question about determining the FLA for a trane ux120960D furnace. According to the nameplate information, the ampacity is 12.9, it has a 3/4 hp motor for the blower drive. The combustion fan is 1/20. The FLA listed in the spec manual which came with it states .71. this does not seem correct to me. Am I missing something here? This is important because I am providing circuits for 8 units which will be twinned together to result in four units. It currently has been engineered for 8 individual branch circuits, and of course the mechanical engineer or designer did not inform the electrical engineer what their plans were during the planning stage. Thing is, these furnaces which are twinned have to be on the same phase in the panel, obviously since there is a low volt transformer for control, the NEC requires that in order to supply more than one motor, (among other things) the FLA has to be less than six amps;hence the question of WHERE DO YOU DETERMINE WHERE THE FLA IS IN TOTAL on these things???? thanks in advance |
| kbsparky | I think you answered your own question with this information:quote: So, I went to my gas furnace, and had a looksie at its nameplate. Mine has a ½ hp motor on it, and its rated Amps is 8.5. With that information, I'd say that 12.9 is reasonable for one with a 3/4 hp motor in it. That other value you stated (.71 Amps) was probably for the 1/20 combustion fan only. |
| lctrc789 | I agree with Ken on this it only makes sense that the FLA is the motors both of them combined.. |
| luckyshadow | It is my understanding you go with the nameplate rating on HVAC equipment. The manufactors base these ratings on how these units operate. Besides when the inspectors go over the installation they look at the nameplate to determine if you have used the correct hacr breaker or fuses. |
| doug | thanks guys for the info, however, I would ask for patience as I further ask: the ampacity is not neccesarily the same as the FLA with motors, correct? In other words, if the manufacturer is required to list the FLA on the nameplate for all pertinent motors associated with the piece of equipment, whether they list the components separately or all together, then seeing .71 under the combustion fan listing and 12.9 under the electrical supply heading, how does one reasonably determine what the TOTAL FLA is concerning this particular model, since the manufacturer should list the totalFLA to start with? I could further ask if this were the case, then is there a particular formula available that anyone knows to field determine what the FLA is for any given motor with certain given information? THANKS MUCH GUYS IN ADVANCE |
| luckyshadow | Another thing to look at is : Does this unit list the minimum circuit amps ? and /or the max fuse / HACR breaker size ? I have seen this information on other units. |