Breaker up or down

[resistance]

MCA is for wire size.
MOCP is for breaker/fuse size.
If MCA is 44.9, I'm pretty sure the MOCP is AT LEAST 50A. Most likely 60A
You can downsize the breaker to 40A, but with an MCA of 45 I think you'll have problems with breaker tripping.

I agree!! But, i?ll go take a look Weds!!

 

[kwired]

Resistance - you should post a link to the unit nameplate values so they can see how the manufacturer provided values for this one and other units. I see almost no increase for MOCP -vs- MCA other than rounding up to the next standard breaker size.

This is a combination compressor, heater, fan unit with the following values:
Compressor RLA 12.8
Outside Fan 0.9A
Inside Fan 2.0A
5KW Heat 20.8 FLA

Summation MCA is 44.9

Add those values up and you do not get 44.9.

You will get 44.9 if you use 125% of the compressor and heat then add the two fans.

You did not mention what the MOCP is.

 

[suemarkp]

A 125% factor needs to be added to the strip heat since it is a continuous load. So MCA would be (12.8*1.25)+0.9+2.0+(20.8*1.25) = 44.9

It is the fact that the spec sheet had two columns "Fuse/Breaker" and "MOCP" that is the confusion. The Fuse/Breaker column said 45. The MOCP column had a "-". So does this mean you can upsize per whatever applicable rules you can find, or are you stuck at 45? Don't know what to do when the maximum fuse is explicitly blanked on the spec sheet.

 

[resistance]

A 125% factor needs to be added to the strip heat since it is a continuous load. So MCA would be (12.8*1.25)+0.9+2.0+(20.8*1.25) = 44.9

It is the fact that the spec sheet had two columns "Fuse/Breaker" and "MOCP" that is the confusion. The Fuse/Breaker column said 45. The MOCP column had a "-". So does this mean you can upsize per whatever applicable rules you can find, or are you stuck at 45? Don't know what to do when the maximum fuse is explicitly blanked on the spec sheet.​

I agree!! Well, we will know by Wed..

 

[kwired]

A 125% factor needs to be added to the strip heat since it is a continuous load. So MCA would be (12.8*1.25)+0.9+2.0+(20.8*1.25) = 44.9

sounds logical, but the blowers that are added at 100% are just as continuous as the heat strip or compressor...

It is the fact that the spec sheet had two columns "Fuse/Breaker" and "MOCP" that is the confusion. The Fuse/Breaker column said 45. The MOCP column had a "-". So does this mean you can upsize per whatever applicable rules you can find, or are you stuck at 45? Don't know what to do when the maximum fuse is explicitly blanked on the spec sheet.

If fuse/breaker column says 45 then it is 45 max fuse or breaker, maybe I got lost in what you said MOCP means same thing - fuse or breaker.

 

[resistance]

Sorry for the delay. Here is the name plate info.. The unit is CPheater052A

 

[texie]

Sorry for the delay. Here is the name plate info.. The unit is CPheater052A

I'm confused. What is the difference between max breaker/fuse and Max OCPD? I don't understand why there are two columns.

 

[suemarkp]

The first column doesn't say max. The second column with the max has a "-" for this unit. That is the confusing question -- is the 45A specified for the breaker/fuse a MAX or not?

 

[texie]

The first column doesn't say max. The second column with the max has a "-" for this unit. That is the confusing question -- is the 45A specified for the breaker/fuse a MAX or not?

I missed that finer point on the fuse/breaker does not say max. I'm not sure that I've seen a label like this before. Are we to assume that the breaker/fuse is the max in the absense of data in the other column?

 

[resistance]

The first column doesn't say max. The second column with the max has a "-" for this unit. That is the confusing question -- is the 45A specified for the breaker/fuse a MAX or not?

I?m going to assume Max. And the breaker/Fuse should be sized for what?s available per NEC 240.6. They do sell 45A breakers, so this one should be used. Again, seeing that this is a combination unit, the calculations have already been done, so need to add any percentages.

 

[Strife]

Sorry for the delay. Here is the name plate info.. The unit is CPheater052A

After looking at the label, I'm not sure what the confusion is about???
The 8th column (Fuse or HACR breakerper NEC) says 45/45 (if that's your heater). So that's that. 45A
Not sure why the MCA is 44.9A(20.8A for the heater times 125%=26-27A, plus 5-6 Amps at the most for the motors, it's only about 31-33), but that's what the manufacturer is specifying.
Allthough if you consider the permissible voltage allowed, then you have about 24A*125% for the heater=30, plus another 5-6 for the motors, it gets close.
Not gonna do the exact math, but it seems the MCA is the heater at 125% and all the motors(including the compressor) at 125%. Not sure why they did the as the compressor and the heater SHOULD be non concurrent loads. However, I have seen AC's who use the heater to dry the air at the same time the compressor is running, so that may be your answer.

 

[kwired]

Not sure why they did the as the compressor and the heater SHOULD be non concurrent loads. However, I have seen AC's who use the heater to dry the air at the same time the compressor is running, so that may be your answer.

Not sure where you have seen this or if that is what you actually saw and not some other reason to run at same time.

Evaporator coils do dry the air - that is why condensation runs off of them - they are removing moisture from the air. Running additional resistance heat would just make for a very inefficient air conditioner. Portable dehumidifiers are nothing more than a small air conditioner the water they collect is produced exactly how the condensate from the whole house AC is produced - making it pointless to run them when you are also running the AC because you are gaining additional heat in the conditioned space from natural heat losses in the dehumidifier.

If the unit is a heat pump they can run heater strips while the heat pump goes through defrost cycle to add more heat to make the cycle shorter in duration.