Dwelling Calculation Separate Blower

[lowell]

Using the 2026 code, in Article 120.53 is the fixed appliance loads information where 4 or more can be taken at 75%, except for the list of items that cannot be used for this. The question is on the Heat and the Air conditioning equipment. The sections state they cannot be used for the 4 or more, but what about the separate blower in a force air furnace and AC system. The blower is for both the heat and the AC and can also be used by itself. When used by itself, it is neither Heat or AC. So, I count it as a fixed appliance according to 120.53 and allow the derating if 4 or more appliances. If all agree that it cannot be used, what do I do with it? Add it to both the AC and Heat before comparing them for the largest load based on 120.6.

Any thoughts would be greatly appreciated.

 

[Dennis Alwon]

You are trying to create a loop hole. It is part of the hvac system so just do what needs to be done with the calculation based on Hvac.

The largest motor load will not be from the heating or a/c units. In many cases that wont even enter into the calculation.

 

[augie47]

Whether it's "proper" or not may be debatable but I have seen Art 220 examples where the author has included the air handler as a Art 422 appliance,

 

[kwired]

Blower alone is typically not all that significant of a load and won't really have much impact on your total load calculation should you include it.

Heating elements or compressors usually are more significant of a load, but are usually a part of the items not allowed to be included here.

 

[wwhitney]

Add it to both the AC and Heat before comparing them for the largest load based on 120.6.

This.

You could also consider a 3rd case under 120.6, namely blower only, no A/C and no Heat. And for that case using 120.53 on the blower would be reasonable. But surely one of the other two cases will be largest, so there's no point in calculating this 3rd case.

Cheers, Wayne

 

[lowell]

You are trying to create a loop hole. It is part of the hvac system so just do what needs to be done with the calculation based on Hvac.

The largest motor load will not be from the heating or a/c units. In many cases that wont even enter into the calculation.

No I am not trying to find a loophole. Since the blower motor can run in three different ways, with heat, with AC or by itself, just trying to find where to put it in the calculation. I know it is a very small load but trying to do it correctly.

 

[lowell]

This.

You could also consider a 3rd case under 120.6, namely blower only, no A/C and no Heat. And for that case using 120.53 on the blower would be reasonable. But surely one of the other two cases will be largest, so there's no point in calculating this 3rd case.

Cheers, Wayne

Wayne you are correct that the blower motor will never be the largest motor most likely. I believe as I stated that since it can be use by itself it is a fix appliance. I am not worried about the largest motor, just how to add it into the calculation.

 

[Dennis Alwon]

Look at it this way. When you use the dishwasher as an appliance the motor isn't considered in the calculation because it is already factored in when you use the nameplate load.

A blower if part of heating system wouldn't be considered because it is in the calculation for that unit. Now if there is no heat and just a/c then in most cases the motor would be considered however that is unusual. I guess the same is true for a situation with no heat or a/c but just a blower---I have never seen the last 2 scenarios.

 

[jim dungar]

No I am not trying to find a loophole. Since the blower motor can run in three different ways, with heat, with AC or by itself, just trying to find where to put it in the calculation. I know it is a very small load but trying to do it correctly.

Do you consider the bathroom exhaust fan an appliance? Why would the HVAC blower be any different?

 

[wwhitney]

Wayne you are correct that the blower motor will never be the largest motor most likely.

My comment was not related to whether the blower motor was the largest motor. It was based on how the blower is being used: either as part of the heating (excluded from 120.53), part of the air conditioning (excluded from 120.53), or standalone for ventilation/air filtration (would fall under 120.53 if it is an appliance).

So sure, consider the 3 different use cases, do the 3 calculations under 120.6, and you'll find that one of the first two is the largest load. Which means in practice you can ignore the 3rd case, and just include the blower with the HVAC.

Cheers, Wayne