What does the 'Use Load Credits' option in Heating / Cooling Loads do?

From the help file, it states:  accounts for heating or cooling “credit” loads that take the form of negative loads. For example, heat that leaves a zone through a partition into another zone can be a negative load/credit.

To exapnd on this, look at a couple of fundamental examples.

In the case of a heating load, it is common to not include internal gains, such as people, power, and lights.  The basic assumption being that these things may not actually be on or in the space to provide the gain. 

However, if you want to consider the internal gains in a heating calculation, the ‘Use Load Credits’ option will do this for you.

For example, looking at a single zone, in the Use Load Credits case, you see the heating load is less due to the credits from the internal gains:

Click to enlarge image.

Taking a look at a cooling load case, in the image below, the two zones have different set points.  Zone 1 is kept cooler; therefore, heat will “flow” from Zone 2 to Zone 1 (indicated by arrow 1).  In other words, there is a load on Zone 2 due to Zone 1.  Conversely, this means there is an internal loss from Zone 2 to Zone 1.  However, if you don’t ‘Use Load Credits’ you don’t see this in your cooling load calculation.  Arrow 2 on the tables below show the partition load, without the credit in Zone 2.  Using load credits allows the reduction of the load in Zone 2, as shown by arrow 3.

Click to enlarge image.

Comments

[Clint Rowley]

There's a lot more to heating and cooling that what appears on the surface and this post is proof of that!