variable fan variable flow 4 Pipe FCU

asked 2018-11-09 10:37:10 -0600

s_pourm

775 ●3 ●11

updated 2018-11-12 13:41:41 -0600

Using OS.2.6

For a 4pipe FCU, if we are using variable fan variable flow, are the low speed and medium speed inputs being ignored?

image description

If I want to have a variable speed fan that goes down to 50% low speed, what should be the inputs?

answered 2018-11-13 15:17:07 -0600

Aaron Boranian

14250 ●86 ●24 http://bigladdersoftware.com/

This OpenStudio HVAC component will be translated into the EnergyPlus ZoneHVAC:FourPipeFanCoil object. If you want to use a variable fan, then there are four operation modes:

off
low flow
medium flow
high flow

The "high flow" is set by the Maximum Supply Air Flow Rate input field above the two input fields you highlighted. The two highlighted input fields are then ratios of low or medium flow compared to high flow. However, these input fields are NOT used for your (variable fan + variable water flow) system -- they should be blank.

If you want to have a minimum fan flow of 50%, you need to scroll down farther below these input fields for the FCU to see the input fields for its internal components -- fan, cooling coil, heating coil. The fan should be a variable volume, and have an input field for setting the minimum flow method (set to Fraction) and ratio of minimum flow to maximum flow (set to 0.5).