Beginner Question on Fan schedule

6 posts / 0 new
Last post

Hi all,

I tried searching for an answer on archives but unable to find an answer.

I in Schematic Mode I set fan to "intermittent" meaning HVAC fan is only on when heating/cooling is needed...

1) if I set it a value of "1" fan is on alwayst on
2) Set 0 Fan is "off"

Since it is in intermittent mode, when i set to 0.... there is never any cooling. what am I doing wrong? Because if i set fan schedule in Detailed edit mod to 1 the fan is always on and I don't want that.

I want intermittment fan schedule but it's either 1 or 0 in the fan schedule...

Thanks!

meneedhelp's picture
Offline
Joined: 2012-06-03
Reputation: 0

Hello Jay,
Do you have the DOE2.2 Reference manuals? DOE2.2Vol2-Dictionary.pdf
explains what the INTERMITTENT keyword means.

See page 361 under INDOOR-FAN-MODE.

The reference manuals are available for download at
http://doe2.com/download/doe-22/

Download the latest edition of each manual and enjoy!

>> Christopher Jones, P.Eng.

Chris Jones's picture
Offline
Joined: 2011-09-30
Reputation: 0

Thanks for the link to the manuals and such, Chris.

I am also investigating "intermittent" as it affects EnergyPro, which
claims to use "DOE-2.1E* v119".

The issue involves using "INTERMITTENT" and how that affects heating
energy. Heating energy drops dramatically when "INTERMITTENT" is
invoked. It drops so far that it does not seem realistic, although no
errors or flags result that I can find.

I have found some references to "INTERMITTENT" causing negative CFM:
http://doe2.com/download/DOE-22/Bugfixes-047h.pdf

Question - Do you (or anybody on the list) have any ideas why invoking
"INTERMITTENT" in a program that uses DOE-2.1E*V119 would show such
effects on heating energy (very, very, very low)?????

Thanks for thinking about this!

Robert Wichert P.Eng. LEED AP BD&C

RobertWichert's picture
Offline
Joined: 2011-10-02
Reputation: 201

I don't think the behavior of INTERMITTENT changed from DOE2.1e to
DOE2.2. The DOE2.1e Supplement has the same wording as the DOE2.2 manual.

I would add some hourly reports - supply cfm, OA ratio, heating
energy and cooling energy. Run for both CONTINUOUS and
INTERMITTENT. There may be some differences in the amount of outdoor
air that is being introduced.

>> Christopher Jones, P.Eng.

Chris Jones's picture
Offline
Joined: 2011-09-30
Reputation: 0

Thanks Chris! I'll try to figure it out. Adding those reports within
EnergyPro may be trivial though.

Thanks again.

Robert Wichert P.Eng. LEED AP BD&C

RobertWichert's picture
Offline
Joined: 2011-10-02
Reputation: 201

Reduced outdoor ventilation air would have been my first guess. I've seen a lot of portable classroom buildings that have a wall-mounted heat pump. Unless they're on a DDC system, they usually come equipped with either a programmable or just a plain vanilla wall thermostat, that's typically set to Auto (intermittent) instead of Fan On (continuous). Same thing for regular classrooms with a roof top package unit. Modeling the two different fan modes can show a significant different in heating consumption

Once the classrooms are up to temperature, there often isn't a lot of heat load as the result of internal lighting and occupant heat gains. On a similar note, where the fan is set to Auto/intermittent, I often measure CO2 levels over 3000 ppm, where a good target is 750-800 and the ASHRAE max limit is 1000 ppm. Not the best indoor air quality to promote the learning environment for the kids.

Mike

Michael R. Busman, CEM

Busman, Michael R's picture
Joined: 2012-07-12
Reputation: 0