[BLDG-SIM] Modelling DDC vs Pnuematic Controls

[David V. Edelstein]

I was wondering how other people approach this modeling scenario.

You have an existing building with a constant volume re-heat system all
Controlled pneumatically.

You want to estimate savings in an EEM for installing DDC controls on the
air 
Handler cooling coil and all re-heat coils.

How would you model this? We have been debating two methods.

The first strategy:

		In the baseline model set the heating setpoint to 70 degs
and the cooling setpoint to 74 degs.
		Then to model the DDC in the measure set the heating
setpoint to 69 degs and the cooling setpoint to 75 degs.

		The argument goes that pneumatic thermostats are not as
accurate as digital temperature sensors and the savings
		would be expected from the reduced cooling and heating load.

The second strategy:

		In the baseline model set the zone level throttling range to
4 deg. and the cool coil control range to 4 deg.
		Then in the DDC model, set the zone level throttling range
to 2 deg. and the cool coil control range to 2 deg.

		The value you would set the DDC throttling ranges are
arbitrary and can be bumped higher or lower based on operating conditions.

		This strategy, I feel reflects the "tighter" control the DDC
would offer over pneumatics.


These strategies only address controls at the coiling and heating coil
level.

I would be greatly interested in how others view this problem.

Thanks for your input!

David Edelstein, PE

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