Sorry to bump this - I'm completely stuck, and I feel like I'm too close
to give up. Let me simplify my question to see if avoiding a wall of
text helps:

Is there any way to pull a calculated variable into a user expression?
(e.g. the previous hour's total end-use energy from the electric meter)

Am I doing this the hard way? How have others done demand limiting (or
haven't you?)

Thanks!

Eric

_____________________________________________
Sent: Wednesday, September 29, 2010 2:25 PM
To: equest-users at lists.onebuilding.org
Subject: Demand limiting / peak-shaving

Has anyone successfully implemented demand limiting? The
project I'm working on has a pretty extreme demand ratchet, and there
appears to be significant cost savings to be had if I can reduce my
peaks.

It looks like the load management feature will have a
"peak shaving" option in a future version, although I'm not entirely
sure it's what I'm looking for either. I'm hoping to modify temperature
settings at the zone level and have the reduced load "trickle down" to
my AHU's and plant. I'd like to avoid resetting my plant, only to have
my fans speed up to compensate.

This is essentially the idea:

Each zone will have 3 temperature
setpoints: Normal, first stage demand limit, second stage demand limit.
Each zone can be programmed individually, so critical zones will have
all three setpoints at the normal level. As the building demand
approaches a setpoint, the first stage limiting setpoints will override
the normal setpoints (approximately 2F warmer). If the demand continues
to rise towards the setpoint, all zones will be adjusted upwards again
to their second stage limiting setpoint (approximately 4F warmer than
normal setpoint).

Ultimately, I think I'm going to need to build a
schedule that has user expressions for my summer daytime hours.
Unfortunately, I really don't know what I'm doing with user
expressions...

I've set 5 global parameters for easy modification:

RegTemp=74
DemTemp1=76
DemTemp2=78
kWlimit1=700
kWlimit2=750

And then I'm going to insert the following into my
temperature schedules (#VALUE is the variable I'm looking for)

{if (#VALUE<#PA("kWlimit1"))
then #PA("RegTemp")
else if (#VALUE<#PA("kWlimit2"))
then #PA("DemTemp1")
else #PA("DemTemp2")
endif
endif}

What can I replace #VALUE with that's going to call up
this hour's (or last hours) demand? Will this work?

Thanks!

Eric