I'm more agnostic about this. ASHRAE Climate Zone 1 (Miami) is very hot as well as humid.
Hopefully, there was some analysis done showing that economizers are not cost-effective
under such climate regimes.
Chris,
More warm weather = less available cooling from outdoor air = less justification for spending money to install economizer controls.
p.s., You must provide minimum outdoor air for ventilation, but need not also cool with outdoor air
1a I understand. But we are looking at a 1b location (Hot/ Dry). Surely the
best approach would be economiser with DB control?
Curiously, in my copy (90.1 2007) economisers are not required in *1b
*(table G3.1.2.6A).
However, the following table (G3.1.2.6B) denotes that economiser high limit
shutoff should be 75degF for *1b*.
Am I missing something fundamental about the physics of non-extant
economisers?
So your understanding is that a mixing box still exists, but the control
that varies outdoor air rate doesn't exist. It is in effect a fixed outdoor
air rate.
*"Curiously, in my copy (90.1 2007) economisers are not required for
1b (table G3.1.2.6A).
However, the following table (G3.1.2.6B) denotes that economiser high limit
shutoff should be 75degF for 1b."*
*
*
Chris
Who knows?
However, and until corrected by another who knows better, I would follow the instruction to leave out an economizer in Climate Zone 1b because it seems consistent with the pattern for warmer climates. My guess is that a zealous engineer mistakenly populated the table (6B) for that zone.
I'm more agnostic about this. ASHRAE Climate Zone 1 (Miami) is very hot as well as humid.
Hopefully, there was some analysis done showing that economizers are not cost-effective
under such climate regimes.
Joe Huang
Chris,
More warm weather = less available cooling from outdoor air = less justification for spending money to install economizer controls.
p.s., You must provide minimum outdoor air for ventilation, but need not also cool with outdoor air
James V Dirkes II, PE, BEMP, LEED AP
Hi Joe,
1a I understand. But we are looking at a 1b location (Hot/ Dry). Surely the
best approach would be economiser with DB control?
Curiously, in my copy (90.1 2007) economisers are not required in *1b
*(table G3.1.2.6A).
However, the following table (G3.1.2.6B) denotes that economiser high limit
shutoff should be 75degF for *1b*.
Am I missing something fundamental about the physics of non-extant
economisers?
Chris
Thanks Jim,
So your understanding is that a mixing box still exists, but the control
that varies outdoor air rate doesn't exist. It is in effect a fixed outdoor
air rate.
??
Many thanks
Chris
Correct.
James V Dirkes II, PE, BEMP, LEED AP
Great. A minor conundrum remains, quoting:
*"Curiously, in my copy (90.1 2007) economisers are not required for
1b (table G3.1.2.6A).
However, the following table (G3.1.2.6B) denotes that economiser high limit
shutoff should be 75degF for 1b."*
*
*
Chris
Who knows?
However, and until corrected by another who knows better, I would follow the instruction to leave out an economizer in Climate Zone 1b because it seems consistent with the pattern for warmer climates. My guess is that a zealous engineer mistakenly populated the table (6B) for that zone.
James V Dirkes II, PE, BEMP, LEED AP