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How is the Minimum Turndown Ratio for SetpointManager:WarmestTemperatureFlow coordinated with the VAV terminal minimum flow rates?

asked 2017-06-01 00:13:58 -0600

Molly Curtz gravatar image

updated 2017-07-24 09:07:28 -0600

I'm looking at using SetpointManager:WarmestTemperatureFlow with the FlowFirst option. (From the IO Reference: "For FlowFirst, the manager tries to find the lowest supply air flow rate that will satisfy all the zone cooling loads at the maximum setpoint temperature. If this flow is greater than the maximum, the flow is set to the maximum and the setpoint temperature is reduced to satisfy the cooling loads.")

There is an input field for Minimum Turndown Ratio. What can I do if the connected VAV boxes have various turndown ratios (rather than the same for all), or if the connected VAV box minimum flow ratios are scheduled rather than constant? Will this SPM work for these cases?

For example: if the SPM input Minimum Turndown Ratiois 0.2, and that flow rate is used to establish the supply air temp setpoint, but a connected VAV terminal minimum flow ratio is actually 0.3, then the zone may be overcooled.

Why doesn't the SPM get the minimum flow information from the connected VAV terminal objects?

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answered 2017-08-27 23:30:06 -0600

I just stumbled across this in the InputOutput Reference while researching SPMs myself:

image description

So according to this the SPM will assume that all VAV boxes have the same minimum turndown.

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Asked: 2017-06-01 00:13:58 -0600

Seen: 197 times

Last updated: Aug 27 '17