[Equest-users] Supply CFM based on heating / cooling mode

[Nick Caton]

I have a few thoughts/ideas, in no particular order – maybe something here helps:

Note these flow inputs exist for the system and zone level – you could be editing one and looking at results for the other.

I think MIN-FLOW-RATIO (minimum flow ratio) can override the (optional) heating minimum flow input.  Required ventilation capacities can override either as well if I’m not mistaken – maybe worth checking.

Just to point out:  a MIN-FLOW-RATIO of 1.0 means the flow will go no lower than 100% of what’s specified (or calculated) for SUPPLY-FLOW.  Consider carefully if and where that should apply to fans in the system you’re modeling.

Another thought is at least some of these zonal inputs will default to the system’s values if you aren’t specifying them separately… perhaps your central system is in cooling, using 1.00, while your terminal units are in heating and you end up with a conflict?

~Nick

[cid:489575314 at 22072009-0ABB]

NICK CATON, P.E.
SENIOR ENGINEER

Smith & Boucher Engineers
25501 west valley parkway, suite 200
olathe, ks 66061
direct 913.344.0036
fax 913.345.0617
www.smithboucher.com

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of ToddGibson at Eaton.com
Sent: Tuesday, June 19, 2012 10:27 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Supply CFM based on heating / cooling mode

Hi,

I’m trying to specify separate, constant CFMs for heating and cooling mode operation (Ex:  5,000 Heating & 7,500 Cooling).

The system I created is Variable Air Volume which serves multiple thermal zones.
The Fan Flow Parameter MIN-FLOW-RATIO is set to 1.00.  I read this as the minimum supply CFM during cooling mode.
The Fan Flow Parameter HMAX-FLOW-RATIO = 5000/7000.  I read this to be the maximum supply CFM during heating mode.
The Fan Flow Parameter HMIN-FLOW-RATIO = 5000/7000 -0.01.  I read this to be the minimum supply CFM during heating mode.

But from the hourly report the CFM supplied, defined by SUPPLY-FLOW = 7,500, is the cooling quantity during heating mode when I would have expected it to be 5,000.  As far as I can tell no flows are specified at the zone level that would override it.  Any thoughts on things to look at would be greatly appreciated.

Thanks, Todd


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