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Carrier HAP unmet load hours

Carrier HAP unmet load hours

Carrier HAP unmet load hours

I have a problem with HAP that I can't figure out.  The version I'm running is the latest upgrade, 4.5.

I am running simulations and the LEED report is showing that I have almost 2000 unmet load hours on the baseline building.  The systems are packaged RTU and VAVs with hot water reheat.  Setpoints (occupied/unoccupied) are 72/79 for cooling and 70/63 for heating.  On the cooling side, I have very few unmet load hours, so I'm good there, but on the heating side is where the problems are.  The RTU unmet load report shows that the cooling is fine, and the boiler plant unmet load report shows that there are not unmet loads on the equipment.  

So there's my first problem.  The LEED report shows unmet hours, but the equipment unmet loads reports don't match the LEED reports.  The system does have unoccupied setback in it. So, I thought that the LEED analysis might consider those first hours back in operation when the system is trying to eliminate the pulldown loads from the overnight float as unmet loads. So, I reduced the number of degrees of float and started the systems back on occupied operation earlier to try to get the temperature to setpoint by the time the people schedule showed as occupied.  This helped, so to test it further, I put the system thermostats to 24 hour occupied operation, but left the people, equipment, and light loading set to typical occupied/unoccupied hours.  This should mean that the systems have no problem keeping the setpoints and eliminate the pulldown loading.

However, I'm now still showing about 400 hours a year of unmet heating load.  The boilers and RTUs are autosized based on the systems' needs, and they are showing no unmet hours at all.  Still, the zone temperature reports are showing that the systems are unable to meet the setpoints for several hundred hours a year.

I'm stumped.

Any thoughts as to where I may have strayed or places to look for those unmet hours?

RE: Carrier HAP unmet load hours

Probably need to look at the your thermostat setpoints and more importantly the thermostat throttling range which needs to be realist and not too small.  

I normally set the cooling setpoint 23oC and 1oC throttling range (ie the peak cooling load is at around 24oC).  Similarly I set the heating setpoint 22oC witha 1oC throttling range (ie the peak heating demand is around 21oC.

RE: Carrier HAP unmet load hours

Myself and a co-worker have had the same problem on multiple jobs.  As a test I tried converting a v4.4 job to v4.5 and the unmet load hours went from below 50 for all buildings to well in the thousands.

I think there's a problem with the program.  I have an e mail into Carrier about it.  The support e mail is software.systems@carrier.utc.com and they're good about getting back to you.

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