Carrier Greenspeed Observations

[isuredo]

Have about 40 of these in customers homes, beginning to see a trend in the ones that are oversized, as per carriers instructions. they seem to overshoot temp settings by anywhere form 1-3 degrees. only thing that seems to help is slowing the rpm down, anyone else seiing anything with them?

[motoguy128]

That seems strange. This is in heating mode correct? Since the controller measures to the 10th degree, it seems like it should modulate using roughly the same control algorithm as their modulating furnace. I wonder if in mild weather is responding too slowly. Does it overshoot all the time or only duirng recovery?

Interesting the limiting maximum capacity/rpm seems to resolve it. That sort of defeats the purpose... although the the 2 and 4 ton units form what I can tell are just the 3 and 5 ton unit with the maximum RPM restricted with some different EXV tuning maybe. I'm not sure the coils or compressors are even different at all. Helpos reduce development costs ot only have 2 compressors. Sort of like ECM's only comming in 1/2 and 1 HP sizes.

[isuredo]

i personally think the UI cant respond fast enough to changes, BUT, what id really like to know is what makes it step up in rpm in the 1st place?, never seen anything that really explains the logic of ramping up or down, and yes I agree it definately defeats the purpose of having a unit thats capable of not utilizing back up heat to a much lower temp, which is the HUGE factor in many of these sales to homeowners who want to save as much as possible. Have had distributors service guru onsite whos been in touch with carrier (supposedly) and they have basically thrown up their hands and said it is what it is

[motoguy128]

I will admit that even on my furnace it tends ro upstage when it aleady nearing setpoint. Basically its loop tuning parameters are off.
have you noticed the issue more on 3 4 or 5tons? I only ask since a 4 ton appears to be a 5 ton restricted, and nobody probably installs 2 ton units, since its basically a 3 ton with a reduced max rpm. Might as well put in a 3 ton and limit heating or cooling rpm if needed.



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