[user_12345a]

Cycling off after 1 minute isn't normal.

on generic controls you can either adjust the deadband or cycles per hour per setting. it sounds like your t-stats are trying too maintain too tight of a deadband.

For controls with cycles per hour for cooling it should be set to 3.

The actual number of cycles may vary but it shouldn't be coming on 5 times in 25 minutes. No way.

i have no idea about your controls.

While it's true that setting it higher for a few hours may cause humidity issues, it shouldn't cause this problem. Your contractor should be seeking out a solution rather than giving you the run-around.

 

[user_12345a]

I wonder if it's a call for dehumidification that's rapidly cycling the system and not for cooling. That would probably be governed by different parameters.

Maybe shut off dehumidify mode or raise the setting high to isolate temp control from dehumidification.

You can also set the setpoint to 79, humidity normal and see if you have the same problem.

Your controls may have an adjustable humidity deadband so you aren't rapidly cycling it.

If i set the humidity to 50%, i would want it to come on at 55% and run until it's in the high 40s. Not maintain a super tight band especially when the space is unoccupied.

All i know is that there's a problem and you're being given the run around.

 

[user_12345a]

maybe you shouldn't change settings but you should at least check them to get an understanding of what's going on.

Manual - http://dms.hvacpartners.com/docs/1009/public/07/systxccitw-07si.pdf

check 6.3.12 section - there's a deadband adjustment for temperature.

i don't see and adjustable deadband for humidity but only quickly skimmed the manual.

 

[user_12345a]

offset is totally different.

a 2f degree swing sounds fine.

can you disable dehumidify or raise the setting? see if the short cycling stops.

 

[user_12345a]

Part of the problem may be the fact that you have a single stage a/c.

It can't run at a lower capacity with one or two zones calling like the furnace can.

I don't know why on earth your contractor had the sense to put a modulating furnace on a zoned system but used a single stage a/c. It's a totally inappropriate choice for your setup - should have given you at least a 2-stage if not their top of the line variable capacity unit.

It may cool very rapidly with one zone calling and cycle off assuming the excess air doesn't get dumped into a hall or something.

Do you have a bypass duct? Or something else to divert excess air to keep the duct pressure in check?

With a bypass into the return you get a low return temp and colder air being supplied with one zone calling. Not efficient and there's a risk of freezing the coil.

With no bypass, your communicating zoning system may still run at a lower fan speed with one zone calling so you end up with all the supply air going to that zone.

If not the variable speed blower motor ramps up, runs a very high duct pressure in a attempt to get proper airflow and you get excessive noise, high power usage, shortened motor life.

Regardless of the that, at the end of the day you get a heck of a lot of cooling in one zone.

I don't think this explains the 1 minute cycles, but certainly the 5 minute cycles.

 

[user_12345a]

I don't know if there are any carrier dealers on this board familiar with their zoning - would be of much better help.

In heating mode in theory it should modulate down to minimum with only one zone calling. So it should work really well zoned, especially with the manufacturer's controls/zoning engineered specifically to work with the modulating furnace.

The single stage a/c needs the full 875 to 1000+ cfm and that will cause issues on a zoned system with one zone calling. It's a good thing your contractor didn't put a 3 ton because it would have been worse.

Not only high airflow requirements to not freeze the coil. Fixed capacity, which either it gets dumped somewhere like a base basement or hall with one zone calling (total waste of energy) or the excess capacity goes to one zone (colder air due to having air dumped into a return or reduced airflow relative to capacity = colder air too) so it satisfies the t-stat quick.

Whichever way you cut it, it's far from optimal.

some here who do zoning may say otherwise; can't agree with that regardless of how much experience they have.

Two-stage is a totally different machine, different model line. Has nothing to do with size. The compressor has a bypass solenoid which cuts it's capaciy in low mode. The indoor fan motor also moves less air on low.

likely it's running at full airflow when one zone is calling and the "dump vents" (do they have dampers btw or are just vents) are saving it.

Do you have excessive noise in cooling mode or is it okay?

I'm curious if you can navigate to a screen that says cfm and static pressure of the furnace.

That would really give you a clue of how the system performs in different modes with different zones calling for cooling/heat.

Now since about 10 pm the fan has been running. Nothing as far as cooling or dehum on the display, just fan on for the last hour now. Fan is set to auto on everything. Oh, the fan just shut off, about an hour exactly.

oh if it's been cycling, that's probably just the fan off delay used to boost the seer rating.

Nothing to worry about.

granted if the fan ran for an extended time by itself without a recent call for cooling with everything in auto mode, i would be concerned. not normal.

if you continue to have issues which aren't being addressed i would be looking for another dealer to deal with warranty and support.

you really need a top notch dealer to deal with a system like yours.