Infinity control schedule

[kartracer22]

I'm puzzled. I have my Infinity zone control programmed for a weekend/weekday program. Something odd is happening: the thermo clearly states that is it the period "evening", which should have a temp of 76, but it says cooling at 74. I've noticed that other times, randomly, the thermo runs to a different temp then the program. I've already made sure that the dates and times are correct, and have even played with the weekend/weekday programs to try to determine where the cooling setpoints may be coming from. I've had the system for two weeks.

Any thoughts from pro's or other system owners?

Thanks in advance.
Ryan
Indy

[plain spoken]

What is your cooling humidity set point and humidity in the space? It could be coming on to dehumidify.

[kartracer22]

Wow, that is a quick response!

The cooling humidity is set at 50%. But, from your response, is it OK to assume that it isn't odd that even though the schedule period is evening and it should cool at 76, the control says "cool at 74"?

[plain spoken]

If your humidity set point is below the actual humidity reading, the Infinity will turn the cooling on in an effort to dehumidify the house. It will over cool the space up to 3 degrees.

[kartracer22]

Thanks. This forum is THE BEST as far as value-added info, for any topic, goes on the internet.

[jrbenny]

When does your next program period start and what is the cooling setpoint for that period?

[plain spoken]

Originally posted by jrbenny
When does your next program period start and what is the cooling setpoint for that period?

Opps, I forgot about that one! That's why you are the man!

[dallasbill]

That "cool to dehumidify" setting is the BEST thing about this Carrier control and the backend it works with.

You will notice that you can set your humidity to the lowest bar -- about 45-46% in our house -- and it works even better. By keeping the humidity lower, you can set your cooling setpoint higher. We keep ours at 77 when we are home and feel just as comfortable because it's drier inside. TAnd, we also burn less electricity too.

Experiment with it!

[tmoss]

So the Infinity is the same as the VP 8k in that it will overcool up to 3 degrees to dehumdify? However, in doing so it will slow the cfm down more than the VP, thus possibly lessening the likelihood of overcooling in reaching humdity setpoint? If this is correct what determines how low the cfm can go before freezing occurs?

[kartracer22]

jrbenny, I see what you thinking. I was within 90 minutes of the next period (sleep). The control may have been starting to cool for the next period.

Pretty cool.

Once again, you guys are great. Thanks for the responses.

[wyounger]

Originally posted by tmoss
So the Infinity is the same as the VP 8k in that it will overcool up to 3 degrees to dehumdify? However, in doing so it will slow the cfm down more than the VP, thus possibly lessening the likelihood of overcooling in reaching humdity setpoint? If this is correct what determines how low the cfm can go before freezing occurs?


No, it's not the same as the VisionPro. They can both overcool up to three degrees. Everything else is different, though.

-The VP just overcools until it hits the RH setpoint. Infinity looks at the temp and humidity together and just aims for comfort. For example, if you're already two degrees below the temperature setpoint, being 2% over the RH setpoint feels fine, and it won't try to control that. I believe the logic of this tradeoff is that for each degree of overcooling, the internal (not shown to customer) RH setpoint raises by 2%. Also the amount of overcooling allowed tapers off at lower room temperatures; at a cooling setpoint of 70, no overcooling is allowed.

-The VP does not adjust blower speed *at all*. If it wants to dehumidify, it just runs plain old cooling mode until the RH setpoint is reached or the three degree limit is reached. The Infinity control is in direct digital communication with the furnace/air handler, and apparently picks a blower speed on the fly based on conditions. I have seen them run at the following CFM/ton rates: 275, 300, 325, 350, 375, 400. It may be that under some conditions they'll do 425 and 450, but you'll have to ask somebody in a drier climate about that- won't happen in Georgia. The ability to run at much lower than normal CFM/ton rates improves the amount of dehumidification relative to the amount of cooling, which does reduce the amount of overcooling that is required in the first place. While the equipment is running, it's taking care of cooling and dehumidification all at once.

How does the Infinity system keep from freezing up? Well, keep in mind that it only works with certain Carrier equipment. They know how low they can go before a freeze-up might happen. That would be tough for a third party control manufacturer to match without a sensor, because Honeywell has no idea whose equipment you're trying to control with their VisionPro. The newest Infinity equipment does have some logic to watch for a possible freeze-up, though, by watching for the change in blower operation that would happen if the coil iced over. I don't think I've ever heard of the early systems icing up, though, so clearly they know what they can get away with.

Also if you are running a low CFM/ton rate on an Infinity system, the reason you're running like that in the first place is that there is a lot of humidity to remove. Under those conditions, the coil isn't going to get unusually cold anyway, because all of the cooling is going to be going into condensing water out of the air onto the coil. Where you get into trouble with low airflow is more when the airflow is unnecessarily low- that's what gets you a coil that gets too cold and ices up.

The operation of the overcooling function does not show up on the display, though. If the setpoint is 76 and it needs to overcool for dehumidification, the setpoint will keep saying 76, but you may find that the actual temperature on the display is 74 (two degrees under setpoint) and the compressor is running anyway. If the setpoint was below what you had programmed, that's going to be because it was preparing for the next programmed period. Remember that with an Infinity system the times and temperatures you program are for when you want it to *achieve* the programmed temperature, not when you want it to start trying to get there.

[dallasbill]

Thanks... that's the BEST explanation of how it works I've ever read. I'm saving a copy of that to give to the next owner should we ever sell!

[jrbenny]

Great explanation!

Clarification on your cfm per ton statement in paragraph 2: 400 cfm/ton is MAX. No 425 or 450 regardless of humidity levels.

[wyounger]

Good to have that little detail clarified. I'd always wondered how they would run in arid conditions. As I understand it, Carrier designs for 350 cfm/ton nominal anyway, so you could say that running a Carrier at 400 cfm/ton is like running other brands at 450 cfm/ton.

As it is we've had an extraordinarily dry spring in Atlanta- not just for lack of rain but also for the freakish lack of humidity. I've noticed that even in Comfort mode, when it gets below about 40% RH in the house, my Infinity system will step up to 400 cfm/ton in cooling. In previous years I generally would only see that if the system was several degrees warmer than the setpoint (like on the day it was first installed).

I'm coming up on my second year with the system, and still love it. It's the logic these systems needed all along; adjust airflow rates on the fly to suit conditions. Provide comfort instead of just temperature control. No more rudimentary controls running dumb equipment, using contact closure to click things on and off. :)