2 Stage HP Cooling Capacity & Power Usage

[jerryd_2008]

Have a 4-ton York 8T Affinity 2 stage HP. After lowering the stage 2 blower speed to around 417 CFM/ton and thanks to a HW VP IAQ tstat and VS furnace it is spending a lot of time in stage 1 cooling. The VS furnace blower is also running in stage 1 cooling at less than 300 CFM.

Can anybody tell me as a percentage of the stage 2 HP numbers:

1) the cooling capacity of the stage 1 HP and

2) the power used in stage 1 HP?

[beenthere]

72% capacity
69% power

[trout lake]

I can see the 72% capacity. How is the 69% on power arrived at?

[amd]

.......................deleted.................... ..................

[beenthere]

I can see the 72% capacity. How is the 69% on power arrived at?
Second stage KW is 3.3
First stage KW is 2.3
2.3/3.3=.6969

[trout lake]

thanks

[jerryd_2008]

72% capacity
69% power

BT, thank you!

Looks like I am running at less than 3 tons most of the time on a house that had a 4 ton split AC/furnace. Pretty good for a house with about 3700 sqft.

But to be honest, wifie won't let me run it below 79 degrees and it does run a lot trying for 50% RH, so I set it at 55%. I realize that a lower temp setting would help with the RH, but ..... Peace is important too.

Also set the Fan On to 40% of blower capacity to get circulation but no hurricanes. I turn on Circulating from time-to-time just to even out temps across house due to sun load or closed door (cats!) bedroom humidity at night.

Thanks again, BT.

[beenthere]

Is the IAQ actually wired up to slow the blower on a dehumidify call.

[jerryd_2008]

Is the IAQ actually wired up to slow the blower on a dehumidify call.

BT, as I have often said, I am an HVAC non-wannabe, as you can probably figure out from some of my ignorant questions:o, but I have been through the HW VP IAQ manual numerous times trying to figure out how to fake it out. If you are asking if I have Option 369 set to Dehumidify with Air Conditioning, the answer is yes. I also have Option 383 set to allow a 3 degree Over-Cooling Limit although it seems to never go down more than 2 from the set point.:confused: The AC does run mostly in stage 1 and the temp is at set point almost always.

By the way we have a YTH9421C1002 which has a remote equipment interface module at the furnace and only 3 wires (it's the the old tstat wiring) to the actual tstat. Is there some other settings you are asking about like in the EIM, VS York furnace or HP? If so, please explain.

PS: The contractor says he has installed many IAQ's but not this high end tstat.

[beenthere]

Their is only 1 IAQ stat fromHoneywell. He may be refering to the Vision Pro stats.

I was wondering if your contractor actually set the jumper in the furnace to allow the IAQ stat to slow the blower.

[jerryd_2008]

Their is only 1 IAQ stat fromHoneywell. He may be refering to the Vision Pro stats.

Believe that is what he said and I misspoke.


I was wondering if your contractor actually set the jumper in the furnace to allow the IAQ stat to slow the blower.

I would really like to achieve 50% RH without continuous running except for 95 degree days of course.

The "YTH9421C1002 which has a remote equipment interface module at the furnace and only 3 wires" that are then wired at the furnace (I think from looking at the furnace control board diagram) to something like 10 terminals (LO COMP, HI COMP, ... C). He has set the 2110 CFM capacity blower to Hi Cool 1670 CFM and Lo Cool 1085 CFM. The blower is running almost totally in low with the compressor at stage 1. Run times are much longer without the old short cycling problem.

I notice that one of the 10 terminals on the furnace control board is DHUM. Is the wiring of that terminal something that you are referring to? :confused:

Also set the furnace Continuous Fan Speed Jumper jumper to 40% of blower capacity. Circ setting for the fan on the tstat which I experiment with does seem to lower humidity some.

I strongly suspect that our temp setting of 79 degrees is part of the problem (but that's what Mom wants:D). A lower setting would probably take out more humidity, correct?:confused:

The contractor suggested caulking the tstat wiring hole in the wall behind the tstat in case there is some leaking from the attic or other locations that affects the tstat readings. Saw this mentioned in another post. Is that a candidate for correction?:confused:

[beenthere]

The Dhum must be wired for the IAQ to control the blower.
If its not. Then it can't dehumidify as well as it should.

Its easier to maintain 50% RH at 79, then it is at 76.

Your system probably still isn't wired or set up right.

[jerryd_2008]

The Dhum must be wired for the IAQ to control the blower.
If its not. Then it can't dehumidify as well as it should.

Its easier to maintain 50% RH at 79, then it is at 76.

Your system probably still isn't wired or set up right.

Right again, BT! The DHUM is not wired at the furnace. He used 8-wire cable from the EIM to the furnace and didn't wire that one.

He is supposed to talk to Honeywell on Monday about getting some larger temp difference between the IAQ temp setting and AC on/off. I am emailing him to suggest that he also discuss the DHUM wiring.

As I have said several times in other posts, the HW IAQ documentation lacks a lot on theory of operation that would enable one to figure out all of the interactions of this complex tstat. I would have been beat up pretty bad for that kind of documentation in my past life. I will renew my suggestion here that there are several topics that if placed where HO's could find would greatly relieve many of the questions we (and our contractors) have. One topic is the IAQ and its settings another is Ryan Hughes' start on explaining the AHRI directory search capability.

Ryan forwarded a suggestion to make permanent his thread on AHRI, but nothing came from it. Could you look into getting his post into a more permanent and findable status?:) The thread is titled "For New Systems: How To Search for Performance Data". Maybe a review and additions by other knowledgeable pros could make this a big winner for confused and uninformed HO's/contractors.

Thanks again!

[Alden_Sloe]

Do you have both manuals for the IAQ? The owners manual is next to useless but I thought the installation manual fairly well documented the settings and operation. It's really not designed to be a theory of HVAC text.

[jerryd_2008]

Do you have both manuals for the IAQ? The owners manual is next to useless but I thought the installation manual fairly well documented the settings and operation. It's really not designed to be a theory of HVAC text.

Alden, I think I have both manuals. I also found a 2006 version of the manual on the Internet that at least gave some suggested settings.

I guess I disagree about the need for the manual to be more complete. When a thorough, commercial contractor with decades of experience and who has done residential but not my particular system and not the IAQ (but did other HW' VP's) misses the dehumidify wiring, I think there is something pretty basic missing in the install docs. Also, he and I could find nothing on: 1) accuracy of the temp/humidity readings, 2) if one can and how to set a differential between the temp setting and when the HP starts (old tstat had +-1 degree, so set at 78, comes on at 79 and runs until 77 obtained).

Another really major deficiency in the IAQ manuals is a complete explanation of how to set stage 1 and stage 2 cycles per hour to address various house environment problems that need to be fixed: high humidity, longer run times, etc.

Another area that I would have thought HW would have included is an overview of how a tstat to EIM interface works using 3 wires for an 8-10 wire connection to the furnace/HP. Can't even find that on their web site. They don't have to go into proprietary coding and communications but they should give enough background to show an installer that there is no need to pull new 8-10 wire cable from the tstat to the EIM.

As I said to BT, I did some fairly technical stuff in my day, and producing technical support and user documentation like that with the IAQ would not have been good for my career. So I again repeat the request for educational threads that HO's and, yes, contractors who haven' done this particular system/device before, can get some of there questions answered before launching into many, many posts with the possibility of questions not answered. I am not talking about levels aimed at DIY's.

[beenthere]

While I agree, it could have beeter written instructions.

It does tell you, that only 3 wires are needed between the thermostat, and the the EIM.

This is more your installers not reading the instructions of both the thermostat, and your HVAC equipment.
Or they would have seen in the furnace install instructions about the Dhum terminal.
Which would have lead them to read the thermostat instructions closer.

Honeywell does rely on the tech/installer, to know what set up is right for his appliacation.