Final issues in all new hvac and ducting

14 years ago

Hi,

Had written a while back about all new ducting and hvac with many responses. Just a few questions if someone will answer. We installed all new ductwork, 3-ton Trane XL15i,

4TEE3F40B1(var speed), 4TWX5036, Honeywell TH8321, Clean Effects(just finished yesterday). From much reading on this site- I was concerned the tstat would not be programmed correctly-and I don't think it is. Someone from the company who assured me it would be is coming this week. I thought I was getting the correct tstat for my high humidity coastal area Hilton Head SC. Now trying to follow up on the work done I'm reading the TH8321 only uses overcooling to control the humidity where the IAQ slows down the fan speed. I'm going to number my issues:

1. Why have the variable speed fan (if only the IAQ makes it vary-what else does it do?)

2.Is the Comfort R feature turned off or on? (DIP switches set correctly?)(on for TH8321 and off for IAQ)

3.Do I need an EIM to make the IAQ work if I have them change it and I'm not even sure what an EIM does other than it is the communication link?

The sales guy had steered me away from the IAQ early on and I thought he told me the TH8321 controlled the fan speed. Does it have a humidistat? Installation talks about if optional humidistat is used, then jumpers are connected differently.

4. Now I just read that the IAQ is not compatible with the XL15i anyway.

Any advice is appreciated. Thanks, Nadine

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Comments (4)

ryanhughes
14 years ago
1. Maintains constant CFM by varying motor RPM. If you had a deficient ductwork system or a very dirty filter, CFM would just drop, whereas the ECM v/s motor can maintain the correct airflow. Also opportunities to dehumidify and have a slow ramp-up and constant fan-on speed.

2. I'm not sure what the factory setting is. If you don't have the IAQ thermostat, I'd leave it on. If using IAQ to control humidity, leave Comfort-R off.

3. EIM is needed. 8321 does not control fan speed (no DHUM terminals on the thermostat for one thing). All the 8321 does is run the system longer until humidity goes down, possibly overcooling, rather than reducing blower speed.

4. It's compatible.
creek_side
14 years ago
The IAQ can control humidity by either overcooling or through the DHM terminals on the EIM. The DHM terminals can either control a dedicated dehumidifier or a VS blower in the air handler. Either way, the IAQ has to be correctly programed, and the EIM DHM terminals have to be wired to the the air handler or dehumidifier properly. No bets on any of that having been done correctly. My new system is living proof that it can be done wrong. This thread reminds me that I need to correct it now that summer is nearly upon us.

Even if the EIM is wired to the VS air handler correctly, the installer still has to program the IAQ for the correct brand. Rheem, for example, is different that most of the other makes.

I recommend that you defend yourself by making sure you have all the relevant documentation on hand. You need at least five documents.

1. The VisionPro IAQ Operating Manual 69-1815EFS-06

2. VisionPro IAQ Total Home Comfort System 68-0287-1

3. Honeywell VisionPro Installation Guide 69-1816EFS

4. Honeywell VisionPro Installation Guide EIM 69-1823EFS-1

5. The installation/wiring diagram for your air handler.

The four Honeywell IAQ documents are all different manuals, although there is some overlap. They are all available on line as PDFs. You will need to do a thorough Google search to get them all. The suffixes following the last dash appears to be the revision number. I would leave that out of the search.

If you have a hard copy of any manual that covers the installer setup, use that instead of a download. Not all the downloads are current. If they didn't leave you one, demand it. Failing that, compare your PDF version with the actual settings on your IAQ. If the PDF is missing a setting or two, you have the old version.

Lastly, you really need to learn all the programming of the IAQ, not just the owner part, but the installer part, too. There are far too many HVAC "pros" out there that don't have a clue on how to set one of these up properly.

It's not just the dehumidification that you need to understand, but the AUX heat lockout settings as well. If not done just right, the IAQ will happily keep a very even temperature in your house by running the aux heat when you don't need it.

That's how mine was left by the installers. Luckily, I spotted it before I got an astronomical power bill.
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thull
14 years ago
One more note on the IAQ- the EIM is intended to make the wiring somewhat simpler. It goes presumably near the equipment, and all the various wires get landed there. Then you just run the single cable to the wall-mounted stat. If you wanted to run all those things from the stat, the wiring would be more complicated. Anyway, that's my impression.

The only thing that could derail using the IAQ for humidity control is if the air handler doesn't allow the external device (IAQ stat) to control fan speed. I don't know jack about your equipment so take that with a grain of salt and check.
classicdave
14 years ago
First, You have a very good system!
Trane has put a lot of effort into it's Comfort R They believe their Comfort R controls humidity just as well as anything out there. So I would let it run in comfort R and see if it does what it should do.

Comfort R
The first minute the fan will come on at 50%
This helps in low air noise start up and getting your coil cold faster.

Then for 7.5 minutes Comfort R controls the fan speed at 80%
This takes out humidity

Then Comfort R will run the fan at 100% if more cooling is required.
When the thermostat satisfies the Fan will then turn off the compressor and drop back to 50% on Fan for 3 minutes for Enhanced Efficiency.

The cfm on the air handler should be set at 400cfm per ton.

Final issues in all new hvac and ducting

Comments (4)

ryanhughes

creek_side

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