do high-end residential heat pumps with variable speed air handlers truly vary the speed to control humidity?

[David Jensen]

. . .

Very interesting reading, Jake. Looks like the product could make sense in certain existing equipment applications. What does a typical residential system "conversion" cost?

David

[David Jensen]

My original post was meant to confirm what I had thought; that despite what my HVAC subcontractor was saying, these high end residential units do have variable speed control beyond the "hard coded" DIP switch settings. Clearly, the installer was out in left field on that one. I think that we all agree with that.

Having confirmed that, I have been trying to determine if any of the Honeywell thermostats offer the same features as the Lennox Signature Stat (the subcontractor installed a Honeywell thermostat that does NOT offer humidity control). Specifically, do the Honeywell units such as the VisionPro IAQ control humidity by slowing down the air handler to remove a greater latent load when humidity reduction is called for and do they properly control the dual-stage compressor? I know that the Lennox Signature Stat thermostat use the full capabilities of the equipment, but I know that my clients would prefer the display on the Honeywell's. I don't want to even consider a thermostat that wouldn't take maximum advantage of the high-end equipment installed. I still have not received a definitive answer on this question from this thread.

We live in Florida and so it seems like, to the extent that we can drop humidity, the client will feel comfortable at a higher temperature and thus the system will be more efficient. We are trying to achieve a balance of maximum comfort and maximum efficiency.

I know that some on this thread were indicating that a bad decision was made in using a 3-ton condenser and 4-ton air handler. It seems that the ARI certification reference numbers that I posted here uphold that decision from an efficiency perspective (someone please tell me where I am wrong here, if I am). I talked Friday afternoon with a Lennox field rep who seemed quite versed on their equipment. He said that you still want to slow the blower down on the 4-ton air handler down to about 1,200 CFM to approximate volume from a 3 ton unit, and that it is the larger coil on the 4-ton air handler where the efficiency gains come from. He was not as much in favor of setting the fan speed to a level that would achieve the 18 - 22 degree temperature differential that the that Lennox factory technician suggested. His argument was that the proper TD depends on the latent load which the

18 - 22 degree rule doesn't take into account.

Yes the house is 2,600 SF but it has low-E glass throughout, R-45 in the ceiling and achieved the best blower door tightness results the technician had ever seen. The duct work and equipment were not sized by the local A/C subcontractor (they wanted to use 5 tons of cooling and told us we were crazy to be using 3). The duct work and equipment sizing were done by

This is their core business and they seem competent at it. Unfortunately, I'm writing from home and don't have their specific numbers for the house with me here.

In closing, it is not that we were getting poor performance out of the unit as far as being uncomfortable in the home. It is just that we realized that the system was not optimized with a thermostat that could best control further humidity reductions. I am also quite suspicious that the air handler DIP switches are still set at the 4-ton default factory setting. Again, it is working, but it does not appear optimized. The way that I see it, if you (or your client) pay for top of the line equipment, you want to make sure that the equipment is optimized. Of course the same holds true for low end equipment also. If is it a Camry or a Corvette, you still don't want to be running with 10 PSI in the tires!

Thanks for your time in responding.

David

[<kjpro]

Just because the efficiency is optimized, that doesn&#39;t mean shit when it comes down to humidity.

[gofish]

I think it would be fair to say that every furnace manufacturer that uses the ECM motor has their own propriatary electronics control module on the end of the motor. each manufacturer would have their own propriatary control algorithms, and to tap into those would require a propriatary type t-sat.

personally never having seen a Lennox Signature Stat, I googled it. Interestlingly enough, it looks identical to the old Invensys series t-stats. So is a Lennox Signature series t-stat merely a re-labled Invensys stat? I do not believe Lennox currenly manufacturers their own t-stats.

I figure its similiar to the Trane thermostats....nothing more than a re-labled Honeywell. Now is Invensys adding esoteric humidity controls to one specific model they are re-labeling for Lennox and calling it a Lennox Signature t-stat? who knows.....but I sincerely doubt it. personally i think its nothing more than sales hype. Like

18.6 seer or whatever.

Have you ever seen a meter or tool that measures seer? Can anybody &#39;measure&#39; your systems seasonal efficiency? If it cannot be measured, how are you to know you got what you paid for?

I too would tend to set the cfm around 1200 for your application