The Pro Doesn't Know (IAQ Issue)

[lksmith]

Today the Trane installers finished putting in two heat pump/dual fuel/ variable speed systems and two Honeywell IAQs. These were the first IAQs the installer had ever seen. He did all the programming and tested the systems. He put "setup function" 345 to "1" just to see if setting the temperature 5 degrees or so above the inside temp would shut off the compressor and turn on the furnace. Didn't happen. The heat pump just kept on running. The installer messed with it for a hour or so then decided to give up and do more research. I'm hoping to hear back from him tomorrow. In the mean time I thought I see if there was some obvious programming problem that I could deal with at the thermostat level. I'm hoping this doesn't fall into the DIY category. I'm just thinking if there's an easy user fixable solution, it will save the installer a trip out here tomorrow. Thanks in advance.

Larry Smith

[BaldLoonie]

The VP will try to use the pump alone first. So if he walked to the stat and shoved the temp up, it might run just the pump for a while to calculate if the heat pump alone can do it, even though you opted for backup. I'm just guessing based on some of the logic I've seen in this stat. You might turn it up and leave it up for a while tonight before he comes back and see what happens. I set them to option 2 so the backup won't come on if the outdoor temp is above 45. Energy saver against someone playing with the stat in mild weather.

[lksmith]

OK thanks. I'll give it a shot. We've let it go for only 5 minutes or so with greater than a 2 degree split. Maybe that wasn't long enough. I'll try it again for a longer time. 15-20 minutes should be sufficient don't you think?

I like your idea of using option 2. Certainly in warmish weather I'd hate for the furnace to come on when the system is just recovering from a thermostat setback.

Larry Smith

[lksmith]

BaldLoonie

Turns out you were right on the money! It just took 20-30 minutes to get the furnace to crank up. On my other system, no matter what I do, I can't get the furnace to go. I suspect there is some kind of a wiring problem because the thermostats are programmed exactly the same. Guess that will be a problem for the installer to tackle.

Thanks again for your help.

Larry Smith

[mark beiser]

Originally posted by lksmith
BaldLoonie

Turns out you were right on the money! It just took 20-30 minutes to get the furnace to crank up. On my other system, no matter what I do, I can't get the furnace to go. I suspect there is some kind of a wiring problem because the thermostats are programmed exactly the same. Guess that will be a problem for the installer to tackle.

Thanks again for your help.

Larry Smith

Was it warming up faster in the area served by the "other" system? They may have some logic in there that makes it keep the heat pump going if it is actually warming up at a good rate.
About the only thing those thermostats will do at the same time every time is the compressor time delay. Everything else has algorithms that change the timing, and the therostat actually adapts as it goes.

[lksmith]

Hi Mark,

On the "other" system the furnace won't come on at all. It fails the "system test" 4, I can't get it on by selecting "Emg. Heat" on the thermostat. It simply won't come on at all. Hopefully it will be a simple wiring issue.

Larry Smith

[lksmith]

Here's what I learned about the IAQ when using a heat pump and dual fuel. Any pros reading this, please correct me if you're sure I'm wrong.

Setting 345 determines whether you're going to get the furnace back-up strictly below the balance point (Opt. 0) or whether it will fire up the furnace if there is a 2 (or more) degree "droop" between the actual and desired setting (Opt. 1). Option 1 is similar to Option 2 except that Option 2 disables the furnace above a fixed setting (Setting 360). The balance point is Setting 350.

Apparently an interior temperature "droop" is not quite accurate because it only requires a temperature split, regardless of whether you raise the desired temperature setting or the actual indoor temperature just decreases.

When I was testing my new systems last night it took about 30 minutes of temperature split before the furnace finally kicked in. Then today, I realized that Setting 346 controls when the furnace will kick in, assuming the desired temperature hasn't been reached by the heat pump alone. Sure enough, my Setting 346 was set at 30 minutes.

So, that's what I've learned. I'm but a lowly homeowner, not a pro, so if I've said something incorrect, please let me know.

Larry Smith

[jacob perkins]

Originally posted by lksmith
. I'm but a lowly homeowner, not a pro, so if I've said something incorrect, please let me know.



, you now have more knowledge of this system set up than "pros" ....jeez dude

Your use of the term "IAQ" seems a little out of place. that usually means just the filters and humidifiers and such. Other than that,you sound more pro than I.

[lksmith]

A little knowledge is a dangerous thing! (But thanks for the compliment.)

But I have yet another question...I have just spoken with the Honeywell folks, actually a lady who I believe was in Rangoon, and the HVAC contractor who had only seen these IAQ's for the first time two days ago. Please bear with me if this is sort of a DIY deal because I have exercised all the "pro" options, except this forum.

The question is dehumidification. I have Setup Func. 370 to 1, to use the built in humidity sensor in the thermostat. I have SF 379 set to 1 to use the a/c to dehumidify. SF 383 is the default 3 degrees of over-cooling. According to the Operating Manual when I select MORE a couple of times I should come up the the dehumidifier page. On that screen, on the left side is the current indoor humidity, on the right side is the desired humidity, selectable with up or down arrows. I got all that stuff showing up. In the bottom middle of the screen is supposed to be some up/down buttons for AUTO or OFF. I don't have these buttons and thus am not able to access this option. The contractor was speculating that because the system was variable speed, it might be automatic dehumidification. I don't think I believe that because when I select a lower humidification, nothing happens. The heat pump doesn't start even when the requested temperature is the same at the desired temperature, i.e. not more than 3 degrees less than the desired indoor temperature.

Any thoughts on how to get this dehumidification option to work? Thanks in advance.

Larry Smith

[thorton]

Originally posted by lksmith
BaldLoonie

Turns out you were right on the money! It just took 20-30 minutes to get the furnace to crank up. On my other system, no matter what I do, I can't get the furnace to go. I suspect there is some kind of a wiring problem because the thermostats are programmed exactly the same. Guess that will be a problem for the installer to tackle.

Thanks again for your help.

Larry Smith

I believe that's why it's best to use outside stats on a duel fuel system. Stats with logic sometimes take too long to make up their mind whether to run the pump or the furnace. Just my opinion.

Thorton
_____________________________
Adversity does not build character…it reveals it.

[rog09]

The "Auto/Off" functionality for dehumidification is only for whole house dehumidifiers, not for A/C dehum.

[rog09]

Sorry, forgot to answer the other question...

Assuming the installer wired the product correctly, anytime the humidity set point is below the current indoor hum level and the inside temp is within your overcooling limit, the A/C will be engaged. If the dehum terminals were wired to the BK terminals, a call for dehum only (not cool) will utilize the low speed fan.

[docholiday]

Originally posted by jacob perkins

Your use of the term "IAQ" seems a little out of place. that usually means just the filters and humidifiers and such.

Other than that,you sound more pro than I.

I suspect he's talking about the Honewell IAQ thermostat...In this case he is not out of place.

[lksmith]

Rog09

Thanks for the AUTO/OFF info. I think about the time you posted I wormed that out of the Honeywell tech who I believe was located in Thailand.

I do think I've got a wiring problem which will take a pro to fix. Not only am I not getting the dehumidification (with all the right conditions set) I'm not getting any other cool fan speeds other than max and off--no V/S.

Something is definitely amiss. Thanks for your help.

Larry Smith

[not a filter expert]

I'm going to stick up for Honeywell and say, I sure am glad that I can call Honeywell Tech Support anytime and speak to someone in Golden Valley, Minnesota...if I can't get my local rep.

I am also glad I only have to install the VPIAQ's on 2 stage cooling with occasional 2nd stage heat systems.

Don't think that all the support is outside of the country!