HONEYWELL THERMOSTAT RTH8500D

[godzilla2k69]

New house construction. Furnace = Goodman GMV90 2-stage variable speed gas furnace, 47/70K BTU. 2 ton Goodman 13 SEER AC. I want the installer to use this Honeywell 8500 thermostat. Will this work well for a 2-stage furnace ?

[karsthuntr]

Very good t-stat, the best thing Honeywell has come out with. You will be pleased with it. Very easy to program. Get the outdoor temp sensor with it, I love mine, 1 look and I can see the outside tempature.

[holabr]

Is the outdoor sensor only for user information or does it also add to the effectiveness of the t-stat to control the HVAC? It seems to me that someone else made a t-stat that actually used the outside temp as a factor in calculating the run cycle for the furnace.

[tpa-fl]

To the original poster: Splurge a bit and have the installer get one of the VisionPro series, available at most contractor supply houses. It'll cost you a little more, but the extra featuers and flexibility are worth it. If you do go this route, the model # you want is TH8320. (with the 32 meaning 3 stage heating, 2 stage cooling). There's also a TH8321 which adjusts the cycles based on temperature AND humidity. There also is a TH8110 (1 heating stage, 1 cooling stage) which won't work well with you system.

karsthuntr: Only problem here is that he's using the consumer version of the stat, hence RTH8500 instead of TH8110/TH8320/TH8321. Quite a few features taken out of that unit, inlcuding the ability to add an outdoor temp sensor. Granted, without a heat pump it's far less important for the stat to have outdoor temp info.

holabr: Not sure what the stat does with outside temp normally. I know it uses that info when running a heat pump to determine what kind of response is best (HP only, HP+backup, backup only) and it might use it to predict when it needs to recover from a seback, but not sure otherwise.

[karsthuntr]

Thanks for the info Tpa-fl. I didn't know that the R meant "lowes special".

[tpa-fl]

From a quick glance at the RTH manual online & the TH8321 manual I have, the following are missing/omitted from the consumer RTH8500 Vision thermostat:

Can't use remote sensors (indoor or outdoor)
Not able to use 24vAC for power (all power from the AAA's)
Not able to work without batteries
No continuous backlight
No auto-changeover
No circulation mode on the fan/blower
Fan mode isn't programmable
Can't handle multi-stage HP installs
No cycle/anticipator adjustment for cooling, very limited adjustment for heating
Requires an external fossil fuel kit when used with a heat pump
Not able to intelligently decide when to use HP & when to use aux/emergency heat b/c it lacks an outdoor temp sensor
No humidity control
No temperature limits
Won't handle 3 heat/2 cooling stage systems
Only has service indicator for filter change, none for UV lamp / humidifier pad / etc.
Can't adjust minimum time between cycles
Can't set upper/lower temp limits for heating & cooling
Can't adjust fan on after heating/cooling
Can't lock out keypad
Can't adjust adaptive recovery compensation

There's probably physical changes that they've made as well to get the price down to the level that bLowes wanted. I'm not sure what bLowe's is charging, but I'm sure it's probably not worth it compared to what the VisionPro series can be had for.

[godzilla2k69]

tpa-fl---
Some of what you wrote I just don't understand. But there is a 8320 on eBay for $167. I'll get that one and give it to my HVAC guy and ask him to install it.
I enjoy this forum. Some of you guys are very opinionated about what you do/brands/etc. I know many of you cringe at the Goodman furnace and AC. But hey, if it is junk you might get an option to service it soon! But as long as your opinions are backed up with credible knowledge and experience (and I have no reason to believe that in this thread they aren't), I respect that. I'm opinionated too. For example, I think Liberals are dangerous when they hold positions of power. But that's just me.

[karsthuntr]

You are going to pay that much for a t-stat and have no warranty. Let your contractor supply the t-stat and you will have a five year warranty.

[tpa-fl]

I'd steer clear from the E-Bay stuff... It's been posted on this board (and I've seen similar things with other manufacturers of other products) that Honeywell won't warranty anything sold on E-Bay. You never know what sort of abuse the seller's put the items through before selling it to you, and thermostats can be damaged if connected incorrectly. Additionally, usually items on E-Bay are marked up substantially (esp. when you add up shipping/handling/etc) compared to what the going rate is for things. Due to forum rules, I can't comment upon this specific E-Bay price here, but tell your installer you want the TH8320. They'll be able to get it at a fair price from an HVAC distributor and you'll have a 5 year warranty to boot.

I don't think the stat has been on the market long enough to know how it handles power surges, but that's where the warranty comes in handy.

As far as the features, some of them won't apply to your system (the heat-pump specific features), and you might not use the keypad lockout, but the humidity control & fan circulation mode are the two features I use most on mine. I also have to admit that having the display constantly backlit is just slick. Too bad mine's hooked up to a builder-grade American Standard. Oh well, most guests won't ever open up the equipment closet anyway. As long as it keeps me comfortable, that's all that matters.

[godzilla2k69]

Very much appreciate your help, tpa-fl. I'll ask my installer to wire mine up to keep the backlight on. As for eBay, I have purchased 100's of items in prep for building thei house. Tools, lights, you name it. Very happy. This T'stat comes in an unopened box. We will see. Again, thanks for your help.

[tpa-fl]

I know we're not supposed to talk about pricing, but I wouldn't pay that price for that stat from E-bay.

[karsthuntr]

Originally posted by karsthuntr
Thanks for the info Tpa-fl. I didn't know that the R meant "lowes special".

Thanks again Tpa-fl. I used this info today, Checked on HP's at customers house. Three honeywell stats, I wasn't sure if we installed or not until I pulled off wall and found the RTH number on back. T-stat had broken pin, "sorry we did not supply t-stat, no warranty, sorry about your luck".

[tpa-fl]

How do you break a pin off these? I could see with some of the other Honeywell stats, but the VisionPro series (not sure about the consumer stats) uses rather thick pins and the subbase practically guides it right into place. Did the HO at least get the wiring correct? Without an outdoor thermostat, he's going to be in for a rough heating season with those stats.

[karsthuntr]

The pin wassoldered on the board really cheesy, solder joint broke (actually didn't see any solder).

The T-stat in question was for boiler not HP's. HO bought the same t-stat for all 3 units. My install guys installed for her while they were there installing the HP's.

They will use boiler for main heating, HP's are for back-up if boiler breaks, the will use mainly a/c side of HP's.

[drc]

From a quick glance at the RTH manual online & the TH8321 manual I have, the following are missing/omitted from the consumer RTH8500 Vision thermostat:

Can't use remote sensors (indoor or outdoor)
Not able to use 24vAC for power (all power from the AAA's)


I wrote to Honeywell on this very topic. Their Customer Service replied as follows:

The RTH8500 can be wired so that it is powered by a 24 volts AC common from the system transformer and use the batteries as a backup when there is power outage. For the thermostat to be able to achieve this there should be a common wire connected to the C terminal.

When the thermostat is powered by the system transformer, the batteries will act as a backup.

Can anyone confirm that this configuration works on a RTH8500?