Honeywell VisionPro TH811OU Problems

[Ben]

Wanting to know if anyone had some ideas about this strange problem......

I installed this Thermostat this past October, and everything worked fine during the heating season. As we hit the cooling season a strange behavior started to occur.

When this thermostat calls for AC, the blower turns on right away, with the compressor. With my old thermostat, the blower would be delayed 30 seconds prior to it coming on.

After around 30 seconds, the blower will shutdown for a brief period of time (no longer than 5 seconds) and turn back on. Compressor stays energised all the time.

I opened up the furnace/blower unit and was reading the wiring schematic. Apparantly there is a built in 30 second delay for the fan to come on for the cooling cycle.

So, whats up with this thermostat? Is it defective? Shouldn't it, when calling for AC, not have the fan energised until 30 seconds.

Using my old thermostat, none of this behavior occurs.

Thanks....Ben

[Tony Hwang]

Hi, Did you go through installer set up options? Double check it.

[Mikepier]

The blower is suppose to come on at the same time with the compressor. There is nothing wrong with that. It could be that the furnace schematic was showing you the 30 second delay for the heat. During heat mode, when the burners ignite, the blower does not come on for 30-45 seconds until the heat exchanger is at the proper temperature. Perhaps your old T-stat was wired wrong and now the new T-stat is wired correctly.

[trader4]

The furnaces I've seen have all had the blower come on right away, however with trying to make everything more energy efficient, I wouldn't be surprised to see newer ones where the blower is delayed 30 secs. It will take that long for the coils to get cool, so saving 30 secs of run time helps.

It's possible some parameter is set wrong in the thermostat. I'd review all the programming settings in the thermostat. That's a great and versatile thermostat, but it does have a zillion settings and parameters. Next, I'd try doing a master reset on the thermostat, then reprogramming. If that doesn't work, I'd call HW support.

[Ben]

Gentlemen, Thanks for the response. I am sure that there is a 30 second on and off blower delay for the AC. The heat blower delay is adjustable via switches on the unit, but no such adjustment for the AC. It says on the schematic, 30 second delay on and off for the blower in AC mode.

But now, get a load of this. Last night this was bothering me to no end. I certainly don't want to ruin a perfectly good AC system. On the thermostat, I disconnected the FAN relay wire (G). On the thermostat, if I try to put the fan on by itself, it doesn't go on.

BUT, if the unit calls for AC with the fan in automatic mode, when I hear the thermostat relay 'click', 30 seconds later the fan goes on. Working as I remember it AND how it was working with my old thermostat.

So...I've looked over all the settings for the thermostat, and there is a setting of: FAN OPERATION: T

0 = Conventional applications where equipment controls fan operation in heat mode 1 = Heat pump or electric heat applications where thermostat controls fan operation in heat mode

But, as you see this has nothing to do with ac...

So, what it looks like to me is when the thermostat calls for AC, it (the thermostat) is not supposed to energize the fan relay, as the fan will automatically be kicked on when the unit calls for AC.

What do you think?

[Mikepier]

I have the Honeywell 6300 RTH, it might be similiar. I think there is also a menu option on those T-stats to set what kind of HVAC system you have: heat,cool,or both. Also it asks you if you have a heat pump or not. Make sure those settings are right. Other than that, if its wired right at the T-stat and the furnace, It should be fine, unless you want that 30 second delay.

[Tony Hwang]

Hi, You mean you can't manually control fan?(settings are on, off, auto) Again went through the installer option setting to the end? Also is it set for auto switching(heat, cool, auto)? You have a VisioPro 8000 right? I installed two of them and encountered no problem at all.

[Mikepier]

I believe the G wire you disconnected is the control lead to put just the fan on manually. The T-stat will still work in AUTO mode when it calls for A/C. There is seperate circuitry on the furnace board to turn on the blower automatically, even with the G wire disconnected.

[Ben]

VisionPro 8000 or TH811OU to be exact. To answer Tony's question..... Now that I disconnected the G Wire, I cannot turn the fan ON just by itself. Befor that, with the wire connected was that when the AC called for cooling, the fan would go on right away. 30 seconds later, the fan would shutdown for a brief second, and power up again (coincidentally at the preset furnace time of 30 second ac delay) I went through all of the options for the stat but can't find anything that might change this for AC. I guess my question for Tony is "does your fan go on right away, when it calls for AC?" My furnace apparantly has a built in 30 second delay.

[Tony Hwang]

Hi, My furnace is Carrier, I set the turn on delay at 30 sec. on 'stat. Fan does not come on right away. And also it does not go off right away. It goes off after set delay on the furnace control board(90 secs.) I still think you missed something on options or wiring. BTW, my 'stats are running on battery.

[Ben]

OK, so I think I got to the bottom of this via Honeywell Support Line. First, since this was a 'trade' thermostat as opposed to a retail version, they basically didn't want to talk to me. I had to ask for a supervisor and he was helpful. What he explained was that all Honeywell thermostats, when a call for AC occurs, the thermostat will turn on the fan. My system automatically controls the fan when calling for AC (Honeywell Furnace controller), no via the Thermostat, 30 seconds in to that cycle. So there was incompatibility in the furnace trying to conrtol the fan as opposed to the thermostat controlling the fan.

Right now, I have taken out the fan 'g' wire. All this means is that I can't turn on the fan all by itself. Never used it anyway. The tech guy at Honeywell indicated that there is something called an Isolation relay, which I'm going to look in to.