Do they make a thermostat that does this?

Before I start looking, I’m sure someone will know if it even exists. What I’m looking for is a thermostat that can kick the fan on by itself. For example let’s say I want to keep the house at 74. If it gets to 75 it kicks the fan on, if it get’s to a certain point beyond that (76 maybe) it turns the AC on. The reason I ask is becuase my house usually has wildly different temps between the front and back and normally all I have to do is kick the fan on to lower the hot side a degree or two rather then turning the AC on. OTOH, maybe running the AC for a half hour is cheaper then running the fan for 1.5 hours, but I’m not sure. Seems like a sound idea, but since I don’t think most houses are this uneven, I’m not sure if I’ll have an easy time finding it. Also, I’m aware it wouldn’t work when the thermostat is on the ‘cold’ side of the house, it would need an override for that.

It be nice to be able to adjust the temp or fan status without getting up.

Hey!
I need one of those, too!
(I have a split-level house, with the thermostat on the lower level.)

Two thermostats used in conjunction?

According to this web page. a medium sized window unit A/C run for half an hour uses more than three times the amount of power than a floor fan uses in an hour in a half.

Split-levels are a bear to keep uniform.

What I did about 20 years ago was take a regular lamp timer and did some surgery on it to separate the on-off switching from the electricity that powers the timer. In other words, I converted the timer into a “dry” switch. I connected the “dry” switch in parallel with the low-voltage thermostat wiring that controls the fan. I set mine up at the box on the furnace that the thermostat wire runs into. “Plan B” would be to run a wire to the thermostat and connect the switch to the R and G terminals - this might work out to be an easier option if your furnace is in the attic or some similar hard to reach location.

Usually, this will be the “R” and “G” terminals, and usually the wire colors are red and green. No promises here - thermostat wiring can vary from one brand to another, and whether or not the original installer bothered to follow the normal color scheme. If you’re unsure, you might want to call a heating contractor - miswiring this will result in anything from nothing happening to damaging the thermostat or even damaging the furnace itself.

This will give you a blower control that’s purely time-driven. You’ll need to figure out what time(s) of day you want the blower to run and set the timer accordingly.

If you want to have the blower controlled by temperature, you’ll need a second thermostat. For this, get an old-style non-powered, non-setback heating and cooling model - you just need a dry switch contact here. Set this thermostat to “cool” and connect the R and Y terminals to the blower control’s R and G terminals. “Y” (yellow wire) is the cooling signal wire - when the temperature exceeds what the termostat is set for, it will make a contact between R and Y.

However you do it, it can be a very worthy venture both in terms of comfort and energy efficiency. The upstairs south-facing bedrooms acted as passive solar collectors and would get uncomfortably warm. By circulating the air, we were able to keep the rooms much more comfortable and there was a resulting energy savings - before doing this, the heat would come on immediately when the setback program called for heating. By starting up the blower half an hour before this time, there was usually a delay of up to an hour before the burner came on.

I think there is an easier way maybe.

It’s a little pricey, but the Honeywell VisionPro 8000 has an additional setting for the fan. In addition to “On” and “Auto” there is a selection “Circ” which brings the fan on 35% of the time at random. It’s a great middle ground between “On” [all the time} or “Auto”.

There is also sensors–thermistors really—that contractors use during construction. It’s a simple probe that is a normally open set of contacts. Usually they close on a temp fall–and so are used for heating. I’m not sure, but I suspect you could get one that closes on a temp rise–for cooling.

Check out the VisionPro 8000. it’s a fantastic thermstat, and IMO, the best stat on the market.

Another idea.

Buy a two stage stat. Stage 1 will be a parallel circuit between R and G. Stage 2 will be the normal Y circuit. It will do exactly what you want for the upstairs.

The only issue is that downstairs there will be a drift of a degree or 2 before stage 2 makes and brings on the compressor.

But that may be exactly be what you want.

(and the Vision Pro 8000 is available in 2 stage also.)

What you’re looking for is a “staging” or “multi-stage” thermostat. Either of these as search terms will get you lots of hits, like this one:

http://www.nextag.com/2-stage-thermostat/search-html

Normally these are used with 2 stage heating/cooling units, or heat pumps, where a small change in temperature turns the HVAC unit on low, while a larger change turns it on high.

But there is no reason you couldn’t wire it to turn on the fan as stage one, then the actual AC as stage two, especially if your system is already wired with a fan relay that allows you to run the fan by itself using the thermostat switch.

Edited to add: what the raindog said. :slight_smile:

I was about to suggest the same thing. One minor correction. The fan wire, normally landed on G would be connected to G and Y1 (1st stage cooling) and the compressor wire would be terminated on Y2. There would be a 2-3 °F difference between stage 1 and stage 2, so if you wanted the house kept at 74 °F, you would have to set the stat at 71 or 72 °F.

And FWIW, I would recommend the Viconics line of thermostats. I’ve had much better results with them than I have with comparable Honeywell thermostats, although I haven’t used the model raindog mentions.

How about a fan with a thermostat built in?

Won’t turn off automatically when your A/c kicks in though.

Why not just run the fan all the time? I have a heat pump/air conditioning unit and I’'ve got my fan running on low all the time. Evens out the temperature just fine.

When the A/C or heat is needed it runs at the required speed.

Look to the homebrewer world. We like refrigerators and coolers to turn ON when they get to a certain temperature, but it’s cheaper to buy a big freezer.

So, you override the main controls of the freezer with one of these thermostats. Plug this into the outlet, the fan into the thermostat, and off you go. Breezy goodness.

Ugly, but available premade, with all the right connectors.

How easy is that to work with? It looks ungodly complicated. Now if I understand right, there are three models (as seen on Graingers website, BTW I do have an account with Grainger). If I’m reading this right, the first one is, more or less, a normal tstat, the differnce being the added feature of it running the fan 35% of the day, I like that. The next two add in the staging. This could be wired to turn the fan on at one set point and the AC at another. The most expensive one can also be set to control a humidifier (Aprilaire type device I assume), so that’s out.

So my question is, how complicated are these two units to work with? How overly complicated is it going to be to wire in the one with staging? And what are the remote sensors for? I assume if you put one outside, all it does is tell you the outside temp, but what if you put it inside, will it use that to determine the temprature as well? Like I said, my house heats and cools rather unevenly, that may help. (BTW it’s only one story)

Yep, I’ve got one of those in my bedroom, attached to a boxfan in the window.
If the room temp goes over 70°F, the fan kicks on. No more waking up in the middle of the night, because the room got to cold.

Now I need to find a reverse one, that would block the fan kicking on if the outside temp was over 75°.

Super easy, and they are fantastic.

There is also an outside air sensor, and a model that that will control a humidifier. (IAQ 9000)

If you’re inclined, PM me or email me and I’ll give you my phone number. I can walk you through it and answer any questions you have.

It is easier than it looks. For sure, you can do it.

Thanks, Rhubarb.

You’re right, it is a G/Y1 jumper, not G/R.

Thinking about this, I don’t think a two stage tstat will work, and here’s why. So let’s say I have one with the first stage set to fan and the second one set to control the AC, and the setpoint is, say 74.
Okay, so the temp raises above 74 and the fan kicks on. It keeps the house even and slows down the temprature rise, but eventually the temprature gets up to 76 and stage 2 (AC) comes on. The AC get’s the temprature under control and brings the house back down to 75 and shuts down. Now if the fan can’t get the house down another degree (sometimes it’ll be able to, othertimes it won’t) the AC is going to come back on. I think what’ll end up happening is that the fan will run most of the day…wait, maybe that will work. Now that I think about it. If the fan runs most of the day until the temprature drops back down and then 35% of the ‘off’ time as well, that should keep the house comfortable Maybe that will work. Dammit, now I need to keep thinking about this.
OTOH, I may go with the not staged model (but using the one that keeps the fan running 35% of the day) in the interest of not confusing people. My wife has a hard enough time dealing with a ‘regular’ digital tstat.

Hey, raindog. Do they sell these at big box stores or do I need to hit a supply house to compare prices.

Honeywell sells through Big Boxes and through HVAC Supply houses. I haven’t seen the FocusPro or VisionPro stats at Home Depot, but I imagine they might. They usually sell other brands like Hunter etc.

I would try a supply house. Fot the VisionPro 8000 you’ll pay between $125 and $160 I think.

Keep in mind that under the VisionPro 8000 name there are different variations; one that is better for humidity control, another that is multistage etc. I would guess you want 2 stage cool 1 stage heat. You choose if you want the enhanced humidity control unit or not. If you have a humidifier on the furnace for winter, I’d spring for the 9000.

Double post. This one deleted.

Actually stats will “stage up” when coming on, as you described.

However, they do not “stage down” on their way to achieving setpoint. In other words, in your example, if you set it to 74° the fan comes on around 75° (or sooner) At 76° or so the compressor comes on.

In your example, the stage 2 shuts down at 75°, and the fan, may or may not, get the final degree to the 74° setpoint.

But that’s not how stats work. If there was enough “drift” that stage 2 was necessary, all stages will stay on until setpoint is reached. In your example, the unit would not shut down stage 2 at 75° if the setpoint was 74°. Both stages will stay on until you reach setpoint, 74°.

I hope that’s not confusing.

One other thing…

They probably don’t sell a 2 stg cool 1 stg heat model. You’ll probably end up with a 2 stg cool 2 stg heat, and just won’t use the second stg heat terminal.

But you probably already knew that.

Also, there is a menu to set this unit up. There is the menu for the homeowner to program setbacks, times etc.

There is another menu however, that is technical. It tells the stat if it’s a heat pump, furnace, setoint limits etc. That is important.

it’s in the literature, but it’s technical information that a technician would be more familar with. If you buy the VisionPro. email me and I’ll give you my number. It will be so much easier if you have someone walk you through it over the phone.

You can do this. We can help. :wink: