VisionPro

[jerrod6]

I don't know anything about relays but this is supposed to be a digital stat that doesn't have that inacurate metal bi metal switch. Why aren't the relays digital or electronic so that there is no sound? Is this not possible?

[tpa-fl]

That loud clicking is the sign of quality relays. There is an electronic equivalent to the relay, the triac, but they tend to be failure-prone, which is why your better thermostats use large relays which can handle the load and then some. My air handler's fan relay makes far more noise than the stat does. For recording studios, I usually put the stats in a closet or hallway and use remote sensors in the studios & control rooms to eliminate all extraneous noises.

[dx]

tpa-fi, I was liking your posts until that last one. You need to brush up on triacs. What do you think is inside of every dimmer in your house? That's 110v, not 24. And they switch on and off 120 times a second. Try to have a relay do that for 10 years. Ask Honeywell why they use relays. I'll bet you a beer they won't tell you triacs are unreliable.

[dan sw fl]

When the temperatures well exceed Design Conditions,
it is rather pointless to look for ANY type of Normalcy.
___ With BOTH People & Equipment! !! !!!

L.O.L.

A/C types KNOW THAT Much Better
than psychologist and weathermen.

NOT so COMMON Sen$e:
Limit your setback to 4'F MAX.
as a compromise between Comfort and Energy $avings.

(Daytime 81'F, Evening 78'F for me).
I guess one may expect
about 1'F decrease in 40 to 60 minutes
during late afternoon conditions.

To Man & Machine,
__ Simply perform the Best you can in Difficult Times!

[resolutetech]

When you set the stat back think about this. Not only does your air temp rise. Everything in your home gets warmer. The furniture, the walls, the carpet, the dog, all get hotter. And you are asking an A.C. system to remove a pile of heat from this mass of materials, not just the air. well if your system is say a 24000 btu (2 ton)system it only removes 24000 btu per hour. A large set back allows a pile of btus to build up in all this mass. Lets make up a number 96000, well it will take 4 hours to remove this much heat plus all the heat entering the house while its removing this heat.

I vote for not setting it back too much unless its a 2 stage system able to pull the heat down rapidly with extra capacity.

Dont you just love this sight!

[sirwired]

For tpa-fl's advice, I thank him very much.

For everyone else... this has been a facinating discussion on the merits of setting back at all, recovery time, etc., but it had nothing to do with my question.

My original question was why the "adaptive recovery" was not turning on the stat prior to the schedule time, as the brochure for the stat says it is supposed to.

For those unfamiliar with the stat, the thermostat is SUPPOSED to measure the amount of time recovery took on previous days, and use that time to turn on the system at an appropriate time so the dwelling is AT the setpoint at the schedule time. This means the recovery time is calculated for you, and adjusts depending the weather.

Most setback thermostats just turn the system on at the schedule time, which means you must figure out what the recovery time is on your own.

This feature was not working at all, which was my problem. My VisionPro was not turning the system on prior to the schedule time. (It did during the winter.)

Does anybody know if it would also take the Outdoor Temp Sensor into account? I think it would for a heat pump during heating season, but I don't know about cooling.

--------------------------

Now, as to why setbacks save money:

Newton's law of cooling tells us that the rate of heat transfer is directly proportional to the difference of temperature between the two objects. That means that when your house is 75 degrees, and the outdoors is 95 degrees, you absorb twice as many BTU's / hr as when the house is 85 degrees. It's that simple. More BTU's / hr over X hours means more total work for the AC.

NOTE: Some adjustment must be made for sunlight, as that is going to cause the house to heat up independent of the indoor or outdoor temperature.

The exact amount of savings would involve some rather nasty calculus, and is dependent on too many factors to determine accurately. (Rate of cooling of the system, insulation, color of the house, outdoor temperature at different times of the day, humidity, amount of light hitting the house at different times of the day (which in turn depends on shade, latitude, cloudiness), etc. You get the idea.)

SirWired

[tpa-fl]

Originally posted by dx
tpa-fi, I was liking your posts until that last one. You need to brush up on triacs. What do you think is inside of every dimmer in your house? That's 110v, not 24. And they switch on and off 120 times a second. Try to have a relay do that for 10 years. Ask Honeywell why they use relays. I'll bet you a beer they won't tell you triacs are unreliable.

I have quite a few triac-based dimmers around the house...and yep, I end up having to replace at least one of them a year. Lutron, Leviton, doesn't matter, they still go out. Even the ETC Sensor modules fail, and those $$$. I do find it interesting that ETC's moving to inverter-based dimming and getting away from the triacs. Everything I've seen which is "mission critical" still uses relays.

[Edited by tpa-fl on 08-05-2005 at 09:33 AM]

[resolutetech]

When you set the stat back think about this. Not only does your air temp rise. Everything in your home gets warmer. The furniture, the walls, the carpet, the dog, all get hotter. And you are asking an A.C. system to remove a pile of heat from this mass of materials, not just the air. well if your system is say a 24000 btu (2 ton)system it only removes 24000 btu per hour. A large set back allows a pile of btus to build up in all this mass. Lets make up a number 96000, well it will take 4 hours to remove this much heat plus all the heat entering the house while its removing this heat.

I vote for not setting it back too much unless its a 2 stage system able to pull the heat down rapidly with extra capacity.

Dont you just love this sight!

[Stamas]

You've got your answer, started good side discussions and still have found room to bitch about those discussions not concerning you.
Nice.

[sirwired]

Stamas,

I just read over my last post, and you are right, I do sound like a bit of a twit. Sorry.

I was simply frustrated that everybody kept telling me that my setback was too large, or that I shouldn't bother, while completely ignoring my actual question, which was about the adaptive feature not working at all during cooling season.

That isn't an excuse, but I thought I would mention it anyway.

I really do enjoy reading this board, and the "Wall of Shame" is a hoot! (You don't have to be an HVAC tech to appretiate the true slack-off artistry of the hacks featured there!)

SirWired

[on call]

The thermostat has a a parameter that sets how agressive the temperature recovery is. Setting parameter 0690 to 3 might help the situation.