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Old 10-10-2011, 08:23 PM   #16
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Dual Stage Furnace


The problem with most of these "free" thermostats, is that the utility is able to control when they want you to use the utility that you are paying for, so be careful. Also, it is nicer to have a thermostat that you can better control swing and differential between the stages, so you are able to better save money.

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Old 10-10-2011, 08:32 PM   #17
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The problem with most of these "free" thermostats, is that the utility is able to control when they want you to use the utility that you are paying for, so be careful. Also, it is nicer to have a thermostat that you can better control swing and differential between the stages, so you are able to better save money.
I know they can control it, but I can over ride what they change and if I can monitor/change it remotely then I have an upper hand in it. All they do is shut off the compressor, the fan supposed to stay on. And they SUPPOSEDLY only do this during high demand. I figure if it does not cost me anything I can always disconnect it and put my old one back or better yet buy my own. Only time will tell.
To be honest there is a lot of hype about energy saving appliances. I purchased my system 2 years ago and have not noticed any difference in savings. I don't think I will ever see it either as long as the cost of gas/electric keep going up.

Thanks for everyone's input. It's put some perspective on my concerns.
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Old 10-10-2011, 08:46 PM   #18
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You have to watch set points for heating and cooling, and other habits in the home, to really see a savings on utilities. Monitoring usage actually makes a evil itself. This past Summer, when I tracked run times, etc with the new thermostat, through a couple of third party programs, it did change a few of our habits, but the bill was still up where it was in previous years, due to how darn hot it was this past Summer. And now, we are going through a Indian Summer, and for the previous three days, I have had to turn the air back on during the day, due to the house was not keeping as cool as I wanted. Even now, it is 76 in here, with the windows open, even though it is 68 outside, due to I had the oven on for three hours to cook a pot roast.

I just gave up on watching use, and the info I learned from watching it, taught me a few things about better utilizing the features available on the new thermostat, and what works best for us.
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Old 10-11-2011, 10:09 PM   #19
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Update:
I read through the manual and it stated basically that with a single stage t-stat it will only go into low inducer, low heat rate and it can change from low fan to high fan.
With a dual stage it can operate at high inducer and high heat rate.

So from what I understand when it gets cold the heat will stay at low but the fan will increase to high speed with a single stage t-stat.

But a 2 stage t-stat will crank the heat up in addition to the fan speed.

I will have to speak with the installers and request a 2 stage t-stat.
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Old 10-12-2011, 04:41 AM   #20
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There is a timer on the furnace board that will cause it to go to second stage after X minutes of run time. If the installers set it up. Its a poor way to control it though. And that a 75,000 BTU furnace, with a 3.5 ton blower.
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Old 10-12-2011, 09:00 AM   #21
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One of the big problems with operating with a one stage stat and letting the board program decide when to use low or high fire is when recovering from a night time or workday setback. If the furnace doesn't kick into high fire for, say, 15 minutes, it will take a lot longer than it should to warm the place up. Much better to make the low fire/high fire changeover operate off a true 2-stage t-stat based on temp differential, usually default of 2 degrees.
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Old 10-12-2011, 09:19 AM   #22
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There is a timer on the furnace board that will cause it to go to second stage after X minutes of run time. If the installers set it up. Its a poor way to control it though. And that a 75,000 BTU furnace, with a 3.5 ton blower.
I checked the manual and it is set via a dipswitch. Currently it's set to 140sec.
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Old 10-12-2011, 04:04 PM   #23
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For best comfort. A 2 stage stat should be used. It would allow the furnace to run for as long as possible in first stage, to maintain a constant temp in your house. helping to eliminate the feeling of any cool drafts from sudden high temp air and then off using the timer.
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Old 11-04-2011, 09:15 PM   #24
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I received a dual stage thermostat from sears. Installed myself-very easy.
When I programmed the setpoints for the week the heat did not turn on (because of an already high temp). So I increased the setpoint by 1 degree manually. I noticed that the fan speed was on high when I did this. I thought with 2 stage it is supposed to start in low-heat low-fan and if needed go to high-heat high-fan?
I did have to change a dip switch on the control board based on the documentation.

The manual states for 2 stage thermostat operation:
24VAC signal applied to W1 & W2 terminals
-same light-off routine as described for single stage thermostat operation except main burners light at High Heat rate,the inducer remains on high speed after ignition, and the FCB will delay blower operation at the High Heat Fan Speed for 30 seconds on Delay Time.
Note: The FCB responds without delay to the presence or loss of W2 (with W1 constant). W1&W2 result in high inducer, High Heat rate and High Heat Fan Speed. W1 only results in low inducer, Low Heat rate and Low Heat Fan speed.

The Heat Off Delay timer is set to 140sec
High Stage Heat On Delay is 30 sec
Low Stage Heat On Delay is 45 sec

Can someone clarify or am I just thinking about it too much.
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Old 11-05-2011, 06:38 AM   #25
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"So from what I understand when it gets cold the heat will stay at low but the fan will increase to high speed with a single stage t-stat."

If this were true, then the outlet temperature would be lower, when you need heat the most. Brrrrrrrrr.
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Old 11-05-2011, 08:58 AM   #26
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On a W1 only call, it should be in low fire with a reduced blower speed, on a call from W1 and W2 it should go to high fire with a higher blower speed. This is the basic standard for 2 stage furnaces.
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Old 11-05-2011, 09:05 AM   #27
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If you are switching from a 1-stage stat to a 2-stage stat you might also need to look at the furnace manual for jumper or dip switch configurations. Some 2 stage units have a "staging" jumper that lets the furnace operate the 2nd stage on a programmed algorithm with only the W wire connected from a single stage stat. If you are switching to a 2-stage stat I think you would need to disable this feature to get proper 2 stage function.
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Old 11-05-2011, 09:51 AM   #28
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Thanks All for the reply posts.
The new T-stat has a test function that checks each stage. I tried it and in low stage it fires at Low heat low fan and at second stage it fires at high heat high fan. I also tried overriding the schedule again and raised the temp by 1 degree and it went into low heat low fan and then I raised it a few more degrees and it went to high heat high fan immediately.
Now I can only assume that it is going to low heat and high heat respectively because I really can't tell unless I use some kind of sensor. It would be nice if the t-stat would show each stage and fan speed.

I did change the dip switch on the furnace control board to operate with a 2 stage t-stat. But I am not clear the function of the Heat off delay so I left it at 140 sec.(this is also a dip switch setting).

All in all it looks like it's working properly but I will monitor.
I am considering the Filtrete 3M-50 for remote management and it looks like it has more control with respect to differential and swing.
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Old 11-05-2011, 09:52 AM   #29
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Heat off delay is how long the blower runs after the burners shut off.
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Old 11-05-2011, 09:55 AM   #30
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Heat off delay is how long the blower runs after the burners shut off.
Ok. 2.5 minutes is good I would say.

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