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Old 12-05-2011, 03:48 PM   #16
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did I buy the wrong furnace?


did they install it properly? set the burner manifold gas pressures etc. why not call the contractor back and have him show U the size of burner flames on low and high fire and explain how it switches firing rates to U.

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Old 12-06-2011, 12:06 AM   #17
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did I buy the wrong furnace?


ok,you guys have given me some good info. NOW,I know that I need a good 2 stage tstat (which I'll get tommorrow either at HD or Lowes)
so can anybody explain exactly how a 2-stage stat works? I mean exactly how does it "fiddle" with W1 and W2 to achieve the desired heat operation? also I read in some string that the jumperss on the control board in the furnace have to be set for .5 sec. is that the only change to the board needed for a 2 stage stat?
and yes, I'm going to pull a new cable with more wires for the stat. how many conductors in the cable?

tnx,
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Old 12-06-2011, 04:30 AM   #18
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did I buy the wrong furnace?


A good Honeywell thermostat, will determine when first stage is at 90% of the homes heat loss load, and go to second stage. Giving you no temp droop.
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Old 12-06-2011, 05:34 AM   #19
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6 ) #18 conductors. you can buy #18 LVT wire at HDepot. need to read the install manual. there is a dip switch for 1 or 2 stage op. the tstat has a built in 1 deg F differential. when it drops from 70 F to 69 1st starts when it hits 68 2nd stage starts. there are cycles per hour adjustments in the tstat programming and you set it for whatever you like. I usually leave it on average setting and shorter ones for elderlys who sit in wheelchairs or feel cold more than the average person.
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Old 12-06-2011, 05:41 AM   #20
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there is no switch for single or 2 stage operation on this furnace. However you can adjust the upstage delay to .5 min. your CPH should be set for 5
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Old 12-06-2011, 05:49 AM   #21
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did I buy the wrong furnace?


thankx for the info. Trane is less than 10% of my market so I don't see too many or have to set them up from new. I wonder if HDepot sells 2 stage tstats as they are more expensive etc. may have to order one online - americanhvacparts.com
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Old 12-06-2011, 06:09 AM   #22
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Looks like HD carries the RTH7600 honeywell stat that can be programmed for 2 stage operation
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Old 12-06-2011, 06:22 AM   #23
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I have a question about what BT posted above... do most 2 stage stats have a way to know when first stage isn't likely to be enough to satisfy the call for heat to the set temp? What if you get to an outside temp/heat loss where you have 100% run time on low fire but inside temp is within the differential so it just keeps running in low fire and not heating up to the set temp.

BT said that at least one Honeywell has a way to use high fire in those circumstances to satisfy the call. Does it do this based on a run time setting? Like if it can't satisfy the call in low fire in x minutes then it upfires? Or does this require an outdoor temp sensor input? I am not sure my 3M-50 2 stage stat has such a function or setting but I guess I need to look into it before it gets really cold.

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Old 12-06-2011, 07:42 AM   #24
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raylo32, I know that the 3m-50 that I use, I can set swing and diff, with the differential deciding when to jump to 2nd stage to satisfy, along with either a fast or slow recovery for 2nd stage. All of them use an algorithm to decide, until you get to the higher end stat's, then you can use either the software, or the stat to tweak out settings even further.
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Old 12-06-2011, 07:48 AM   #25
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Greg, I was hoping you would weigh in since you have a 3M-50. Yes, I understand the swing and diff and how it can use high fire all the way to the set temp when recovering from a setback if you have it configured for fast recovery.

But what about in normal ops... say the indoor temp drops 1 degree (my swing) and the furnace comes on in low fire. But meanwhile the outdoor temp drops enough that the low fire can't keep up but not enough that the temp drops below the diff (2 degrees in my case). It would just run and run (which is OK) but not maintain the set temp... in fact it could be up to 2 degrees below the setting. I think BT called it "droop". Just wondering if there is a way with the 3M-50 to avod that... and, if not, which stats have the necessary logic to handle this and how they do it.

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Originally Posted by gregzoll View Post
raylo32, I know that the 3m-50 that I use, I can set swing and diff, with the differential deciding when to jump to 2nd stage to satisfy, along with either a fast or slow recovery for 2nd stage. All of them use an algorithm to decide, until you get to the higher end stat's, then you can use either the software, or the stat to tweak out settings even further.
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Old 12-06-2011, 08:21 AM   #26
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did I buy the wrong furnace?


Quote:
Originally Posted by analogmusicman View Post
ok,you guys have given me some good info. NOW,I know that I need a good 2 stage tstat (which I'll get tommorrow either at HD or Lowes)
so can anybody explain exactly how a 2-stage stat works? I mean exactly how does it "fiddle" with W1 and W2 to achieve the desired heat operation? also I read in some string that the jumperss on the control board in the furnace have to be set for .5 sec. is that the only change to the board needed for a 2 stage stat?
and yes, I'm going to pull a new cable with more wires for the stat. how many conductors in the cable?

tnx,
I work on Trane everyday and that unit is set up 2nd stage from the board not the t-stat. You have dip switch on the board and need to see if its set right. The setting are on the wiring diagram. I don't have the board in my truck to show you were those are but just read the wire diagram
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Old 12-06-2011, 10:06 AM   #27
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did I buy the wrong furnace?


raylo, mine runs in low stage if it drops 1 degree. I have the swing set for 1, diff for 3, unit is set at fast recovery (setting 4).
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Old 12-06-2011, 10:50 AM   #28
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Greg, you're missing my question still: if running in low fire isn't able to heat the interior up to the setpoint (think an equilibrium situation where it gets cold enough outside that heat loss equals low fire furnace output) but it IS enough to hold it above the diff so that high fire does not kick in the furnace would just run constantly and temp would hover in the range between the setpoint and the setpoint-diff range... unless there is some logic that understands by some criterion that low fire isn't enough due to high heat loss. I don't think the 3M-50 has such logic... but will keep checking.

I tried to PM you but looks like you are not accepting PMs. Even though this is pertinent to this thread I'll maybe post a new topic later to get out of the OP's topic. Meanwhile I have asked the RT support board but that place is overly moderated and therefore slooooowwww..


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raylo, mine runs in low stage if it drops 1 degree. I have the swing set for 1, diff for 3, unit is set at fast recovery (setting 4).
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Old 12-06-2011, 11:28 AM   #29
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did I buy the wrong furnace?


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Originally Posted by Tator1076 View Post
I work on Trane everyday and that unit is set up 2nd stage from the board not the t-stat. You have dip switch on the board and need to see if its set right. The setting are on the wiring diagram. I don't have the board in my truck to show you were those are but just read the wire diagram
so you're saying that a 2 stage tstat would be useless with an XV80?

tnx,
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Old 12-06-2011, 12:21 PM   #30
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raylo32, no I read your message. Mine takes about 15 min's to heat up the house, and stays on stage 1 the whole time. The reason is, that the house is a part of the hvac system. What that means, is that if the house is leaking so much air through chimney effect, leaky windows, wall outlets, doors, the hvac system has to work harder to keep up. That means that it would have to move into stage 2 to pump out more heat to bring it to temp.

Before I went around and sealed around the retro windows that were installed probably late 90's, sealed around the outlets, we were leaking a lot of air, especially around the windows, due to no insulation at the top, and there were gaps around the edges. Now they do not leak any air, due to I have sealed around the outlet boxes, and windows, so the hvac system actually runs like it should on stage 1 for normal heating. Then cycles about once an hour on stage 1 for aprx 10 to 15 min's to satisfy house temp. Evenings, the house stays warm enough, due to the Plasma tv puts out some heat, so pretty much the furnace does not cycle, as it does during the day, when no one is home.

Now, when the setback goes from 64 to 68, the furnace automatically jumps to stage 2, due to how the 3m-50 works, then drops to stage 1 when it gets within 1 degree to satisfy room temp.

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