Tempstar 2 Stage Furnance and A/C - two stage works?

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Old 06-17-12, 10:18 AM
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Tempstar 2 Stage Furnance and A/C - two stage works?

My repairman/installer is useless - a nice guy but clueless on modern electronics and two stage Heat and Air. I am very frustrated.

My house is 1200 square foot, split level, and in a moderate climate (SF Bay area). In the winter I had a new furnance and AC installed, a Tempstar IIS 80, f8mt and a Tempstar R-22 13 seer 3 ton A/C installed.

The furance is two stage but the motor is "standard" (whatever that means) but I know it is NOT a variable speed, but i assume it is two speed. The A/C is single stage.

The winter heating was great - nice even heat and (I would guess a low fan speed) through the winter. It never seemed to need or use a second stage. But the summer has been very disappointing. The air flow is cold, but low, even in 95 degree weather and the cooling barely keeps the house down to 77 to 82 degrees. The a/c air seems easily cold enough, but the flow is way low compared to the old single stage unit. When does it kick into a higher blower speed?

I assume that the blower is supposed to go to a higher speed when heating or cooling demands it. But all I ever get is low speed (a gentle flow) from the vents. In summer this is really way to low and I am cooking.

How do I get the higher blower speed for summer (as I said, the winters are so mild I never noticed it being used for heating). ??????

PS I am having theromostat replced, although it is supposed to be a two stage.

Roasting...

Max
 
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Old 06-17-12, 12:19 PM
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Open up the blower compartment of the furnace and make sure that there's a wire connected to the Y terminal on the circuit board.

If it's not connected, find the control wire which leads to the condenser unit (a/c)...

The control wire should have two conductors - one on the C terminal and one marretted to the yellow (it may not be yellow) wire from the t-stat...

Remove the marrett, untwist both wires, and put them under the Y terminal.

The blower motor in your furnace most likely has 3-4 speeds, three of which are in use...

High is usually cooling
Medium high or medium low is used for high heat
Medium low or low is used for low heat

In most multi-speed two stage furnaces, the low heat speed is used when there's a call for fan but not cooling.

----------------------------
It's not possible to properly charge an a/c when the blower speed is incorrect - get it serviced after correcting the problem.
 
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Old 06-17-12, 12:23 PM
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PS I am having theromostat replced, although it is supposed to be a two stage.

Read more: http://www.doityourself.com/forum/ga...#ixzz1y51U6XT3
Make sure there are at least 5 wires inside the t-stat cable, otherwise the new t-stat won't be able to stage the heat.

The majority of 2-stage furnaces are installed with single stage t-stat; low heat runs for the first 5-20 minutes (depends on the board) of each cycle. (high runs for the remainder of each cycle)
 
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Old 06-20-12, 11:15 AM
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Many thanks for the reply, very clear. I checked the wires as you instructed, they seem correct. I am going to change out the thermosat as it has four wires and a jumper (not sure the purpose). That just might be the problem.

Also, is there any way to manually force different speeds on the blower? My confidence in the unit is pretty low at this point. Id like to see some proof that the unit can actually blow at more than one speed (checked model numbers, it is a two stage furnance).
 
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Old 06-20-12, 02:30 PM
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The thermostat won't have an impact on the blower speed. The jumper between R and Rc should only be removed on older systems which use a separate transformer for cooling.
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Does the furnace control board have a Y2 terminal on it? If yes, try jumpering Y1 and Y2.
^Check this first

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The cooling blower speed might be set too low.

Check blower motor hp - it should be printed on the furnace rating plate. If it's 1/3HP (up to 3 tons of cooling), it definitely needs to be on high.

There should be a schematic diagram on the blower access panel which shows the blower motor connections...

White is neutral and the other wires are color coded. (color indicates speed)

The black* blower motor lead should most likely be connected to the cooling terminal on the circuit board.

*The lower speeds are used for heat (there are exceptions to this - depends on the duct system and size of a/c)

If the wiring looks okay, you can confirm that the board is energizing the right terminal (when there's a call for cooling) with a clamp on ammeter.
^Not recommended if you're not familiar with electrical. Do so at your own risk.
 
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Old 06-20-12, 05:13 PM
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http://icpindexing.toddsit.com/docum...4101210101.pdf

The stat Y wire is wired in to the furnace Y/Y2. The jumper would also accomplish this.


 

Last edited by Houston204; 06-20-12 at 06:02 PM.
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Old 06-20-12, 05:25 PM
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If you install a 2 stage stat, you will need to verify that SW1-1 is On.

 
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Old 06-20-12, 06:40 PM
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^That board looks just like carrier's

---------------------------------
If you install a 2 stage stat, you will need to verify that SW1-1 is On.

Read more: http://www.doityourself.com/forum/ne...#ixzz1yO6Nc8Tx
+
5th wire connected to W2.
 
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Old 06-20-12, 07:07 PM
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The wiring diagram on page 48 looks like Carrier's as well.
 
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Old 06-21-12, 08:03 AM
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Thank you all, great iinformation. I will check it out.

Max
 
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Old 06-27-12, 10:43 AM
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MANY THANKS TO ALL. After weeks of frustration your simple advice resolved the problem I bought a true 5 wire two stage thermo, made sure the dip switch was set correctly and hooked up the Y2 and W2 wires as instructed. IT WORKS.

Why this critical information is not in the owner's manual (rather than the blower manual) is a mystery.

NOW I have one remaining problem. Maybe i should dup at AC forum. The Tempstar one stage SEER 13 AC unit charges up to 65lbs (low side) then after activation a few minutes later it "hisses" and drops to 56lb. As specs call for 65 to 70lbs on the low side this concerns me. I am afraid of ice up or faulty cooling.

Any advice?
 
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Old 06-28-12, 11:01 AM
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Y2 shouldn't be connected, given that you have a single stage a/c.

When the stat calls for low cooling, the blower speed will drop. I recommend disconnecting Y2 and following the two stage stat with single stage a/c wiring diagram in the manual.

The Tempstar one stage SEER 13 AC unit charges up to 65lbs (low side) then after activation a few minutes later it "hisses" and drops to 56lb. As specs call for 65 to 70lbs on the low side this concerns me. I am afraid of ice up or faulty cooling.

Read more: http://www.doityourself.com/forum/ne...#ixzz1z70nrS00
Pressures alone don't mean much.

Call a tech to verify that it's charged properly.

Liquid and suction line temperature readings are required to actually see what's happening.

Why this critical information is not in the owner's manual (rather than the blower manual) is a mystery.

Read more: http://www.doityourself.com/forum/ga...#ixzz1z71RsbcE
Setting up the equipment properly is the installer's responsibility.
 
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Old 06-29-12, 10:52 AM
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My error, I meant to say I hooked up the Y/Y2.
 
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