project_x
Registered Users
Posts:25
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| 10/30/2008 10:58 AM |
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I have set up a 1-wire temperature measurement system to monitor my Waterfurnace.
What I've noticed, is that my first stage heat measured at the furnace output is approximately a gain of 22* over the return air.
If I force the furnace into 2nd stage, the fan comes up to high speed, but the gain at output is only 18*.
I have checked all the dip switches, and I think all is ok with that.
I also set the diagnostic dip switches to"
Verify that the thermostat signals were being sent correctly (also measured with a multimeter)
Verify that the appropriate stages are turning on
Verify that it is low, medium or high fan,....
All the diagnostic lights, say it is running correctly, but the temps, don't look correct.
What can I look at next? How does the 2nd stage function? Could it be that the compressor is wired incorrect (i.e. stage one and stage 2 reveresed? Or low refrigerant (all though, I thought it would at least match the output of the 1st stage)
Any ideas? Thanks, Rob |
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tuffluckdriller
Registered Users
Posts:416
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| 10/30/2008 11:10 AM |
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Temp. rise is merely a part of the equation. One thing that would tell you if it's correct is the BTUh output of the system.
BTUh = CFM x 1.08 x delta T
If the Delta T (change or rise in temp) is 22 vs. 18, that doesn't tell anything. You'd have to know the rest of the equation to know if it's really putting out more BTUs in the 2nd stage. |
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Clark Timothy (clark@pinksdx.com)
VP sales, Tuff Luck Geothermal Drilling
Geothermal, Heating and Cooling that's Dirt Cheap! |
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project_x
Registered Users
Posts:25
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| 10/30/2008 11:45 AM |
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Posted By tuffluckdriller on 10/30/2008 11:10 AM
Temp. rise is merely a part of the equation. One thing that would tell you if it's correct is the BTUh output of the system.
BTUh = CFM x 1.08 x delta T
If the Delta T (change or rise in temp) is 22 vs. 18, that doesn't tell anything. You'd have to know the rest of the equation to know if it's really putting out more BTUs in the 2nd stage.
Making some assumptions, and using the ARI output data for my furnace.
2nd stage of the furnace should produce 39% more BTUs that 1st stage.
The dip switches are set for 1500 cfm (medium) and 1950 (high), which is a 30% increase in cfm (I will assume that these are correct for my simple comparison, i will verify later).
As a result, using your calc, one should see a marginally greater temp increase (about 7%) at the output in 2nd stage.
I know there are additional factors playing on this, but....
Does anyone know if there any direct measurements I can make?
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tuffluckdriller
Registered Users
Posts:416
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| 10/30/2008 1:49 PM |
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Using the same formula for BTUh, you should be able to calculate the cfm for each stage using your electric heat.
cfm = btuh / (1.08 x delta T)
With the electric heat, you can determine the exact BTUs it puts out from the Amps and Voltage applied. P=IE, or Watts = Amps x Volts. From this, let's say it's a 5 kW strip heater. It should, at 240V, be drawing 20.8A.
Now we need to convert the Watts into BTUh. 5000W x 3.413 = 17,065 BTUh output from the electric heat. Keep this number in mind.
Next, take a temp. measurement of the return air at the unit, and the supply air off of the unit. Make sure the supply reading is measured out of "sight" of the electric heat, or radiant heat may skew this number. Now figure your delta T. Then just plug in the numbers.
If delta T = 18 with the strip heat, I'd have: CFM = 17065 / (1.08 x 18) = 878 cfm.
With this accurate info, you'd be able to see the actual btuh output of your system with your system's duct. Just apply this cfm number to the equation and use the compressor now to heat the air in first and second stage.
I do agree with you, though, that your 2nd stage may not be running as it should. Hopefully this helps you determine.
Maybe a simpler way to tell would be to measure the current (amps) of the compressor unit in first stage vs. second stage. Now I feel like I went completely around the point before getting to it.... |
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Clark Timothy (clark@pinksdx.com)
VP sales, Tuff Luck Geothermal Drilling
Geothermal, Heating and Cooling that's Dirt Cheap! |
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engineer
Registered Users
Posts:445
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| 10/30/2008 4:38 PM |
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Does your unit have the ECM or PSC blower? Supposedly the ECM blowers will move the set amount of air against any static pressure up to the blower's rating, typically 0.50 or 0.75 " WC. The blower somehow knows the flow and varies RPM to make it happen. My blower (ECM) definitely turns faster when just a small zone calls alone (higher ESP)
If you have or can beg borrow or steal an AC clamp meter measuring the compressor current should quickly reveal second stage operation. With mine I perceive no change in compressor sound but amps jump 50% or so. |
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Without data, you only have an opinion. |
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project_x
Registered Users
Posts:25
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| 10/30/2008 4:57 PM |
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Posted By engineer on 10/30/2008 4:38 PM
Does your unit have the ECM or PSC blower? Supposedly the ECM blowers will move the set amount of air against any static pressure up to the blower's rating, typically 0.50 or 0.75 " WC. The blower somehow knows the flow and varies RPM to make it happen. My blower (ECM) definitely turns faster when just a small zone calls alone (higher ESP)
If you have or can beg borrow or steal an AC clamp meter measuring the compressor current should quickly reveal second stage operation. With mine I perceive no change in compressor sound but amps jump 50% or so.
I put my oscillosope and current transformer, and got exactly the same current measurements on each stage.
The call for Y2 is certainly going to the waterfurnace, but what it's doing with it, who knows.
I will review the docs to see if i can make any other measurements, but if any one knows where to look, i'd love to hear.
BTW: It is ECM |
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geodean
Registered Users
Posts:651
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| 10/30/2008 5:31 PM |
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| Check the entering and leaving water temp. ON second stage, the heat pump should be taking more heat out of the water |
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Dewayne Dean
PalaceGeothermal.com
Why settle for 90% when you can have 400%
We heat and cool with dirt!
visit- http://welserver.com/WEL0114/- to see my system |
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project_x
Registered Users
Posts:25
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| 10/30/2008 5:52 PM |
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| It is taking less ( about 5.5* versus 4.5*) in 2nd stage.
I guess I need to figure out where the 2nd stage of the compressor gets turned on, to ensure it is getting signal. |
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geodean
Registered Users
Posts:651
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| 10/30/2008 6:02 PM |
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| The heat pump low voltage wirings have a Y1 and a Y2 terminal. Y1 is first stage and Y2 is second stage. Since the delta T on water temps doesn't increase, it doesn't sound like the second stage is working properly |
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Dewayne Dean
PalaceGeothermal.com
Why settle for 90% when you can have 400%
We heat and cool with dirt!
visit- http://welserver.com/WEL0114/- to see my system |
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engineer
Registered Users
Posts:445
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| 10/30/2008 6:20 PM |
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There should be 24 Vac on both Y1 and Y2 during a call for high stage.
I agree that it sounds as though 2nd stage isn't staging. The reduced Delta - T on the airside and no increase in Delta-T on the water side are both clues
2nd stage flips a solenoid closing bypass ports in the compressor scroll. There is no change in speed.
Isn't solving this an issue for the installing dealer? |
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Without data, you only have an opinion. |
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project_x
Registered Users
Posts:25
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| 10/30/2008 6:25 PM |
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Posted By geodean on 10/30/2008 6:02 PM
The heat pump low voltage wirings have a Y1 and a Y2 terminal. Y1 is first stage and Y2 is second stage. Since the delta T on water temps doesn't increase, it doesn't sound like the second stage is working properly
I had already check the low voltage connection and signals already, all seemed to be fine.
I followed Y2 all the way to the high pressure switch, where it then goes to the low pressure switch and finally to micor controller that controls the compressor (which I think is P10) I will chase it through the pressure switches after dinner.
Thanks,
Rob
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project_x
Registered Users
Posts:25
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| 10/31/2008 8:47 AM |
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Posted By engineer on 10/30/2008 6:20 PM
Isn't solving this an issue for the installing dealer?
Agreed, I just want to make sure I understand what is going on. The voltage to the solenoid looks good (13.5VDC) and solenoid resistance is good (36ohms), so maybe it is stuck.
I'll call service next week. |
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ground.loop@yahoo.com
Registered Users
Posts:4
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| 10/31/2008 5:54 PM |
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Rob
if your high speed blower or second stage blower speed is to high then the temp difference will we be a bit lower, you could set the blower speed differently to allow for a warmer air discharge, be sure to set it with in the shaded area on the manual so as not effect the refrigerant level on the compressor cycle.
The envision unit has a 78/22 % split on the capacity so your 1st stage is set to deliver 78% of the total capacity of the unit and when it goes to second then you get final 22% this is not a huge additional heat gain on the delta T for the discharge so look at the blower speeds.
using the dip switches you can verify what stage the unit is in and what the blower speed is currently, however you best leave that to the installing contractor to verify unless you feel comfortable getting into that.
usually I set it up so as to utilize the dehumidify fieature in the dip switches. |
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project_x
Registered Users
Posts:25
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| 10/31/2008 6:10 PM |
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| The dip switches are set for M 1500cfm and H 1950cfm.
Through the diagnostic dip switches, my multimeter and oscilloscope, I have verified that it is switching to 2nd stage and high speed fan, except for the compressor solenoid is not switching. The solenoid voltage is there, coil looks to be the correct resistance, it just doesn't switch to 2nd stage.
The furnace thinks it is 2nd stage, but the compressor solenoid fails in to first stage, which is why the temp is less (higher blower speed).
I will have to try the waterfurnace warranty |
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engineer
Registered Users
Posts:445
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| 10/31/2008 10:29 PM |
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Nowhere hear do I see the model series or the number of the unit. If it is any using the Copeland Ultratech 2 stage compressor the capacity split is 67%. That there is no change in compressor current with Y2 energized strongly suggests 2nd stage ain't happening.
13.6 VDC? I would have expected 24 Vac. Control signals on pretty much all residential HVAC gear are 24 Vac. I'm not saying I haven't missed a subtlety of this particular unit, but I expect 24 Vac.
What WF series and model is this unit? |
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Without data, you only have an opinion. |
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project_x
Registered Users
Posts:25
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| 11/01/2008 5:24 AM |
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Posted By engineer on 10/31/2008 10:29 PM
Nowhere hear do I see the model series or the number of the unit. If it is any using the Copeland Ultratech 2 stage compressor the capacity split is 67%. That there is no change in compressor current with Y2 energized strongly suggests 2nd stage ain't happening.
13.6 VDC? I would have expected 24 Vac. Control signals on pretty much all residential HVAC gear are 24 Vac. I'm not saying I haven't missed a subtlety of this particular unit, but I expect 24 Vac.
What WF series and model is this unit?
It is a Envision 5ton dual speed unit, ECM, scroll and DSH.
The comfort alert unit converts the 24VAC to DC for the solenoid (black and red wires at the bottom). There is a document available in the engineering section of waterfurnace.ca, that has Envision troubleshooting and covers this.
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engineer
Registered Users
Posts:445
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| 11/01/2008 7:36 AM |
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You're ahead of me. I need to check out that .ca site for docs not on us site. I'm glad I included a disclaimer about missing a subtlety of this unit, because apparently I have..
I believe that once you get into the Comfort Alert, solenoid, and compressor itself you are fully into what WF buys from Copeland / Emerson climate technologies.
I have a similar unit - 3 ton.
Are you on a single thermostat or a zoned system?
Do you know if it will go into high stage in cooling mode?
If you isolate the solenoid and energize it with 12 volts from an independent source (current protected to reduce chance of releasing factory-installed smoke) does it seem to move or click in the manner typical of solenoids?
Of course further fooling with this is ill-advised since it is presumably under a warranty which will be void if you let any smoke out of anything...
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Without data, you only have an opinion. |
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project_x
Registered Users
Posts:25
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| 11/01/2008 9:54 AM |
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Posted By engineer on 11/01/2008 7:36 AM
You're ahead of me. I need to check out that .ca site for docs not on us site. I'm glad I included a disclaimer about missing a subtlety of this unit, because apparently I have..
I believe that once you get into the Comfort Alert, solenoid, and compressor itself you are fully into what WF buys from Copeland / Emerson climate technologies.
I have a similar unit - 3 ton.
Are you on a single thermostat or a zoned system?
Do you know if it will go into high stage in cooling mode?
If you isolate the solenoid and energize it with 12 volts from an independent source (current protected to reduce chance of releasing factory-installed smoke) does it seem to move or click in the manner typical of solenoids?
Of course further fooling with this is ill-advised since it is presumably under a warranty which will be void if you let any smoke out of anything...
My unit is a single zone, I don't know if it goes into 2nd stage cooling. I will call for service next week.
Cheers,
Rob
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a0128958
Registered Users
Posts:191
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| 11/01/2008 11:03 AM |
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Posted By project_x on 11/01/2008 5:24 AM
It is a Envision 5ton dual speed unit, ECM, scroll and DSH. The comfort alert unit converts the 24VAC to DC for the solenoid (black and red wires at the bottom). There is a document available in the engineering section of waterfurnace.ca, that has Envision troubleshooting and covers this.
I have the exact same model. The above description of how the control circuit operates for 2nd stage is accurate I believe.
Simply putting an ammeter on the compressor wires to measure current draw values, on 1st stage, versus 2nd stage, should clearly show if 2nd stage is working.
Best regards,
Bill |
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