With relatively low Delta T and Delta P (used to determine GPM) one has to beware measurement errors. If a 0-100 psi scale pressure guage is used for the Delta P measurement, it might be easy to be off 1/2 pound or so. Same might apply to Delta-T. Instrument error can introduce a large calculation error, although if the same thermometer is used any error should cancel out.

Where are you measuring EAT? If at a return grill check it right at the unit's coil. Return air can be cooled by leakage into duct from unconditioned space, or heat loss.

Desuper will divert 5-15% of heat from air, depending on its entering water temperature. Try taking your LATs with it off.

Desuper should have no affect on HE, and you are right to be concerned with that.

Your numbers check out.

"Check out" in which sense - is his system shorting him 20%, or are measurements within expected range?

Did you confirm his table lookups?

Low HE suggests unit is somehow operating in a partially 'unloaded' state. LAT looks OK, so it doesn't appear to be low airflow. Low refrigerant charge is my next knee-jerk reaction, but I know low charge is often inappropriately suspected.

Tine for me to kick back and 'listen'.

What I meant to say is " your math and logic are correct"

I did check the specs and he has the right numbers.

If the gpm is wrong, then the HE is not accurate. Since the gpm came from the installer, it might be suspect.

If the unit is short on HE by 20%, then low refrigerant needs to be evaluated.

Especially in light of JoeinOKC's experience.

We're on the same page - cool.

I dislike that we have to call into question installer's apparent data, but recent experiences suggest that avenue.

I appreciate the feedback. I understand the possible instrument errors, but for the key measurements (EWT, LWT), I used the same instrument, and plugged right into the line at the unit. I would think this measurement is the most accurate of them all. I can only assume the tech has the GPM right. Bottom line, based on these calculations using the same process the tech did when he came out, I am under spec.

The reason I wanted to confirm my readings and calculations is my installer wants to blame things on lack of insulation in my house, and the need to have more supplemental heat. When he installed the unit, he said I would never need the electric heat pack. Matter of fact, he added a switch on the unit so we could simply turn it off. Now that the unit cannot keep my house heated, he has changed his story and says if it is 30 degrees or less outside, the heat pack will need to run. I understand the heat pack may be needed occassionally, but hey, lets at least get the system up to spec.

I will run additional test today. Are there any other suggestions? What might I expect in addition to adding refrigerent? What is the best way to caculate the loop GPM? There is a flow meter on the loop, but it is not working. There is also a pressure meter on the input loop. It reads about 30 PSI, but seems to fluctuate plus or minus 5-10 PSI. After reading some prior post, I am wondering if I have some loop issues with either the flow rate or pressure.

Appreciate your help. This forum has been extremely helpful.

Mark

If you have or can get the pump curves for your water circulating pump and can get the differential pressure across the pump (discharge pressure minus suction pressure), you should be able to determine the pump flow rate.

Alternatively, if you can measure the voltage at the pump motor along with the current being drawn by the motor, and you have the manufacturer's gpm rating for the pump at a given power consumption (W = V x I), you should be able to roughly calculate the percent of rated output of the pump.

Refresh my memory here, what size heat pump do you have (looks like a ttv064)? I Presume it is closed loop? Did you turn the DSH to run your tests? When was it installed? What antifreeze and pct do you have (table based on 15% methyl we tend to use more here)?
Climatemaster's manuals are incremental by 10* on entering water temp, so to say it should be.......based on the table, means you should also have 40* EWT. The other thing we need to do is test the thermometer in a glass of ice water. If it is a few degrees off and you are rounding up on the table, a 20% disparity would be easy to come by. The table also varies by airflow so CFM is part of the equation and it is based on 70*DB EAT.
At a glance, you would have to be off several degrees in your measurements so I agree that something doesn't seem right, but let's first test the test equipment and look at CFM. Also make sure all test are done without DSH running.
Good luck,
J

OK, back to having some time to evaluate things. The unit is the ttv064 5 ton. I am going to take some more readings tonight. What is the easiest way to turn off the desuperheater? Also, with my EWT around 37 F, and 15GPM, I read the manual as saying I should expect a 4 - 8 degree drop throught the head exchanger. Is there some reason why this would be on the low side versus the high side? Regarding the tables, I am rounding to the low side, meaning I am taking values from 30* when my EWT is below 40.

thanks,

Mark

Is there a switch on front of unit controller desuperheater pump? WF Envisions have that, not sure about CM

DSH is hard wired- spade connectors in the control panel.
Still struck by a 25% greater delta between EWT and LWT without change in leaving air temp.
Turn off the DSH and remeasure.
j

If the CFMs also rose by 20-25% during a Y2 call that could happen, although I'm surprised it stayed at exactly 91.5 in both stages.

I've been fiddling with my zone board, allowing Y2 to kick in for the first time since forecast lows are 10 below design tonight and tomorrow. LAT hangs in the 89-92 range in both stages, but CFMs pick up. I've picked some different CFM settings within a fairly narrow range, same result.

My ear can't tell what stage compressor is in, but amps rise from 7 to 10 and LWT drops 3-4 degrees in concert with the Y2 LED, as expected.

Generally, we would split the difference on the tables. Also while you have the unit open you to deactivate the DSH (remember there's 220v in there so be careful and disconnect power before pulling connectors on DSH), you can read the LEDS on the board to determine which stage you are in. The chart in the manual refers to 2nd stage.
J

My zone board (when I pull the cover off) tells what stage it is calling for but for Pete's sake why couldn't WF indicate actual stage (and aux, if installed) on the unit panel display?

OK, done ranting.

Can I join your rant ??

Sounds like you need to confirm that your heat pump has the right refrigerant charge and also that your getting adaquate flow through the unit. What is the the ground loop application? Trenched or drilled? Adaquate pipe lenght and amount of it in the ground, and again proper flow to the heat pump. If your having issues with adaquate entering and exiting temps., look at the simplicity of the system mechanics to ensure your math calc. to be correct.

They did.

See page 30 of Envision Installation manual.

Lights can be set up to show inputs to unit (Heating/Stg1 - Y1, Heating/Stg2 - Y1 & Y2, Heating/Stg3-Aux - Y1 & Y2 & W, and Heating/Emerg - W only).

Alternatively, you can even configure it to show which phase (1 through 4) of Stg3/Aux heat the unit is in.

Best regards,

Bill

HE will vary as a function of many parameters - it won't be constant.   If you're looking to conclude if your unit is not performing properly, and you don't have a HE number that is grossly wrong, it's quite possible that measurement error accounts for the bulk of the 22% or 23% 'below spec' you note above.

See below for an example of HE for my 3 ton and 5 ton units (both operating in 1st stage exclusively).

For my 5 ton unit 'spec' says HE = 41 KBTU/hr @ 65° water.  It goes up to 43 at 70° water, and down to 38 at 60° water.

The black line shows that while I occasionally come close to 41 KBTU/hr, there are other values depending on many factors.

Best regards,

Bill

Doh!

Didn't read the book thoroughly

Learn something every day...thanks