joe.ami,

Ok I lied...One more question. I talked to a co-worker with an electrical engineering degree (who knows nothing about these systems mind you), and his only concern was that the single pump would try to work twice as hard to pump the volume through. I didn't think that would be the case, but wanted to run it by you.

Scratch my idea of running 1 pump in first stage and 2 pumps in second stage. I just looked at the pump curves for a QT flow center and if you currently have a QT flow center with two (2) UP 26-99F pumps in service and are getting ~13.6 gpm flow, then your total system head is ~43 ft. The maximum head on the curve for a QT flow center with one (1) UP 26-99F pump is only ~31 ft at 0 gpm. At ~8 gpm for a single UP 26-99 pump, the maximum head is ~25 ft. Based on your loop design, one (1) UP 26-99F pump is insufficient.

Don't be too quick to rule it out Arkie. If head loss of 43 ft. is only at the 13.6 GPM flow rate, then at 8 GPM, head loss may only be in the range of 15 ft. We aren't looking at a static height pressure head. The pressure losses are friction and they drop off exponentially with reduced flow.
http://www.pacificpumpandpower.com/docs/Friction_Loss_Table.pdf

My 4 ton HP runs with 1 pump on the loops only, B & G 1/6th horse power, I believe that is simular to the 26-99.

5 loops of 400' 1" pipe.

I like Joe's relay idea.

Chris

Yeah the relay idea sounds interesting. I've been discussing it and it seems fairly easy to try.

I just don't know enough to know if there would be any negative impacts if it doesn't work. Other than poor performance.

Can you manually isolate or disconnect one of the pumps? If so, for a test, just disable one of the pumps and re-check your water pressures and temperatures at the unit with only one pump in service.

Can you manually isolate or disconnect one of the pumps?

Yeah that's what I was going to do first. I can just unhook one of the pumps and recheck my readings. We are sure I would need both pumps on Stage 2 though right? I would obviously need to get the relay in place for that.

Posted By mtrentw on 04 Dec 2013 12:46 PM
Don't be too quick to rule it out Arkie. If head loss of 43 ft. is only at the 13.6 GPM flow rate, then at 8 GPM, head loss may only be in the range of 15 ft. We aren't looking at a static height pressure head. The pressure losses are friction and they drop off exponentially with reduced flow.
http://www.pacificpumpandpower.com/docs/Friction_Loss_Table.pdf

If you are having 13.6 ft of head flow, your pressure drop is more in the range of 47.5 ft/hd, since you must account for the added viscosity of the antifreeze. Running with 1 pump brings you down to 10 gpm of flow at 26 ft/hd, perfectly fine for a 4 ton unit.

Posted By lomax0990 on 04 Dec 2013 02:09 PM

Can you manually isolate or disconnect one of the pumps?

Yeah that's what I was going to do first. I can just unhook one of the pumps and recheck my readings. We are sure I would need both pumps on Stage 2 though right? I would obviously need to get the relay in place for that.

No, you would not need this for stage 2 either. 10 gpm is fine for stage 2. Your delta T is going up by 1 degree, not a big deal if you save $80 for pumping / year.

Ok I will take one pump out of the mix this evening and update my readings.

Updated Readings w/ 1 pump:

EWT : 39.5
LWT : 35.2
EWP : 10
LWP : 6.5
Temperature at Closet Register : 90.5

I haven't had a chance to calculate the heat extraction yet, I wanted to get these numbers posted. But I suspect it's still wtihin spec. The temperature reading at the closet vent actually went up a little bit. Previously 89-89.5 was all I could get out of it. Now i"m seeing 90.5 - 91 degrees consistently.

You can look here to see an example of air temps from a 5 ton 2 stage unit that's similar to your 4 stage 2 stage unit:

http://www.welserver.com/perl/plot/...rTemps.png

(5 ton unit is solid lines; 3 ton unit is dashed lines.)

This is one of the 16 charts from the residential example Web Energy Logger system at http://www.welserver.com/WEL0043 (my residence).  This chart shows supply air (what you're measuring) and return air temps (along with the difference) for the past 4 weeks, sampled at 45 minute intervals.  (Physical measurement points are just after the air filter for the return air (Entering Air Temp - EAT) temp and a couple of feet away from the blower fan for the supply air (Leaving Air Temp - LAT) temp.)

A few points of comment:

1. Be careful making interpretation of what you measure yesterday versus what you measure today when the values are within a degree or so.  For example you can see my supply temp is centered up at about 90 degrees F, similar to your system, but, it can vary plus or minus 5 degrees over a 4 week period, depending on a number of factors.  It's possible your observation of a 1.5 degree hotter value is not related to your pump change.  To draw this conclusion you'd probably need to look at the average supply temp over a reasonable period of time, before pump change, and then look at the average supply temp over the same period of time post pump change, and compare the difference.  (This is an example of where you really need a data logger to do this kind of study.)

2. Be careful making too much judgment on the absolute value of supply air temp.  These absolute values will be highly dependent on blower fan speed.

3. Thus, be careful looking at the illustrated 3 ton numbers (dashed lines).  This 3 ton unit has a 3 zone air distribution system on it.  Thus parameters for blower fan speed are highly tuned for minimum duct noise and maximum summertime cooling mode dehumidification.  Don't get alarmed that your system too should exhibit 105 degree supply air.  This system simply has the blower fan speed slowed down to a minimum acceptable speed to accommodate the zoning and to run longer in cooling mode.

4. The example shown is almost all first stage operation (for both units).  There are a few exceptions (for the 5 ton unit; the 3 ton unit is almost always locked out of 2nd stage) when a few weeks ago I installed Ecobee tstats and I've been fine tuning the tstat settings to minimize or eliminate the need for 2nd stage.

5. The arithmetic technique to produce an air temps chart as shown is to 'sample' only when the unit is running.  A 'sample and hold' function is fully supported within the WEL. It nicely eliminates the charting 'noise' that otherwise would be present due to the supply air temp measurement swinging between an operational temp and an idle temp.

Hope this helps. 

Best regards,

Bill

As predicted you have about 10.2 gpm. Congratulations, you just found out that not restricting the flow and reducing the pumping power can result in a better performing system!

The level of expertise and advice on this site never ceases to amaze me. Hey lomax0990, you have a bunch of pretty amazing consultants on-call here that all deserve a nice Christmas card or something.

From thousands of miles away these folks have determined that the heat pump is performing as expected, and is producing the right amount of air-side BTUs from the right amount of water flow. The loop appears to be OK, and a good lesson has been taught about optimizing pumping power use and flow rates. The heat load demands of this building envelope are simply requiring a near continuous first-stage output of 20,000 btu/hr to maintain indoor temp when outdoor lows are +15F, which appears to be just because of either insulation, duct leakage, or building envelope air leakage. And the next steps are doing a duct-work blower test, and a whole-building blower-door test, followed by addressing any issues found with the ducts or with air leakage, and starting with whatever gets the most bang for the least bucks. (which could wind up being a few more inches of cellulose blown into the attic, if nothing else is found).

Now keep in mind that I'm just a homeowner/amateur... but given that the airside delta T between hot air register and return register is well below what is expected, and the water-side numbers are all right on the money, is anyone besides me wondering if there's a HRV or other sort of air-exchanger or make-up air vent attached to the ductwork in this house that is letting all those nice warm BTU's out? Or is this delta T reading just low because the measurements were done at the registers, as opposed to at the unit?

Air side delta T is of little value if not taken near the unit.

Just a quick question about the 26-99 flow center. If you disable one of the pumps will it hurt the flow center at all?

I am assuming that it is fine to disable one pump, does it matter which pump you disable the top vs bottom. I was thinking of putting a three way switch on it. So that you could run one pump for a period of time and then switch and run the other pump for a year.

As long as your flow is ok, you can disable one pump. Disabling one pump will not hurt the flow center. You should check your GPM, but normally it doesn't matter which pump you have disabled.