Problem with Water furnace ND038
Last Post 29 Jul 2014 12:41 AM by docjenser. 26 Replies.
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MFRichardsonUser is Offline
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26 Jul 2014 09:20 AM
The system was installed six years ago and was running well until about six months ago. The system One vertical package unit NDVO038A111cbc W/Super heater One split unit NVD038A10ac One FC2-FPT Flow control unit Six months the relay that turns the flow control pumps on went bad and was replaced by the installing contractor. A month it went bad again and was replaced again. The relay lasted another few months and went bad again. I called the local dealers and gave him a shot at fixing the unit. They stated that the installing contractor had left the flow control center wide open and stated they adjusted the flow to the proper flow rate. Then the pumps started shutting off without the relay going bad and the units tripping off on high pressure. Re-setting power for five minutes the units would come back on but would trip out if they ran a lot. No A/C for two days and I made the local dealer change the flow control pumps out. After the units came back on it took over 12 hours to cool the house. I have a FLIR camera the ground loop was up to 105 and the pumps were a little over 130. The system has stabilized somewhat ground loop in 97.5 and out 99.9 pumps around 125 to 130. The technician seems stumped. I am thinking low water flow. The flow center is mounted horizontal. Besides the ground loops valves on the front of the flow center I have a brass valve on the top and bottom. Are these brass cover just access cover or do they adjust the flow. If they are access covers how do I adjust the flow. I was thinking of very slowly increasing the flow rate. Any help would be appreciated.


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26 Jul 2014 09:22 AM
Add to the original Post the ground loop has six 250 foot closed loop wells


Bill NeukranzUser is Offline
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26 Jul 2014 09:50 AM
Posted By MFRichardson on 26 Jul 2014 09:20 AM
... They stated that the installing contractor had left the flow control center wide open and stated they adjusted the flow to the proper flow rate. ...


Does the flow control center use (a) variable speed pump(s)?  Otherwise, how can the flow rate really be correctly adjusted other than by changing out the actual pump(s)?

Best regards,

Bill


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26 Jul 2014 11:22 AM
I don't know how they adjusted the flow, but the only thing one could do is reduce the flow which is not likely helpful. It's possible there is something upstream of the relay causing trouble (a signal that is interupted intermitantly that would be difficult to diagnose). Mixing eyeballs on the system is not getting it done. You have a history of succsess with the installer vs the new guy.
It's possible the loops are flat (low pressure) and pumps are going off on internal overload.


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26 Jul 2014 11:29 AM
The flow control center does not have variable speed pumps. There is some method of adjusting the flow in the flow control center. I am trying to increase the flow rate I think it is to low. Does anyone know how to adjust the flow rate in a FC2-FTP?


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26 Jul 2014 11:32 AM
Posted By Bill Neukranz on 26 Jul 2014 09:50 AM

Does the flow control center use (a) variable speed pump(s)?  Otherwise, how can the flow rate really be correctly adjusted other than by changing out the actual pump(s)?



I answered my own question by going off and studying the FC2-FPT Flow Center Installation Manual.

This is a GeoLink flow center with 2 pumps and 1 in. FPT connections with a cabinet.  Each pump is 1/6th HP at 246 W.  The pumps are manufactured by Grundfos, and are model UP26-99.  For 6 tons total, this flow center is designed for a closed loop system that presents at least a 33 feet of head pressure drop, and presents no more than 45 feet of head pressure loss (pipe friction, pipe fittings, one-way valves if any, flow center 3-way valves, water-to-refrigerant coax heat exchanger, etc.)

I got the above numbers by using the manual's published minimum (2.25) and maximum (3.0 GPM/ton) flow rates for WF units, assumed 6 tons total present, assumed 2nd stage, and then read the head pressure loss numbers from a chart in the manual for the UP26-99 motors.

There doesn't appear to be any flow adjustment mechanism that's part of the flow center.  That makes sense since the design is such that you choose the appropriate model to match up pump motor capability to the pressure loss as presented by the closed loop system.  So the flow adjustment capability must be isolation valves outside of the flow center.

While it doesn't appear to me that using these valves is the optimal way to adjust flow, still, closing them down slightly does impose additional water flow resistance, which does increase the closed loop systems amount of head pressure loss presented, which does lower the flow rate.  The chart that I referenced above does a nice chart in the manual showing this.

It would look to me that the only reason to adjust flow rate is if it's outside the boundaries of the minimum (2.25) and maximum (3.0) GPM/ton, for the protection of the coax water-to-refrigerant heat exchanger.  And it would look to me that only very light adjustment would be appropriate, assuming that the flow center model in use has the pump motor size that's 'in the ballpark' for the closed loop system present.

Certainly no adjustment looks to be appropriate for the purpose of heat pump performance.  I don't see where the heat transfer algorithms would support this.  It sure looks to me that it makes no performance difference if the units are running at the minimum 2.25 versus the maximum 3.0 GPM/ton.

Further, if flow rate is actually being adjusted, unless it's a special type of valve, isolation valves have little ability to 'fine tune' flow.  It's pretty coarse in fact.  So much so that I would think that it wouldn't take hardly any flow valve adjustment to really 'starve' the heat pump of enough water.

My 'electrical engineer talking about a mechanical engineering subject' advise is to immediately open up whatever flow valves you've got.

Best regards,

Bill





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26 Jul 2014 11:37 AM
Posted By MFRichardson on 26 Jul 2014 11:29 AM
The flow control center does not have variable speed pumps. There is some method of adjusting the flow in the flow control center. I am trying to increase the flow rate I think it is to low. Does anyone know how to adjust the flow rate in a FC2-FTP?

It's not there.  Google on an FC2-FTP flow center and you'll see no mention of flow adjustment in the Installation Manual.

My guess is you have isolation valves in-line to/from the flow center.  This would make sense to enable an easy pump change out maintenance. 

Find these valves and immediately open them up.

You have a closed loop 6 borehole field with each hole at 250'.  Assuming it was constructed with reasonable sized pipe, (i.e. you're not using 2" pipe for each hole), I believe your Grundfos UP-99 pumps are appropriately sized.  I'd get those isolation valves opened all the way up ASAP.

Noting the characteristics of your borehole field it's hard to imagine any situation where you would want less flow that what you're getting (again assuming loop is properly designed WRT to pipe sizes).

Or, assuming your local repair person understands the fluid hydraulic principles in play here, he/she must be seeing some other part of your system that you're not yet describing, that is causing a much lower (less) loop system pressure loss than otherwise what the UP-99 pump motors need to see.  Still, I would think the right solution would be to change the motors, not restrict the flow with valves that aren't designed for flow restriction purpose.

Best regards,

Bill


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joe.amiUser is Offline
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26 Jul 2014 11:47 AM
I'm with Bill


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Bill NeukranzUser is Offline
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26 Jul 2014 11:56 AM
Additionally, water flow in a closed loop system is not difficult to check yourself.

Go get yourself a pressure gage like this: http://www.pbase.com/neukranz/image/106018293 , purchase the needle insert accessory pictured, and assemble.

Find the Pressure/Temp (P/T) ports - they need to be near the unit. They look like this: http://www.pbase.com/neukranz/image/86087130  .

Run your system for at least a few minutes to stabilize everything.

Stick your pressure gage into a P/T port, and write down the pressure. Do the same for the other P/T port. Be sure to leave the gage in the P/T port for as little time as possible.

Subtract the two pressure readings. This is your pressure differential across the coax heat exchanger.

Google for an Installation Manual for your Envision series of heat pump.

Find the pressure differential versus flow rate chart.

Read the flow rate.

Hope this helps.

Best regards,

Bill


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MFRichardsonUser is Offline
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26 Jul 2014 11:57 AM
Thanks for the help. I did find lever values on each unit that are set to approximately 50% closed. I am going open to 75% and see what happens


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26 Jul 2014 12:03 PM
Posted By MFRichardson on 26 Jul 2014 11:57 AM
Thanks for the help. I did find lever values on each unit that are set to approximately 50% closed. I am going open to 75% and see what happens
No.

All the way open.  Changing classic isolation valves from 50 to 75% open probably will have little influence on flow.  These are not valves designed for anything other than on/off.

Plus, the hydraulics scenario I wrote about earlier strongly and additionally suggests that wide open flow is what you want.

Recommend you reconsider and open up all the way.

Best regards,

Bill



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MFRichardsonUser is Offline
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26 Jul 2014 12:12 PM
Here is a picture of the Valve installation

Attachment: WP_20140726_002.jpg

MFRichardsonUser is Offline
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26 Jul 2014 12:28 PM
OK the valves are open 100% two pumps are pulling 3.2 A

I will let it run tonight Thanks for the help


Bill NeukranzUser is Offline
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26 Jul 2014 12:42 PM
Absolutely!  These are as I thought - isolation valves.  No other purpose than on/off.  For use only when changing out something broken.

Now wait for more diagnostic data - will be easier for many here (maybe even me) to offer advise.

Again (remember), there is no change in the heat pump's performance as a function of incremental water flow adjustments.  This is sometimes a hard concept to appreciate.  And not all repair professionals, particularly those that don't work on geo systems, understand this.

Best regards,

Bill


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26 Jul 2014 01:24 PM
Posted By MFRichardson on 26 Jul 2014 12:28 PM
... two pumps are pulling 3.2 A


OK.  Each pump theoretically, in design test conditions, should pull 1.1 Amps.  Times two is 2.1 Amps (due to rounding).

You're at 3.2 Amps (I'm assuming at 230 V).  That means you're over 50% high.  This could mean:

1. Nothing, because of possibility of test measurement error/accuracy, or deviation from pump design conditions (including voltage present).

2. Your motor run capacitors were not replaced at the same time as your pumps, and are near failure.

3. Your brand new motor run capacitors are not functioning properly.

4. RPM is higher than design.  But, it doesn't take a lot of increased RPM to start really increasing Amp draw.

5. Your closed loop's pressure loss due to everything present (pipe, fittings, coax heat exchanger, one-way valves, etc.) is less that what might normally be expected due to using larger pipe that what would be normal or some other reason.

6. You no longer have Grundfos UP-99F pump motors in your flow center - when recently replaced something else was put in that consume more power (like putting in what I have - UP-116F pumps)

7. If your water loop was opened up as part of replacing your pump motors (not smart enough to know if this would be the case) then if it wasn't purged of air then pumps may be moving mostly air with little water, at a high amperage.

8.  Something else.

Noting that some of the ideas noted above could be costly to fix, especially noting you've so far used 2 repair professionals, two Premier2 PCB replacements, and two pumps, and thus there easily could be some 'finger pointing that it's not my fault - it's his/hers.'  Such that you get seriously charged for everything going forward.

Noting all this, if it was me, I'd start working on verifying/affirming you've really got 3.2 A for the pump motors.

If so, then I probably would not wait for more diagnostic failure info.  Instead, I'd go affirm you really have replacement UP-99F pump motors.  If so, then I'd work on understanding how much 3.2 Amps is within the your external pumps relay contacts published specs of "1/2 HP Total."

If 3.2 Amps is affirmed accurate, affirmed well within contactor ratings, and the pumps are indeed UP-99F, then  maybe I'd wait.  If the run capacitors on the motors are still 'original issue' then maybe I'd replace them myself, just to eliminate stuff.

Past this point smarter people than me would need to contribute.

Good luck!

Best regards,

Bill


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MFRichardsonUser is Offline
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26 Jul 2014 04:57 PM
I have confirmed the pumps are grundfos up 26 116 F and should pull 1.8A at 230 volts Volts 243 amps top pump 1.62 Bottom 1.66a 1 1/4 inch pipe to six way header in yard 6 x 250 wells 1" Pipe in Wells Loop in 101F Loop Out 105F Pumps 134F

Attachment: FLIR0022.jpg

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26 Jul 2014 05:31 PM
Posted By MFRichardson on 26 Jul 2014 04:57 PM
I have confirmed the pumps are grundfos up 26 116 F and should pull 1.8A at 230 volts Volts 243 amps top pump 1.62 Bottom 1.66a 1 1/4 inch pipe to six way header in yard 6 x 250 wells 1" Pipe in Wells Loop in 101F Loop Out 105F Pumps 134F

OK.  This explains some things:

Your flow control center amperage reading is now about where it should be, noting that when you had your pumps replaced whoever did it 'upsized' you from -99F to -116F pumps.  They're both 1/6th HP.  The -99 is 245 Watts and the -116 are 385 Watts (each).

The -99 has a flow range up to 34 GPM, the -116 goes to 38.5 GPM.  The '99 accommodates a Head range of 32 feet, the -116 accommodates a Head range of 37.5 feet.

What this all means to you is that you've moved from 490 watts now of pumping power to 770 watts.  And for the increase (280 Watts), you're moving more water now (GPM.

For example, if you were moving 13 GPM (the minimum 2.25 GPM/ton) before, you're now moving 19 GPM (3.2 GPM/ton, which is greater than the recommended 3.0 GPM/ton max).  If you were moving 18 GPM (the max recommended 3.0 GPM/ton) before, now you're moving 23 GPM (3.8 GPM/ton, well over the 3.0 GPM/ton max recommendation).

Both of these examples show that you probably have pumps too big for the resistance presented by your closed loop.  That's why you had -99s before.

And now we know why the pump installer wanted valves not designed for flow regulation to be used for that purpose anyway.  He/she may have known he was upsizing you on your pumps and knew that he needed to introduce flow resistance into the loop to compensate.

If it were my, I'd insist on getting the right pumps put back in. 

You might say, well why not leave in the pumps and change out the isolation valves to some other valve design intended to provide variable resistance.  The answer is it's wasteful.  Yes you can get the loop GPM flow back between 2.25 and 3.0 GPM/ton, but, your burning through a whopping 280 Watts (difference between 2 -99 pumps and 2 -116 pumps) for the 'privilege' of turning down a valve.  And, to replace these isolation valves opens up the loop and now you're faced with another loop purge.

Get the motors appropriately sized instead. 

By the way, you've also now eliminated pump problems causing Ext Pump contactor failure on the Premier2 PCB.  I've got two -116 pumps for my 8 ton system, and they're both connected to the same contactor, and so far have not had a problem.

If it was me I'd now be working on getting your flow correct.  Either get someone out there who know how to measure the flow, or do it yourself (as I posted earlier today).  And then get those -116F pumps out of your flow center.

Best regards,

Bill


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26 Jul 2014 05:55 PM
Posted By MFRichardson on 26 Jul 2014 04:57 PM
... 1 1/4 inch pipe to six way header in yard 6 x 250 wells 1" Pipe in Wells Loop in 101F Loop Out 105F Pumps 134F

You've got more work to do.

Another major theory is that you're suffering from annual borehole heating.  I.e., every year your average EWT is higher than the previous year because your borehole loop field is just not adequate.  This is why you've gone 6 years with no problems but now you're seeing pumping related problems.

If it was the Dallas area, where I'm at, you would have gotten another 50' per borehole.  I.e., about 300'  I.e., I've got 8 tons and 8 holes at 300' each (and spaced 20' or more apart).

My average EWT for the last few weeks has been 75°F.  See http://www.welserver.com/perl/plot/...ilyAvg.png   You can see from this chart that my annual daily average high is never more than about 82°.  Even right now the 24 hour EWT average is 76.5°F.  See top diagram at http://www.welserver.com/WEL0043/ .  And I'm in Dallas where it's darn hot right now.

Your over 100° EWT measurement makes no sense, and, you're in real trouble if it's accurate.  Summer's just getting into full swing now and you're going to go higher before you go lower.

Something's wrong with your measurements, your borehole field or somewhere else.

The pump at 134°F makes sense.  It's about 30°+ above the water temp.  My pumps are pretty warm but still easily touchable.  With my EWT of 76° and your 30°+ over EWT pump temp, that's about 106° for me - Yep it's possible my pumps are at this temp.

Lastly, the change from -99F to -116F pump motors is not good for you in another regard.  The -99Fs are good for about 230°F water; the 116Fs are only good for 150°.  You're only 16° away from the pump manufacturer's maximum temp.  All the more reason to get those new -116 pumps out of there.

Best regards,

Bill



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27 Jul 2014 08:22 AM
Posted By MFRichardson on 26 Jul 2014 09:20 AM
The system has stabilized somewhat ground loop in 97.5 and out 99.9 pumps around 125 to 130. The technician seems stumped. I am thinking low water flow.


2.5 degree differential does not suggest low water flow. Do you really have 2 UP 116's for a 3 ton system? You probably only need one. Your loop temp seems high. Where is the home? I guess if it is in Phoenix or South Florida it would make sense?


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27 Jul 2014 10:43 AM
OK Two --three ton units with a flow center with 2- UP 116 pumps
I am trying to get better measurements. All I have right now is a flir camera.
Location Charleston SC
On the metal fitting outside the unit on the heat exchanger I am getting a approximate drop of 4 degrees 91 in 95 out with both unit wide open
Current ambient temp is 88
Expected high today 98 and very humid
With the two 116 pumps the tech measured excessive flow across the heat exchanger. He is a pretty sharp tech so I assume he measured correctly. He tried to reduce flow by partially closing the service valves at each unit. I will talk with him on Monday to verify what the flow rate he measured
I am pretty sure they replaced the pumps with the same model that were originally installed.
It sounds like the two pumps are oversized.
Good new is the units are working fine again after I opened up the partially closed valves.


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