jimc
New Member
Posts:14
 |
| 28 Nov 2008 01:34 PM |
|
My two Grundfos UP 26-99 f pumps have failed after ten years of service. In researching replacements, I noticed that it appears I only really need one pump in my application.
I have a five ton Carrier Weathermaker GT-G unit on a six 1-1/4 inch horizontal loop system buried at six feet.
Do you think that two pumps is overkill on this application? If so, would one Taco 0013-F3 - 0013 Cast Iron Circulator, 1/6 HP would be a good replacement?
Thanks in advance for any thoughts.
Jim |
|
|
|
|
|
|
engineer
Veteran Member
Posts:2749
|
| 28 Nov 2008 02:54 PM |
|
Both failed at the same time?
How did you conclude you need only one pump? |
|
Curt Kinder <br><br>
The truth is incontrovertible. Malice may attack it, ignorance may deride it, but in the end, there it is - Winston Churchill <br><br><a href="http://www.greenersolutionsair.com">www.greenersolutionsair.com</a>
|
|
|
jimc
New Member
Posts:14
|
| 28 Nov 2008 03:09 PM |
|
No. One has been dead for awhile. The other just died.
I've not reached any conclusions and am not a flow engineer. Just observation that it runs ok on one and when looking around similiar systems seem to use just one. Overall flowrate specified by Carrier is 3 gpm per five tons = 15 gpm. Pump maximum is 34 gpm. I don't know the calculations for the pipe resistance and approximate six foot of elevation difference.
|
|
|
|
|
engineer
Veteran Member
Posts:2749
|
| 28 Nov 2008 08:17 PM |
|
In closed loop elevation is of no consequence, odd though that may seem. You can approximate flow by measuring Delta-P across the unit's heat exchanger and comparing with mfg specification.
Does the Taco have a pump curve similar to the Grundfos? |
|
Curt Kinder <br><br>
The truth is incontrovertible. Malice may attack it, ignorance may deride it, but in the end, there it is - Winston Churchill <br><br><a href="http://www.greenersolutionsair.com">www.greenersolutionsair.com</a>
|
|
|
TechGromit
Advanced Member
Posts:634
|
| 28 Nov 2008 09:00 PM |
|
Posted By jimc on 11/28/2008 3:09 PM
No. One has been dead for awhile. The other just died.
I've not reached any conclusions and am not a flow engineer. Just observation that it runs ok on one and when looking around similiar systems seem to use just one. Overall flowrate specified by Carrier is 3 gpm per five tons = 15 gpm. Pump maximum is 34 gpm. I don't know the calculations for the pipe resistance and approximate six foot of elevation difference.
How long ago did the first one fail? Perhaps it can run on one pump, but maybe with a smaller load with two pumps allows them to last a lot longer then using one pump alone. If it's a part that fails often, perhaps the whole point of having two is to pervent interuption in service, so you could replace them as needed. |
|
|
|
|
geo fan
Basic Member
Posts:408
|
| 28 Nov 2008 10:29 PM |
|
In my experience in hydronics it is doubtfull 2 pumps would be required , unless you wanted your water at the max possible volocity, which I cant imagine because that would likely adversly effect you heat transfer rate/ effeciency
Maximum** Flow Rates (Gallons Per Minute)
Pipe Type 1/2” 3/4” 1” 1 1/4” 1 1/2’ 2”
SCHEDULE 40. 4 8 13 22 30 50
SCHEDULE 80. 3 6 11 20 26 46
CLASS 200. NA 10 16 26 36 55
TYPE L COPPER 5 7 12 19 26 48
P.E. (DRIP)* 4 gpm 8 gpm 13 gpm NA NA NA
* 1/8” P.E. –10 G.P.H., 1/4”P.E. – 20 G.P.H., 3/8” P.E. –100 G.P.H. |
|
|
|
|
Palace Geothermal
Veteran Member
Posts:1609
|
| 28 Nov 2008 11:16 PM |
|
What is the length on the six 1 1/4" ground loops?
If you can tell me the length and the pressure drop on your heat pump, I can tell you if one pump will do the job. |
|
Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
|
|
jimc
New Member
Posts:14
|
| 29 Nov 2008 10:46 AM |
|
From the Carrier installation manual:
5 ton system 2.25 to 3 gpm per ton => 11.25 to 15 gpm required
Pressure drop - 1.8-3.1 psi @70 degrees F
Loop: 7- 1" x 250' long loops tied to a 1 1/4" manifold (sorry for my confusion yesterday on this).
Thanks!
|
|
|
|
|
Palace Geothermal
Veteran Member
Posts:1609
|
| 29 Nov 2008 10:55 AM |
|
How much pipe is in each loop? You say they are 250' long. Do they double in the trench so there is 500' of pipe or are there 4 pipes in a trench so there is 1000' of pipe? |
|
Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
|
|
jimc
New Member
Posts:14
|
| 29 Nov 2008 11:04 AM |
|
7 trenches with 250' of pipe in each trench. Yes the double back. One at 6' and the other at 4' deep.
The two manifolds that the seven 250' loops are tied to are about 100' each and in the same trench.
Seven loops in parallel to a common manifold. |
|
|
|
|
Palace Geothermal
Veteran Member
Posts:1609
|
| 29 Nov 2008 12:40 PM |
|
On the attached graph, the blue dot is the target flow rate.
The pink line labeled FC1 is the output of a single pump, grundfos UP 26-99.
The orange line labeled FC2 is the output of two UP 26-99.
It looks like a single pump will do the job.
Any pump that can produce 14 GPM at 24 ft of hd will do the job.
|
 Attachment: Resize of ScreenHunter_9.jpg
|
Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
|
|
jimc
New Member
Posts:14
|
| 29 Nov 2008 01:16 PM |
|
Thank you for the calculation!
Would you suspect that two were originally installed as redundancy or some other reason?
|
|
|
|
|
Palace Geothermal
Veteran Member
Posts:1609
|
| 29 Nov 2008 01:21 PM |
|
I would suspect that two were installed using rule of thumb instead of calculating. |
|
Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
|
|
jimc
New Member
Posts:14
|
| 29 Nov 2008 03:47 PM |
|
Would you recomend placing the single pump on the inlet or outlet of the heat pump? |
|
|
|
|
Palace Geothermal
Veteran Member
Posts:1609
|
| 29 Nov 2008 04:02 PM |
|
I would probably have the pump pushing into the heat pump |
|
Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
|
|
joe.ami
Veteran Member
Posts:4377
|
| 30 Nov 2008 11:47 AM |
|
Not sure if you still have any components under warranty, but if you do be careful you don't alter installer's design and take ownership of the thing.
J |
|
Joe Hardin
www.amicontracting.com
We Dig Comfort!
www.doityourselfgeothermal.com
Dig Your Own Comfort! |
|
|
jimc
New Member
Posts:14
|
| 30 Nov 2008 09:43 PM |
|
No worries there. It's been mine for awhile now! |
|
|
|
|
jimc
New Member
Posts:14
|
| 30 Nov 2008 10:14 PM |
|
I ended up with two new pumps and decided to try running with one and then two to see if there was any measurable difference. A graph of Loop In minus Loop Out temperature for the two cases is attached. This is a 15 or so minute run with loop input temperature at 62.3 degrees F. I used a switch to turn the 2nd pump on and then off.
It looks to me like the 2nd pump is wasted and detrimental to the efficiency of my system. Two pumps takes the temperature drop out of Carrier's specs (4-8 degrees F).
Comments appreciated!
|
Attachment: pumps.JPG
|
|
|
|
Palace Geothermal
Veteran Member
Posts:1609
|
| 30 Nov 2008 10:32 PM |
|
Posted By jimc on 11/30/2008 10:14 PM
It looks to me like the 2nd pump is wasted
Comments appreciated!
I would agree.
|
|
Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
|
|
engineer
Veteran Member
Posts:2749
|
| 01 Dec 2008 03:48 PM |
|
What pump did you select and how many Watts does each consume? |
|
Curt Kinder <br><br>
The truth is incontrovertible. Malice may attack it, ignorance may deride it, but in the end, there it is - Winston Churchill <br><br><a href="http://www.greenersolutionsair.com">www.greenersolutionsair.com</a>
|
|
|