The Pumps

The Pumps (Or the Flow Centers)

The Pumps also known as the Flow Centers… 

The pumps circulate the fluid in the Loops.  You may have an Open or Closed Loop system; but, the purpose is to get fluid To and From the GSHP Unit.  

The Water/Antifreeze solution goes through the Loops, the Pumps and finally the GSHP units.  For Closed Loop systems that can freeze, please make sure you follow federal, state, and local regulations with regards to the Anti-Freeze in the pumps.  Some states banned methanol or ethylene glycol.  Also, ONLY use manufacturer (pipes, pumps, and Heat Pumps) approved fluids.  Typically the solution is 80% water and the rest the glycol.

An issue in my case was the distance from the Pumps to the GSHP.  Typically, most vendors like these two items to be very close together… like no more than 5’.  In new construction, you can plan for this.  In my case, I inadvertently, placed the Pumps and the GSHP 25’ apart in order to maximize the “natural” layout of the basement.  This added a “pressure” drop problem that caused concern for the Pump vendor. 


These pumps have manual speed control (low, medium, and high) and will draw .6, .8, and 1.2 amps.

This picture of my pumps were taken earlier in the process.  The silver “ports” in the front are actually quick connects for the Flush Cart.  The unconnected HDPE pipe in the right middle of the picture was disconnected in favor of a new setup.


The tubing between the Pumps and the GSHP is typically a rubber hose that can handle 150psi.  Due to the length involved with my installation, I used 300psi pipe hoping that the extra thickness of the rubber hose would not add to a pressure drop.  This was a complete guess.  This tubing may or may not come with your GSHP unit, in my care I wasted some money buying the connects for the tubing and the not needing the tubing that went with the connects.


The pumps are arranged in a push/pull configuration… pulling in fluid from the manifold for one and pushing out fluid to the other manifold for the other pump.  I was close in the calculations to needing only 1 pump; unfortunately, all of the extra Loop in the pond put me over the edge…I have to run 2 pumps.  Since I’m only running 3 Loops right now, I probably only need 1 pump.  When I put the 4th Loop back online, I’ll need the second pump.


My original plan was to install the pumps as soon as the Loops were done; but, the nice folks at the Flow Center place wouldn’t sell the Pumps to me unless they were sure about what I was doing.  In this case, they were trying to keep me safe by forcing me to give them correct information before I under or over purchased a Flow Center (the Pumps).  The integrity was refreshing.


The issues that affect Pump/Flow Center selections are:

            Length of Loops

            Diameter of Loops

            Length of Header

            Diameter of Header

            Pressurized or Unpressurized System   (Pressurized systems lower pump costs)

Typically your HDPE pipe can handle 150 PSI.  Generally, it is only charged to 30-

40 PSI.  This is determined by your GSHP manufacturer.

            Distance of Pumps to GSHP

            Pressure drop from GSHP

            Size of the GSHP system… A 2.0 ton system will require less flow than a 5.0 ton system.

            Use of antifreeze and Antifreeze type  (Methanol lowers pump costs)

                        (Must be approved by Pipe, Pump, and GSHP vendor)


If you know all of this, your pump vendor can help you select the correct pump setup.

My thinking was that I would put the Loops in and then buy the Pumps and then buy the GSHP.  You really have to know what GSHP you are going to buy before you purchase the pumps.  (I already knew the Loop information.)  In my case, I asked the manufacturer of the GSHP for the Pressure Drop of the unit before I purchased the unit.  I got a very poor response from the manufacturer. I had to ask the Pump Vendor to call the GSHP manufacturer to get the Pressure Drop from the unit.  I was a bit ticked at the GSHP vendor and the pump vender was frustrated with me for having to do my work… although the pump vendor could see that I was stuck.

*Note: The poor response was due to the nature of the “deal” I had with the GSHP re-seller.  They wanted to move a unit without putting a lot of time into this.  Also, it was the height of the cooling season and they were busy.  The manufacture of the GSHP typically only deals with re-sellers, so I was really stuck because I was not a re-seller and they were really busy and giving me a great deal.

Another problem in the dance of “when you do things” is knowing the interaction between the GSHP and the Pumps.  More sophisticated GSHP’s can directly increase the amperage to the Pumps depending on the needs of the GSHP.  This will increase fluid flow.  I did not know this and bought pumps that could be manually adjusted; but, not adjusted through the control of the GSHP.  So… you need to settle on the GSHP and the options you can get with it and then decide how you are going to handle the pumps.  Even if you have to get pumps through the GSHP vendor (a definite cost issue), I would pay the extra cost for piece of mind since the GSHP and Pumps are probably matched.


The following is a great site for more information overload…

The pumps run in a 115V or 230V configurations.  I’m told, and I do not understand why, that the 230V pumps are more energy efficient (and more costly) than the 115V pumps.  I’ve heard this a number of times, and I will trust that.  I went with the 230V pumps.
And the answer...  from a reader!
You probably have the answer by now...... 230v pumps are less costly to run, and more efficient because they operate on all three phases of the grid, verses two phases for 115v.  Example; imagine a man-powered merry-go-round on a playground.  There are three positions for kids to turn the ride, but only two kids are turning the wheel...... this represents 115v-2phase.  Now, another kid comes along and takes the third position.  The third child reduces the work load of the other two children, increases momentum (less running amps), improves balance, and lessens impedance (less friction/ voltage drop) for the wheel (rotor), resulting in less work per child for all three children. 

From here we go to the GSHP.  This is covered in the next section, so I’m skipping it here.  Coming out of the Heat Pump, you can add a “Check Valve” (Wikipedia).  Check Valves do not allow back flow.  You only want fluid to flow in one direction.  Check Valves help ensure this.  This is really helpful when you have multiple units. 

Filling your system is pretty easy…  Simply fill up the tank on the Flush Cart and turn it on.  It’ll take all of the fluid in the reserve tank and push it into the Loops.  Be ready with a household hose to re-fill the tank while it is putting fluid in your Loops.  If you plan on putting anti-freeze in the system, drain the flush cart reserve tank and then fill it with antifreeze and turn on the flush cart again.  Let the cart run for a few hours for the antifreeze to disperse through the system.  If you are dealing with flammable substances, do this in smaller increments. 

An essential thing you have to do in the Loops is purge the system with a Flush Cart once the Loops and GSHP are hooked up.  This is the only time you HAVE to do this.  A Flush Cart will capture debris that got into the system, remove air bubbles and pressurize the system if necessary.  The Pumps have a flush “port” on them that allows you to hook a Flush Cart into. 


You can see the sub-panel and the electricity going to the Pumps.  The Flush Cart is flushing the pond side of the Loops.  The Geo unit is NOT hooked up and neither are the connections going to the GSHP.

This is a Flush Cart getting all of the junk out of the system.  


The Flow Centers have a number of configurations for you to properly flush the system.  They can isolate the flow of fluid from various portion of the system.  They can vary flow from:

1. The GSHP to the Flush Port.

2. The Loops to the Flush Port. 

3. Loops, GSHP, and the Flush Port. 

4. Normal Operations… Loops and GSHP only, no Flush Port.


By choosing what configuration you need, you can segregate what portion of the system you are Flushing, Filling, or Pressurizing.  You can’t fill just the Loops… minimally you need the pumps in place before you can Fill, Flush and Pressurize.  You don’t need the GSHP in place to do that; but, it’ll cut down on your rental costs.

The directions for redirecting fluid flow are a bit obscure; but, if you read them a few times, you’ll catch the hang of how to change the configuration of it.  For my pumps, there is a half inch “square hole” that a ratchet driver would fit into and you just turn it to 1 of 4 positions.

While getting air and debris out of the system, I’ve seen folks run the Flush Cart over 24 hours straight just to “make sure”.  I think this is a good practice.  Also, at times, you want to reverse the flow of the water for a number of hours just to “make sure”.  Assuming you get most of the air out of the system, pressurizing it only takes a few seconds.

Pressure, Pressure Drops, Foot of Head Pressure….are all things that I have a very BASIC idea of.  The more fluid you put in the system, the more pressure you will have...once it is filled up.  That is about the extent of my knowledge.  If anyone wants to fill some of the void in here, please fill me in.

The pressure of the system can be dictated by the GSHP unit.  I pressurized my system to 40psi when the weather was warm (it dropped to 30 because of the Loop leak) and now that it is cold, the pressure is running in the mid 50’s.  A p/t port on the system will allow you to add fluid (and pressure) after the fact.  Getting a device to do this is probably a good idea.


This is picture of the Goodyear Washdown hose coming out of the pumps and going to the GSHP.  This is 1” tube that can take 300psi.  Typically, you want this pretty close to your GSHP.  Mine is about 25’ away a little too far away.  This will add to a pressure drop.  This is how the Pumps were finally connected to the GSHP.