Posted By docjenser on 21 Nov 2010 03:31 PM

Posted By stuart.wyss on 21 Nov 2010 01:36 PM
That would be safe to try? If I could get 2-3 gpm flow per loop with only one pump, that would be awesome?

It would be cool to hook it up that in stage 2 both pumps come on, but in stage 1, only 1 comes on.  A couple relays...

I would shoot for a minimum of 2.5 gpm/outside loop (assuming 3/4 pipe outside) everything below that and you pay a penalty for loosing turbulent flow outside, and your delta T will go up too much.

The way the impeller is designed, you will have quite a pressure drop pumping through a disengaged 26-99. If you get more than 2 gpm/ton with the second pump disengaged, I would actually put some pressure drop calcs behind this exercise and see if you can get by with one pump. Just remind me, what size is your individual loop diameter? 0.75, 1,0 or 1.25 inch? How long of a header pipe inside? What size inside? 1.25 inch?

Well, I did it. I shut the power off, disconnected one of the two 26-99s, then powered the system back up and turned up the thermostats.

With the manifold flow adjustment screws as wide open as possible, with one flow-pump operating, I get 3 gpm per loop x 4 loops = 12 gpm total. I cannot turn the gpm up any more.

With 2 flow pumps operating, I get more than 4 gpm per loop x 4 loops = 16-20 gpm. The flow gauges only go to 4, but the little marker/floats disappear up into the manifold and get pegged at what I guess would be 5 or more. Not sure how accurate they are once you pass the graduations on the tubes.

So now you have an easily connectable spare pump (at a 30% discount!)  

glad it worked out

There's nothing wrong with just running the one pump, and letting the water in the loop "run through" the non-operational pump? Is the impeller resisting at all, or the fact that I still get 3 gpm/loop indicative of satisfactory flow?

I guess...in a nutshell...is it safe to run with one motor or should I get the 2nd one removed by the contractor?

They make a plate that covers where the pump bolts onto the housing. The plate normally comes on a one pump flow center.  See attachment . If you can find one, it would be easy to take out the unused pump.

By doing so,  you might get a little more flow through the loops.  Leaving is not a big problem either.

Great!. That will save you 230 watts/hour. I addition, just to make sure, you want to check the delta T for the source in/out and the source flow through the heatpump. You can do so by measuring the pressure drop though the heatpump's source coil.

Posted By geodean on 21 Nov 2010 08:51 PM
They make a plate that covers where the pump bolts onto the
housing. The plate normally comes on a one pump flow center.

Although I haven't opened one up, I'd expect that removing a pump
requires more than just a cover plate. You'll probably also need a
short piece of pipe (with flanges?) where the pump body used to be.

Posted By Looby on 21 Nov 2010 11:55 PM
Although I haven't opened one up, I'd expect that removing a pump
requires more than just a cover plate. You'll probably also need a
short piece of pipe (with flanges?) where the pump body used to be.

I have been though this.  The cover plate is all that is needed.  The impeller housing stays in place, only the motor and impeller are removed.

Measuring the pressure drop through the source coil....that would a pressure gauge on the self-healing p/t ports right where the loops connect to the geo unit? Can you point in the right direction for the right pressure measuring tool?

Yes, that's where to measure pressure drop. Any appropriately ranged pressure gauge mated to an athletic ball inflator will work. Wet, soap or apply a bit of KY on the needle before inserting it into the port. Calculate the Delta-P between the in and the out ports and look up flow in the pressure drop table for your model geo.

Posted By stuart.wyss on 22 Nov 2010 07:47 AM
Can you point in the right direction for the right pressure measuring tool?

If you want to go digital (and spend about $160):
http://www.geothermalheatpumpforum.org/maintenance-and-troubleshooting/4056-checking-pressures-and-temperatures-3.html#post32656

P.S.  You may want to buy 1 of each gauge adapters (the part that inserts into the PT port) if you are unsure as to the size (1/8" or 1/16") to cover yourself as insurance against another $8-12 of shipping charges.  Of course, you can ask your installer what size port they installed.  I like the 1/8" gauge adapter, if it will fit, since it seems more sturdy.  Also, Looby gets full credit for this design!

I found the dwyer online for $125. Yikes! You got a deal if it was only $89!
If I read it right, the "snubber" then changes the fitting of the digital part to match to the probe, and then you got the 'needle probe' from flow center?

Wrap all the connections with teflon tape, and shove it into the P/T port. Read each one while running, and subtract.

Dwyer has it on their online catalog for $93.50 now (I remember that Grainger was very high):
http://www.dwyer-inst.com/Products/Product.cfm?Group_ID=479&Product_ID=834&sPageName=Specs
Then click on the pricing/ordering link,
Then click on the "What Type of Service Do You Require" drop down box to select "Compatible Liquids and Gases"
The black model is the correct one for our application.

I believe the snubber just evens out the pressure fluctuations to get a reading that doesn't vary as much as without the snubber.

"...and then you got the 'needle probe' from flow center? Wrap all the connections with teflon tape, and shove it into the P/T port. Read each one while running, and subtract." That's what I do, after the unit has been running for 10-15 minutes. You will get different pressure readings depending on the stage you are in, so make sure both readings are in the same gauge.

Also, you can check loop pressure with the system off to make sure the pressure is appropriate. While you are already paying for shipping from flow center, you may want to also consider getting a RAM-1 or RAM-2 (depending on the design you like) to set loop pressure as necessary. The RAM-1 was about $55 if I recall correctly. It has a pressure gauge on it, but I like the digital better.
http://www.flowcenterproducts.com/accessories.php

If you need it, you may want to get a digital thermometer while you are at it, but I have not purchased the model that flow center has.

You can get pretty close for quite a bit less with a conventional pressure gauge and needle inflator. Absolute accuracy is not as important since the differential is the needed figure.

I finally found a good LCD thermometer with a much narrower than normal probe - a Cooper DFP450W - much easier to use in PT ports.

Posted By stuart.wyss on 22 Nov 2010 07:47 AM
Measuring the pressure drop through the source coil....that would a pressure gauge on the self-healing p/t ports right where the loops connect to the geo unit? Can you point in the right direction for the right pressure measuring tool?

You can get them at your plumbing supply shop, we use a 0-60 range, they have a hollow needle which you insert into your p/t port. With the pressure drop between in and out, you can look up the tables in your installation manual and determine the flow. Get the temp delta first, if you are at less then 8 degrees F delta in second stage, you should be doing OK. As you see, your $60 savings per year for using only one pump evaporates pretty quickly ....

stuart, if the Delta T is in the 6- 10 °, there is not much need to buy a pressure gage.

Thanks Geodean,

What I really need to get hold of is 1 of EVERYTHING! Just kidding. The manifold has an analog gauge, but only 1 and you have to swap it between the supply and the return. Rather silly, really. Why not just have one on each? I've tried using an infrared thermo, but the distance you have to hold it, plus the fact that the manifold and most of the piping is somewhat reflective screws up the readings. I'll look at getting the suggested Cooper thermo.

If you are going to measure with 2 gauges then you really do need to ensure accuracy. Most of the techs out there swap one back and forth as it is hard to get 2 to agree.
J

Exactly. If a 0-60 gauge is off by two pounds, that would totally compromise a psid reading made using a 2nd gauge. That same error carried between the two ports gets canceled out

Hope that makes sense.

I agree with Dewayne as well - if the unit is running properly on the airside and the water temp diff is 6-10, you are good to go.