Can I activate GT loop pump on demand?

15 years ago

I have a geothermal closed loop system. The loop field pump runs continuously Â 24x7 Â even when there is no demand from the heat pumps. I originally thought that the reason for this was that the amount of energy required to get the fluid moving was a big power drain (I have a 12 ton system with 3 heat pumps, all sharing a loop field with 290 gallons of coolant in the ground loop) and that it was more energy efficient to just keep the pump running all the time. But after hearing several people tell me that this isnÂt the case, I would like to activate the pump based on demand calls from the heat pumps.

Can anyone tell me how I can do this? I imagine I would need a 220V relay that would engage based on a low voltage signal coming from heat pump controller or Tstats. Can you tell me what type of relay I would need and where I can get it? Where would I tap into the heat pump to get the low voltage signaling? How would I connect the leads from all 3 heat pumps?

I am very handy with electronics, and I have tied in humidifiers into the heat pump units so I am familiar with where to find the control wires Â but I need to know which control lines to tap into. I have Econar Geosource 2000 heat pumps.

Thanks

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Comments (7)

zl700
15 years ago
I would look into adding 3 RIB relays, perhaps with 24VAC coils, wired with fan contacts, run in parallel so that any or all three would activate a simple circulator relay

http://www.functionaldevices.com/ChartPilot.html

It is important to have flow at all condenser coils before compressor starts so, 3 simple time delay relays could be installed on the low volt side of contactors set for 2-3 minutes so that pump has time to start and get things flowing.

http://www.supco.com/images/10%20Time%20Delays%20&%20Motor%20Protection.pdf
sniffdog
Original Author
15 years ago
z,

Thanks so much for the info. When you say "wired with fan contacts" - do you mean tapping into the HVAC fan control? If so, I know exactly how to do that since my humidifers tap into that contact as well.

I really like the idea of tapping into the fan control because if I decide that I want the loop pump to run all the time (during extreme hot days/nights or cold days/nights - when I know I will have lots of HVAC cycling) then I can just push the tstat fan switch to ON and the GT pump will run continuously. Otherwise it will cycle with the HVAC calls.

I also get the time delay - makes perfect sense.

I presume that the way this would work is when the tstat calls for HVAC, the heat pump fan will kick in first, and that would start the loop pump. A few seconds later, the heat pump controller would send a compressor ON singal but the time delay device would hold it for 2 minutes before the compressor started, thus allowing the fluid in the loop to get flowing first.

Thanks for the help - tremendous!
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cs That is the same in my area. There is really only 1 company that has been doing GT for a long time - something like 20 years. Everyone else - just a few - are newbies. And you have to factor all of that into your decision. For the install, you could have a company travel from a distance to do the job. But what happens when things go wrong - if (when) you need service? I have had a contoller board and a fan relay fail on one unit within the first 12 months - both of which seem to be related to a power surge. But when heat is out, and it is cold outside, I want it fixed right away! And I mentioned it before - put whole house surge protectors in your main panel to protect your HVAC equipment (see www.smarthome.com, Panamax Whole House Surge Protectors). Make sure you spend the money and get good equipment, read the warranty and post with the equipment recommendations to get second opinions. I also think that if your company is a distance away, having some guages on the system so you can trouble shoot with your HVAC guys over the phone will help. Some of the tools the HVAC guys use (like temperature probes) are not expensive, so you could do things like check loop input and ooutput temp, air input & output temp - the basic things they would do to trouble shoot a problem. Have them explain to you what to look for on the contoller board when there is an issue - and how to reset it if your compressor locks out. With mine (Econar GeoSource 2000) the lights on the board will tell you if the compressor is locked out or if there was a pressure alarm condition. In my last home, I had gas heat and electric A/C. I found a great HVAC company and never worried about the system - knew very little about it. When it broke, I just called my guys. With my new home, I want to know everything about my GT system - not just because I find it inetersting, but because I know that if that one company who installed it goes belly up, there are very few people around here that know anything about GT or how to maintain the system I have. I also recommend that you install some form of backup heat if you live in a cold place. I chose to install direct vent fireplaces that are rated as heaters. This decision has turned out to be one of the very best investments we made in the house. When power goes out - or the heat pumps break - I can fully heat the house with one wood burning fireplace and two gas fireplaces. All of the fireplace units units have blower fans and thermostats - so they can be set to operate just like a heating system. All fireplace electronics are connected to the backup generator. I can live without A/C on a hot day, but cannot live without heat on a very cold night. Just some ideas to think about.
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cuffs054
15 years ago
Wouldn't the fan coming on early give you a blast of cold/hot air out of vents?
zl700
15 years ago
Cuffs
Thats possible it could happen however these units or the stats often have time delays.

Sniff, not seeing your wiring diagrams, I'm saying this is the only way to do it, just a starting point.
sniffdog
Original Author
15 years ago
z,

I am already all over this thing. I have sent the Functional tech support people a wiring diagram to ask them if this configuration (which I adapted from one of their application notes) will work. If so, I can use 3 current sensing devices and 1 dry contact closure relay (see picture).

The current sening device I am looking at is thge RIBXK420-20 and the dry contact relay is the RIB02BDC. The neat thing about this is that it is self powered - no separate low voltage supply is needed.

I am not worried about the delay of the HVAC fans blowing ahead of theloop pump start up. I can tune that delay to as low as 6 seconds if I want. My guess is that a 30 to 60 second delay will work just fine to get the loop fluid moving, and that isn't a long time to wait.

If this works - it's easy to implement. It also potentially solves another challenge with a BROAN ERV that I am going to add in the fall. The BROAN unit runs continuously, but I want it to run when the HVAC fan from the main 6 ton unit (that will have the ERV attached) is running so that the HVAC blower can cycle the fresh air from the ERV through the main level and basement. I should be able to use the same current sensing device on that 6 ton HVAC fan that feeds the loop pump to also trigger a seperate RIB relay to energize ERV fan.
zl700
15 years ago
Current sensing relays are nice as long as they are self-powered. This makes them reliable. The plus side it they wonÂt draw from system TX or need to share with other loads.

You are on the right track!

So are you ready now to add variable speed to the ground source loop circ controlled by temps to maximize pump efficiency and control HP input temps for max efficiency?
Or a dual head or perhaps 2 circs in stages?
LOL
sniffdog
Original Author
15 years ago
z

I was actually in the hunt for a way to completely monitor my geothermal system and I discovered a guy named Phil who has a site at www.ourcoolhouse.com with a system called the WEL that he developed that does it. However, when I started to think about a monitoring system the thought occured to me that having the ability to control components is what I really needed. Unfortunately, the WEL only monitors and displays.

I have found a few microcontollers like the Rabbit based processors that are programmable that could monitor and control. They make 3rd party software that provides a visual way to program it. The problem is time - and I don't have enough right now to dive in to a project like that. But it would be a lot of fun. Someday I will get to that. The RIB approach is easy - probably doable in a day and with no computer programming.

Thanks for all the help. I will post back if I get any updates on the RIB configuration or when I have results.

Can I activate GT loop pump on demand?

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zl700

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Can I activate GT loop pump on demand?

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