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

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!

Wouldn't the fan coming on early give you a blast of cold/hot air out of vents?

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.

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.

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

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.