Hello all.  It's me again.  Thanks to everyone's help a few weeks ago I was able to determine that my system was functioning as expected.  (and learned a lot along the way).

Unfortunately, now I have a new problem.  When I woke up this morning I discovered the house was cooler than normal and shortly after discovered the compressor on my Tranquility 27 had locked out.  I shorted the test pins on the CXM board and it's displaying a fault code of 4, which according to the manual is an FP1 (Water Coil Low Temperature Cut-Out Limit) fault.

I reset the unit and started it back up and it's been running fine for the last hour or so.

As everyone knows I'm a novice with HVAC, but I was hoping you guys could give me some things to check or maybe give me some ideas as to what may be causing this.  At this point the only cause I could come up with would be a faulty thermistor.  We also had a similar circumstance a few days ago, only with that instance there was no fault code when I checked it.  But same deal, I reset the unit and it ran fine for a few days until this morning.

EWT: 32.8
LWT : 27.1

Without checking all prior posts, do you have antifreeze in the system and have you cut the JW3 jumper?

Yes there is propelyne propylene glycol is the system and yes the JW3 jumper has been cut.

Ok so I think may issue may not be enough propelyne glycol and thebwater is getting to cold and "thickening". I don't think I have enough water pressure going to the system because of this.

My question is should I use propelyne glycol? Or can I use straight antifreeze? I ask because it's supposed to be warm today so im hoping the water temp will rise and then start flowing normally again. If thats the case i would like to get something added immediately. Only problem is with the holidays I can't get the propelyene glycol and will have to order it tomorrow.

What's the pressure drop through the coax?

FP1 is not about pressure, it's about temperature. More is not better with propgly

FP1 is not about pressure, it's about temperature.

Well this was my original thought. But I didn't think my EWT and LWT were out of question for the system. I think they are lower than they should be, but not out of the question. The only thing I know for sure is the QT flow center is not pumping near the capacity that it normally does. Almost like there is a blockage somewhere. Which made me think I didn't use enough propgly when I filled the system. At this point I directly wired the flow center to run all the time. Still not pumping nearly as much as it should be. Measuring EWT without the compressor on just running the QT flow center is now 37.

At this point I haven't had any heat for 2 days so any advice input would be greatly appreciated.

I just fired the unit back up to see what would happen. Here are the numbers I took:

EWP : 5
LWP : 4
EWT : 37
LWT : 27

Everything looks off to me. I just don't know enough to know what the problem could be. Compressor has been running for 10 minutes now.

Before I think I was getting something like these numbers:

EWT : 39.5
LWT : 35.2
EWP : 10
LWP : 6.5

When you started the thread you had a EWT/LWT DT around 5 now it's 10F? Your flow now appears to be slow (which will cause LWT to plunge and trip FP1

Right that was at the beginning of this. Like I said one night the compressor kicked out and I didn't think much about it. Turned it back on and it ran fine for about a day. Then it started locking out again and the compressor would only run a couple of minutes.

The unit hasn't been on in about a day or a day and a half. I just turned it back on and those were the numbers I was getting.

When I first hooked up the flow center to run full time it was barely pumping anything. It seems to be doing better now but the sun is out and its' a little warmer toady. I also drained some water out of the flow center below the outlet tube so I could make extra sure it was pumping. I suppose that could cause the pressure drop. I will fill it back up and see if that changes anything.

Your flow now appears to be slow (which will cause LWT to plunge and trip FP1

Let me fill teh flow center back up and take some updated readings. But something was definately going on with the flow before hand and I believe that's what was/is causing the tripping.

Pressure readings seem to be about the same after filling the flow center back up.

So is my original theory still plausible? After the water temp gets to a certain degree there isn't enough propgly and causing it to thicken and slow down the flow? Also, will a 27 LWT cause the FP1 fault? I thought that was within the operating parameters.

Your 1 # Delta P appears to be the problem. More cold PropGly means thicker harder to pump brine. Your original post did not indicate the trouble you are indicating now. (note 5 DT suggests good GPM).
Pumping power could be the root as could too much or not enough antifreeze.

Pumping power could be the root as could too much or not enough antifreeze

That is what i'm suspecting. So is there a way I can tell if I have to much or not enough propgly? Should I just empty the entire system and refill it?

What would be the recommended amount of propgly for a 5 circuit loop field? Each loop is 600ft.

Each loop is 600 feet total? Or 600 each way for 1200 per loop?

What size is the loop pipe diameter? You need to calculate or know how many gallons of liquid the loops gold, then you can substitute the right percentage of glycol for freeze protection.

Mine is 100 gallons (if I remember) of liquid, so 25 gallons of glycol and 75 gallons of water for a 25% solution! freeze protection to 15f, I think.

Each loop is 600ft total of 3/4 HDPE. So total pipe length would be 3000ft.

My quick math suggests you have about 70 gallons of liquid. I used this site...

http://www.biohydronic.com/bivolume.html

And put in your pipe radius (.03 feet) and total length (3000)...

BUT...I (disclaimer) am not a pro! I hope Joe or Doc or ? Can confirm or correct....I'm happy to learn if I'm wrong or right. Please don't do anything until someone else backs anything up.

About 70 gallons is what I came up with as well. Which at 25% of propgly suggests 17.5 gallons. Which is close to what I should have. I honestly can't remember how much was put in when the unit was put in service but it was either 15 gallons or 20 gallons.

Let's assume either 15 or 20 is the 2.5 gallons either over or short enough to cause this problem?

Something else I don't understand. Currently it says my EWT is 36 degrees. When I started my troubleshooting thread a couple weeks ago I was hovering around 37-36 degrees. And everything was good for a few weeks. The water temp has risen back up because the unit hasnt' been running. Shouldn't the flow have returned to where it was a couple weeks ago?

A few gallons either way shouldn't cause that much difference...your freeze protection is somewhere between 10 and 20, but your codes are about low flow, not low temps. Even if the EWT is 36, your "water" isn't/shouldn't be turning to gel even if glycol does tend to thicken at lower temps.

I am not sure what,s causing the low flow, but many systems out there have glycol and run with EWT at less than yours, and have enough flow to operate....my LWT has been in the high 20s on really cold days with ice on the manifold, but even with 1 pump on the flow center, I get enough flow to heat the house just fine. And I've got at least as much water and glycol as you.

In the future, a refractometer would be used to check glycol percentage. I got one when my exchanger was freezing up causing shutdown....found out the guy only put in 10% glycol.