Three times my system (4 ton GeoMax, closed loop, two 300 foot wells, each containing 2 loops) in the last 3 weeks has gone into Lockout.  Annoyingly, nothing lights up anywhere when that happens.  I have to deliberatly notice that the compressors are off, but the unit is blowing warm air.  It may have happened several times more, I can't tell.  I swear the entire thermostat should light up RED or something. 

Anyway, shorting the "test" terminals on the circuit board gives me error code 4, which according to the manual means entering water temperature too low.  In english, I guess this means the water from the ground loop isn't picking up enough heat and is getting below the cut-off...

I'm in contact with the HVAC installer.  But this isn't good, right?

iI am no unit expert but you may investigate this. Most units come from the factory set up for open loop with freezeprotection for the coax enabled. If you are running a closed loop with anti freeze present, there is a setting or a jumper to cut to enable the unit to run below the protected temp. They usually hide this info somewgere in the install manual. Hope it is an easy fix.

I was thinking the same thing as Eric. You may want to start recording EWT's in the hope of getting a reading close to the time the unit locks out.

Stuart, I 100% agree with you on the thermostat alert. Our thermostat will do this, but it was not hooked up by the installer. When they come back out in the next 2 months, I will have them hook it up, and/or an audible buzzer. It seems to me that the expense will be justified by not having aux engage without anyone noticing it during a lockout. I'll post the details after the alert is hooked up.

@waterpirate: Thanks...I did spot that jumper and it looks like it was cut by the installer, so that's ok. The temp sensor on the manifold is analog and I've been unlucky finding anything digital and more accurate. I know for a fact that the temp sensor often reads right around 30, so it's clearly going below.
Question: If it did have anti-freeze, would it be ok to run the system with EWT below 30 F ? The minimum specs for the unit are 20 F for start up but 30 to 70 normal operation. I'm concerned my ground loop isn't working properly.

@geome: Good idea. I know there's an alarm relay that goes active inside the unit, but it's not hooked up to anything. I may tap my own 5 volt circuit across the relay and run some RED leds up through unused thermost wires and around the outside case or something. It's intolerable that the unit could be in lockout for days before anyone realizes it.

It's intolarable, too, that the unit isn't working properly!

Stuart, just make sure your modifications are ok with your installer/warranty coverage. Wouldn't want to void your warranty.

I am not an expert, but I wonder if air in your loops can be causing your lockouts? I remember your system was recently installed.

You wouldnt be the first or last with air in your loops. You need to verify flow through the heat pump. Do you have P/T ports?

Fortunately, the installer likes to "tinker" and has shown me some of the inner workings. I'm keeping him informed about my utility bills to help him "sell" the product. I know there is an alarm relay which can me made "dry" (isolated contacts) by clipping a jumper. I plan to run a small adaptor (5 volts or something DC) to the relay contacts, and through a pair of unusued thermostat wires, then put maybe 4 red LEDs around the back plate of the thermostat so that the whole wall glows red in lockout mode. I will clear it with him/show him when he comes over.
I've also discovered that the zone damper for one of my zones has a damaged gear wheel....the plastic teeth are torn off. That's the same zone that gets up to 1300 cfm in a 10x10 duct. Could excess pressure damage the teeth??

I do have PT ports, but I don't have the equipment to check. I guess he will need to do that. Frustrating that the loops are producing.

I meant...AREN'T producing!! Not ARE. If they were producing, I'd be happy!

Looking at the above with only 150' of well per ton of capacity, it is possible that your vertical heat exchanger is marginal for your tonnage.  2 loops per well is not going to gain you much over 1 loop per well if the type of earth surrounding the well cannot move the BTUs.

Can you give some more details regarding your vertical heat exchanger wells? 

What is the well diameter?  What is the spacing in feet between the wells?  What kind of formation did the well driller encounter while drilling the wells?  Was water encountered during the drilling?  Assuming the wells are grouted, what kind of grout was used?

You're asking me questions I don't know the answers to. I know that the water table is at least 400 feet down. The distance between wells is about 10 feet. They were grouted, but the kind of grout is ?????? It's Pennsylvania soil in the Piedmont....clay, mostly!

<!--[if gte mso 9]> Normal 0 false false false MicrosoftInternetExplorer4 <!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0in; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";} @page Section1 {size:8.5in 11.0in; margin:1.0in 1.25in 1.0in 1.25in; mso-header-margin:.5in; mso-footer-margin:.5in; mso-paper-source:0;} div.Section1 {page:Section1;} --> <!--[if gte mso 10]> I’m no expert on this by any means and have just gained knowledge researching for my own system that has yet to be installed (still building the new home).  Maybe some of the guys that know more about this will chime in.

 

Around here where it is usually <50’ down to rock or shale and the water table is about the same depth.  Typical vertical geothermal wells are on the order of 175’ to 200’ per ton of capacity in this area.  Rock generally has better thermal conductivity than clay, and wet rock definitely has better thermal conductivity than dry clay.  And the recommended spacing between wells is 15-20’ minimum.

 

Bentonite grout is pretty common and inexpensive for sealing wells, but if it isn’t thermally enhanced with silica sand, is a poor conductor of heat.  If straight bentonite was used for grout, then you would need more length of bore hole to compensate.

 

Based on what you posted above, I am even more inclined to think that your vertical heat exchanger loops are less than you need.

 

Take a look at the following geothermal heat pump newsletters for more useful info:

 

Outside the Loop Newsletter

Agree with Arkie6. In talking to several GSHP installers at our local Home Builder's Show, distance between wells should be at least 15 feet; more if available. Dave

your ground loop seems to have the right size, although I wold put them further apart I think 10ft are still ok. Many things can produce lockdown with a #4 error code. 1) Is the right jumper cut? it should be JW#3, however there was a printing error in some of the installation manuals referring to JW#2., which is incorrect. 2) is the correct amount of antifreeze in. We used glycol and our supplier sold us the wrong kind, it only contained 60% glycol instead of 100%. Of course everything was off. What did the reflectometer read. What kind of antifreeze was used, glycol or methanol? 3)are both circulation pumps running? These are the most common issues in my experience. You need to have entering and leaving water temperature for us, as well as pressure drop over the coil in the heatpump, so we can troubleshoot further.

docjenser, how would having the correct amount of antifreeze in the system have any effect on his unit locking out on low temperature? Is it possible that his lines are freezing up and blocking flow?

Maybe he has too much antifreeze in the system? More antifreeze = lower freezing point, but it also means lower specific heat and less heat transfer than pure water. More antifreeze than needed could in fact lead to lower loop temperatures in heating mode.

The lines typically freeze up inside the heat exchanger after the pump stops, since this is the coldest point and the water suddenly is static and then the flow is blocked. I have seen it happen without enough antifreeze. I agree that too much antifreeze is bad too, more for the viscosity and the increase in head loss than the loss in heat transfer.

Yes - excess pressure arising from the system attempting to force 1300 CFM through a 10x10 duct might increase damper actuation force enough to strip teeth. Damper hardware should be rated for max air pressure, any rating of 2" WC or more should be able to withstand your blower regardless of duct size

Add a sport ball inflation needle tip to a $10 0-60 psig pressure guage (you'll need an adapter or 2 from Lowe's or HD) and you should be able check your PT ports. Pressure diff across the ports gives a table lookup of loop fluid flow through the unit.

Keep in mind that the brine factor for water is about 500, for 21% methanol it is about 485, I believe glycol is 475, which means you loose about 5% heat transfer capacity when using glycol, not enough to cool the loops too far down.