Geothermal Issue: E5 - Frze Detect FP1 errors w/ Waterfurnace Series 7 & Ground Loop

[stevelion]

I’m looking for expert advice on what may be the cause of my problem and suggestions on what to do to resolve.

I have a 3.5 ton (042) Waterfurnace Series 7, vertical, closed loop system (more details on the ground loop to follow) installed in a 2625 SQFT home. In the coldest days of winter, I’m experiencing repeated E5 - Frze Detect FP1 errors which typically result in a system lockout and switchover to emergency heat. The system was installed in 2014 in Southeastern, Pennsylvania. The system performs very well in warm weather and cold weather except when we have repeated days where the mean/low temperatures drop into the teens and single digits (Fahrenheit). We experienced 124 of these E5 errors during the 2014/15 winter.

When this problem first started, the installer worked with the WF engineers and decided to look at changing the glycol/water (I believe it is glycol based) ratio in the loop suggesting that the installer had used too much glycol thereby reducing the heat transfer capacity of the system. Additionally, the single, variable speed ground loop pump was set to a fixed, high flow rate to increase the turbidity in the loop.

On making these changes, things got markedly worse in terms of numbers of E5 errors in the weeks after. The theory then was that air was inadvertently injected into the system during the rebalancing of the glycol/water ratio. On next attempt at repair, the loop was primed again with a larger pump and it was believed that, in fact, air was removed from the system. However, by the time this work was completed, the heating season was nearing its end and temperatures rose consistently into the 20’s and higher and so it was unclear whether this action had any real impact on performance. Now we are experiencing the first significant, prolonged cold weather of the 2015/16 season and the problem has reoccurred.

The ground loop is made of 4 loops consisting of 11 total bores of varying depth as follows. The nomenclature below is: Loop # / # of bore holes / individual bore length summed for total length of loop in ft.
Loop 1 / 4 / 60+50+50+40 = 200’ total
Loop 2 / 3 / 70+50+70=190’ total
Loop 3 / 2 / 95+90=185’ total
Loop 4 / 2 / 90+95=185’ total

The reason given for the odd setup was related to the challenges met when boring in our heavy clay. Water was entering the bore holes as early as 20’. It is my belief based on talking to the drilling sub-contractor, that little casing was used, but much more grout was used than anticipated.

To reiterate my goal, I’m looking for expert advice on what is causing my issue. It is my belief that the ground loop does not have enough capacity which could be either due to an under-sizing issue, a configuration issue with the unusual number of bore holes looped together, or some combination of both. My plan is to continue to work with the installer to get resolution. To date, they have been very responsive and have been in the HVAC business for long time in this area. I’d also like to have opinions on what might be an acceptable solution. e.g. increase length of existing loops, add a fifth loop, start over and re-drill, etc.

Thanks in advance to anyone willing to help.

[wahoo]

My guess would be that your ground loop is not adequate for the heat loss of the home. Do you know what the outdoor loop temperature is when this lock out occurs?? We've received a few ground source units that were set up for the wrong temp. ranges than what we experience and the units needed a field adjustment prior to start up to eliminate lock outs like these.

[stevelion]

My guess would be that your ground loop is not adequate for the heat loss of the home. Do you know what the outdoor loop temperature is when this lock out occurs?? We've received a few ground source units that were set up for the wrong temp. ranges than what we experience and the units needed a field adjustment prior to start up to eliminate lock outs like these.

Thanks for the reply. I do not have it in front of me but am fairly confident the lockout was occurring when the loop temperature reached right around 20 deg f. I also don't recall if that is on the incoming or outgoing. For some reason, AWL is not working correctly for me so I cannot check this remotely. I can verify later today or early tomorrow.

[pecmsg]

20*f loop temperature? I hope you have glycol in there.

[stevelion]

I'm about 95% certain the antifreeze used is glycol. The installer went through great lengths to get the ratio of antifreeze to water correct per Waterfurnace guidelines.

[stevelion]

One update - I have a 4 ton system, not 3.5 as stated in original post. Currently, it is 20 deg f where I live. The EWT is 36.2 deg f and the LWP is 29.5. The system is extracting 27621 Btuh. Entering air temp is 70 and leaving is 93.2. WaterFlow rate is 8.4 GPM.

[hvacvegas]

Some geo's have to be told they're an anti-freeze system, and come shipped programmed as non-anti freeze. Hopefully that was configured.

[wahoo]

You're not set up for the proper loop temperature. Tell the tech to change the freezestat to the low temp loop setting.

[pecmsg]

You're not set up for the proper loop temperature. Tell the tech to change the freezestat to the low temp loop setting.

Test the glycol freeze point before lowering it!

[stevelion]

You're not set up for the proper loop temperature. Tell the tech to change the freezestat to the low temp loop setting.

I'm fairly confident that the Waterfurnace engineers and the HVAC tech agrees that the system is set correctly at around 20 deg f and that it is operating properly by shutting down when LWTs are getting to around 20 deg f. This is to protect the system and seems completely logical to me. I think 20 deg f is the lowest setting WF recommends for this unit. At this point, I believe the only question remaining is what can be done to keep the loop temps from getting this low. e.g. changing glycol/water ratio (to be correct per specifications), increasing loop pump speed to increase turbidity, etc. Of course, "etc." may be limited which is what I'm trying to find out. I'm no expert, but the only conclusion I can draw at this point is that the ground loop is not performing adequately either because it is not operating at full capacity (e.g. one loop is locked out perhaps with air) or the loop is undersized. Of course, I'm hear to get expert opinion and so am happy for any other ideas.

[wahoo]

I thought you said your ewt temp was 36 and lwt was about 30 and unit was locking off due to low loop temp? If unit is locking off at a 20 degree loop temp then the loop is under-performing OR the heat loss is exceeding the loop's capacity to keep up. Same result either way. Assuming you have adequate circulation capacity, then you need a larger loop. IMO anyway.

If I remember correctly the low temp setting is about 20 degrees F.

[stevelion]

I thought you said your ewt temp was 36 and lwt was about 30 and unit was locking off due to low loop temp? If unit is locking off at a 20 degree loop temp then the loop is under-performing OR the heat loss is exceeding the loop's capacity to keep up. Same result either way. Assuming you have adequate circulation capacity, then you need a larger loop. IMO anyway.

If I remember correctly the low temp setting is about 20 degrees F.

My initial response to your question was 20 deg f. I may have confused things a bit when later I posted current conditions including outdoor temp, loop temps, extraction Btuh, loop flow rate, and air differentials. I am also of the opinion that the loop is either underperforming or undersized as you said and, also as you state, same result either way. I'm not sure what you meant by "circulation capacity" unless you are referring to the ability obtain/sustain a certain flow rate through the loop. However, if this were an issue, I'd think (again, I'm not an expert) we would not be achieving the 20 deg f temps on the loop, but instead, would be limiting the Btu exchange rate of the loop and the result would be underperforming heat extraction reflected in insufficient differentials between the incoming and outgoing air temps and an inability to satisfy the thermostat. For me, satisfying the thermostat is not an issue until the system locks out. i.e. it ramps up to full speed (12) and runs until the 20 deg f loop temp is hit.