Indiana New system questions

I got a 3 ton vertical loop system installed in September, so I'm new to geo. Not yet 100% sure what to expect, but when the system was sold to me, I was told the aux heat should almost never have to come on. Fast forward to December, and the heat pump can't keep up with even moderately cold outside temperatures, and I have to run aux heat if it's below about 20 degrees out. The EWT is 30 degrees, which I would think is cold for so early in the season? Installer insists this is all normal. Am I right to be concerned?

 

Sounds like an undersized loop field. What are the specs on the loop? What is the size of the house?

 

Where are you at? Your location determines the outdoor design heating temp as well as what the deep ground temps are. EWT does seem too low way too early in the season. I'm in central NJ and when my system was started in Oct this year EWT was 54 (essentially undisturbed deep ground temp) and it is now 42. As Eric indicated, need specs to get a sense of how undersized the loop may be.

 

Location is central Indiana. What I know about the loop is that it's supposed to be 150 feet per ton = about 450 feet. They bored four holes, which ended up being an average of about 9.5 feet apart, I think each one was a little over 100 feet deep. How would I find other specs, and is there a way of verifying the loop is actually as long as it's supposed to be?

The house is 5500 sq feet but there is another (gas) system that shares the burden. We replaced a 3 ton air source heat pump that did just fine with all the same ductwork, insulation, etc. Let me know anything else you need to help me figure this out, I can find out for you (obviously I'm not a pro!!) Much appreciated...

 

central Indiana should have the same deep ground temp as central NJ - mid 50s (you can search for maps online) and if they put in 900 vertical feet of bore total (4 - 225ft vertical bores) for a 3.5 ton unit, that actually seems like an excessive amount of bore length. (150ft per ton is a rule of thumb but it can vary depending on geology - more length is better). Is the intent to replace the gas unit in the future with a gshp plumbed into this bore too (explaining the extra bore)? 9.5 feet apart sounds too close - 15ft is the standard and I pushed mine to 20ft spacing but with all that extra bore for a 3.5 ton unit, I generally wouldn't think the spacing would matter that much in its current configuration.

Are the gas unit and heat pump on separate zones and not attempting to heat the same zone? The only thing I can think of is that the gas unit isn't doing its share (for whatever reason) and the heat pump is trying to heat its zone plus portions of the gas unit's zone (or all of it) resulting in the full capacity of the 3.5 ton unit being utilized continuously and the back up heat coming on (because it isn't sized for both zones). That would probably drive the water temp down so dramatically early on in the season too with all 3.5 tons being utilized continuously to keep up. Its a head scratcher given the stated specs. Maybe describe how these units are intended to be zoned/work together?

 

I'm only familiar with my horizontal loop field, so not sure what to expect, but I would echo gsmith. How much pipe did they actually put in and how well did they back fill and grout the bore holes? Is there a problem in how the thermostat is programmed to control the heat pump and aux?

 

30 EWT means the heat pump is removing heat from the loop but Eric might be onto something with the grouting. I would expect the loop water temp to be higher but if the loop piping doesn't have contact with the surround soil/rock at the bore sides it can't pull heat from the ground to warm up the loop. Any info on the bore grouting?

 

Okay, so turns out I had the wrong number stuck in my head. 150 ft/ton is what my documentation says. The bores are backfilled with bentonite, not sure how to tell about contact with the ground. Any tricks there?

The two systems are zoned in a weird way. The gas system never has done much work, I know that because January gas bills are like $50-70. I'll turn up the thermostat on the gas system and see if I can get it to pull more weight.

The system is set up so that the aux comes on at a hair trigger. I have it set to 69 degrees 24/7 and the aux still comes on in mild weather for reasons I don't understand. So I disabled aux, and the first time it was 20 degrees out, indoor temp dropped to 66. Hence my desire to troubleshoot.

What I'm thinking is with the new setting for the gas system, I'll give it a couple days and report back. Thanks for the help so far!

 

As gsmith indicated, if your unit is running somewhere close to 100% of the time your loop temp will drop to 30* due to the HP pulling heat from the area immediately around the loop pipes faster than heat can move thru the ground. That is not really a problem. However, if you can shift some load to the gas furnace it would lower the load on your HP.
I have a 3T unit in my 1400 sq ft house NE Ohio. At 0-10* it is running 80-100% of the time in 1st stage. Seems like you are on the right track.

 

I think you need to figure out with certainty what bore/pipe you have in the ground. 900ft is alot different than 3.5 x 150 = 525. I doubt 900ft of bore (properly grouted) would be a problem for a 3.5 ton unit; 525 could be but is certainly within a reasonable range.

Bores wouldn't have been back filled with bentonite- it's a clay that expands when wetted. So they would have mixed dry bentonite (it comes in sacks like premixed cement) with water and pumped the fluid into the bores from bottom up. That mixture then hydrates in place, solidifying and sealing bore. If this mixture wasn't thermally enhanced and you have 525ft of bore, that could be an issue. Bentonite by itself tends to be more of an insulator and can limit heat transfer between pipe and ground. In the past silica was used as thermal enhancement but graphite is more common now to be mixed into bentonite grout mixture.

$50 of gas in January sounds like a natural gas furnace that doesn't run that much. So effectively you have a 3.5 ton geo unit attempting to heat a 5500 sq ft house. Unless this is an ultra insulated house, I can't see that working. The gas furnace must be larger tonnage than the geo, no? It sounds like it needs to do more than 50% of the heating and is doing like 20%. Your loop should recover if the furnace starts doing its share. If it doesn't recover with the furnace doing its share, then probably look into the loop as a problem at that point.

 

My concern is that your system may not be utilizing all 4 bores. Was the loop field flushed properly?

Chris

 

Update: increased the thermostat on the gas system, EWT recovered to 33 degrees temporarily but it now back to 30 and it's not even very cold out (30 degrees, maybe).

I am not sure about anything with regards to the install... it was a turnkey project. The HVAC company is insisting everything is fine, but it doesn't seem fine to me. How would I be able to tell things like how much loop was actually installed, or whether the system was flushed properly? Perhaps I should find a pro with no skin in the game to give me an impartial analysis?

 

If the same size air source heat pump could keep up there is something wrong.

I would ask them to bring their flush cart back out to give the loops a better flushing.

Do you have just 2 large pipes coming into the house/basement? Sometimes they bring each loop in and make a manifold in the basement, in that case they would have been able to isolate each loop to purge the air out of each loop separately. Harder to flush/purge when the manifold is outside underground.

My installer had to spend a few hours flushing mine to be sure all the air was out.

Chris

 

ChrisJ, I'm not saying that proper flushing of the loops isn't a potential problem, but I don't know how you conclude that as a possibility given what has been presented. He isn't sure of what was even installed.

Poiuyt350, why did you get rid of the ASHP? Was it actually working okay and wore out or was it also not working? I don't think what you are experiencing is normal and I would be suspect of the contractor saying this is normal unless they are terrible at what they do. No one purposely installs a geothermal system only to have to use electric resistance heat for the bulk of the winter.

For NJ, the Department of Environmental Protection required permits to install the vertical bores and a master driller (its a drilling license) was on site the whole time who also filed well logs. You can go online to the NJDEP and view all three well permits and well logs (one for each well). In my case, the well logs tell you how deep they are, what soil/rock strata they were drilled through, what piping was installed in them, and how they were sealed. If Indiana has a similar setup it might be the best way to independently verify what was done. You could ask your contractor too but who knows if you will get truthful answers (or any answer) since you are already asking questions about how the system is working/supposed to work.

As an aside, turnkey construction projects that function properly and meet all of your needs that do not involve your input don't exist, regardless of how much money you spend and/or the quality of the team you hire. Being uninvolved in any construction project sows the seeds for problems, especially when important components are buried and essentially un-inspectable. No truer words were spoken than "trust, but verify."

 

I only have two pipes coming into the basement, so it looks like the manifold must be outside.

The ASHP kept up just fine... when it was working. Cooling season started this year, and I had a shot compressor, then lots of problems with startup. Spent about half the summer with no AC. 11 service calls later, I decided it was time to replace that 12-year-old hunk of junk. I live in an area with lots of temperature extremes, so I figured geo would be more efficient.

I looked at the permits, the only one ever filed was for the HVAC work. Nothing for drilling. This might actually be legal... Indiana is pretty lax, unfortunately.

 

Seems much too quick for the EWT to be at February temps at the beginning of the heating season.

Giving the driller/looper the benefit of the doubt they at least did 4 @ 150' (rule of thumb).

 

can you describe the overall system better. how are the gas furnace and gsph (prior ashp) laid out and function to heat and cool the house? Do they have separate ducting to different locations or do they supply forced air in the same ducts to the same locations (or some combination thereof)? Was the ASHP used to heat the house or just for air conditioning, heat during swing seasons, and then gas furnace take over in the winter (ie the furnace is the backup heat for the ASHP given your cold winter climate)? Wondering if the ASHP was primiarly used for air conditioning and swing season heat with gas furnace as winter heat (a common situation in cold winter climate) so maybe the gshp and its loop were sized for cooling and swing season heat only?

 

When "they" say 150' per ton, that is bore depth, not down and up 150'.

What brand of heat pump? Is it a split system, meaning the compressor is in one location and the refrigerant lines go to an air handler somewhere else.

 

The gas furnace heats half of the lower level and part of the upper level, thermostat is downstairs. The geo heats most of the upper level and some of the lower level, with two zones: one thermostat on each level. Each system has its own set of ductwork to their respective locations. I'm not sure what the old system design was supposed to do, all I know is it was effective (lowest outdoor temperature since I've been in the house is about 0.)

The old system had 36000 BTU of heating from the ASHP and 51000 BTU from resistance heat. The new system seems to be set up with similar specs, but in reality (according to the gauge on the pump) I'm not getting more than about 18000 BTU.

It is a split system, Bryant GZ. It creates a boatload of noise seemingly transmitted through the freon line, which is another thing I've been annoyed by with it and I was not warned about prior to purchase. If I measure from a few feet away, it's in the 65-70 dB range. I can't read anymore in the room above it because it's like I have the Tell-Tale Heart under my floorboards.

 

That's a two-stage heat pump. Hard to tell exactly what the issue is, but I can think of a couple things that could be setup wrong.

For example, if you look at the "product data" for your unit on the Bryant website, it should be putting out around 19000 to 20000 BTU with 30-degree entering water temperature in stage 1. If you are getting 18000, then it's possible the thermostat was not wired correctly to activate the second stage and you are stuck on stage 1. If that's not it, then there could be a problem with the water flow.

You should have a tech look at the basic parameters: measure the water flow, entering and leaving water temps, and entering and leaving air temps. From that, you can calculate the heat of extraction and see if things are working to published specs. It shouldn't be hard for a tech to do.

The hair trigger use of AUX heat could be a thermostat setting issue. You have 3 stages of heat--low, high, and AUX. Thermostats will have differentials for when to activate each stage. Some thermostats allow you to adjust the thresholds. For example, the default for Waterfurnace is 0.5/0.5/0.5, meaning AUX will activate when the indoor temperature drops more than 1.5 degrees from the set point. If you are stuck in stage 1, AUX would be expected to come on quickly. Once things are working correctly, you should be able to adjust the differentials (if your thermostat supports it.) You should also be able to set a lockout temperature above which AUX is not used.