South Carolina High loop temps already this season

All,

I am seeing what I think is high loop temperatures already this season. I usually do t see them reach this level until maybe sometime in late August.

I have two systems tied to my loop field. One is WF series 7 and the other is a WF series 5. They are approximately 4 years old and this is the first time I have seen the loops this high this early in the season.

I have posted some pics, do you see anything alarming?

Thanks,
Joe

 

Have you checked your filter? Delta T on the air side is kind of high. What tonnage do you have?

 

Doc,

Air filter is a month old and is a merv 11. Series 7 is nominal 3.2 ton and envision 5 is a a nominal 2 ton split.

I have 4 closed loops, each I think are 600 feet long for a total of 2400 feet.

 

I assume you have a 3 ton 7 series and a 2 ton 5 series split. Don't know what your loads are, but in my book 2400 of horizontal pipe is usually not enough to support 5 tons of equipment well from both a flow and capacity standpoint.
So we need more info. Pipe diameter, loop field layout, cooling loads of the house.
Thanks

 

How is the loop plumbed to the flow center and units? I have seen some folks get creative and daisy chain units on a VSD pump, so the loop would go into one unit, and than into another unit and than back to the loop. I doubt that is the case here, but could there be something else going on inside where you are making a mini loop inside and only partial water getting to the loop?

 

doc,

Pipe diameter is 3/4" and the loop is field is two ditches 300' long and 6' deep. Each trench has two 600' loops of which they are each stapled to each side of the ditch. All four loops come to one central header before making there way into the basement. I have not been able to find my original cooling load information, but will post as soon as I find it.


ACES,

I have attached a picture of my flow center.


My installer came out yesterday was not able to find anything wrong. The loop field pressure was low (about 10 psi) and he juiced it up since he was here. He did verify that the EAT and LAT reported by the AID tool (almost 30 degree delta) was off. He measured the delta T to be 19 - 21 degrees.

Maybe all is well, I was just concerned about the high loop field temps this early in the season.



thanks to all,

 

Is it just me, or are those in line shut off valves with a relatively low CV? Also, the 2 pump flow center with a constant speed pump as first stage. The biggest problem in this picture is that you are pumping through both heat pumps all the time. Plus 4 pipes at 3/4" is a heck of an additional flow restriction for the 16 gpm the units nominally calling for. Not to mention the likely lack of capacity of 2400 feet of horizontal pipe for a 3 ton 7 series and a 2 ton 5 series, explaining your high loop temps. I am just surprised that theses issues are showing up the first time now, if the system is 4 years old.

 

Yes they are inline shut off valves. If I am not mistaken they were using them to control flow, but don't "quote" me on that. Yes the system is 4 years old. I have been monitoring my system with a monitoring system for about 3 years now. I will take the time to go back and look at EWT and LWT for this time period in 2014 and 2013 for a comparison.

 

Let me just be clear here and explain things a bit better:

In general, you want to your loop water to flow without restrictions, because you you want to minimize your pumping power. Sometimes that has to be done with balance valves, but one should try to design a system without balance valves on the circuits. Balance valves are flow restrictors, it is like pushing your car's accelerator pedal fully down, and regulating the speed with the brake pedal. Your valves are not full port valves, thus causing a flow restriction itself, even when fully open. Keep in mind, you are paying for the pumping energy. Why you now have 2 restricting valves in each circuit, when it would be enough to have 1 each to regulate flow, is hard to understand.

The 7 series runs 2.5 to 3 times as much due to its capability to modulate (slow) down. Waterfurnace has a relative inefficient pumping solution for its larger variable speed heat pumps, because it has a constant pump coming on as 1st stage, and then the efficient variable sped only as second stage. Since the 7 series spends most of its time modulating in lower stage and runs 3 times as long, served now by the constant speed pump, also running 3 times as long. this setup cannibalizes much of the savings the 7 series brings.

Now in your case it is worse, since they piped it to have permanent flow through both heat pumps. That means that even if very little flow is needed, or only 1 heatpump is turning on, you are getting pretty much full flow through both heat pumps. So you are using about 10 times as much pumping energy as needed....

A smarter way would have been to have a constant speed pump serving the dual stage, and a variable speed serving the 7 series. Or have a single variable speed serving both heat pumps, with a modulating valve on the 7 series, and a motorized valve on the dual stage.

In addition, 4 circuits of 3/4" inch pipe also have way too much flow restriction for the 15-20 gpm Waterfurnace is specifying when both heat pumps are running.

While I mentioned before that 2400" of loop is a bit shy of serving a 5 ton load well, if they are stacked up on the wall of the trench, that makes it worse. If one line is at 6 ', the other one is probably at 5' or 4'. When stacking up the loops above each other, one has to understand that stacked loops perform not as well as loops on the floor of the trench. The pipe needs to get rid of heat, the ground above gets heated by the sun, so that is warm, so the only way to get cold ground for heat rejection is from below (and to a a more minor point from the sides). But below is already the other pipe, which has heated up the ground. So the upper pipe it is missing its main heatsink.

So the combination of increased pumping energy (which will end up as heat in the ground!, besides as missing $$$ from your wallet), likely lack of adequate capacity of the loop field, and the design of the loop itself fully explains your current loop temperatures this early in the season.

Now runtime is increasing since your loop temps are running high, and your capacity and efficiency tanks with higher entering water temps in cooling mode. So this becomes a vicious cycle.

 

Doc,

Well, it looks as though I have fallen victim to yet another poor installation. That seems to be a common theme on this forum when someone is having issues.

One clarification, the two loops in one trench are not stacked on top of each other. One is run on one side of the ditch and the other on the other side. So one is run out on one bottom corner othe ditch and comes back stacked to the same side a couple of feet above the run out. The other loop in the ditch is run the same just on the other side.

Thanks again for the information

 

Rather than beat up on the initial installation, we should focus on the system ran for 3 years fine. Year 4 presented this issue. something changed or is different in year 4, than previous years. As a side note, I hate smart thermostats. IMOA they cause more issues than they cure or help. IMOA the lion share of problems are created by the thermostats set up wrong, parameters of operation changed by homeowner by accident, or they are receiving/sending faulty data that controls the machine.

While all the data about your systems poor install may be true, that is not it's current problem. The difference is the systems reported poor performance via the thermostat. First rule of service: address the problem you are presented with, do not attempt to re-invent the wheel in your image.
YMMV
Eric

 

Eric, I did not try to beat up the initial installation, I tried to explain why the issue possibly exists. It is possible that the problem existed the last years and was not recognized. How else are we going to help people who come here to seek help? Of note, ParrisJR was not displaying of a thermostat, but reading out the systems data via the aid tool from Waterfurnace, which plugs into the control board. I don't think he ever mentioned a smart thermostat.
If he has 92F EWT this early in the season, there is a current problem with his loop. And seeing his pictures, this is not his only problem. As we all know, there is usually not only 1 problem if the installer is not experienced or un-evolved.

 

If the return is stacked on top of the supply the effect is pretty much the same as described before. It seems that your loop runs out at 6 ft and comes back at 4 ft, directly stacked above. That means your loop is relatively short to begin with, 50% of it is at 4ft depth, and cannot get rid of heat well, since the pipe below heats up the ground already and prevents it to be connected well to cooler ground.
Again, you are also putting additional pumping energy in the ground, and your heat pumps need to run longer and less efficient, which is also contributing to increased loop temperatures.

It is rarely one thing, it is usually like peeling an onion, where you discover another layer. This is important to realize, since it makes a quick fix unlikely.

 

My comments were for the owners benefit. So many come here seeking help and go away thinking their entire system is fubar. If it worked for 3 years.....

Eric

 

Well, shall we point out here what we see wrong when people come here with problems, in this case contributing to the problem surfaced, or shall we close our eyes and, despite knowing better, not mention potential things we see? I don't see how the latter would be to the benefit of the homeowner.
While internet opinions always have to be taken with caution, isn't the entire purpose of a forum like this that informations (and opinions) are exchanged freely, for the benefit of the homeowner and others who read it. Isn't that how we all become better?
Sure, in this case the system worked for 3 years, and obviously it works now! But as an industry, don't we own customers systems which not only work, but also work efficient? Isn't that the main reason why people pay a lot of extra money to get geo installed in the first place?

Here a customer paid a lot of money for the most expensive and most efficient heatpump out there (7 series), and combined it with another small dual stage heatpump, the second most expensive one out there. So he paid a lot for quality and efficiency. At an EWT nearing 100F the EER of the 7 series drop from the "rated" EER of 36 down to an EER around 13, in his case certainly to less than an EER of 10 due to the inefficient pumping solution. This is worse than a standard A/C!

His initial problem are high loop temps early in the season. The problem he might not realize is that the efficiency is shot.

So he has not enough pipe in the ground, the loop is too shallow and the stacked design diminishes the heatsink performance. Having a balance valve on each circuit on the source side is bad, having 2 balance valves on each circuit is very bad. So is pumping permanently through all heat pumps when only 1 is calling, especially with a constant speed pump combined with a variable speed compressor unit.
This is not another problem we should not point out to not beat up on the installer, who does not think anything is wrong. This is the problem!

We all have done mistakes. I still do them! But if we don't want to hear about them, then we do not seek to learn from them.

My milage might vary.

 

All,
Thanks for all the comments from all. I think the debate that has ended up is interesting.

First, my thermostat is a WF TPCC32U01. This is what came with my unit.

Next, I may have been a little premature saying this is the first time my loop has been this high this early. Granted it is somewhat higher than previous years.

My good friend Matt Davis at Ground Energy Systems from who I got my monitoring equipment from has pulled some information for me that I will attache for you to see.

His comments were:

He looked at cooling degree days for this year and last and also the lack of precipitation this year and came up with the information in the attached file.

Let me know what you think.

 

MMMM
I love good data. Given that I am just a dumb ass well driller. That data looks like you are suffering from the oppressive heat from this year. It also shows a very nice pendulum effect between the 2 major seasons. It works. Continue to gather data and monitor and enjoy your geo!
Eric

 

Eric,
NO one is dumb in this conversation.

This data does not mean I still don't have issues and that I am not reaping the most cost effective and efficient system that I could have. From what I have heard it sounds like at this point I will have to live with some of the mistakes (loop field). Now, maybe the plumbing of the control center can be updated to be more efficient, but what is that worth without updating the loop field?

 

There is a point of diminishing return for everything we do. Fight with Mrs. Pirate, or do not. The data did not look that far off from last year given the degree days. correcting a loop design issue is not in your best interest financially. If you want to re plumb and address some of the issues that were brought to light? I would want to get a cost vs. return on that expenditure before commencing anything.

There is always room for improvement on any design/install. The trick is to not fall down the rabbit hole, with no reward, return. This is not cavalier or flippant advice. It is based on having been tasked with the very problem that you face now, almost weekly. Geothermal is a wonderful advantage over other means of heating and cooling. It is not a " net zero, or pay me back, or my energy bill will be $6.00 proposition.

I strive to find the balance between upfront costs and savings that are most beneficial to the people I work for. That is the true savings of geothermal IMHO.

Eric

 

I could not agree more. Many times an improvement is not worth it. In this case it would not have increased the upfront cost to make the inside plumping right from the beginning. Would have loop costs being higher to size them adequately? Sure, but shouldn't that be the expectation for someone who designs the ground loop? Touch to fix the ground loop. But may be the installer is willing to make the inside right? It might be worth a try. The impact on the operational costs of the pumping is often underestimated.
The data is nice, it suggests that the problem is not new, the loop was running warm before.