Michigan New Geo-Flo GPM circulation pump noise

Ok, so outside of the circulation pumps being oversized for my system I was curious how the math added up for energy cost annually for ONLY the circulation pumps. I made only a few assumptions and based my math off of DTE's current residential rates. I can use DTEs rates because all of the geothermal equipment is on a separate meter. This does not include distribution or delivery rates.

Circulation Pump draw = 800w draw for the two pumps(385w * 2 pumps = 770, rounded up to 800w).
Avg. yearly runtime = 3000 hrs.

Annual use in kWh (3000h * 800w) = 2400 kWh

Rate breakdown for seasonal use for on and off peak hours:

June-Sept (1/3rd or .333)
On-peak = 11.050 per Kwh
Off = 3.826 per kWh

Oct-May (2/3rd or .666)
On - 5.199 per kWh
Off - 3.882 per kWh

On/Off peak hrs by day
On peak = 9hrs
Off peak = 15 hrs

9/24 = .375 or 3/8ths
15/24 = .625 or 5/8ths

June-Sept (.333 * 3000 = 999)
On-peak = .375 x 999 = 374.625 kWh * .11050 (11.050 cents) = $41.39
Off-peak = .625 x 999 = 624.375 kWh * .03826 (3.826 cents) = $23.88

Oct-May (.666 * 3000 = 1998)
On-peak = .375 x 1998 = 749.25 kWh * .05199 (5.119 cents) = $38.95
Off-peak = .625 x 1998 = 1248.75 kWh * .03882 (3.882 cents) = $48.47

Total Annual Pump operating cost: $157.69 or about $13/month.

To me that estimate seems extremely conservative. Am I missing something here?

Mainly I wanted to see if the kWh argument held water if I needed to take it to the installer. If that estimate is even remotely close I can tell you it is a fraction of what propane would cost me out here. Of course if I can reduce that cost by half or better then that's ideal - especially if there is increased risk for reduced life of my heat pump by having oversized circ. pumps. That alone is a compelling argument for right-sizing the circ. pumps.

Curious for others feedback. Does my math check out?

 

Some quick math:

A single 26-99 pump running at the highest speed would save over half the annual operating cost: 200/800 = 1/4 cost. = .25 * 157.69 = $40/yr or $3/mo.

Two 26-99 pumps ran in series at the highest speed would save about half on annual operating cost: 400/800 = 1/2 = .5 * 157.69 = $78/yr or $6.5/mo.

When you start to look at it that way you can really start to see the savings.

 

I am still waiting on loop configuration information from the installer - he is coming to the house tomorrow so I hope to have it in hand then.

Is it possible this installer used an oversized pump based on the loop configuration? He mentioned to my GC that he sized the pump to keep turbidity within specification, there were some other comments that didn't quite add up. From what I could gather on this forum you must keep turbidity within specification to get good heat transfer? Would you use an oversized pump to achieve this?

 

One size does not fit all. Now the need to run ROI numbers on the fix.

 

It's nothing to me as this is a brand new geo system for a brand new house. Believe when I say whatever needs to be fixed is not coming out of my pocket.

 

I agree, just saying. Good luck.

 

Take the $10 savings per month forward for 25 years, add in the average 4% increase in electricity cost annually, and you end up paying $4,997.51 more over the lifetime of the system. Just for pumping you don't need. Why?

 

Well, shouldn't the best loop be the one which transfers the heat needed with the least amount of pumping power at the lowest initial costs? A Reynolds number of 2500, although somewhat arbitrarily picked by IGSPA, is generally accepted to ensure good turbulent flow for good heat transfer, although I would argue that number is much lower. However, Why don't you ask what your Reynolds number is.

 

Sorry if I sound like I'm learning... it's because I am! I will ask installer tomorrow what the Reynolds number is.

 

I would caution you as to what you want to believe here as " A properly designed and installed " geo system. If a designer wanted to design a system to the perfection degree being bantered about here they certainly could. That is a design choice by that individual. It has no bearing on what constitutes the statement above in quotes. A quality residential design balances upfront costs with operating costs vs. the performance of other hvac methods. I refer to this as the net zero myth, and it is not for everyone.

Labor is expensive. So is the time needed to generate close out documents listed above. Someone has to pay that. You may be requesting info that was not included in your initial purchase price. Ask yourself how much more labor is required to install 2" geo pipe and fittings vs. 1.25 pipe and fittings for a small residential system. As to your pumping costs, if your system could run on 1 circ pump not 2, then pull the wire off 1 pump and be happy. Requesting that the entire flow center be reconfigured based on design opinions here is a battle you will never win with the GC and the original installer. You will never be able to litigate design choices of your installer.
Your mileage may vary
Eric

 

I certainly understand where you're coming from. I am definitely NOT asking the installer to reconfigure the entire system - yet. All I really wanted for them to do was address the noisy pump that appeared to be failing. Equipment failure for such an expensive system , to me, constitutes either defective equipment or installer error. Both of which should be addressed by the installer.

All of the other advice I've received on this forum, while valuable, is not anything I've confronted the installer with, though I did plan to gently pry him for information. Believe me I understand how trades guys work. There are two cardinal sins from homeowners: one is telling a contractor how to do their job and the other is telling them how bad/crappy/whatever they are and trying to get them to fix or complete a job to homeowner satisfaction after that.

So maybe it's worth considering my goals in terms of priority here instead:

1) fix or replace faulty or defective equipment

2) longevity and reliability of equipment due to proper installation

3) Long term cost savings versus oil and gas supplied hvac

Those are really it. The up front costs,labor, equipment, material, etc. you are referring to should have been included I the price I paid for the system. I also don't understand how the installer could have right sized the entire system without knowing some or all of the data that has been asked for unless they were just going off of their "experience".

Ultimately I was leaning on my GC to work with a reliable installer here, and didn't have any issues with other parts of the home. Both the GC and I are disappointed in the issues we've experienced with this installer. We are hoping the installer addresses the issue with the noisy pump first and foremost and then we'll go from there.

 

Installer sent some guys out this morning. They replaced the bad/noisy pump, flushed lines in the house, and also provided the loop worksheet.

The pumps sound 1000% better. On top of that the guy the installer sent out lives about 1 mile away and gave me his number if I ever had any issues or questions.

So for now I feel good about the system. It has been performing well (providing good heat in single digit temps here in Michigan) and now the noise is gone.

Here is the loop field worksheet though I'm still trying to make heads or tails of it:

 

Their own worksheet shows that at the 9 gpm required for the 3-ton system, it is right on the pump curve of a single 26-99. see the pump graph.

 

I see that. What I want to know if there is any significant benefit/disadvantage, besides concerns about energy consumption and equipment wear and tear, to having (2) oversized pumps?

I want to assume that the installer installed the pumps they did in the configuration they did for a reason. I feel like I am running out of room to complain to the installer here if my system is meeting my HVAC needs, on top of replacing the noisy pump. Of course I would like to squeeze the system for optimum energy efficiency and also not reduce the life of my system, but again energy efficiency is relative to what I would be paying in propane/wood burning costs. And I have no basis to argument for equipment longevity other than tossing some numbers up at the installer and saying, "These aren't right!".

 

Eric, good points. We all live by them on a daily basis. The question is "What is the standard?" and do we own a customer what you call a quality residential design. Indeed, many times it is a balance of upfront versus performance.
In this case it is not a balance up upfront costs, a 2 pump 26-116 flow center is the highest costing solution apart from variable speed inverter driven technology. Unfortunately it is also the least efficient one, without a good reason to put it in. One did not have to play with the cards he had, this is a new built house and a new built system. And specifically in the ever important comparison to other HVAC methods, why would you make a system inherently inefficient without having to do so?
Take into account that this is 3 ton residential new built. These are cookie cutters. For drillers it usually means 1 borehole, 400-450 ft deep, 9 gpm, combine it with a single 26-99, and you will be around 10 gpm, plus or minus 1 gpm. It is not rocket science, it is standard practice. You don't have to do a pressure drop calculation, you should know that putting 3 flow circuits of 0.75" pipe and combining it with a single 26-99 will get you to the required 9 gpm.
This is not about design perfection, this is about the minimum standard which should be expected by a customer. To earn a perfection degree, you would have put in a variable speed pump doing the job with 50 watts. This is not what we are talking about.

So is commissioning of the unit the standard? Actually it is and it is required for the warranty. The industry calls that quality control and quality assurance. It takes 10 minutes to commission a unit, measure flow and temperatures, and to calculate the heat extraction to ensure the unit runs up to the specs. Much higher flow would have been surfaced.
Also in this case, their own documents now shows that a single 26-99 would have been enough, and they though they put in a dual 26-99, when in effect they put in a dual 26-116.
I personally think we own our customers the promised efficiency on high priced geo systems, after all this is why most customers decide to get them. It is not a legal issue alone, it is a moral and credibility issue. So yes, my milage might vary from others.

If my company for whatever weird reason would have installed it this way, I'd be coming in with my tail between my legs, apologize profusely, hope that people understand that humans make mistakes, put in a single 26-99 flow center, and make good on the customer. I don't even understand why this is a discussion, and why my milage has to differ.

 

There is no downside to over pumping, except earlier erosion of the heat exchanger coil, and significantly higher energy bills. I think the rest I answered in he post above.

 

To the OP, I meant no offense only a better understanding of the info being provided to you. I think you have all the info and smarts to do what is right for you and your system.

Now for Doc,
Being a leader on this forum comes with a level of responsibility that you time and time again fail to exercise. You constantly tell people that if their system was designed correctly, implying that if it does not fit your cookie cutter design parameters that work for you in your local are not met in other locals, it is inferior and incorrect. Please stop. People come here looking for information and guidance. Your mantra leads them to believe that their systems are incorrect. It is irresponsible based on location. That is why your mileage does vary from other locations. If you asked me to drill 1 borehole to 450' for a 3 ton system in my area, I would fall off the rig laughing. To steal a line from the realtors, it is all about location.
P.S. Geothermal does not have to be expensive, installers and drillers make it expensive.
Eric

 

Well unfortunately, that called-on-the-carpet moment was long overdue for sure!

Thanks for your leadership Eric.

Warm Regards,
IronOak

 

Eric,

maybe the 450' borehole was a bad example, but this is why I said "usually". It is a good rule of thumb and works in most location, and no, I don't want you to fall of the rig. Pressure drop is independent of location, and I challenge you (or others) to come up with a loop design for a 3 ton, 9 gpm system which cannot be served by a single 26-99 pump. It is one of the smallest systems residential multistage systems (except a rarely used 2 ton) and wether you put in 1.25" of pipe in a single 300', 400' or 500' of 1.25" pipe, wether you put the same amount of pipe in (2) boreholes, or in 3 boreholes, wether you use 0.75" pipe in 2, 3 or 4 boreholes, wether there are now 100', 200' or 300' deep, you will always end up between 8 and 11.5 gpm with a single 26-99. No matter how you design your loop field. No matter where your location is. It is really hard to screw this up to not make a 26-99 work. As I said, I sometimes feel guilty to "waste" 230 watts of a 26-99 since a smaller pump would do the job too.

While you take the position that this creates the perception that people believe that their system is incorrect, and call this irresponsible based on location. What am I am missing here? No matter what your location is, no matter what size loop you need anywhere in this world where geo is doable and makes sense, a 26-99 pump will provide 9 gpm +/- 1 gpm, or even a bit more.

Now, indeed someone comes here for advise and now has a pumping solution using 3-4 times as much electricity as needed. Shall we tell him, or shall we just pretend we don't know better, and that everything is fine. We would just lie to ourself. Then we are not better than those who give geo a bad rep.
People who don't seek better, or don't understand simple physical principles about how to deliver those systems so they work well and efficient, are detriment to the industry.

Geo is expensive, but people who buy them know that ahead of time. They rightfully expect a return for their investment, by expecting an efficient system. What they don't know is that not all systems work efficient, because some people do either lack the know how on how to make them efficient, or know better but decide to cut corners. And I am not talking about a healthy compromise between upfront cost and efficiency.

On a side note, the physics do not change with location, pressure drop calculations do not change with location, nor do the flow requirements for a 3 ton system change with location.