Bought this house (2400 sq ft) a couple years ago and it has an open loop system. Can't remember the name of the unit but it is a 3.5 ton off brand unit manufactured in 2004 I think. It looks like the previous owner replaced a propane furnace as the duct work wasn't upgraded. They added 600 sq ft edition sometime in 80s and the edition has a good size duct but they only ran it in the new edition and connected to the plenum on the furnace with two 8" flex duct hung terrible. Needless to say they added 2 electric baseboards and a window AC unit in the edition. I was able to rip the flex out and put in trunk duct from the plenum to the existing duct in the new edition. This helped with keeping the edition heated but the other side of the house has suffered a little as that duct is still undersized. Now I believe the return is also probably restricted. Last year right before the real frigid cold hit I had a fitting fail right outside of the well casing and the 4" well pump burned up pumping all night with no real load on it. Early on last year I noticed the thermostat that I was using didn't have enough adjustment and I was using some setback that had the 10kw electric backup coming on as the geo was taking too long to warm the house. I got a better thermostat, ditched the setback and all through the frigid cold later in the year the unit never needed backup heat but I keep the house at 68F with a droop of 1.5 degrees. The backup was setup to turn on if the temp drooped 2 degrees from setpoint. The unit still seems to run fine and this year I have worked on documenting stuff so I can track the changes. So now I have a water meter and a temp sensors to record what the unit is doing. I still need to hook up the current sensor so I can track electrical input but the unit seems to be running at a lower output than what the model number says it can do. I was happy with the bills last year as with the real frigid cold my highest bill was $245 with an all electric house. That was about what I would pay for electric and natural gas at the old house with a decent furnace but it was only 1400 sq ft. The numbers I am getting now are EWT 55.74 LWT 41.23 GPM 3.5 Suppy 89.49 Return 65.86. My calculations show just a little over 2 ton pulled from the water. Flow varies from 3.0 to 3.7 gpm depending on pressure of the bladder tank. I am surprised I was heating the house last with 2 tons so I am not sure if performance has degraded or that is just what it is. Do my numbers look right? Isn't that pretty bad for 42K unit? Still need to get current in to calculate COP. Any suggestions that I should look at doing? Still working on the program and haven't got the error handling yet but you should be able to see it real time here if it hasn't died: https://freeboard.io/board/urZVyI
I dug up some whole house power plots from last January and it looks like the geo is using ~3700 watts and then another ~950 watts when the well pump is on. House idles around 350 watts at night. From those numbers it looks like the COP is around 2.0. I need to get all the data back in one spot and taken at one time so the numbers are calculated all at once. The 30 minute run time below is 17F outside temps. I also did find the Model #VPY042C01AR. Date of Manf. March 04. Addison Products Company Orlando, FL 32810. The well has iron bacteria but I don't see fouling in the coil. I am guessing the unit has never been flushed. Do you think I should start there to see if I can bring performance up? I know the water flow is lacking but I think I can increase that to 5 gpm pretty easily. Just hooking a hose to the outlet and double checking the flow of the water meter I can get almost 5 gpm as they ran 1/2" line to and downstream of the unit.
If your numbers are correct you are extracting 25, 392 BTUs/h, which seems fine for 3.5 tons. Add the 12,324 BTUs/h from the compressor, assuming that all the electricity is converted to heat, the unit COP is 3.06, add the well pump and it is 2.45. Not very good for an open system.
Okay I think I understand it a little better now. I was thinking the heat absorbed was the output of the unit. I was trying to figure out why a 3.5 ton was only doing 2 ton. The energy from the electricity goes somewhere so it needs factored in which I didn't understand. I assume that includes blower power not just the power to run the compressor? I have a current sensor that I would like to hook up yet but my current data device doesn't have any built in AD converters so I'll have to switch devices over. Do I just place the sensor on the one leg of the 220 feed line or only the compressor line to not include fan power? Just taking a quick look at a newer piece of equipment's specifications a 3.5 ton unit is rated at 37.5k total output at 50F EWT and 68 EAT basically the standard ground water rating. The heat absorbed is 28.3k and it says the power input is 3.08 kw for a COP of 4.1. So my unit is using more power to absorb less heat from the water compared to the unit above and my EWT is 5 degrees more than the standard rating. Is this just from being 10 years old or can there be other reasons? If I get my flow up will that increase heat absorbed? I guess if that doesn't increase the compressor power then I would be better off except at the expense of some more pumping losses. I am just trying to get an idea of where this unit is at. After I adjusted some controls last year it seemed to do pretty good even with the frigid winter. To keep the house at 68 I never electric backup heat which when I moved here I figured I would need since all the rooms in the newer addition had electric baseboards and the geo has 10k backup also (although something is wrong with it as one of the coils is grounded somewhere). I also kinda hate to replace something that isn't broke unless I am sure I will see some good benefits.
I would love to understand your monitoring system. I have a similar open loop system and monitor everything but have no way to connect to my computer which at this point is dedicated to the cameras. I do have visual monitors and a camera so I can watch while we are away. I think this is key to getting these systems to optimal performance.
I've kinda just put something together. It depends on how much you want to fiddle and if you don't mind learning a little. The Web Energy Logger is your best bet if you want something out of the box and you don't have to tinker. http://www.welserver.com/store.htm It doesn't include a flow meter so that would be additional cost. In my open system my flow varies with the cycle of the pump and pressure tank so I decided to get a meter as I also wanted to see how much water it uses. If you want to save some cash and don't mind learning a little bit you can put something together using a Raspberry Pi computer ($40). I have mine tied in with an Ethernet cable but you could pick up a USB wifi dongle for $12 or so. I bought a 1/2" 1 pulse per gallon meter for $90. My lines going to and from the Geo are 1/2". In hind site I should have paid $20 more and got the 3/4" model. I have been looking at my system overall and I have found I have 20 psi on my exit line from the flow and head loss of the 1/2" pipe. I am looking at ways to minimize pumping loss also. The temp sensors are 1-wire digital type and I have two of TSENSE-SS1-1M like what welserver sells in their store for the EWT and LWT. I also had some bare 1 wire sensors that had and used them to make the supply and return sensors. The Raspberry Pi is basically a small Linux computer. I wrote the software in Python. The dashboard is a free website where you can push the data to. I also have written to google drive spreadsheets if you want to save it for long term. I am not a professional programmer and have just kinda learned python from tinkering in past year or two. There are plenty of tutorials online. When I decided to hook up the flow meter it took about an hour to get it reading in the Pi but 1/2 hour was spent figuring out that I had a stuck reed switch that does the pulse in the meter. Getting the data to the dashboard that I screen capped above was just 1 line of code after you install the module. The Pi is a wonderful learning device. Let me know if you would like more details. I can even give you the Python code or the whole list of items you would need.
Thanks, I did look at the welserver and it looks interesting. I am some what familiar with sensor based computer systems and would love to tinker a bit and build my own. I have not done any programming for a while but I am sure I could get up to speed on a new language. It will have to wait though as I am on a mission to finish our house. All that is left is the upstairs trim. Currently I have Cu temp wells on the water in and out with Ranco temp controllers/monitors so I can automatically dump water to keep the well at temp. I purchased a 1" flow meter which I use to set up or adjust the flow. We have a constant pressure pump in the well that can deliver 20gpm so the flow is very consistent. I am using remote wireless temp sensors in the air plenums. I measure the current for a given setting with a fluke meter at each point so I can optimize. I would like to add the heat pump pressures and temp (for superheat and sub cool) so I could watch it real time as well but the delta T's are OK for now. All theses visual readings are monitored on a panel with simple cameras hooked to a base computer that I can log into and watch remotely. It is a bit of a kluge but after calibrating each sensor and watching it for this past year I have a good idea how the system is performing. (Not as well as I wanted but very comfortable) This summer I may decide to remove our current Geo Heat pump 5T and replace with a 2-2.5T. The house has out performed the Manual J prediction by a mile but now we know it is not just speculation. When I do that I will see what I can put together to have a good real time monitoring system that logs all the data and I will keep your offer in mind. Thanks Dan
Sounds like you got most of the stuff already just need to get it into one spot to monitor. If you have had any type of programming you can pick Python up easy. I have only had formal Fortran programming long long ago. Pick up a Raspberry Pi at http://www.adafruit.com/raspberrypi now sold on Digikey also. Adafruit has great tutorials and that is where I found how to read a pulse into Python using an interrupt while the main program is reading temperature sensors and updating the web dashboard. Check out this page as they do a really good job at helping a person learn: https://learn.adafruit.com/category/learn-raspberry-pi Here are the temperature sensors I use for the ducts and the EWT and LWT. https://learn.adafruit.com/adafruits-raspberry-pi-lesson-11-ds18b20-temperature-sensing I also bought my EWT and LWT sensors there but didn't realize they were 6mm and not 1/4". Had to clamp down on them a little more than usual to prevent a drip here and there. Fun fun.
Thanks for the links this sounds like fun and lots of toys... We are about to heat south for the rest of the winter and this would be fun to play with an prepare for when we return. Thanks bunch, Dan
