OK, HVAC pros out there here is my question. In January of 2020 my home was hit by lightening it took out my 12 year old Goodman 4 ton single stage heat pump system. I had it replaced with a Trane 4 ton multi-stage unit. It is costing me more to run the Trane than it did to run the Goodman. I have had the installers back and they blamed it on fan speed, the fan was not speeding up when the compressor did. They adjusted that but I have not seen any improvement in my operating costs/KWH. What is wrong with my Trane unit it should be more efficient. Any thoughts?????? Thanks Jim Aug 1154 kWh | $122 | 72° | Billed on 09/15/2020 1004 kWh | $109 | 72° | Billed on 09/13/2019 Jul 1149 kWh | $122 | 74° | Billed on 08/14/2020 1112 kWh | $120 | 76° | Billed on 08/14/2019 Jun 1170 kWh | $124 | 77° | Billed on 07/16/2020 1127 kWh | $122 | 75° | Billed on 07/16/2019 May 1092 kWh | $102 | 71° | Billed on 06/16/2020 887 kWh | $86 | 70° | Billed on 06/14/2019 Apr 1051 kWh | $87 | 52° | Billed on 05/15/2020 1058 kWh | $89 | 55° | Billed on 05/15/2019 Mar 766 kWh | $67 | 48° | Billed on 04/16/2020 517 kWh | $48 | 47° | Billed on 04/15/2019 Feb 786 kWh | $69 | 37° | Billed on 03/17/2020 402 kWh | $41 | 30° | Billed on 03/15/2019 Jan 1232 kWh | $99 | 30° | Billed on 02/14/2020 824 kWh | $78 | 24° | Billed on 02/14/2019
On paper the Trane 2 stage compressor should be much more efficient than the 12 yr old Goodman. Im surprised the Goodman lasted 12 years. If I had to guess Id say its not charged correctly. Tranes like 10* sub cooling. Check charge in High ( 2nd stage) fan speed 100%. Other factors could be the location of the condenser.
No Two consecutive seasons are the same. For this reason your unit may have had to work harder and consume more energy to maintain a given temperature. Plus, you may have experienced a significant rate increase after the later months of 2019. “ComEd energy price rises to highest level in four years Households buying power from Commonwealth Edison will pay 7 percent more for their electricity, beginning today. ... The cost will be 7.224 cents per kilowatt-hour, up from 6.723 cents from June through September, according to the Illinois Commerce Commission.Oct 1, 2019”
We have a Rheem 5-ton system that is only two years old. We recently found that despite the AC unit running all night, the house wasn't coming down to the set temperature. I had an AC technician out to the house yesterday; he found that a circuit board in the air handler had fried and the fan defaulted to low. The technician bypassed the board and the fan is permanently set to high. Last night the house came right down to the set temperature and the AC unit cycled as it should. If the fan was on low, both the air handler and the condenser unit will work much longer. It is also wise to get the system balanced in your house so that the air distribution is as efficient as possible. The Tech is coming back at the end of next week to do just that.
I used KWH as my unit of measure for comparison so electric rates are not a factor, I am strictly looking at usage. Each month has the average temperature shown so I can account for temperature changes. The house and duct work are 44 years old and the Trane is the third Heat Pump so I do not understand how balancing would help. I do not have the expertise to say what is wrong but I am confident I have an issue with the multi stage portion of the Trane. It was double the price of a replacement Goodman, $10,000 plus, so It will never pay for itself. Thanks for the thoughts and suggestions I really think I just bought a piece of JUNK!!!! I will get the tech back out and check the charge as suggested. Briz what is 10* sub cooling? Thanks again guys
Been an AC contractor for 40+ years. Engineers don't always get it right. But like Steve says without knowing subcooling and superheat versus design it is impossible to answer. Then there is the issue of duct size error for that particular AC unit and airflow issues not being considered. IE... I will not replace a unit in the Haile Plantation Subdivision because the ductwork in most the those upscale homes was undesized or terribly installed and there is no way to properly condition the spaces resulting in homeowners never being satisfied and mad at me. In another install a brand new air handler fan was running backwards from the factory. Their tech spent two days trying to figure why it kept freezing up. The owner knew me through a friend and asked me to come by. Took me two minutes to find the fan spinning backwards. The sad part is most techs have no idea how to diagnose heating and cooling issues. Mikey
View all Refrigerant liquid is considered subcooled when its temperature is lower than the saturation temperature corresponding to its pressure. The degree of subcooling equals the degrees of temperature decrease below the saturation temperature at the existing pressure. Subcooling Formula = Sat. Liquid Temp.
I do enjoy these lessons on HVAC . We are getting ready to have ours replaced so knowledge being power I'm feeling pretty powerful.
Freon type different- Prior unit versus current? Also average outdoor temp. did not include humidity levels. It takes more to cool moist air. Honestly though the cost and power consumption differences are negligent. imho.
Once was called in on a issue like this where the installing contractor could not figure out the problem. I spotted it as soon as I walked up. Condenser was placed in an area where it got very little fresh air flow and there was a low hanging awning over the top of the unit that directed the hot air back into the unit. Relocated the condenser and problem solved.
Inside the panel on the condenser outside is a psychometric chart for determining subcooling temps. Here is a very good layman's explanation. https://www.acservicetech.com/post/the-hvac-subcooling-charging-method-explained Mikey
Thanks for all the information. I have learned that a good HVAC tech is a very hard to find and has a very specific skill set to do their job. I will get it looked at again to see if my Trane unit can work as well as it was supposed to. Yes the electric usage is minimal but I spent twice the money to get a efficient system that can not equal the efficiency of my old single stage. So I am out the 5K plus the extra electric charge each month which aggravates the hell out of me. Thanks again if I get it working right I will let you know. Jim Great article Mikey
In most cases when a customer ask me about super high efficient systems I tell them its not really worth the additional expense and they will in most cases never see the ROI. In your case you should see a savings on the improved SEER rating alone even if you purchased the base 14SEER equipment
I wish I had thought to ask here before I had the new Trane installed. But I was in SW Florida and had a house without heat, in the middle of winter, back up in Illinois. I made a mad dash North before everything froze, so not much effort was put into researching my replacement. Thanks again Jim