Replacing Heat Pump - Question on Balancing
Hi, I have been reading through a number posts here which have been very helpful to me in understanding what things to consider when replacing a system, but I still am having trouble deciding which proposed system to go with.
I have an 8-year old heat pump that is leaking R-22 and has had other repairs needed in the past, and I have decided to replace the system due to the cost of maintenance this system has required. I have estimates from two reputable companies, one offering Trane and the other Lennox. One did a load calculation and the other will prior to installing the system, so I feel confident in the sizing, although one wants to install a larger heater package (20 kW vs. 15 kW) per his calculations. The new heat pump will most likely be a 4 ton, 2-stage system (from previous 3.5 ton). The company that did not recommend changing the heat strip size (until the calculation was done, at least) mentioned that typically they install 20 kW heater packages on 5 ton systems, due to the airflow required (is there a minimum airflow required for a 20 kW heater?). Current return is 20x14 and an 8" will be added to this same duct to serve the basement.
The Trane dealer is offering the 15i or the 16i with the Tam7 air handler and XL802 thermostat. I asked about the XL803 thermostat, but he said that for our area (Maryland) Comfort-R works very well. He also offered the 20i which came in a bit more than the Lennox XP21, but I don't think I want the complexity of 2 compressors, added controls, etc. Can someone explain how the XL803 can handle staging of the 16i? I understand it will use high stage when needed, but I was not sure if it would down-stage also or whether it would allow the setpoint to rise by a couple degrees before engaging 2nd stage. These were my main concerns.
The system I am considering from the Lennox dealer is the XP21 with the CBX32MV air handler and iComfort thermostat. This dealer plans to replace the current trunk dampers due to 1 of the 3 being broken and given the accessibility of them once they get the system out. The Trane dealer actually wants to use a balometer hood to balance the airflow of each register, but remove all trunk dampers. I was not sure how the system could be fully balanced without the dampers -- I do know that some of the registers are balanced with bended metal plates just inside of the register, so I guess the idea would be to adjust those. I'm not sure how he plans to permanently balance each register without accessible dampers -- has anyone used one of these devices on residential systems? He would also do a Manual J. This sounds like a great course of action to get the system balanced, and they would credit the cost of these services if we went with them for the replacement.
These two companies were very thorough and both brought up good points, particularly regarding a few ductwork changes. There are just a few things that I wanted to clarify, and I also wanted to see if anyone had any opinions on the equipment offered. I understand the Lennox control would be more sophisticated, but like the idea of aluminum coils in the Trane units. Both systems have 10 year parts, 2 year labor warranties with extended warranties available.
To summarize my main questions are: 1. 15 kW vs. 20 kW and airflow required for 4 ton, 2. thoughts on the method of using a balometer hood to balance each register but removing the 3 dampers close to the air handler vs. just replacing the dampers only, 3. opinions on the XL16i, Tam7, XL803 system vs. the Lennox XP21 iComfort system -- particularly whether the 803 thermostat offers good control over the 2-stage system with Comfort-R.
Thank you for your time and advice. I tried to provide as much information as possible, but can provide more if needed -- both proposals include a complete change out of existing equipment, new lineset, thermostat, air cleaner, etc.
The xp21 is a more efficient unit ,as for the heat strip size you want enough strip heat that if the outdoor unit breaks you can heat the house on emergency heat also the heat strip can be staged so you dont have it all just for defrost .the main difference in the 802 and 803 is the 803 has a humidistat and the thermostat will under cool to maintain humidity level .im not up on the lennox icomfort but i beleive it will slow the blower to lwer humidity .
Thank you for your reply - the Lennox dealer spoke of the benefits of the iComfort system, particularly in its ability to control the humidity in the summer time. I believe he said it does slow the blower down to accomplish this. The consensus seems to be that this ability to control the blower speed to dehumidify is an advantage over the Trane system, which would use the 802 or 803 thermostat and Comfort-R. I would like (and am led to) believe that both methods would be sufficient and an improvement over what we have.
I am leaning toward the Lennox system, but can anyone give their opinion of whether my ducts could handle the airflow needed for a 4 ton system with 20 kW backup heat? Both companies agreed the ducts could handle a 4 ton, but the Trane dealer worries about having enough airflow (2000 cfm) for the 20 kW heater. How much cfm is necessary for the 20 kW heater? I know the Lennox EvenHeater system is included.
Return: 20x14, split going upstairs and main level; 8" tapped into this just before the media filter
Supply: 14x8 transitioning to 16x8 for first floor, 12x8 for upstairs (?) and 8x8 for family room.