Brand new variable speed furnace only running at one speed
So, I spent $600 more and decided to go with the ECM variable speed furnace. It is a Rheem Prestige 80 two stage (photo below) paired with a Honeywell RTH6350 thermostat with fan set to Auto. Problem is, it doesn't do a soft start or soft stop, rather it immediately comes on full speed and then immediately turns off when the thermostat temperature is reached. I certainly notice when the second stage kicks in, but as far a variable speed, this blower is acting NO differently than the single speed furnace this replaced. The furnace housing says variable speed on it, and the motor itself says ECM 3.0 on it, so I have no doubt a there's a variable speed motor in there. Do I need a special thermostat to achieve more gradual ramp up/down speed or is the control board inside the furnace responsible for that? If it's the control board's job, might there be a dip switch setting to adjust this? I did a lot of research before deciding to pay $600 more for the variable speed motor, but I am not convinced I am receiving all the benefits it has to offer. Sure, subtle speed differences when filter is clogged will be extremely difficult to notice, but I assume there should be little more noticable variation in speed when it cycles on/off throughout the day than what I am experiencing. Any advice on how to troubleshoot this or potential ideas on why it's not performing a soft start/stop would be much appreciated!!
Comments (10)
mike_home
8 years agoRelated Discussions
Variable Speed / TWo stage...come on!
Comments (15)"Variable speed will make me more comfortable and is more efficient---still no explanation as to how" - In the summertime, a fan running on lower speed for longer times pulls more humidity out of the air. In the winter using the heat pump, you don't get the blast of cold air at start-up because the fan gradually ramps up. These are the "more comfortable" part. Since it is a DC (direct currrent) motor, it costs less to run than the typical AC (alternating current) motor. This is the "more efficient" part. Not sure that the variable speed motor will help you at all with floors seeing different temperatures as Daddo stated previously. Ceiling fans will help this and so will running the furnace fan all the time in the summer. The key is to circulate air thru the house to try and equalize temperature. "Variable speed is a gimmic that actually costs more to operate." - This is Bob Brown's opinion. They cost more to repair for sure, but you have to do some experimenting to figure if they cost more (based on run time, power consumption, and cooling effect). I chose not to get a variable speed with my new heat pump. The air handler that I bought has 3 fan speed settings so I get to play with only 3 speeds. The Goodman variable speed air handler has dip switch settings for 4 fan speeds for each mode: heat pump/ac, heat pump + electric back-up, and electric emergency only. It also has a trim adjust dip switch of +15% or -10% CFM for the 4 settings for each of the 3 modes. For this variable speed motor, running the unit in "fan only" on the thermostat sets the fan speed at 30% of the heat pump/ac setting. You get a lot more to play with with variable speed motors. Hope this helps....See MoreNew Arcoaire Variable speed unit with Honeywell tstat - wiring/ju
Comments (3)"was told to leave humidity control on t-stat to 55% and not set it lower" Who gave you this advice? Why did you go from a 4 ton to a 5 ton heat pump? In my opinion the key to comfort and savings energy is low humidity. I try to keep the humidity in the 40-45% range. With the humidity in that range I find it comfortable at 78 degrees. I fear your 5 ton condenser will be over cooling on a regular basis. You will have to monitor the temperature and humidity to see what is the optimal setting for your house....See MoreVariable Speed vs 2 speed discussion
Comments (17)gorilla, Apparently, I don't have a choice. When the pool and spa were plumbed, they were done so as separate bodies of water. There's an overflow pipe from the spa to the pool, but they are not fully integrated. I'm told that I will need two complete systems to handle this. I'm not sure why my contractor and the pool plumber built it this way. I wasn't informed enough at the time to ask or know any better. I'll try to search this forum for info on the VF and solar. Maybe, as poolguynj seems to be alluding to, the folks trying to use the VF with solar have been using one of the lowest speeds and that has not been adequate. If you know any more, I could use all the advice I can get....See MoreWill single stage AC benefit with variable speed 2 stage furnace?
Comments (19)Your first answer confirmed that the extra run time on AC does provide some additional dehumidification but now you say it is a "gimmick" that I "fell for". Only with a 2 speed air conditioner. BUT it's still mostly a gimmick. WHY? a 2 speed air conditioner's first stage (most brands) is approximately 70% of capacity of the machine. It is more or less in dehumidification mode when the unit runs in 1st speed. (It must be a 2 speed AC condenser.) However, 1st speed turn on is not determined by humidity it is determined by temperature. Do you see the problem with that? The kick to 2nd stage is often times determined by time. Usually in the realm of 8 to 10 minutes or the temperature difference from set point to current temp of the structure (usually greater than 3 degree difference will initiate stage 2 within a few minutes). Humidity again plays no importance / no determination from ramp up or down --- it's all decided around temperature set points. How about now? Do you see a problem with that? So when in cooler seasonal temps --- the system will nearly always over cool... very much like a single stage air conditioner does all the time. PS: I'm not angry. But you should be for being 'duped', by the super slick advertising nonsense of the HVAC manufacturers. If I was angry why would I then turned around and explain things to you further so you understand the point being made here? What does 'SERVICE' mean to you? This is a service business, you will ALWAYS need service... better hope it's the kind you really want. I service the Katy, Texas area....See Morembgreen52
8 years agomike_home
8 years agotigerdunes
8 years agombgreen52
8 years agomike_home
8 years agoHere is the instruction manual for your furnace.
I found this on page 42:
So the installer decided your furnace should stay on low for 20 minutes. I guess he doesn't believe is setting back the temperature at night. What is probably happening is your furnace shuts off before 20 minutes and you never go into high stage.
You could put the DIP switches back to the factory setting, but the manual is saying it doesn't matter. When W2 is energized the furnace will go into the high stage. What we don't know is how the thermostat algorithm decides when to go from the low stage to the high stage, and then back to the low stage. This is a good question for Honeywell.
I am just curious as to why you are fixing the installer's poor installation. Is it because it is easier to fix it yourself rather than deal with him?
mbgreen52
8 years agomike_home
8 years ago
mrd inmb
3 years agolast modified: 3 years ago
tigerdunes