1. You are asking about the "balance point" which is the temperature at which the heat pump can no longer provide enough heat for the home. The balance point is based on several factors including home construction, insulation, windows, ductwork, heat pump btu capacity, etc. I would start at 30F and take it from there. You may be able to go to the upper 20s if you have a well-insulated house. Propane is one of the most expensive fuels for home heating. Heat pumps are the least expensive way to heat a home. You need to maximize the use of the heat pump for low operating costs. 2. If the house is all-electric, the auxillary strips will automatically come on to suppliment the heat pump. A new digital thermostat will sense that the house is losing heat and cycle the strips on and off to help the heat pump. With an old mercury thermostat, the house has to lose 2 dergrees before the aux heat comes on. Make sure you have a digital programmable thermostat for your new home. You can turn off the heat pump by switching the thermostat from "heat" to "emergency heat". I think that this is what they were trying to explain to you. A heat pump is always cheaper to run the straight electric resistance. As outdoor temps drop into the single digits, the heat pump puts out cooler air and it runs constantly. Some people shut the heat pump of at these temps for these reasons. 3. I would ask April Aire directly. Best to you.

I am thinking of going with the company that has proposed installing the duct work in the attic, plus switch out the equipment. So currently, I have: 2 ton carrier AC unit ('91) 3 ton ADP coil ('06) 80,000 btu trane xp 80 furnace ('07) The proposal from company #1 that I am thinking of going with is for: 2 ton carrier perfom. 16 #24ACC624 66,000 BTU (80% efficiency) furnace #58CVA070-12 2 1/2 ton coil (#cnpv3014). Cost w/ duct work $8800 I had another company propose to put in a 3 ton carrier system, with a 3 ton coil, and 2 stage variable furnace, 70,000 btu. The cost for this (no duct work) would be $9300. I am leaning towards going with the company that will provide equipment and duct work for $8800, but I am wondering: - why am I going from a furnace with 80,000 btu to a furnace with 66,000 btu? Is more btu's better? - is the use of insulated flex duct and metal splitter boxes standard in attic installations? Are there any downsides or upsides to using this? Durability, noise? When you talk about calculations, are you talking about a "manual j"? I have asked various companies about Manual Js and have been told that they are like $600, there are too many factors that are unknown like wall insulation, and that a similar calculation was done when the house was constructed ... so I get the sense they are not basing their estimates on such a calculation.

Yes - that is the other reason I bought the Broan. I only had to make one 6 inch penetration through the house which has a stone veneer on it. It wasn't easy, but I made a perfect 6 inch hole through 1 large piece of stone - got lucky. Doing two of those perfectly would have been too much to expect. The Broan vent is very interesting. It is an areodynamic design that pushes stale air upward and takes fresh air from below. Seems to work just fine. My Honeywell Vision Pro IAQ stat has a dry contact relay on the interface module for the Ventilator (it also has relays for a De-humidifier and Humidifier). When you program the stat for the Vent, it turns on the HVAC fan and closes the Vent dry contact. I programmed my 2 IAQ stats for the Vent, but they don't know that the ERV is not attached. I just use the HVAC fans to circulate the fresh air coming into the basement from the ERV to the rest of the house. To connect the ERV to my HVAC system, I would use a RIB 110V Relay with dry contact activation. I would connect the dry contact inputs on the RIB to the IAQ interface module Vent contacts. When the IAQ Vent dry contact closes, it would thgen activate the RIB relay which would and power up the ERV. The only problem with this approach is that it would probably mess with the Broan controller timing while in Auto mode. When you put the unit into Auto, it has a 20 minute ON, 40 minute OFF or Recirculate cycle. It also has the tempreture limit settings - the unit runs for a few minutes and sense the external temperature. I fthe limits you set are exceeded, the unit either shuts off or recirculates. When you remove power to the controller (which would happen if I used a RIB relay to periodically provide power to the ERV), I am not sure what would happen to the Broan contoller internal timers - probably a reset. I was told by the Broan engineers that the unit was designed to run constantly and they recommended the standalone mode. I guess they added the Auto mode becuase there probably are some instances when you don't want the ERV on. For exmple, when it is zero degrees outside, I want all holes into my house plugged up!

Sorry for delay and thank you for your interest brickeyee. Aprilaire Humidifier model 760 flow through system. When HVAC was here in September doing fall furnace check he installed a new AA feeder tub ("NP OTP" on bill), saying the old rubber tube may have weakened and splayed at its end over the years and pose a water leak risk. He also put in a new water panel and #35 pad. There was no discussion of the Solenoid valve assembly nor of the water inlet orifice. No problem was noted on testing the humidifier except for water leakage from the gas water heater branch supply: the "saddle" valve controlling hot water supply to the dedicated humidifier line leaked. All was turned off until further investigation of this saddle valve. Below are pictures of the water valve above the gas water heater: some say it is a saddle valve (which, as all or nothing" is not allowed I gather) and others, including the company's plumber say it is a turn valve. The company plumber tightened up the nut a bit on Friday and the leak seemed to stop. The system was turned on for test, but after the plumber left I noted the continuous water running to the humidifier, heard it spraying into the box and saw the constant stream from the outlet to the sump pump so I turned it all off again. Here are key points Aprilaire owner's manual makes on the 700 models: "The correct water flow is determined by an orifice equipped with each drain type humidifier. When the humidifier is operating, there will be a small, steady stream of water to drain, which flushes away most of the trouble-causing minerals. Do not use the saddle valve to regulate the water flow. It is designed to be completely open or closed." Here are some photos-sorry can't seem to resize them on PB: http://www.aprilaire.com/themes/aa/en/manuals/Owners_%20Manua_Model_400_%20500_%20600_%20700_10006899.pdf to be completely open or closed." Basically, the Aprilaire Humidifier looks like this and has separate humidistat on return. Thanks for any advice.