Choosing an HVAC system (size, that is)

[blackhat]

It is with a 2 stage.  Disable second stage cooling.

OP, You're probably looking at a 90ish,000 BTU furnace to have enough blower for the HP.  A 2 stage furnace would be my first choice there with an ECM blower.  For staging, insist on either a 2 speed compressor or one with unloaders, not bypass.  Discuss how you are going to control staging, run time, temp difference inside or temp difference outside.

[fredhargis]

The furnace would likely be a 120K btu for the 5 ton HP, 100K for the 4 ton, and labeled a "modulating" furnace (variable output). It will heat as low as 60K btu. The transition from HP to furnace is another variable. It can be set to transition on a programmed logic (not enough heat rise from HP, cut over to furnace) or a set point (also variable). Yes, the blower is ECM, and the furnace will have outside temp sensors for the control. To Roly, yes, I am saying I want less cooling BTU's, so the unit will run longer and dehumidify. Also bear in mind, I don't live where it's 100º 25 days a year. We've had summers where we just barely hit 90 on a couple of days; so I'm cooling (to dehumidify) down to temps in the low 70's. OTPH, we do get some winter storms with wind chills down to -35º, so I darn sure want adequate heating. Fixtureman: the replacement unit will be staged, so i can have the upper output exceed what i have for heating, but be lower for cooling.

[blackhat]

Buy beg or steal the longest warranty you can get.  Repair costs on modulating furnaces are horrific.  IME a major component can easily eat 10 years worth of the energy savings over a 2 stage.

[fredhargis]

10 years parts and labor long enough? That's what they come with. Hooked to the HP, I wouldn't expect this one to run more than 10-20 days a year (that was my experience with the last split system I had).

[blackhat]

The furnace blower and circuit boards are going to be involved in every cycle of the system. 10 years is the best you'll get. Put a good surge protector in front of the equipment.

[fredhargis]

Thanks. Lots of useful stuff here, though I still haven't pulled the trigger. I think I'll decide early next wekk so i can get going on the installation.  Thanks to all for the advice!

[JamesWhitlock]

See basically there are n number of unit are available in the market now a days. So choose wisely between these choices if still you are confused which system will be suitable for your home then consult some professional to give you the proper advice. Such things happened to me in case of generator maintenance NJ.

[fredhargis]

I guess I'll conclude my part on this: I've decided to go with the 5 ton system, despite my reservations about the cooling being larger than I want. With a 2 stage HP the lower stage should do much better than the current system, but if not I'll add a high quality dehumidifier to the house. I'm going with the firm that installed my last system, pretty much the same thing except size, 6 years ago in our last house. The equipment will be Carrier, and the installers I know to be top notch; which is really why I picked them. One of the other quotes I requested never replied, and and a third was a joke (not cost, a long story for another post).

[fredhargis]

Thanks, I wasn't really considering a consumer level dehumidifier, at least I don't think I was. Something more like a Santa Fe or maybe an Aprilaire. But I'll ask as we wrap up the details.