Considering a new furnace...looking for advice/recs

[live4ever]

We're considering replacing our 75 year old gravity furnace as part of a major renovation on the house (everything is opened up so ductwork/wiring isn't too difficult). The gravity furnace has served us well, but it's not terribly efficient, and we may sell the home in the near future and would rather just update it since we're updating everything else, as opposed to having the octopus relic remain in the garage (flashback to that scene in Home Alone...). Not to mention, getting rid of the octopus from the garage shop would clear up a lot of valuable real estate for me while we're still here!

The house is only 1400 sqft, but with a downstairs basement/in-law type of unit, I'd like to consider a dual zone system. I really know nothing about these - zoned systems to me always meant more than one furnace, lol. Good idea? Brands/models of gas furnace to consider? Ways to keep costs down (e.g. sub out the removal of old furnace and ductwork - possible asbestos - myself rather than one-stop shop? Higher efficiency units really worth it?

I'd just like some general information before I get HVAC guys in here. Unfortunately, not too many honest trades folks left in our city - and definitely not the best first source of information IMHO.

Thanks much, appreciate whatever thoughts/experience you all can provide!

[Woodenfish]

I upgraded my home's gas furnace from an 80% efficiency to a 95% single stage gas valve w/variable drive blower and A/C unit from 12 to 14.5 SEER. The home is very well built and insulated so I was able to drive my heating costs down by a fairly large amount monthly in comparison year over year. The additional expense of these units will create a savings payback to be measured in years. Meanwhile, the home's air temperature is much more comfortable and monthly energy usage is way down even considering warmer winter/cooler summer thermostat settings than usual.

If moving soon, you will not get back any savings versus the expense nor will you see any increase in home value. Having any new furnace might help in a home buyer's perceived value of your property over another and make selling it easier. I can't see any justification to install a dual zone HVAC system in a 1400 sq/ft home. You might have a air balance problem that could be easily addressed.

[live4ever]

The dual zone thought has more to do with the downstairs basement/in-law. It's a space that has been rented in the past and many potential buyers of this home would likely be looking at it as an income suite. So it should probably have its own thermostat...

[John Mihich]

With your size house you should be able to balance the zones with baffles - those can be automated.

W/O a doubt get a high efficient furnace - does save you cash each month. There are multi speed models. I went with single speed probably would have gone with multiple speed now - our house is really closed up and the slower speed would work well in our house now.

[live4ever]

So how do the multi speed models work exactly? I assume the multi-speed allows one to vary the rate of heating, and consequently the noise from the fan?

Is the speed controlled from the thermostat, or on the unit itself?

[John Mihich]

I'm not really sure except that I know at certain times the fan will run slower. I know I would love that now since I spend so much time in a room next to the furnace room.

[blackhat]

Essentially there are 2 kinds of multi speed furnaces, 2 stage and modulating. 2 stage furnaces are typically run in one of 2 modes; a single stage thermostat will start it in low and it automatically jumps to high fire if the demand is not satisfied in a set time frame or, a 2 stage thermostat starts the furnace in low or high fire based on the difference between room temp and set point. A modulating furnace starts at low fire and ramps up in a sequence of jumps based on an algorithm programmed into the furnace. Some zoning systems use a 2 stage furnace and run low for a single zone call and high if both zones call.

Consider what constitutes a legal suite, here it must have fire separations and seperate utilities including meters for each suite.

In your case I would look for an installer that does a proper heat loss calculation, has a good reputation with local referrals and purchase a 2 stage system. Insist on return air in all parts of the house.

[Robert Adams]

The variable speed fans are nice but check the replacement motor cost on one before you buy. The motors can be extremely pricey. I have seen some that are $500 just for the motor which sadly is not much different than the price of a new furnace.

[GHR]

live4ever said:

---

Unfortunately, not too many honest trades folks left in our city - and definitely not the best first source of information IMHO.

Thanks much, appreciate whatever thoughts/experience you all can provide!

---

If you are going to rent out part of the space, dual zone might be a good idea. Heat pump might be a good idea also.

I don't know how cold it gets near you. Or how hot.

[paulmaine]

My garage klunker oil furnace was replaced three years ago with a Bosch gas furnace. We gained space as two 275 gallon oil tanks are replaced with two outside 80 gallon propane tanks, The instant on hot water means the bulky water heater is gone, the bulky oil furnace is gone, and the new furnace hangs on the garage wall.

A Modine heater is on the zone previously used for hot water-this heats my basement shop.

The Bosch has a five year parts and labor guarantee. Total parts and installation was about $8600. Heating is reasonable for the large house... no regrets.