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Completely confused about new furnaces. Help me please.

Meljean Member Posts: 2
edited April 2019 in THE MAIN WALL
I am at a loss about what to do. We need a new furnace and central air unit. We are on propane in this town which is in a rural county in NW MO. The house is over 100 years old, Dutch Colonial. 1536 sq. feet. Furnace is 40+ year old Amana, not sure on AC. Most of house is off of one breaker meaning a small electric space heater will trip it, until 4 years ago, fuse box was the old glass round fuses. New breaker box installed then and breakers put in but wiring is what was in house when we bought it in 2006. Insulation will be blown into attic when find someone to do it. Main part of house is 12 inch or more walls. This past winter was hard and used 1800 gallons of propane, of which 250 is still in tank, so 1550 gallons of propane. Winter here was brutal, temps consistently below 10 degrees F for weeks at time, 2 months of that, and lower. House is not completely tight around doors, windows sealed with plastic. 2 bedrooms upstairs of which one has vent shut, although not completely due to style. Other bedroom vent maybe 1/4-1/3 open on the wall which keeps room okay. At some point both of those won't be used, spousal unit is 75 and stairs won't be an option anymore. 10 floor vents downstairs. 1 wall vents in each of the 2 bedroom upstairs.

I have spoken to 2 heating contractors for costs and installation. I have gotten conflicting information, and am not sure what they are talking about to begin with in much of this. Hence my plea for help.

Things I do not understand: Heat loss per hour. HE Furnaces run most of the time to heat. Pipe is exhaust/drain pipe out side of house. Can't use the old chimney flue. Furnaces have lockout system now and shut down if load isn't right. Using propane ventless space heater to supplement heat downstairs will not tell thermostat house is warm. 95% of heat made will be heating the house versus maybe 50% of it now going to house. Condensation is a problem with new furnaces, and pipe needs to be run slight angle 1/4in per foot back to furnace. Will furnace running more be expensive on electric. Do they make no 'simple' furnaces now.

One has said will need PVC run across ceiling to wall and out for 95% HE furnace. He did the calculations and said 77,000 BTU 3 ton 14% would be his choice, Rheem brand. He said doesn't see cost effective way to be able to use a 80% furnace that won't have to have PVC pipe run across the ceiling. Has been in business 20+ years. Can put it in first week of May. He came out to make estimate within days of calling him, and got back to me same week with recommendations.

The other said 80% furnace, he installs Lennox, would not have to have pipe run across ceiling to vent/drain outside. And could use the old chimney flue being used now for this old furnace. He is much newer to this whole thing than the Rheem man. He took longer to get back to me about estimate and didn't call to tell me he wasn't going to come day he had said first, he did come week later and look at this, I haven't heard back from him on recommendations at this point or timeline of when could install. He is young and maybe done this under 5 years.

This is a big expenditure of course but main thing is I want to make sure this makes sense to people who understand what is going on. I understand horses, sewing, pets and some other things. The only thing I understand about this is I understand nothing at all.

Any help would be greatly appreciated.


  • Jamie Hall
    Jamie Hall Member Posts: 21,106
    Well let's see here...

    First thing: please stop using the ventless space heater. They are OK for barns or garages or sheds, where there is plenty of ventilation -- but not in a house. Even the best of them produce some carbon monoxide which really isn't good for you even in small concentrations, and reduce oxygen levels. They are not meant for routinely occupied spaces. (I don't care for them in barns, either -- fire hazard).

    OK. That's off my mind.

    Heat loss per hour -- usually quoted as BTUh. This is the single most important number in sizing a hot air furnace or hot water heating system. It isn't that hard to calculate -- there area several on-line calculators which do the job (I like the Slant/Fin one, but there are others). The heat loss is determined by the size of the building and how the walls and windows and all are built and insulated. The first thing any contractor should do is to do this calculation (you can probably do it yourself, just to check) -- otherwise the furnace or boiler size is just a guess.

    High efficiency furnaces produce relatively cool combustion exhaust -- that's how they get the high efficiency. It's also why they generally use a direct vent exhaust and inlet -- as you note across the ceiling to the outside. Indeed, in most cases they really shouldn't be used with a regular chimney -- unless it is specially fitted -- because the exhaust has water condensate in it which is very corrosive and ruins regular lined or unlined chimneys very quickly. The intention is that that condensate runs back to the furnace (hence the slope of the pipe) and is collected and disposed of; there are various ways to do that.

    Non high efficiency, non condensing furnaces can use a regular chimney -- if it's properly lined and in good shape. Don't take that for granted!

    Do they make simple furnaces any more? Um... well, not really. The various mandates for higher efficiency -- both economic and often regulatory -- makes it so they really aren't usable. The upside -- they use less fuel. The downside -- they take more, and more careful maintenance and often don't last as long. It is what it is.

    Will a new furnace, either one, use more electricity than the old one? Most likely not -- in fact, it may use less.

    Both Lennox and Rheem are good, established makes. Because these things do need service -- and occasionally repair -- I would suggest going with whichever supplier you are most comfortable with. Age is a recommendation -- but a young person starting up may be more familiar with the newer equipment; can't tell just by length of service!

    I doubt I've answered all your questions or doubts -- come back with more or different as need be!
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    JUGHNE Member Posts: 10,568
    A point sometimes overlooked when installing a condensing furnace that has it's own PVC exhaust is the existing water heater.

    If you have a gas water heater venting into the existing chimney and remove the furnace, you then have an "Orphaned" water heater. The chimney may not vent properly in cold weather without the added furnace exhaust.
    The "Orphan" may need a smaller flue liner just for itself.
    EBEBRATT-Ed Member Posts: 13,438
    Everything said above by @Jamie Hall & @JUGHNE is correct. I would put some effort into windows, doors and insulation as a first step. This will lower the size of the furnace and air conditioner making it's replacement less costly and the home will be more comfortable.

    I would inquire with your town/county/state you may be able to get a free energy audit or some rebates for this work although maybe not with propane as a fuel......but it's worth checking.

    Couple of other things. Guessing is bad news but the 77,000BTUH sounds about right as a rough guess.

    I would caution against covering any old wiring in the attic with blown in insulation unless you have an electrician give you the ok. Older wiring was rubber covered and HEAT is it's big enemy.

    While your attic gets hot now the heat can disapate from the wiring. Burying old wiring in insulation is usually not good.
  • Meljean
    Meljean Member Posts: 2
    Thank you all! And had not thought about the possibility of wiring in the attic at all! So double thanks EBEBRATT-Ed.

    And the water heater maybe being hooked in to the chimney flue....will ask about that. Thanks JUGHNE for that.

    Jamie Hall Wall heater is infrared, the Rheems man said a blue flame would be less problem. We sometimes have power out for day or so depending on winter storms, guessing that is why the original buyer put it in. He said same thing about smell of this one and fumes too.

    You have put my mind at rest. Thanks.
  • DanInNaperville
    DanInNaperville Member Posts: 40
    I'm just a very experienced homeowner, but I've been a big user of boilers and furnaces for many decades.
    There are a couple of things you could ask about.
    Given that you're trucking in Propane and costs are very high, I'd consider a 95% efficiency furnace. The chimney is not necessarily a problem since it can be used as a chase through which you route the PVC exhaust pipe. Air intake can be routed from anywhere (try to keep it away from the prevailing wind side of the house).
    High efficiency furnaces are more complicated, so they cost more and don't last as long, but you might be able to save $500 a year on propane so maybe this is one of the few cases where it makes sense. Usually I'm a fan of inexpensive, long-lasting "standard" efficiency furnaces and boilers that don't use a lot of unique parts that become unavailable after 10 or 15 years, but not when you're paying for trucked in propane.
    Blown in insulation is horrible if you ever need to work in the attic (plumbing vents, electrical, HVAC ductwork, etc.). It's like trying to work on something at the bottom of a swamp.
    If you hire someone to work under those conditions, he's going have a very hard time doing even a half-assed job, it will take twice as long and cost twice as much (or should, anyways). Feeling for rafters under a foot of fluff so you don't go through the ceiling, banging your knees on conduit and invisible corners, digging your way through to whatever it was you went up there for. A dropped screw is gone until you accidentally drive it into your knee or hand. At least buy the guy a couple of beers if you send him into that mess.

  • GW
    GW Member Posts: 4,605
    Maybe get some more quotes to help you with the learning curve.

    In our parts it’s rare to install 80% in an owner-occupied home
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
  • mikeg2015
    mikeg2015 Member Posts: 1,187
    The standard efficiency furnaces are usually pretty base model. You aren’t really adding much reliability by not having a secondary heat exchanger.

    The Rheem R96v is a good quality furnace. I’m biased but I think it’s a higher quality unit than the Lennox and very easy to service.

    Some Lennox AC units are really noisy too.

    However you will need to address the water heater. Could switch to a tankless and vent that with PVC and abandon the chimney.
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,597
    It would be a rare time to ever install an 80% furnace. The savings on fuel alone will pay the extra few hundred dollars for a high efficiency unit. There are many 95% efficiency furnaces out there which are 25 years old and just now failing. Just by switching appliances you will likely save a minimum of 1/3 off your propane bill.

    The water heater needs to be addressed though which may add more to the installation. What are your electric rates, and what are you paying for propane? We can help steer you in the right direction.
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • GW
    GW Member Posts: 4,605
    Solid, if the installer does a poor job the savings may be zilch, that’s a fact

    Pitfall 1 (by a landslide) pvc furnaces need about 40% more airflow, but even still a majority of hvac guys can’t wrap their heads around this

    Pitfall 2- lame filter, filter connection and bad air leaks
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,597
    edited May 2019
    Very true! We all know returns are always the weakest link with scorched air. However, hoping the new (condensing) furnace is sized according to heatloss and oversized ductwork from old unit will be beneficial. Crappy filters always bad.

    I guess my findings with high efficiency scorched air have been that they are actually pretty resilient compared to our (my) loved boilers, both water and steam.
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!