Getting around to replacing my old, low efficiency (<60%) forced air/natural gas furnace though I will wait for better weather. This is
the original equipment and is now 20+ years old. Still works but I figure that I am on the short end of the leash.
Most offered around here (Ottawa, Ontario, Canada) are 95% efficient.
A few questions: in-store mock-ups use plastic pipe as the exhaust. Is this for real? Seems I remember a big screw-up with this arrangement several years ago. Is there a consumer choice of materials? What are they? Pros/cons?
Will also install a new central ac unit. Systems offer SEER ratings from 13-20. I appreciate that “you get what you pay for”; however, is there a way to evaluate how much do I really need based upon the amount of air conditioning required (degree days?), energy costs and payback time? How much more efficient is – for example – a 16 rated machine vs a 13 rated system? Would I see a difference in electricity consumption month-to-month or would it be a little bit that adds up over time?
Any other pointers appreciated.
Replies
I installed a 17 seer hybrid heat pump/nat gas system last summer, replacing a 50+ y/o gas furnace and 20 y/o A/C unit.
Cooling costs have dropped by close to 50% with greater comfort and the heat pump works down to around 12F. I realize you're in a much colder climate, but I'm pretty darn impressed with this system. My heating bills have been about 50% less as well, but we're experiencing a much colder winter.
And yes, the PVC exhaust is for real. Little or no heat going into the flue, but lots of moisture.
http://www.quittintime.com/ View Image
Yes, all high efficiency gas furnaces use the plastic flue. They must use plastic since the moist, acid flue gas would corrode normal metal flues and destroy masonry ones.
Note that the high efficiency furnace will also need a condensate drain. This can be just a hose into the basement floor drain, or run outside (in warmer climates where this is permitted), or it may require installation of a condensate pump (not too expensive) to pump the condensate up and over to the washing machine standpipe or wherever.
My understanding is that SEER is, roughly, inversely proportional to energy consumption. Ie, a 10 SEER AC will use about twice as much electricity as a 20 SEER AC to produce the same amount of cooling. It is, of course, calculated as an "average" over some mythical cooling season, so you can't exactly take SEER to the bank, but the numbers really do mean something.
One important thing is to make sure the installer uses the right components. A 16 SEER condenser unit may only do 13 SEER if the wrong A coil is installed -- be very leery of someone who wants to reuse the existing A coil or use an off-brand one.
There was a recall on Plexvent - a type of plastic venting system for moderately-high eff furnaces & boilers. There has been some controversy regarding PVC as a venting material, although the test of time seems to be showing it works well. Polypropelyne is preferred by a few manufacturers while others require stainless steel to carry the exhaust. The higher the efficiency, the lower the exhaust temperature & the more likely plastic is suited. Condensate - a by-product of the combustion process - is mildly acidic and you'll produce aprox 1-gallon per each 100K BTUs burned for gas & 1/2-gal for oil in high eff boilers & furnaces. Condensate grants a boost in eff when collected and its latent heat is extracted for heating. It's easily neutralized & should be treated before being discharged to the plumbing system. With the cost of fossil fuels on the march upward (again), your best investment is in a 90+ model instead of an 80+ chimney-vented appliance. Typical ROI (return on Investment) is well above 10%. You can project the ROI if you know two things: the difference in cost between the 80+ and 90+ eff models; and the projected fuel savings. Divide the cost diff into the fuel savings. EX: $2,200.00 more for the 90+ model with $300.00 projected fuel-cost saving = .14 or 14% ROI.
A hybrid heating system (furnace coupled with heat pump) adds about $600.00 & allows you to switch between electricity & fossil fuels if one is less than the other for heating. Right now electricity via a high-HSPF heat pump beats fossil fuels, but that's going to flip following deregulation of electric utilities. 80% increase is being projected for my area.
SEER ratings: for each rise of 1-point, you will see an average reduction of 10% in operating costs from the previous point level. So, a 26-SEER unit will operate at half the cost of a 13-SEER unit. Mini-split inverter (variable speed drive) units are available with 26-SEER and 13-HSPF. Mini-splits give you the ability to spot-cool/heat just the area(s) you're occupying instead of the whole house = additional saving$.
However, for central systems, there are a ton (pun intended) of options from inverter high-SEER units to two-stage to single speed. ROI can be calculated the same way as outlined above.
It's your money and your investment to make. A/C units last an average of 16-years, so R-410a is the best option for refrigerant in spite of R-22 units still being available. 2010 marks the end of manufacturing R-22 units & 2015 the end of making R-22. R-22 equipment purchased today at discounted prices may well bite you in the rear when, or if, service is required.
I also installed a Hybrid system this past year and have the same results as another contributor here. You are further North than me so your circumstances may be different. Just wanted to add the following. The heat pump on my system is staged. Runs slowly when only needing a little cooling. This feature saves a lot of money. It will run longer at a lower output which keeps the temperature inside of the house more constant and because of that a higher thermostat setting is more comfortable. The gas furnace on my system is 95% efficient but is either on or off. I noticed there are a few furnace manufacturers that are now offering variable output units. Low output when only needing a little heat. This seems like a feature that can keep the home comfortable with using a lot less energy.
a few furnace manufacturers that are now offering variable output units. Low output when only needing a little heat. This seems like a feature that can keep the home comfortable with using a lot less energy.
That's true with my system. We seldom realize it's on. None of the hard cycling as with the old system.
http://www.quittintime.com/ View Image
Well you already have 3 stages of heating. There is no need to have more in the furnace..
William the Geezer, the sequel to Billy the Kid - Shoe
Low output when the heatpump goes into defrost mode is nice.
Bill: Since the first week in December till this week the outside temperature has keep the heat pump off. What I was referring to was the gas portion of the system. I normally keep the fan on low in the winter. I am heating 3 floors and that seems to even out the heat. When the heat pump is off and the system calls for heat it shuts down then the gas burners kick on and when it decides that the heat exchanger is warm enough the fan kicks back on. I have seen newer systems wear the gas unit kicks on with a lower amount of heat and runs for a longer time. This keeps the inside temperature constant. If the newer unit scenes the amount of heat it is providing is not keeping up it will step up the number of burners it is firing. My gas portion of the system is either on or off.
If the newer unit scenes the amount of heat it is providing is not keeping up it will step up the number of burners it is firing.
That's how mine works - low fan speed with a few burners running longer times. If it gets colder, burners are added and fan speed increases. http://www.quittintime.com/ View Image
You might be right. Just doesn't seem that way. I have a service guy scheduled for May to do yearly service. I will ask him if your thought is correct. Jay
I went down stairs and read the installation manual. The furnace has the capability for low,medium, and high heat depending on the need if certain trip switches are set correctly. . If those switches are set differently it will only come on at one heat level. I will have the service guy check these settings. Thanks for the info.
Edited 2/11/2009 10:03 pm ET by Jay20
Biggest thing is the installation, not the name on the box or the company salesmen.
PVC pipe is OK for vent material. Have it installed with 2 pipes- one for intake, one for exhaust.
Most people that live where it snows will never see a payback from a high SEER straight AC unit... that 16 SEER unit is quite a bit more money than the 13 SEER unit. The SEER ratings also encompass the rest of the HVAC system (ie: ductwork) and a fudge factor. If you want to measure the true efficiency you need to look at the EER ratings which is simply a number arrived at from the btu's you get from the kW you put in.
Nothing wrong with a heat pump, but you have got to watch the specs. Performance of most air to air units goes down as it gets colder outside. Some single stage units provide more heat than multi stage units. For most, register temp is lower than fossil fuel.
So far, the only exception to the above is the Acadia from Hallowell.
Multi stage or modulating furnaces do not maintain their efficiency rating at less than full output. Heat stages/modulation is there to improve homeowner comfort, not to save money on utility bills. You still need #### number of btu's to heat or cool. Multi stage equipment is pointless if you do not use the correct thermostat.
Your energy savings will come from installing a properly sized piece of equipment... that means a load calculation.
Improvements in the thermal envelope of the home will return more in energy savings than a high dollar HVAC system.
The best bang for the buck in equipment and energy savings would be a variable speed blower. That savings will be maximized if your ductwork is done correctly. A VS blower connected to bad ducting could cost more than a PSC motor because the VS electronic feedback system will try to develop/maintain the cfm the computer tells it to deliver despite duct/filter restrictions.
Do not reuse any component of your existing AC system- especially the lineset if going to R410A. That R410A system must be installed properly or it will die an early death (it will make it thru the 1 year warranty, but the problems will happen). Micron gauge and nitrogen purge while brazing are important.
I was also shopping for a replacement system, looking for a spring or fall install, but the deals out there right now were too hard to turn down. New system was installed last week.
i got advice on here from Junkhound a couple of years ago and he was right
when you talk gas are you talking propane or natural and what cost per mil btu,s
gas furnaces are 95 % efficient
oil is 85% efficient , however there are more BTU,S in a gallon of oil than A gallon of propane
gas furnaces are cheaper to install , one of the reasons installers push them
they always talk about the furnace efficiency gas vs oil none i found will ever discuss BTU,s i found
after working it all out i found oil was cheaper than gas
PS , i live just south of Ottawa near Winchester so weather is the same only we dont get any hot air from the Hill !
Did you get your energy audit done yet ? The audit will cost you around $350 but you get 150$ back from the Ontario government and the audit will give you a $1000 rebate for the furnace upgrade. You can also get other rebates for other upgrades such as new windows, doors, low-flush toilets, etc.
I'll post more on furnace later, my daughter as a fever and is calling me...
Some of the answers digressed into heat pumps, which shouldn't be an option in Canada or here in Wisconsin. I changed out both the heater and the A/C at the same time last year, even though both were fairly efficient. They were just noisy, and I got rid of the Lennox Pulse heater, which sounded like a German buzz bomb in the vents when running, and a York compressor that was just too loud outside for comfortable grilling and relaxing. Now all I hear is a faint air movement inside and nothing outside. The contractor was a bit baffled that they both still worked welll and I wanted them out of here, but I'm 61 and I just didn't want the noise and wished to change it while I could still afford it. I guess the answer is to do what you want for the long run and can afford. As to what size to get, leave it to them -- I think they do a good job of judging by my expeience. Be sure to mention any additions like finished basement you might be planning for the future. Oh, I have the variable speed fan and two stage heater -- worth it for comfort and energy cost.
Edited 2/11/2009 9:44 pm ET by BARMIL
Edited 2/11/2009 9:46 pm ET by BARMIL
I'm amazed that there were any Pulses still out there. Thing must have been about 30 years old, and it was one of the first-generation condensing furnaces.
The modern conservative is engaged in one of man's oldest exercises in moral philosophy; that is, the search for a superior moral justification for selfishness. -John Kenneth Galbraith