This all started because I went to get a new pilot burner for my carrier furnace. While there I made the mistake of complaining that I have replace all most every part on the thing, blower motor, control board, etc.
They asked how old was it I said 18 years ( really twenty I found when I got back). Of course they said “you should just replace it the heat exchanger is probably cracked and they have some good prices now.” I plugged in the co detector and replaced the battery when I got home.
They will sell me a 95% afue, single stage coleman for under 700.00. Said it is the lowest price they have seen in years. Started pushing on the ac too.
The question I have is how much cfm does one need? It comes in a 1200, 1600, and 2200 cfm at 80,000 btu’s. I am thinking 1200 that matchs my current plenum size. Is that correct on my part the house is just under 1100 sf, single story, ranch.
Also am I correct in that AC is 400 cfm per ton.
Any input on single stage vs two stage vs multi stage.
Wallyo
Replies
>>IIRC the change process requires a review and comment period via the Federal Register. This takes a couple-few months to do.
Good move.
Put it in the bedroom of the most medically vulnerable person in the house - infant, oldster, long term sick, etc.
Mount it higher in the room rather than lower.
Does it have a digital readout? They are mush more sensitive than those without.
Best to have on on all living levels of the house.
>>the heat exchanger is probably cracked
I don't know of any reason to consider that likely on a carrier of that age.
Sizing is a complex. Try looking for a contractor trained in sizing issues at http://www.certaincomfort.org/index.cfm?p=page&id=3
"Ask not what the world needs. Ask what makes you come alive... then go do it. Because what the world needs is people who have come alive."
Howard Thurman
It does have a read out. I am more after the higher afue then fear of the furnace but I know I would of got it on this web site if I did not have a working detector. On a side note I have noticed the detector we have is picky on batteries, it only likes high end alkaline batteries.
Edited 12/17/2008 1:06 pm ET by wallyo
"On a side note I have noticed the detector we have is picky on batteries, it only likes high end alkaline batteries."
Yes, I noticed that too, thought it was just me though, and my unit is hardwired, battery backup!
Wane yes i noticed it with certain smoke alarms too. must be due to something with milli amps of the battery?Wallyo
It comes in a 1200, 1600, and 2200 cfm at 80,000 btu's.
I'm not familiar with Coleman units so thake this witha grain of salt.
Most 90% + units come with multi tap motors. They may come prewired for a certin cfm, but may be changed to the other speeds bt switching the spade/stabs conections on the control board.
And the most efficient is the variable-speed DC motor -- usually worth the extra $$ in electrical savings.
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
Dan I think the fed expired but I noticed that the units you describe qualified for 150 tax credit on the gas side and an extra 50 on the electric side.Wallyo
Coleman is a branded verion of York. Same product, different sticker.
Coleman is a Luxaire. I used to sell them. Occasionally they would get shipped to us with Luxaire plates in them. We would just pull them and put the Coleman tags on.
Same=same.
Family.....They're always there when they need you.
Coleman AND Luxaire are both made by York.
Yep. I couldnt remember the third name.
Thanks
Family.....They're always there when they need you.
Any input on single stage vs two stage vs multi stage.
I had a new 17 seer HP with 95% multi stage gas backup installed this summer. The furnace only comes on below 20F. So far, the furnace has only been on 3 times and then it's been running so low we can't hear it. Prevoius gas furnace was loud and cycled frequently and there was a 1 or 2 degree variance. Now the house just stays at whatever the thermostat is set at. My total elec and gas bills are running $100+ a month less than last year and it's been colder and we're much more comfortable.
Don't know if the heat pump is an option in your climate, but I'm sold. At current prices, the system I bought ought to pay out at 7 years.
http://www.quittintime.com/ View Image
Some people in our area do install HP alone or with back up, I am in Boise Idaho. I don't know if I want to go that route we are not going to be in this house too much longer. Just a year or two with any luck, so I am not into pumping a big wad of cash at this. What did you system run?
What did you system run?
I paid around 11K, but it was not a simple swap out. Moved the outside unit to the other side of the house to get it away from the deck and had to add intake/outlet for the gas furnace. All the work was done above finished drywall. I'm guessing about 9K would have covered a simple swap out. I plan to not move anytime soon, so I figure at $120 or so a month, I'm getting a darn good return on my 11K investment.http://www.quittintime.com/ View Image
Last I checked there are several versions available for gas valves and for blower motors.
Gas valves: single stage (i.e. on/off), two stage (off/low/hi) and modulating (off or "self adjusting" on). For residential furnaces the first two are the most common and I'm not sure what you mean by "multi-stage". Whatever the case, stick with single or two stage. I prefer two stage because, regardless of how well the unit is sized to to the load, "off design" comprises most of the operation. The two satge unit will spend 60 to 80% on low fire (and lower air flow.fan speed), will cycle less, last longer and provide better comfort.
Blower motors: multi speed or variable speed are the only options realistically available for a residential furnace. Multi-speed has a fan control board with four "taps". The fans has four speeds available, usually the high or medium high are used for cooling operation and low or med-lo are used for heating (two stage heating will use two lower speeds instead of just one). The fan control board "tells"the fan which one to use based on the signal from the thermostat. With a variable speed fan, the motor has a much greater variaty of speeds available to it and they are set with dip switches on the board. Typically, these are associated with multiple stage furnaces and/or multpile stage air conditioners. There is a low (ventilation/circulation) speed that is always on, a low fire heating speed, a high fire heating speed, a cooling speed or two. The unit "ramps" from speed to speed and also varies the induction blower motor speed at different firing levels. This type of unit provides the greatest comfort and efficiency, if set up properly. Personally I recommend a two-stage variable speed furnace.
400 cfm/ton is a nominal value for DX (direct expansion, i.e. what you have) air conditioning. It is a basic place to start if you have to guess, but in area with much humidity, not a place to operate the average system. In Boise ID, 3 tons in 1100 sf seems a little high, but I don't know the specifics. Residential furnaces and ACs are usually oversized. When its 95 degrees outside, does it run for 10 hours or 20?
How much air flow does one need? As others have already stated, that depends. IF you were happy with the operation of your present unit, replace it with one of similar capacity and air flow. If you are not happy with the operation of the present unit (current service issues aside) seek a coulple of professionals in your area for their recommendations.
It should be pointed out that a variable-speed DC fan is much more efficient than the multi-speed AC fan -- could pay for itself in a year or two.
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
Hence, the statement, "This type of unit provides the greatest comfort and efficiency".
Tim thanks to you and all for your replies with the Holidays I have not checked in that much.
I guess by multi stage I meant variable speed modulating valve. So if i am getting this right there are single speed, multi speed 2 or 4. or variable speed blowers. Then as you say single, two or modulating valves which all come in any combination of blower type to valve type.
I think in my case as you say a two stage valve and multi speed or variable speed furnace would do fine but is it worth the cost of the modulating valve and variable blower?Wallyo
Edited 1/4/2009 2:53 pm ET by wallyo
The variable speed blower is generally accomplished with a DC motor. This takes much less current than an AC motor, especially at low speed. The difference is 1-2 amps, and if you run the fan continuously this is 2-5 KWH per day, maybe $100-200 a year if I'm figuring correctly. (Of course, if you don't run the fan continuously it's less.)
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
To clarify, there are multispeed blowers and there are variable speed blowers. In the mainstream product offerings for residential furnaces, there are no single speed versions of which I am aware. If there is, don't buy it.
There are single stage, two stage and modulating gas valves/controls. In any case, based on my experience, I suggest two-stage gas valve with a variable speed blower. I don't know the relative costs of the modulating gas furnace, nor do I know how it is controlled. It is a relatively new feature in residential furnaces.
Personally, I believe modulating gas valve technology is not appropriate for a residential system. The controls available and resonably affordable for residential systems could not take advantage of a modulating gas valve. In commercial systems, modulating gas valves are typically controlled with a discharge air temperature controller and sometimes with a room temperature "reset".
Tim thanks for the clarification it makes much more sense now. Wallyo
Actually, there are no true modulating resi furnaces. Multiple steps, but none using a maxitrol.
As a rough guide, 1 cfm per sqft would be about 'normal', so sounds like your 1200 cfm unit should do the job. It takes more cfm on cooling than on heating, FYI.