View Full Version : What Features do I need?
02-01-2005, 10:40 AM
Currently researching furnaces for a possible purchase sometime in the upcoming year. Right now I have the original furnace in our home from 1979. It is a Carrier and I guess it is an 80% efficiency rated furnace based on specs (100k out / 125k in) with electric ignition - probably top of the line at the time? There really isn't anythhing wrong with the furnace except its age, its loud, and the temp variations we see. We plan on living here for probably at least 10 more years - maybe more.
The home is an 1800sf ranch - furnace is on one end, so we find that the other side of the house is always several degrees cooler than the other side, and even on the warm side the temperature variation is kind of irritating since the furnace cycles on/off alot unless its very cold outside (below 0). I am betting the furnace is oversized but I haven't done a load calc - and I will do one, as well as having the contractor do one when we get to that point.
Anyways, I was thinking we want at a minimum a 2 stage furance with variable speed blower. But I'm not sure if it is worth it to get a 90%+ model. For one the added cost and two, the extra cost to have the chimney lined for the water heater. The one furnace I really like is the Rheem/Ruud modulating furnace but I suspect that is quite pricey when compared to others. I know you can't comment on prices, but do you have any suggestions on what features I should look for or even a recommendation on efficiency?
BTW - We live in SE Micigan just outside of Detroit.
Thanks for any input or suggestions.
02-01-2005, 12:51 PM
For your cold area, the Mod would be the perfect furnace. No fancy controls just the ultimate HEATING machine. It is slightly more than a 2 stage VS 90 with good stat but worth it in a cold climate. I would think with today's gas rates, 90+ would be worth it in a few years time. We're a bit warmer than you and 90s are a good investment. You would need a chimney liner for an 80% furnace into a chimney too most likely.
Don't go by 125/100 rating, that is constant output not a reflection on annual efficiency. Your 1979 would be a 60% furnace. And at 125K, probably is too big for 1800 sq ft ranch of that vintage.
02-01-2005, 11:27 PM
Just my opinion for what it is worth, I think variable speed is a waste of time and money, granted they sound cool and can help guarantee CFM on questionable duct systems, but I have found them to be unreliable. I don't know how many Carrir variable speed air handlers I have gutted and change over to standard blower motors. I would probally go with the 90% furnace and a standard blower I recommend a Lennox G51, also Lennox's blowers are a little stronger than most others should help push air to end of duct run. One other thing older furnace may have dirty blower wheel and/or indoor coil restricting airflow. It's probally not worth much but that is my two sense, and Rheem/Ruud can't made a standard unit worth a crap so I can only imagine what their 2 stage variable speed would be like.
02-02-2005, 06:25 AM
Rheem/Ruud can't made a standard unit worth a crap
I think you are in the minority with that unprofessional statement. Care to elaborate?
02-02-2005, 07:33 AM
No offense meant but around here you would be in the professional minority. Just my opininon like I said before, but their indoor coils leak like a sieve, I have seen several of the gas furnaces with cracked heat exchanger, several heat pumps and ac units with bad compressors. Like I said I just don't put much faith in them. But then again you may not put much faith in Lennox, but it does not really matter like I said that is just my opinion, but most of other service guys around here agree with my point of view.
02-02-2005, 08:11 AM
With all due respect, I dont think you have seen a cracked hx in anything by Rheem since the Drum unless you had a airflow issue from lack of maintenence or poor ductwork. (or the unit was dropped). Yeah the drum was a disaster, but then again all mfg's tried oddball stuff in the late 80's to get a leg up on the furnace market. The pulse was just as bad if not worse. Then there was everything that used plexi-vent. Remember he isnt buying old equipment, he is replacing it with new stuff.
Just my 2 cents, keep the change.
Now Jdew, has a problem with temperature at the end of the house. That is not a furnace issue, its a distribution issue. No matter what he puts in there his duct will limit his comfort. 92-94% is as efficient as anyone makes so efficiency is not an issue, comfort is and frankly there is no furnace on the market that can match the mod's comfort.
Jdew, make sure you get your ductwork looked at.
02-02-2005, 08:17 AM
VARIABLE SPEED VARIABLE SPEED VARIABLE SPEED VERY RELIABLE
saves boo coo dollars.... very Dependable
Trane there's NO SUBSTITUE
anyway VARIABLE SPEED ... get the picture???
90+ only way to fly anything else you'll wish you had got the variable speed...
DID SOMEBODY SAY VARIABLE SPEED?
02-02-2005, 09:15 AM
We just changed our first tubular heat exchanger. The first one our distributor gave out. It was fine, just the plastic piece where the inducer mounts was deteriorating. That heat exchanger dates back to 1992 in the 80s and 1993 in the 90s.
What position are you finding leaking evaps in? We do pretty much only up/down and I can count on one hand the leakers we've replaced since 1992 when they came out. Some of the others on here have had more problems but in the horizontal position.
Now about those miserable Costa Rican pressure switches :(
02-02-2005, 11:45 AM
Thanks for the input so far. As far as the one end of the house - the supply seems to be ok. I mean if I close the dampers a little on the side close to the furnace then I can easily get more air-flow on the other side of the house - albeit at a lower temperature. But even doing this there is still a temperature difference. I suppose if I just shut off the one end then it would even out but I don't think that would be a smart idea.
I really think the problem is the return air. I actually posted a question about this a few months back. There is just almost no flow going into the return air intakes on the far end of the house. I would bet that at least 50% of the return air gets pulled in through one vent located almost directly above the furnace. I have sealed any obvious leaks in the duct work that I can access but it doesn't seem to make a difference.
One thing I have noticed though is if I leave the furnace fan on, it seams to help even out the temps throughout the house. I am hoping that a VS motor would help do the same with lower fan speeds and longer run times.
02-02-2005, 01:08 PM
Before you get too much of a migrane going, why don't you have a contractor come out and "do his thing." You already know the importance of a load calculation so insist this be done. Hopefully, a quality contractor won't have to be prompted to do this. You can relate to him your concerns and ideas and then let his professional expertise take over. Please keep in mind that we can only speak in the most general terms on this site, as we have not seen the job, and probably won't. In any case, you did not mention how long you had been in the home. Hopefully if you are as conscientious as you would appear, you have been having the system serviced with regular frequency. If that person has provided you reliable, loyal work, then that would be the best place to start. After all, through that loyal, reliable relationship, he has earned the opportunity above the rest to perform this work for you. Once you have your proposal in hand, come back with follow up questions, ONLY if that contractor can't answer them. Again, we would remain at a distinct disadvantage as we have not see the "whole picture." God luck.
02-02-2005, 01:52 PM
I definately will let the pro do his thing but it's just in my nature to try to have a really good understanding of what is going on what will most likely be the best solution. Plus with enough research I may be able actually understand what I'm being told and whether or not to ask a question about something they propose. I don't expect you guys to give me definate answers here.
We've lived in the house for almost 4 years now and we've used a local HVAC company to do the cleanings and 1 repair that was needed. I trust them - never tried to sell me anything I didn't need. In fact the one repair that was needed was the flame sensor - probably the wrong terminology, but its the thing that detects if a flame is present and if not it shuts the gas off. Well he could of easily just sold me a new one but instead he just cleaned it and actually showed me where it was if it needed it again - only charged me for the service call.
But here's my question about these companies. I know some contractors only sell and install a certain brand, but what about those that are independent. The company we use for instance I believe is independent and not tied to any one brand. Is there a benefit or disadvantage to using a contractor like this?
02-02-2005, 02:23 PM
Most dealers limit themselves to 2 or 3 brands. Some brands won't sell to just anyone so no dealer can get any brand at least directly. The advantage to sticking with brands and not constantly changing is that the techs & installers get to know it which makes it easier to install & service. You know a product better if you deal with it daily and have had training on it.
02-02-2005, 04:51 PM
Sounds like you got a good one. when you do replace the system ask them to do a manual J and a manual D. With the D they can evaluate your exsisitng ducts. When I say distribution, that is the duct system as a whole including supplies, returns, branch ducts, and even grilles and registers. Distribution is just easier to say.
As for the equipment goes, you may want to take his recommendations. The mod was mentioned but if he has never installed one, he probably hasnt been through the training.
You're on the right track.
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