View Full Version : Variable speed sounds pretty good, but...
03-04-2005, 10:42 AM
So I had my mind all made up on what furnace I was going to go with, a single-stage 90 percenter Trane to replace my dying heat pump.
As the time gets closer (currently waiting for gas company to run their gas line in), I find myself questioning my original decision.
Through the reading I have done the last couple of days, it sounds like variable speed is a real nice addition to the comfort of a home. I could upgrade to the Trane XV90 for about another $1k above the single stage. I know it won't increase the efficiency, but I can definately see how it would maintain a nice even temperature.
I am planning to be in hy home for at least 10 years, and want to enjoy my time there and not skimp out on something that could increase our comfort.
So, anyone out there that has variable speed in there home: is it worth it? Would you pay $1k more for it?
03-04-2005, 11:08 AM
Another advantage of variable speed is that they are quieter, since if sized correctly they will run most of the time on low speed. This is especially nice if your ducts are undersized, which is common.
03-04-2005, 12:01 PM
The Trane Variable drive is not just quiet,it also starts in low stage and if after ten minutes of operation the goes to high fire stage. This would save alot more than just single stage furnace.As for the blower it can be set to maximize the comfort level to your duct system. This is in cooling mode also. The average savings here in Texas vs multi-speed is between 12/17%.The life of the system is also increased with better design of returns and supply , this would be a question I would ask the contractor..
New Suction/Liquid Lines
Supply Manuel D
Ductwork R-Value/collars sealed/mastic
Secondary drain pan/safety switch
3" PVC pipe /Flue termination
03-04-2005, 12:51 PM
Hey Why Not Get The Best of Both Worlds?
Check this out a Trane XL19i Heat Pump Condensing Unit matched with a XV90 Furnace or even a XV80, this way you get immediate benefit of comfort, efficiency and reliabilty, while you wait for the gas company to do their thing. Because you can use the heat pump to heat your home most of the time but when you cant you have the gas fired furnace which can be LP or Natural Gas and with today's rising fuel costs electricity is usually cheaper. FYI-This type of system is called dual fuel.
As a long time home owner who made major appliance decisions much the way you are, I can empathize with your dilema. And I agree with your process of getting several bids. I have since found it interesting to review the material I collected a year or two after the purchase to see if what I thought was important at time of decision is what I think is important now.
I'd love to tell you something on the variable speed decision but I am not. Instead I'm going to give you a suggestion that can possibley complicate your current decision and breifly take us a little outside the HVAC realm.
In earlier posts you said something about a new water heater in addition to the furnace replacement. You might want to look into eliminating an internal Tanked water heater system and go for a tankless water heater. Espically if a family is in the possible mix for your future.
These offer quick, endless hot water, a high tech electonic interface, in a unit the size of a suitcase. The leader appear to be Nortiz and Takagi. I installed a Noritz. The US venting on these units is expensive, so I decided to try the full Japanese treatment and mounted the unit outside - freezing weather and all. They run about 4 times more expensive than US tanked units but you can take it with you.
The on demand water heating has been popluar in both Europe and Asia for decades. But the new generation of Japanese units sport a remote digital control (in laundry room) and are quick, endless and accurate.
Now to return to HVAC. How did I get into Tankless Water heaters? After laboring on a tanked water heater replacement some years ago, my unit failed after 5 years. Why, because the sole supplier of the blue polyethelene like ciculation pipe ($5) decided to change its formula. This caused 1000's of units to prematurly disintegrate and resulted in laswuits and thousands of bad units.
The moral of the story, if there is one, is that you should probably do the best you can at the time with the info available, but know that a single service call or component failure can eliminate any economic advantage you sought by saving energy.
I also note that I cant higly recommend that you go tankless as It's only been in use for 9 months - its an evaluation at this point. But I can say I dont see how I lived without before. And I would only recommend Noritz or Takagi. Try coming home after skiing with a big family and everyone wants hot water showers.
I applogize if this is too off topic.
03-04-2005, 01:27 PM
I like the duel fuel suggestion - I would love to go that route if I had the money. Would definately be a nice system.
I will be replacing the water heater after we get gas, I am still evaulating the tankless designs. On one hand I like the concept, but they seem to have a lot of things that can go wrong, lots of stuff crammed into those little boxes...
I wish I knew someone that had a variable speed furnace so I could see their system operate. They sound nice, but as with everything is it enough to justify the cost...
We are in Idaho and use the heating system a fair amount.
In your tankless evaluation you are right to be concerned about the complexity, though my Tanked failure story shows what can happen with monoplies of simple products.
However, as a computer designer, I can tell you that the complexity is a lot simpler than the computer your using to make posts. And it may mean you repalce a PCB for $15 every 15 years versus a known tank failure of $250 every 20 years.
Also rememberer that electonics for severe envirnonments is a very established art - look at your traffic signals.
any way reliabity is something to consider but you probably wont find any meaningful data on either technology. Its just that we are used to the known failures in the tanked versions.
Other than that you proably need to ask, can millions of Asian and European consumers be wrong? I'm not touching that question
cheers - rfc
My experience with a variable speed American Standard furnace has been great. It is nice to hear muted duct sounds (vs. loud ones) as it runs on low speed all the time. If you can spare that extra thou or so, I think you will be glad you did it.
Down the road when you replace AC equipment, this can be part of efficient combinations that a single-speed cannot.
Best of luck -- P.Student
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