We just replaced our 35 year-old furnace, 10 year-old AC with brand new Tranes. (sorry, don't have the model numbers.) The AC is a SEER 16 unit & the furnace is a high-efficiency (95% if I remember right.) -- the only thing disappointing about the installation is how ugly the exhaust pipe looks! The fan motor is a DC variable speed motor.
The installer recommended running the fan continuously to keep air circulating, even when temps are such it's not heating or cooling.. It also came with a fancy Honeywell AIQ thermostat. One of the settings on the thermostat is called "circ" -- the manual says that will run the fan "randomly", averaging 35% of the time. The house itself is 35 years old, seal broken on a lot of the windows, so not terribly air-tight, although it has 18" of insulation in the attic. (two story colonial.) Should we run the fan continuously, or use the "random" 35% setting, or have it only run ("auto") when actively heating or cooling?
You bought equipment from someone whom I assume you trust. Why are you now second guessing his opinion? Has he done something that warrants not trusting him anymore?
Why is the exhaust piping ugly? Did they dual pipe the furnace? Did they use a concentric vent kit?
Use the continuous fan or circ fan for heating and when no call for either heat or cool. In cool mode, run fan in "auto" mode... to run continous fan in cooling mode will actually raise the humidity in your home. Here in the south, thats not a good thing...remember that 90% of air conditioning is humidity control.
I trust his judgement that it won't hurt the fan (e.g., shorten its life particularly) to run it continuously. He may not have the same trade-off between comfort and the cost of running it I do -- on the other hand, I read somewhere that it may only cost $30 a year to run the fan on low continuously!
Code here requires the fresh air intake to be 10 feet away from the exhaust, if that's what I think you might be referring to. What's ugly is the exhaust is just an "S" bend made out of two PVC elbows with a six inch or so piece of PVC at the end -- I was expecting (not based on any knowledge) only a short nicely rounded stub sticking out of the side, not such a big monstrosity.
other hand, I read somewhere that it may only cost $30 a year to run the fan on low continuously!ot such a big monstrosity.
Some of the other guys may know better than I, but if I remember correctly a variable speed motor uses around 120 Watts or so; which is equal to a couple of 60 Watt light bulbs. So don't fret over it. Also motors are similar to car motors, it's the stopping and starting that does most of the wear and tear. So it's not going to kill the motor to let it run a little. The benefit to running the fan is that it keeps the air mixed up. If you spent the extra money on 16 SEER equipment then you should go ahead and spend a little more and fix the windows and any other air leaks you may have. They are costing you more than you think. Good Luck, Rodney
Code here requires the fresh air intake to be 10 feet away from the exhaust, if that's what I think you might be referring to. What's ugly is the exhaust is just an "S" bend made out of two PVC elbows with a six inch or so piece of PVC at the end -- I was expecting (not based on any knowledge) only a short nicely rounded stub sticking out of the side, not such a big monstrosity>
That could probably be done a little different if I understand what you are saying. We sell Trane (actually American Standard) and we normally just terminate with a 90 deg ell or a Tee. Rodney
Ah, that makes sense then (yes, we can get snow easily several feet above the ground). Anything about how far out from the structure it has to be? If it has to be a significant distance, that would explain the foot-long or so piece of pipe at the end of the second elbow.
1) If the ducts are leaky (normally are) the air exchange rate of the house will go up. If the house goes positive in the heating season due to dominate return leaks. Warm moist air will be pushed into the wall cavities and can condense. This can cause failure of the building structure and health issues. If the house goes negative in the cooling season due to dominate supply leaks. Warm moist air from outside can condense in the walls and cause building structural failure and health issues
2) If there is a central return and the doors are closed the pressures in the house will increase the air exchange. In the rooms with supply and no return will go positive in pressure forcing warm moist heated air from in the house into the wall cavities. This can cause failure of the building structure and health issues. The room with the return will normally go negative in pressure and in the summer will pull the warm moist air into the walls. This can cause failure of the building structure and health issues.
So, if the ducts do not leak and there is no pressure differential between the rooms then running the fan all the time will not increase the heating or cooling load and not cause condensation in the wall cavities. There are only a very small percentage of homes in the world like this and they require special detail during design, construction and commissioning.
The recommendation is to have a Whole House Performance contractor test your house for this.
Seals in the windows leak: Do you mean you have thermal pain windows (two pains of glass)? If this is the case this will not cause the house to leak more air. Technically the conductive value of the window will go up a minor amount since the air between the glass will have more moisture in it. The main reason to change the window will be for aesthetics.
Only 120 watts: Lets put this in perspective. I will make some assumption on the cost per kWh of your local electricity. I=92m also not an expert on the actual wattage of a fan motor. One has to actually put a meter on it to get its actual wattage. Amps * Volts =3D Watts.
120 Watts * 24 hours per day * 365 days per year =3D 1,051,200 watt hours
1,051,200 watt hours / 1,000 watts per kWh =3D 1051.2 kWh=92s. So if you pay $0.10 per kWh
0.10 $ pre kWh * 1051.2 =3D 105.12 dollars per year
If the thermal envelope is correct and the HVAC is designed correctly one does not need to run the fan 24/7
A concentric exhaust kit would have been just a short stub and never freeze up. Maybe your contractor was trying to save you about $200 or more. Lowest bid sometimes omits certain bells and whistles. I am not aware of anything that has an S vent on it though. I am in South Dakota. If money is not a problem... You might consider changing to a Concentric system. It might cost more as it is not part of the original job. Vents are prone to freezing shut in this end of America if not protected properly.
Let me also add that in a concentric system combustion air intake is legal. in the entire continent at the system intake. Also Minnesota combustion air intake laws are the same as ours. I do a bit of work in all 5 surrounding states. 10 feet is not what the code is. Your contractor may have found it more convenient to have the second PVC pipe that far away. There is a lot of space used up putting in fresh air intakes, combustion air intake, Venting, Humidifiers, air energy transfer systems.
Yes... Should be at least a foot above normal snow level and should be insulated so as not to freeze. We use Armalite, but only if our outlet is well below snow level and requires an extension to correct this.
We can cure that! How much do you want? It was still snowing the first of last week and rained until Yesterday. You just have got to love this damned Global Warming. ;-p
There are reasons for not using a concentric kit on every install... snow loads can limit the use of such items. Which I would guess is the problem in this case.
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