Regular Guest
I live in an area with a very dry climate. Generally in summer months the outdoor humidity is somewhere around 20%. The inside generally runs about 35-40%. I have been reading through alot of the posts on here in regards to indoor coil size, fan settings and also CFM and how they all relate to the amount of humidity.
My goal is to raise the humidity level of my home slightly while also cooling the air. I know this seems to be far from the norm here. What is a comfortable humidity level? Everyone in the house is suffering from very dry skin and my son has frequent nose bleeds. Both issues could be solved by perhaps having a little more humidity in the house.
Short of having stand alone humidifiers running, does anyone have any ideas? My neighbor runs a swamp cooler and A/C simultaneously, which seems to me would put unnecessary loads on the A/C.
I was thinking that running the fan after the A/C turns off might blow some of the moisture on the A-Coil into the house. Another possible solution could be to ask my contractor about turning up the blower speed on the A/C? I have an Amana AMH8, and I'm not sure the blower speed is adjustable. My thermostat is a VisionPro 8000, my A/C is Tempstar 14seer. I also have an Aprilaire whole house humidifier, but pretty sure there is no way to get it to run in the summer, and that also seems like it would create unneccessary load on the A/C.
Thanks for any suggestions. Hopefully there are some pros or homeowners that live in an Arid climate and could offer some suggestions.
Regular Guest
I forgot to mention that I mentioned this issue with my installing contractor. Apparently they make it a common practice in this area to upsize the indoor coil by 1/2 to 1 ton.
I had other contractors provide estimates and 3 out of 4 suggested this. I have gone with 1/2 ton larger indoor coils, but I don't see any benefit so far.
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Operating the fan "on" mode will raise the indoor %RH, if the indoor coil is getting wet. Drink plenty of liquids. 1lb. moisture raises 2,000 sqft. 4%RH. Dry is healthy. Cooling 1^F raises RH 2%. Glad that not many live in CO. TB
Professional Member*
Upsized coils give you more sensible cooling, less latent (moisture removal). As it is you don't have much of a latent load to begin with.
Even though you live in a dry climate, it's still a good idea to tighten up your house. Infiltration is one reason why your house interior is dry. You can gain humidity within the house via cooking, cleaning, laundry, house plants, aquariums, showering, etc. If the house is tight (but not too tight) your interior humidity levels will be less diluted by dry outdoor air seeping in. With your upsized coil and a higher blower speed you might be able to hold a higher interior humidity level with a tight house and some added interior humidity generation, such as outlined above. You can also leave the blower set in the "on" position, which will blow off some of the moisture that collects on the coil...but you're not collecting as much due to both your upsized coil and a lower latent load. You have just the opposite problem as I do in my considerably more humid climate!
Psychrometrics: the very foundation of HVAC. A comfort troubleshooter's best friend.
Regular Guest
Jasruby,
I live in a desert climate (Phoenix) that is way drier than yours (2 - 10% humidity) and don't have any problem maintaining a comfortable indoor humidity (40 - 50%) with the A/C's fans on Auto. My house was built around 1975 and so is not very "tight" at all. You must have excessive air inflitration. Do you have an open fireplace damper? Malfunctioning kitchen/bathroom vents?
I have found that running my A/C with fan ON just blows warm air after a while. Maybe you could install a time delay relay that would run your fan for just 3 - 5 minutes after the compressor shuts down - this would return the moisture to the inside air without the warm air problem...
BTW, I know evaporative coolers well and your neighbor is insane if he is really running it at the same time as his A/C! Don't follow his advice...
Regular Guest
You mention a higher blower speed. Is it possible for my contractor to "speed up" the fan on my furnace for more airflow? I have a new Amana AMH8 Gas Furnace. I read some of the literature that the HVAC contractor left, and I don't see anywhere that the blower speed can be changed. I see there are different speeds for different modes (i.e. Med is 1st Stage heat, Med-Hi is 2nd Stage Heat, and High Speed is for Cool.)
I know the installer said he would leave the factory setting of HIGH for cooling.
Here is the info for my furnace: Nowhere does it say anything about this model having any sort of DIP switches or similar to change speeds.
http://www.amana-hac.com/Portals/1/pdf/SS-AMH8.pdf
I just don't want to have a service call to change the blower speed when it's not even possible on my unit.
Thanks again...
Regular Guest
Thanks for the advice, I completely forgot to check my fireplace damper. Not sure, but it's completely possible that it's in the open position.Originally Posted by jchunter
As far as the time delay, all of my ducts are in the "conditioned" space, and they are also insulated, so if I leave the fan "on" the air coming from the register generally feels cool. The VisionPro has an option to circulate the air every now and then so I have been leaving it in that mode.
You would be surprised how many people I see that have window A/C units AND evaporative coolers. I have one of those whole house fans, perhaps I should open all of the windows, turn my A/C on and then flip on the whole house fan, eh?Just blow that cool air right back out! I bet those fans aren't too popular in Phoenix, not too sure who would want a 115 degree breeze!
Regular Guest
IMO, the best use of an evap cooler is to precool the air intake of an aging A/C condenser coil. I know engineers who have done this (carefully) and made significant reductions in the power consumed by the A/C. However, the evap coolers are a PITA to maintain in this mode and excess water will corrode metal quickly.I don't recommend this, either.
God Speed, Jim. We'll miss you - 2-26-23
Just curious, what temp do you keep your house.
Professional Member
Your unit probably does not have DIP switches. More likely it just has four taps for the four different speeds of the blower. Page 5 details the different CFM at each speed and states that the unit is shipped with high speed set for cooling and medium speed for heating.
If your installer left the cooling in the high speed tap then you will not be able to increase it from there. What size of A/C and which model furnance do you have?
Professional Member
Outside of running the fan all the time on the highest speed, I could suggest hang drying your laundry indoors, get your wife lots of house plants, or buy an aquarium
Maybe a protable swamp cooler as a humidifier.
The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.
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Regular Guest
Usually keep the house at 72 during the day unoccupied. 70 when occupied and when sleeping. Do you think the temp is part of my problem?
Regular Guest
The furnace is an Amana AMH80703AN. The A/C is a 2 ton Tempstar T4A4 outside unit, with a 2.5 ton ICP A-Coil (Not sure of exact model number)
Professional Member
Looking at your chart on page 5 shows that model of furnance can handle up to a 3 ton A/C condensor and has a rated 1,273 CFM at .50 ESP (resistance in the duct work). Typically, a 2 Ton condensor would have about 800 CFM and maybe 900 CFM in an arid area such as yours.
If the installer did in fact leave the blower set for the highest speed then you have a LOT of air flow for a 2 ton unit. May just want to get it confirmed what the blower speed is set for in A/C mode.
Regular Guest
It is possible to use the Aprilaire humidifier independent of a heat call. If the unit is connected to hot water (140F would be best) and wired to run with the fan a mode 600 would evaporate about 0.50 gallons of water per hour. It will increase the load of your A/C, but may give you some relief.
You would want to make sure the unit does not run 24/7 to allow the humidifier to "dry out" for an hour or two per day by turning the fan periodically.
Doug
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