View Full Version : Air clearner and humidfier
09-24-2005, 01:18 PM
I have a NYC brownstone with two Trane systems - a split 7.5 ton system with roof condenser and basement air handler/furnace, and a 5 ton single unit roof top system. I want to add humidification for the winter and also put in some air filtration (for dust, etc). A few questions:
1) What are the advantages of electrostatic vs HEPA filters? I was advised to put a HEPA unit (Honneywell) on the 7.5 ton and an Aprilaire 5000 on the 5 ton. Does this make sense?
2) Will I notice the effects of a humidifier? The air in the winter feels very dry every year. Do I need a humidier on both units? it is much easier to install in the basement (where there is water) than the roof, but the roof system goes to the bedrooms.
09-24-2005, 01:58 PM
12.5 tons? What is this, 10,000 sq ft?
09-24-2005, 02:14 PM
Must be real big bedrooms.
A humidifier on both would be best, but may not be practical on the roof unit.
Since the 7.5 does the bedrooms, you may be ok will one just on it.
Electrostatic air filters tend to be too restrictive, so media, or electronic are better. But electronic need to be cleaned too often.
HEPA can not be done on that unit! Electrostatic have to be washed every month. Electrostatic is no better than a pleat. that is a very big range between a HEPA and electrostatic. Put a humidifier in the duct on both units (nothing on the roof)
09-24-2005, 03:27 PM
I'm curious if the HEPA filter you were talking about is a real HEPA filter like this. (http://yourhome.honeywell.com/Consumer/Cultures/en-US/Products/Air+Cleaners/HEPA/Default.htm) Or were they incorrectly referring to one an electronic air cleaner (http://yourhome.honeywell.com/Consumer/Cultures/en-US/Products/Air+Cleaners/Electronic/Default.htm) as a HEPA filter?
To reiterate some of what was said: Electronic is good but very high maintenance. So for most people it's a bad idea. Electrostatic is mediocre to bad and always restrictive. A true HEPA filter as linked above has relatively high capital and ongoing costs. A good media filter (http://www.aprilaire.com/category.asp?ID=0608882CF5E24282A28CB590D83D5B76&catID=0B10B06EA1EA4D14A4722CD120E8C7F6) (They call that one electronic but it's more akin to a media filter.) is the best compromise in my opinion. Obviously the package unit would require ceiling mount media filters.
Keep in mind that ANY improved filter will likely have a higher static pressure drop than a cheap fiberglass filter. Since so many systems have improper airflow I am a big advocate of cheap filters, depending on the application of course. Unless your airflow has been measured in some fashion you do not know what it is. If you don't know what the airflow currently is, how can you know if reducing it further will be acceptable?
09-24-2005, 03:33 PM
You sure you have a 7 1/2 ton on a house? Thats 3phase equipment. Most neighborhoods are single phase. (at least they are here)
09-24-2005, 03:58 PM
Definately 7.5 ton. Three phase current comes into the house (found out as I tried to install a coupler-repeater for X-10). The Aprilare 5000 is the one I am looking at, as well as the Honneywell HEPA unit. Thanks Irascible as those are the exact products I am looking at. I am being told that the Aprilare 5000 is too small for the 7.5 ton unit - is that right?
Also, from reading the responses, it sounds like I should get the humidifier in the ducts but not on the roof. That may be hard as I would rather not rip into walls. Can a humidifier unit go into the return vent?
09-24-2005, 04:05 PM
You would need 2 5000s on a 7.5 ton duct system. Certainly can be done.
HEPA would need to be a bypass system where only a small part of the air goes through the HEPA filter. The 5 ton and 7.5 ton blowers aren't strong enough to go 100% through a true HEPA media.
Fan powered hum on the return won't do much. A big bypass type if you can get to supply and return would work. General 1099 has highest capacity of all.
09-28-2005, 03:34 AM
So does it make more sense to use one Honeywell Whole-House HEPA Air Cleaner or two Aprilaire 5000 units on the 7.5 ton system?
Also, is there a rule of thumb as to what installation should cost?
09-28-2005, 07:07 AM
Depending on your humidification requirements, you might consider a steam generator if the home is that large and you have 3 phase avaialable.
09-28-2005, 09:26 AM
If it feels dry to you, then yes, you will notice and appreciate a humidifier. I wouldn't recommend an electric steam generator with your utility rates, though, unless cost is no object; they really burn through the electricity.
Sounds like we're talking about a package unit on the roof. If that's the case, the only way to put a humidifier on that system is to locate it indoors where the ductwork is accessible. Otherwise it will just freeze up and leak. If you can't get a humidifier rigged up on the rooftop unit, you may want to try just setting up the basement unit with a humidifier and see if that is enough. If not, Aprilaire does make a self-contained humidifier; you mount it in a wall and connect it to hot water, and it uses its own fan distribute humidity.
Depending on how much infiltration the building has, you may be able to get away with one BIG humidifier on the basement system- bypass or fan powered doesn't matter much, but if it's fan powered it will have to be installed into the supply plenum. While it would be unusual, I don't see why you couldn't use twin humidifiers (either type) on an unusually large system like that if you needed that much capacity.
Given my guess as to the square footage of this structure (please let us know!), it probably would need two or three HEPA systems for the HEPA to be truly effective. When they say "whole house" they make certain assumptions about how big a house might be, after all. If you're mostly concerned about dust, though, HEPA is overkill and just too pricey. I'd only recommend HEPA to be used in addition to a more traditional filtration system for people that have media filters and are still having allergy/health problems.
For almost any filtration solution on the 7.5 ton system, you will need to split the airflow in two use two filters. HEPA and electronic filtration are a can of worms in my book; I'd recommend using regular "media" (5" thick pleated) filters instead. In some cases you can get away with a single filter on a 5 ton system, but you're usually better off with twin filters even at 5 tons. Otherwise they can get too restrictive. This sort of setup gets you similar results as electronic air cleaners (ok, you give up a little bit of filtration ability on the ultrafine, sub-micron particles) but the maintenance requirements are very low, instead of being very high as they are with electronic air cleaners. *Electrostatic* filters are a nightmare, though; while they do work they are far too restrictive to be used.
09-28-2005, 09:39 AM
NYC, you probably use Steam to heat that building. Check with this heating site to see if you can use that steam to humidify.
09-28-2005, 12:45 PM
Take a look at the Lennox HEPA. They are pretty easy to retrofit into just about any system. You will really need to watch the restriction with the Apriliare 5000. You will probably need 2 in order for it to provide the proper static pressure and allow good airflow.
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