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Thread: Clean Effects vs Lennox PureAir
10-07-2011, 09:13 AM #40Regular Guest
- Join Date
- Sep 2011
Can you help me not with a particulate efficiency question, but with a question on resistance efficiency?
The static pressure drop on many electronic units ranges from .18 to .27. In the same range as some of these 4 or 5" thick non-electronic media filters.
How can I think of pressure drop when:
- eg my AHU/DUCT system measures .5 SP no filter in? ( I chose .5 as I read this is a max objective for sp on a system)
- filter sp rating is .25
- filter note says filter at .5
- the AHU operates up to .8 sp
So when filter is new, sp is starts at .5 + .25 = .75.
This looks to me like I only have .05 of static to raise before I have to replace the filter!!
Is it correct to think of this that way? Margin for loading the filter with particulates is way too low?
What am I missing?
10-07-2011, 09:35 AM #41Regular Guest
- Join Date
- Sep 2011
So this would be the same as a in-shop room air filtration system, but instead of the air circulating in the shop, it would discharge into the house circulated air (which I was trying to keep isolated from my dusty air) (but now it would be as clean as the filter would allow) and the passive return would allow heat pump heated air back into the shop so I would then not have to heat that separately.
Maybe then too, I dont have to worry so much about going to a filter in the AHU that would capture any escaped woodshop dust, as the HEPA installed as you describe would do the main work. Not sure I need to go HEPA .. MERV 15 ..do you think so? I guess that would be safest. Espeially if I forgot about going to a MERV 11 filter in the AHU and went to the MERV 5 my contractor wants to put in which has an initial SP rating of only .08. So low. 5" media and elecontronic SPs are up around .23 or so, so much higher I have concerns with that as expressed in the post above.
Are you thinking of a home made blower in a box and just stick in a HEPA filter?
You mentioned a smallish passive return. Why smallish?
This IS A REVIEW OF WHAT I HAVE: tHE smallish passive return gives the shop negative pressure and minimal return of house air back to the shop. In the AHU area which is in a heated area of the basement, there are 3 ducts out from the AHU - study, hallway, AHU area. The cold air return for the basement is in the hallway (to move it further away from the woodshop) and it is sized so there is a positive pressure to the heated basement area, so the woodshop air does not drift into the clean area...the clean air drifts to the woodshop, not the reverse. Given that, we now have +ve pressure in the clean air zone and -ve pressure in the dirty air zone....so...even more clean air flows to the woodwork shop. Ok that is good. Dont want the reverse. What you suggest works with what was earlier planed.
10-08-2011, 04:03 AM #42
COPD is for life, do yourself a favor and don't skimp -- get a HEPA filter. The finest dust is the worst for your lungs and that's what a HEPA filter captures.
10-08-2011, 04:32 AM #43
RJ, I found this link which recommends venting outside:
Doing that would also maintain a negative pressure in the shop. In any case, the HEPA filter would only protect people in the rest of the house, and wouldn't be sufficient to protect you or anyone else in the woodshop.