Static Pressure

[hvacmike85]

Where are you located and I will see what code you are under? I have been teaching code compliance for many years and have never heard of this and would like to know what code it is under and why?

do all water heaters in indianapolis have to be on stands or just the natural vented? I see alot on stands just never thought about it I guess, not much of a code guy I guess so I need you on my friends for when i have a question lol

[hvacmike85]

Basically if you need 0.8 static pressure and your fan can only product 0.5 then you will get less air flow as seen in your far runs.

I would get a measurement of all the airflow at your supply and return registers. Then see if your supply airflow levels match your return airflow levels. Most houses (at least in California) have a single return... so instead of adding more returns, you might be able to just enlarge your return that is 5' from your furnace. The fancy 4" filter is great for air quality, but seems to add 0.2 in static pressure loss. Maybe the easiest fix is to just replace your 4" filter with a 1" standard filter, but I don't know how your allergies are or it you like the extra filtration.

I dont know a lot about codes but I'm sure that a 4" filter is way more efficient than a 1" seems backwards but no doubt about it!

[hcong]

I dont know a lot about codes but I'm sure that a 4" filter is way more efficient than a 1" seems backwards but no doubt about it!

I haven't done that much research on static pressure loss of a 4" vs. a 1" but I think all the manufacturers I saw... a 1" has lower pressure drop. I could be wrong though.

[udarrell]

I haven't done that much research on static pressure loss of a 4" vs. a 1" but I think all the manufacturers I saw... a 1" has lower pressure drop. I could be wrong though.

When considering pleated filters the 1" deep filter has the most pressure-drop, it is one of the worst; the deeper filters have deeper pleats therefore, more surface area & a little less pressure-drop.

The cheap throw-away media filters have a low pressure drop but require large filter areas to achieve lower velocity through them.

The initial airflow velocity through a media filter is 300-fpm; Pleated often start at 500-fpm, but they would perform better with less pressure-drop if their area was sized for an initial 300-fpm velocity...

[hcong]

Good to know, thanks udarrell.

[hvacmike85]

When considering pleated filters the 1" deep filter has the most pressure-drop, it is one of the worst; the deeper filters have deeper pleats therefore, more surface area & a little less pressure-drop.

The cheap throw-away media filters have a low pressure drop but require large filter areas to achieve lower velocity through them.

The initial airflow velocity through a media filter is 300-fpm; Pleated often start at 500-fpm, but they would perform better with less pressure-drop if their area was sized for an initial 300-fpm velocity...

What is better than a 4-5 inch filter? I dont have alot of faith in eac units but I know they came out with the filter/eac in one yrs ago havent seen too many though. I have heard of hepa filters in holmes but I would think that would have to have a good blower to overcome a 13-19 merv?

[second opinion]

What is better than a 4-5 inch filter? I dont have alot of faith in eac units but I know they came out with the filter/eac in one yrs ago havent seen too many though. I have heard of hepa filters in holmes but I would think that would have to have a good blower to overcome a 13-19 merv?

Depending on the merv rating of the filter has a huge impact on the pressure drop across the filter along with the velocity of the air traveling across it.

You can have 1 inch pleated filters with a pressure drop above 0.35 and have a 5 inch merv 16 with a pressure drop of 0.36 new out of the box rated at 1200 cfm and 375 feet per minute.

The other factors to look at is at what cfm and face velocity that the filter was tested under using ASHRE 52. standard. The velocity used during testing can be less than 1/3rd of the velocity in a home system.

The bottom line before changing to a higher merv filter have the system tested to see what the available static pressure is left after all other items have been installed in the airflow, then determine what filters are available that will work with a lead-way for loading as the filter is in use.

[Gurney]

hcong,
The dew went away yesterday. It was extremely damp and threatening to rain but never did. I'm taking that the condensation had to do with that. The wet part was not on the interior, but I'm not sure if it was outside or middle.
I only have a return in the basement, but the return was made with a standard supply type register, meaning I have the ability to shut it out.
I did check yesterday and I have a 20X25X4 filter on this trouble basement system already. My upstairs has teh 16x25x4.
This puts me back at a loss on how to get my static pressure from .8 to the standard of .5. The idea I saw earlier that I've gone from 100 watts in using the fan to a potential of 300 watts, seems to be something that should be fixed. Correct?

[hvacmike85]

hcong,
The dew went away yesterday. It was extremely damp and threatening to rain but never did. I'm taking that the condensation had to do with that. The wet part was not on the interior, but I'm not sure if it was outside or middle.
I only have a return in the basement, but the return was made with a standard supply type register, meaning I have the ability to shut it out.
I did check yesterday and I have a 20X25X4 filter on this trouble basement system already. My upstairs has teh 16x25x4.
This puts me back at a loss on how to get my static pressure from .8 to the standard of .5. The idea I saw earlier that I've gone from 100 watts in using the fan to a potential of 300 watts, seems to be something that should be fixed. Correct?

Fixing it may be ideal but a lot of systems out there are worse off it might be an expensive fix

[Shophound]

I haven't done that much research on static pressure loss of a 4" vs. a 1" but I think all the manufacturers I saw... a 1" has lower pressure drop. I could be wrong though.

For the same MERV rating, a 4" pleated media filter will have less pressure drop than a 1" pleated media filter. It's all about surface area.

[Gurney]

hvacmike85,
So do you think the fan is working 2-3 times as hard as it would if I were at the right Static Pressure?
When you mention repair would be expensive, is that resolution to add more returns or something else?

[jpsmith1cm]

hvacmike85,
So do you think the fan is working 2-3 times as hard as it would if I were at the right Static Pressure?
When you mention repair would be expensive, is that resolution to add more returns or something else?

Neat quirk of most blower wheels.

When they are restricted like that, they actually do LESS work than if they were properly supplied with air.

That doesn't mean that it is a great idea to starve the fan for air, just that you aren't overloading or overworking the blower by doing so.

[second opinion]

Neat quirk of most blower wheels.

When they are restricted like that, they actually do LESS work than if they were properly supplied with air.

That doesn't mean that it is a great idea to starve the fan for air, just that you aren't overloading or overworking the blower by doing so.

jp that is true for a standard PSC motor but not for a variable speed ECM.

When faced with higher static resistance from the system the ECM will increase its rpm to maintain selected CFM, and in doing so the energy consumption will sky rocket and the efficiency of the system goes out the window.

Think of it like your car with the emergency brake partially on you are still moving but it is taking more energy to do so.

[hvacmike85]

hvacmike85,
So do you think the fan is working 2-3 times as hard as it would if I were at the right Static Pressure?
When you mention repair would be expensive, is that resolution to add more returns or something else?

its def not working 2-3 times harder at .8 but the return isnt for sure your culprit either,we cannot know without being there to test ourselves, total static of .8 is really about average for an ecm sytem and quite honestly your duct cant be too bad or it would be higher. If you have a 4" filter thats the first step, keeping it changed 3-4 times a year is next. when I say expensive it could be replacing duct to fix it, but it doesnt sound like you have much of a problem, was the system acting up/?

[hcong]

I checked your furnace... a 0.8 compared to a 0.5 is only roughly 35 CFM less for your system.

http://www.docs.hvacpartners.com/idc...s315a.45.7.pdf

[Gurney]

hvacmike85/hcong,
Thanks gentlemen, i think you've got me where I need to be and to understand. Let me see if I can summarize and let me know if anything is incorrect...
So, I'm at .8 and ideal is .5 static pressure. .8 is higher, but still within normal operating parameters (even in the data sheet). The comment that was made to me that normal is the elctricity of 100W bulb is standard, but the comment that I'm using 2-3 time was totally incorrect. If I can remain at .8 static pressure, sounds like I should shut off that return that is in the basement.
Net here being, .5 is ideal, .8 is still normal, and net sounds like it may minimal SEER impact and maybe a few pennies for electricity, but nothing significant. To alter my system to ideal would probably be a few hundred dollars and how to achieve such would have to be reviewed by an expert.
After spending several thousand dollars on this 17 SEER system, I can live with it's not perfect, but it's within normal ranges.
Sound accrate?

[hvacmike85]

hvacmike85/hcong,
Thanks gentlemen, i think you've got me where I need to be and to understand. Let me see if I can summarize and let me know if anything is incorrect...
So, I'm at .8 and ideal is .5 static pressure. .8 is higher, but still within normal operating parameters (even in the data sheet). The comment that was made to me that normal is the elctricity of 100W bulb is standard, but the comment that I'm using 2-3 time was totally incorrect. If I can remain at .8 static pressure, sounds like I should shut off that return that is in the basement.
Net here being, .5 is ideal, .8 is still normal, and net sounds like it may minimal SEER impact and maybe a few pennies for electricity, but nothing significant. To alter my system to ideal would probably be a few hundred dollars and how to achieve such would have to be reviewed by an expert.
After spending several thousand dollars on this 17 SEER system, I can live with it's not perfect, but it's within normal ranges.
Sound accrate?

You got it!

[motoguy128]

I still wouldn't call it "pennies".

FOr comparision I looked at a Trane XV80 (jsut because i had it handy) data sheet.

With a 60kBTU 3 ton blower, at 1200CFM nominal and 0.5" your at 440Watts. 0.8" = 480 Watts and you lose 50CFM because you're "falling off" the blower curve and getting close to max RPM.

With a 80k BTU furnace with 3 ton blower (wider furnace), it's 370Watts @ 0.5", 430 Watts @ 0.8".

With a 80k BTU with a 4 ton blower, 285 Watts @ 0.5", 370 Watts @ 0.8".

Just something to consider. With the Evolution series, you should have a 4 ton blower on the smaller furnace sizes, and Carrier runs at 350CFM/ton or less for normal airflow.

But I think I showed that the difference could be anywehre fo 40-90Watts. That's still significant. At 85F, that could be anywhere from 1-4% in 2nd stage, or as much as about 0.6 SEER.

So I was a little off before.

But then again, if the unit is oversized and short cycles it can impact effciency by as much as 25%.

[Gurney]

Hvacmike85,
Thanks.

motoguy128,
So I don't follow quite everything your stating. But backing up. I had a 75,000 BTU Heil single speed furnace. I've upgraded to this Bryant Evolution 90K variable speed furnace. End of the day, am I not using significally less electricity than I had before?
I pulled the data sheet from Bryant that was included in a prev thread reply, it shows for my unit CFM airflow setting 1050; External Static Pres Range (0-1.0); @ .5 = 1040; @.8 = 1030. I don't really see how this all equates to energy usage to run the fan. But if I'm hugely less than what I originally had, and only off optimal a little, I'm happy. Thoughts?