Page 4 of 7 FirstFirst 1234567 LastLast
Results 40 to 52 of 79
  1. #40
    Join Date
    Jan 2009
    Posts
    386
    Quote Originally Posted by Ed Janowiak View Post
    Your putting the cart before the horse.

    You need and accurate load done before you can determine what the total air flow required is.

    Lets start out slow.

    More air flow (higher sensible heat ratio) = more efficiency.

    Less air flow (lower sensible heat ratio) = lower efficiency

    More air flow quicker to satisfy the thermostat.

    Less air flow longer to satisfy the thermostat.


    What is you ultimate goal? As I read ti your not happy with the amount of run time you have (too much), lowering the fan speed will increase run time.
    Reading this again, I have a question. What about the increased face velocity across the coil with higher air flow? The velocity increases when you increase the CFM. The higher the face velocity, the higher the coil bypass factor. The higher the coil bypass factor, the less efficient the coil is. This seems somewhat contradictory to what you've stated.

  2. #41
    Join Date
    Mar 2007
    Posts
    3,140
    You should expect your house to smell kinda funny for about a week or two after the service.

  3. #42
    Join Date
    Aug 2007
    Location
    South Texas
    Posts
    373
    You can have a good air split, but not capacity. If you slow the blower down to get a better split, it doesn't mean there isn't a refrigerant issue.
    You can have a dirty coil with a 23* split, and still be low on refrigerant and the system won't cool the home properly.
    Let the tech check everything out before you present him with graphs and temp readings and such. He may find a problem and the time you spend discussing and going over all that info will be wasted time. Simply state the problem and let him do his testing. Leave him alone- you only slow things down and it's hard to concentrate with some one talking to you and following you around. At least it works best for me that way.
    Then if he finds nothing wrong, present your info and see if he has any further ideas.
    I always check the house out as I work- I look to make sure soffet vents haven't been covered or removed, the ridge vent is open, insulation is correct, windows and doors tight, or any infiltration issues. This takes little time while walking around the home inside and out and to the truck. Did the customer go from a white to a red roof, paint the house a dark color exposed to the sun (older homes mostly), loose a lot of shade, pour a new concrete slab that now directs reflected heat on a window side. Maybe not one issue, but add a few and it makes a difference.
    The outdoor unit should be washed with water/cleaner- not blown out with compressed air as I found some have done. Changing filters is no guaranty the indoor coil is clean- in fact as a filter loads up it traps more and also bacteria or slim could be coating the surface of the coil- etc.
    You could have any number of problems that would retard cooling.

  4. #43
    Join Date
    Jan 2009
    Posts
    386
    Quote Originally Posted by ktechnical View Post
    You can have a good air split, but not capacity. If you slow the blower down to get a better split, it doesn't mean there isn't a refrigerant issue.
    You can have a dirty coil with a 23* split, and still be low on refrigerant and the system won't cool the home properly.
    Let the tech check everything out before you present him with graphs and temp readings and such. He may find a problem and the time you spend discussing and going over all that info will be wasted time. Simply state the problem and let him do his testing. Leave him alone- you only slow things down and it's hard to concentrate with some one talking to you and following you around. At least it works best for me that way.
    Then if he finds nothing wrong, present your info and see if he has any further ideas.
    I always check the house out as I work- I look to make sure soffet vents haven't been covered or removed, the ridge vent is open, insulation is correct, windows and doors tight, or any infiltration issues. This takes little time while walking around the home inside and out and to the truck. Did the customer go from a white to a red roof, paint the house a dark color exposed to the sun (older homes mostly), loose a lot of shade, pour a new concrete slab that now directs reflected heat on a window side. Maybe not one issue, but add a few and it makes a difference.
    The outdoor unit should be washed with water/cleaner- not blown out with compressed air as I found some have done. Changing filters is no guaranty the indoor coil is clean- in fact as a filter loads up it traps more and also bacteria or slim could be coating the surface of the coil- etc.
    You could have any number of problems that would retard cooling.
    Thanks for the advice, ktechnical. I appreciate it. I will try my best not to follow him around, but I like to see what they're doing.

  5. #44
    Join Date
    Jan 2009
    Posts
    386
    Quote Originally Posted by BergerMech Rob View Post
    You should expect your house to smell kinda funny for about a week or two after the service.
    Yeah, I heard you HVAC pros don't wash often. Nothing some Lysol shouldn't cure.

  6. #45
    Join Date
    Jan 2009
    Posts
    386
    No response to my question about the CBF, Ed? I don't see how the coil is more efficient with more air flow (hence a higher coil bypass factor).

  7. #46
    Join Date
    Feb 2008
    Location
    Dallas & Longview, TX
    Posts
    629
    I'm sure there may be some velocity limit to hinder efficiency but that's not your problem.

    Regarding the furnace CFM- It was mentioned that to low CFM and the HX cracks but it's also important to hit the plate rating range because to high CFM can cause rusting of the HX. Don't think it was mentioned but I'm also not a pro but pretty sure about this.

    Get the tech to give you all his readings:
    Indoor wetbulb
    OAT
    liq. line temp and pressure
    suction line temp and pressure

    Post back after getting this if he doesn't find a problem.

    Pro's may be able to add to what they would need to diagnose an issue.

    Have him check each return/supply take off and connection for proper seal. Mastic is a plus.

    Good luck.

  8. #47
    Join Date
    Jan 2009
    Posts
    386
    Quote Originally Posted by Ed Janowiak View Post
    Your putting the cart before the horse.

    You need and accurate load done before you can determine what the total air flow required is.

    Lets start out slow.

    More air flow (higher sensible heat ratio) = more efficiency.

    Less air flow (lower sensible heat ratio) = lower efficiency

    More air flow quicker to satisfy the thermostat.

    Less air flow longer to satisfy the thermostat.


    What is you ultimate goal? As I read ti your not happy with the amount of run time you have (too much), lowering the fan speed will increase run time.
    OK, I get what you're saying now after reading some more. The coil bypass factor still plays a role, but I see how you can remove more sensible heat with higher airflow. The only question there is, with higher airflow, your split will be lower, right? So, if I move 1400 CFM across the coil and get a 23 degree split, I can't also get that 23 degree split at a higher airflow of say 1700 CFM, correct? The temp split would be lower at the higher CFM.

  9. #48
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    "because I've got 0.35" W.C. PD across a brand new blue fiberglass filter (something that should have a 0.05" - 0.10" W.C. PD new, "


    That's very high,are you sure of it?

    What size and cfms?

    What ESP do you have and where did you test it?

  10. #49
    Join Date
    Jan 2009
    Posts
    386
    Quote Originally Posted by dash View Post
    "because I've got 0.35" W.C. PD across a brand new blue fiberglass filter (something that should have a 0.05" - 0.10" W.C. PD new, "


    That's very high,are you sure of it?

    What size and cfms?

    What ESP do you have and where did you test it?
    1550 CFM and 20" x 12"
    The filter drop was tested right before and right after the filter.

  11. #50
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Quote Originally Posted by skizot View Post
    1550 CFM and 20" x 12"
    The filter drop was tested right before and right after the filter.

    Cfms are too high for that size filter,so PD will be high.

    What about the ESP,or as you stated TESP?

  12. #51
    Join Date
    Jan 2009
    Posts
    386
    Quote Originally Posted by dash View Post
    Cfms are too high for that size filter,so PD will be high.

    What about the ESP,or as you stated TESP?
    I think that's the root of a lot of my problems. The return drop is way too small for the size of the furnace and A/C. [T]ESP is around 0.8 with the coil dry and the blue fiberglass filter. I calculated the face velocity to be about 930 FPM with that much airflow and that size of return drop. That's why I was asking about the coil bypass factor earlier; it's very high with a velocity of 930 FPM coming into the air handler.

  13. #52
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Can you post a link to the fan data chart?

    .8 is high,what speed was it on when tested and where did you test supply and return,what was the supply and return ESP?
    Can you post pics of the indoor unit and connecting ducts?

Page 4 of 7 FirstFirst 1234567 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event