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  1. Replies
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    ACCA Manual D requires 300-fpm velocity through...

    ACCA Manual D requires 300-fpm velocity through low-cost low-pressure-drop fiber-glass filters:
    To get the initial clean filter velocity down to around 300-fpm, you need a 24X24 filter for 2-Ton-...
  2. If it's 18 yrs. old (1997) it falls within the...

    If it's 18 yrs. old (1997) it falls within the 10-SEER minimum or 10, 12, to possibly the 14-SEER category we had in 1998, & I believe in 1997.
    I can't remember 'for sure' if the max was 14-SEER in...
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    It least +1200-CFM for a 3-Ton Heat Pump... ...

    It least +1200-CFM for a 3-Ton Heat Pump...



    What are you saying concerning the 1050-CFM MAX; air handler Rating or tested airflow?

    Actually a Manual D should have been performed, as best...
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    That might indicate that the filter area &/or the...

    That might indicate that the filter area &/or the type of filter used has too much pressure drop; which actually would normally reduce airflow & increase temp-rise-split.

    It might be that there is...
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    They didn't do the proper trouble shooting for...

    They didn't do the proper trouble shooting for short cycling; should have checked the CFM airflow & temp-rise before condemning the limit.

    The evaporator coil & the blower wheel blades probably...
  6. Replies
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    Well, is there any way you can get more airflow...

    Well, is there any way you can get more airflow through the furnace?
    An 80F temp-rise even with a Return air of 75F is only 155F; a 90 is 165F; well below the trip point you're seeing.

    Make...
  7. Replies
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    At what degree reading is it actually tripping...

    At what degree reading is it actually tripping at?

    Most Oil furnace limits would be 200 to 250F; maybe it is tripping at too low a temperature.(?)

    Some Oil furnace limits are adjustable,...
  8. Replies
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    917

    Well, it appears to be the limit tripping. Is...

    Well, it appears to be the limit tripping.
    Is the blower wheel blades clean?

    What kind of airflow level is coming from the diffusers & airflow temp of nearest diffuser?
    I do NOT understand why...
  9. Replies
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    It may not be the limit switch or an airflow...

    It may not be the limit switch or an airflow problem; it could be that the Control Relay is pulling in, but not holding due to poor connections causing voltage drops & possible chattering of the...
  10. Thread: 1973 ductwork

    by udarrell
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    287

    The return duct sizing can be as large as you...

    The return duct sizing can be as large as you want; as you can have a direct feed into the return chamber with only a filter area causing a pressure drop resistance.
    What size Return Air filter...
  11. In most homes, it is nearly impossible to size...

    In most homes, it is nearly impossible to size everything large enough to efficiently flow even 1800-CFM with the correct static pressure.
    A major problem is the high efficiency evaporator coils...
  12. If no one will do the static pressure readings...

    If no one will do the static pressure readings for you; or if they do them, they may not do them right so the final CFM is correct from the mfg'ers chart; or, they may not trouble shoot to correct...
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    Okay; winter; 25-runtime +7-off-time is;...

    Okay; winter; 25-runtime +7-off-time is; 23-runtime/32-total cycle-time is 0.71875% * output of furnace (75000*.80%) 60,000 *0.71875 is 43,125-Btuh load when everything is very inefficient. Doing...
  14. The manual J software is easy to use, anyone can...

    The manual J software is easy to use, anyone can print out the instructions and practice using it until you become proficient.
    There are a lot of factors that go into how equipment performs,...
  15. Replies
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    You reduce the diameter-size of the duct to...

    You reduce the diameter-size of the duct to preserver static pressure as that is what moves the air into a lower pressure area; there is also velocity pressure that figures into the equation.

    For...
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    904

    I thought beenthere or someone would chime-in &...

    I thought beenthere or someone would chime-in & clarify that the RM-TH only registers Sensible temperature, therefore, we TECHs would look up the sensible-ratio & therefore we'd use the sensible load...
  17. Replies
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    When the air conditioners are way oversized as...

    When the air conditioners are way oversized as yours appear to be, when oversized A/C will pull the temp too low with the extra runtime; A/Cs need to be sized right to control humidity.

    Even with...
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    I am wondering where somanychoices is at; he is...

    I am wondering where somanychoices is at; he is not responding.

    Regarding my last post; it may well have been 1400-btu sensible as I selected a leaky construction house.

    I am fairly sure I...
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    That is true it would have to have a light latent...

    That is true it would have to have a light latent load to get +0.85% sensible; but I believe that was a typo it may have been 12,006 the total was 16,326 @76% sensible that would be 12,408-Btu...
  20. Replies
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    I ran a quick LoadCalc on the 1200-sf 2nd floor,...

    I ran a quick LoadCalc on the 1200-sf 2nd floor, using FL Energy Code factors for 1997:
    It could run a little higher depending on amount of window areas on different sides of the home, I had front...
  21. Replies
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    The main duct sizing is about right for a 2-Ton...

    The main duct sizing is about right for a 2-Ton A/C not a 3-Ton; at 1200-CFM 144-sq.ins is one sf; 1200/1 is 1200-Fpm velocity which is too high.

    An 18X10 is 180-sq.ins / 144 is 1.25; 1200-CFM /...
  22. Replies
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    There are many important factors in addition to...

    There are many important factors in addition to noise, as kdean1 indicated.

    Depending on the size of your furnace & A/C system & type of filter used, it may need more physical filter area than...
  23. Replies
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    If it could actually achieve 600-CFM volume of...

    If it could actually achieve 600-CFM volume of airflow the velocity would be around 3,057-fpm.

    600-CFM * 60 minutes is 36,000-CFH. If ran continuously for an hour or more, in very cold or hot...
  24. Replies
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    HVAC companies need to have techs that know how...

    HVAC companies need to have techs that know how to perform ACCA Manual D duct checks to see where changes may be needed.
    That is the best way to know if the airflow system is designed right......
  25. Replies
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    Well, it is rather difficult to provide precise...

    Well, it is rather difficult to provide precise information concerning your setup without being there; too much we can't see and then sort out.

    Of course, we have some Great PROs here that may...
  26. Replies
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    It is important to keep the return ducting as...

    It is important to keep the return ducting as large a possible going into the return chamber of the blower; especially because a filter will usually be installed after the 90ell, - which will also...
  27. Replies
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    I like the fact that most cabinets have a shorter...

    I like the fact that most cabinets have a shorter height, because it allows for more transition room between an oil furnace with a large heat exchanger way too close to the bottom of the evaporator...
  28. Replies
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    I doubt that your load-calc was anywhere near...

    I doubt that your load-calc was anywhere near accurate; as that sounds like way too much Btu/hr.

    Read all the instructions carefully; you should print the instructions.

    The Seattle NW Puget...
  29. Replies
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    Most furnaces are way oversized; get a load-calc...

    Most furnaces are way oversized; get a load-calc performed so the right size furnace is installed.

    Where do you live? We like to know the type of climate.
    You should be able to find a furnace...
  30. Thread: CFM

    by udarrell
    Replies
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    749

    Because there are so many systems NOT delivering...

    Because there are so many systems NOT delivering near enough CFM through the evaporator, nor to the home's rooms; Testing Delivered CFM is one of the most important things all of us should be doing. ...
  31. You will need to have a load-calc performed on...

    You will need to have a load-calc performed on those rooms; could try doing the load-calc yourself.
    http://www.loadcalc.net/

    I have a very small & quiet half-ton 6,000-Btuh window unit cooling...
  32. Mini-splits are also very efficient; good choice.

    Mini-splits are also very efficient; good choice.
  33. Replies
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    "To most consumers SEER is THE number for HVAC....

    "To most consumers SEER is THE number for HVAC. SEER means rebate/no rebate, and maybe a lower utility bill."

    That is the incentive to buy higher SEER equipment; which we all understand.
    Now....
  34. Replies
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    First, we need to know how much heating mode &...

    First, we need to know how much heating mode & cooling mode CFM, - that it needs to move through a 1" inch deep 16x25 filter.

    Figure 2-CFM per sq.in of physical filter area; which is 15x24 or...
  35. Replies
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    Right-on 54regcap. SEER calc for a single...

    Right-on 54regcap.

    SEER calc for a single speed compressor w/fixed speed indoor fan:
    Basically, it's the EER at 82F ambient, 80F indoors adjusted by fudge factors.

    Therefore, that's a mere...
  36. Replies
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    Before making a decision, I'd get several...

    Before making a decision, I'd get several contractor bids.

    If you want an opportunity to get a quality install; have them 'list the sequence of all the things they will do' to insure a quality...
  37. Replies
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    IMO; too much weight is assigned to SEER Ratings....

    IMO; too much weight is assigned to SEER Ratings.

    SEER calc for a single speed compressor w/fixed speed indoor fan:
    Basically, it's the EER at 82F ambient, 80F indoors adjusted by fudge...
  38. Replies
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    509

    IMO; too much weight is assigned to SEER Ratings....

    IMO; too much weight is assigned to SEER Ratings.

    SEER calc for a single speed compressor w/fixed speed indoor fan:
    Basically, it's the EER at 82F ambient, 80F indoors adjusted by fudge...
  39. Those contractor's are talking about 9-Tons of...

    Those contractor's are talking about 9-Tons of cooling; if you are trying to control humidity levels you do not want to be oversized even by a little. How big is your home; lots of windows, etc.(?)
    ...
  40. On sizing; I'd do a Manual D on the duct system &...

    On sizing; I'd do a Manual D on the duct system & air handler to see what CFM it will handle without retro-work; it may not handle 1600-CFM of a 4-Ton.

    Can you do anything to substantially reduce...
  41. If you're using a low-cost-throwaway 1 inch deep...

    If you're using a low-cost-throwaway 1 inch deep filter; for 3-Ton 1200-CFM airflow you would need a 30 x30 filter or, (2) 25x20 RA filter grilles in the conditioned area & none in the furnace.
    ...
  42. Replies
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    You need to measure the velocity through your...

    You need to measure the velocity through your 25x20x1 filter & then figure its Ak so you could figure what it would be through a 30x24 filter.

    The normal filter size would be 30x24, not 30x25.
    ...
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    Do a load-calc on your home. Orlando, FL, at...

    Do a load-calc on your home.
    Orlando, FL, at 2.5% summer design is 93F dry bulb, 76F wet bulb.

    Do your own Load-Calc - No cheating, :angel:
  44. Replies
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    We can't see the rest of the main duct system so...

    We can't see the rest of the main duct system so it is difficult to figure how much that situation is going to affect a pressure drop & airflow.
    That is an awkward setup.

    That appears to feed a...
  45. Replies
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    If you want to shell out that kind of money there...

    If you want to shell out that kind of money there are several brands; but I can't say which are the best for what you may want.

    Any good working thermostat (especially a programmable) will handle...
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    Including what the other PROS have said: There...

    Including what the other PROS have said:

    There could be a problem with the room thermostat (TH) location in respect to supply air or, cold air from within the wall adversely affecting it.

    A...
  47. We don't normally double filter paths to the...

    We don't normally double filter paths to the return air chamber as it can cause too much pressure drop in the system.

    An ACCA manual D ought to be performed to see if there is enough Available...
  48. What all of us need to do in this industry, is to...

    What all of us need to do in this industry, is to do all of the testing & math on the existing duct system & airflow; both air conditioning & heating cannot be upsized when many times the existing...
  49. Are those "filter grilles," or just RA grilles? ...

    Are those "filter grilles," or just RA grilles?

    If they are filter grilles you have to figure the open-air-area (Ak), of both the grille plus the filter; which means it would need considerable...
  50. Never double filter a return air path. The...

    Never double filter a return air path.

    The important factor is whether the filter has sufficient open-air-area (sf or Ak) to keep the velocity through it low enough; which reduces pressure drop. ...
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