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  1. #14
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    Quote Originally Posted by Adlerberts-Protege View Post
    Be interesting to see if it's short cycling. May be time to invest in a good data-logger?
    Heat doesnít run long when I was there, but then again it was in the 40 and 50 so not even close to a design day.

    Sounds like a jet engine coming out of a few of the diffusers.


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  2. #15
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    Sep 2005
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    Atlanta GA area
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    Question: What do we tell a customer... when a heat wave comes along and the system will barely hold high 70's???
    And do we keep the account??? or does the customer run to a hack who does 'bigger is better'???

    We need to not make a god of load calcs, rather use them as guidelines, not limiting numbers... rather explain the reality of BTU capacity to temps... and especially explain what happens when weather exceeds 'normal' (design).

    What good have we done the customer, the environment, and the greater good...
    If the customer goes to a hack and gets a larger system???
    GA-HVAC-Tech

    Your comfort, Your way, Everyday!

    GA's basic rules of home heating and AC upgrades:
    *Installation is more important than the brand of equipment
    *The duct system keeps the house comfortable; the equipment only heats and cools (and dehumidifies)
    *Cheap is not good, good is not cheap; however expensive is not a guarantee of quality!
    Choose your contractor wisely!

  3. #16
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    Thread Starter

    Load calc cant be right.

    Quote Originally Posted by ga-hvac-tech View Post
    Question: What do we tell a customer... when a heat wave comes along and the system will barely hold high 70's???
    And do we keep the account??? or does the customer run to a hack who does 'bigger is better'???

    We need to not make a god of load calcs, rather use them as guidelines, not limiting numbers... rather explain the reality of BTU capacity to temps... and especially explain what happens when weather exceeds 'normal' (design).

    What good have we done the customer, the environment, and the greater good...
    If the customer goes to a hack and gets a larger system???
    I think itís more about managing expectations and educating the customer. You have to sit down with them and say hey, when itís 105 outside for the 2 day freak period we get once every 10 years, your system is not designed to keep your house at xyz temp. Explain it will run all the time, but may be 3-5 degree over setpoint. But since it is running 24/7 it will pull a lot of moisture out of the air so the comfort lever should still be reasonable.

    Itís all about informing them of what the system constraints are. Informing them of why we donít size for those freak days, and inform them about mechanical issues that arise from oversized. Itís all one big fine line we walk.

    Additionally, manual j produces numbers that have a slight fluff factor already in them. Using the numbers I get, I have, to my knowledge not had complaints about a cold house in winter or hot one in summer.

    On top of that still yet, equipment only comes in so many sizes. Letís look at mine. 17 cool 25 heat. That means Iím putting in a 24 cool 40 heat. Now I have double fluff.

    Iím not saying load calls are end all be all, but I do think they need to be used more in our industry. In the last two weeks I have seen two units, different buildings, that are 60 cool and 120 heat, and both calcs came to 24 cool 40 heat. Thatís a problem.

    Education is key.


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  5. #17
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    Jan 2015
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    Quote Originally Posted by jbhenergy View Post
    I think it’s more about managing expectations and educating the customer. You have to sit down with them and say hey, when it’s 105 outside for the 2 day freak period we get once every 10 years, your system is not designed to keep your house at xyz temp. Explain it will run all the time, but may be 3-5 degree over setpoint. But since it is running 24/7 it will pull a lot of moisture out of the air so the comfort lever should still be reasonable.

    It’s all about informing them of what the system constraints are. Informing them of why we don’t size for those freak days, and inform them about mechanical issues that arise from oversized. It’s all one big fine line we walk.

    Additionally, manual j produces numbers that have a slight fluff factor already in them. Using the numbers I get, I have, to my knowledge not had complaints about a cold house in winter or hot one in summer.

    On top of that still yet, equipment only comes in so many sizes. Let’s look at mine. 17 cool 25 heat. That means I’m putting in a 24 cool 40 heat. Now I have double fluff.

    I’m not saying load calls are end all be all, but I do think they need to be used more in our industry. In the last two weeks I have seen two units, different buildings, that are 60 cool and 120 heat, and both calcs came to 24 cool 40 heat. That’s a problem.

    Education is key.


    Sent from my iPhone using Tapatalk
    Yes that's a good way handle it with customers. A thing people of miss with Manual J is that the equipment is only sized correctly at design conditions. At all other conditions it will be either over or under-sized (assuming a non-variable speed system). Man J is designed to compromise over a range of scenarios taking into account a balance between efficiency and keeping people comfortable. Plus in a lot of cases you have to round up to the next available size anyway.

  6. #18
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    Oct 2011
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    Culver, Oregon (Central OR)
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    Explain to them the importance of modulating heat, variable capacity AC. Oversize those suckers and know it will kick ass in all extremes. They dont want to pay then educate them on what to expect from systems undersized, oversized, and properly sized.

  7. #19
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    Quote Originally Posted by Adlerberts-Protege View Post
    Explain to them the importance of modulating heat, variable capacity AC. Oversize those suckers and know it will kick ass in all extremes. They dont want to pay then educate them on what to expect from systems undersized, oversized, and properly sized.
    Yeah as comfortable as they may be, I canít see the justification. Even in my own house at my cost 2 stage is good enough. Canít say for an extra 2 grand I need modulation


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  9. #20
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    Culver, Oregon (Central OR)
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    Quote Originally Posted by jbhenergy View Post
    Yeah as comfortable as they may be, I canít see the justification. Even in my own house at my cost 2 stage is good enough. Canít say for an extra 2 grand I need modulation


    Sent from my iPhone using Tapatalk
    True, I just mean let them know what could be available, in order to temper the expectations for what they are actually getting.

    You're a smart guy and I'm sure you know this. Just an FYI for anyone lurking.

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  11. #21
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    Sep 2005
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    Atlanta GA area
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    Quote Originally Posted by jbhenergy View Post
    I think itís more about managing expectations and educating the customer. You have to sit down with them and say hey, when itís 105 outside for the 2 day freak period we get once every 10 years, your system is not designed to keep your house at xyz temp. Explain it will run all the time, but may be 3-5 degree over setpoint. But since it is running 24/7 it will pull a lot of moisture out of the air so the comfort lever should still be reasonable.

    Itís all about informing them of what the system constraints are. Informing them of why we donít size for those freak days, and inform them about mechanical issues that arise from oversized. Itís all one big fine line we walk.

    Additionally, manual j produces numbers that have a slight fluff factor already in them. Using the numbers I get, I have, to my knowledge not had complaints about a cold house in winter or hot one in summer.

    On top of that still yet, equipment only comes in so many sizes. Letís look at mine. 17 cool 25 heat. That means Iím putting in a 24 cool 40 heat. Now I have double fluff.

    Iím not saying load calls are end all be all, but I do think they need to be used more in our industry. In the last two weeks I have seen two units, different buildings, that are 60 cool and 120 heat, and both calcs came to 24 cool 40 heat. Thatís a problem.

    Education is key.


    Sent from my iPhone using Tapatalk
    Yes, agree...
    We really need to sit down with the customer and explain it to them!

    On 'those freak days'...
    We had 6 weeks of 5-6*F above design literally EVERY DAY last year...
    Lots of folks were not happy!

    Most of the time, I install 1/2 ton over with a VS furnace (what this really means; is I do not reduce the size as much as a LC would dictate)... this seems to work out two ways:
    The 'ramp up' feature tends to de-humidify... and the extra capacity will keep the indoors cooler on peak days.

    Most folks are happy with that.

    During the 'Q&A' time I try to do with most of my customers (find out what their lifestyle and expectations are)...
    If they are fussy about comfort... we try to move them to 2 stage AC or inverter drive.

    Most of the time, if we can get folks to sit down with us and go over what they want/need... we can get them comfortable!
    GA-HVAC-Tech

    Your comfort, Your way, Everyday!

    GA's basic rules of home heating and AC upgrades:
    *Installation is more important than the brand of equipment
    *The duct system keeps the house comfortable; the equipment only heats and cools (and dehumidifies)
    *Cheap is not good, good is not cheap; however expensive is not a guarantee of quality!
    Choose your contractor wisely!

  12. #22
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    Location
    Atlanta GA area
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    Quote Originally Posted by Adlerberts-Protege View Post
    Explain to them the importance of modulating heat, variable capacity AC. Oversize those suckers and know it will kick ass in all extremes. They dont want to pay then educate them on what to expect from systems undersized, oversized, and properly sized.
    Be careful with this...

    In a hot and humid climate (SE America)... a too oversized variable capacity AC will not dehum properly...
    I know, because we have installed them...
    GA-HVAC-Tech

    Your comfort, Your way, Everyday!

    GA's basic rules of home heating and AC upgrades:
    *Installation is more important than the brand of equipment
    *The duct system keeps the house comfortable; the equipment only heats and cools (and dehumidifies)
    *Cheap is not good, good is not cheap; however expensive is not a guarantee of quality!
    Choose your contractor wisely!

  13. #23
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    Oct 2016
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    Slightly oversize and keep the flow at the bottom acceptable range...350 cfm/ton or so.

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