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Old 05-31-2020, 12:50 AM   #16
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Re: Heat pump size recommendation


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Originally Posted by roughneck View Post
The entire link you posted is based on square footage. Including the big map that gives sizing ratings based on “zones”.
This kind of graph/map doesn’t exist for sizing. Links like you posted have people wind up with oversized equipment that performs poorly.
Sizing, unlike your opinion, is quite difficult and requires theory, science and mathematics to get right.
Did you actually look / read the site.


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Old 05-31-2020, 06:37 AM   #17
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Re: Heat pump size recommendation


In the theory of sizing it seems the known fact that -- moisture is removed first -- has been lost, then the air temperature changes.
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Old 05-31-2020, 07:16 AM   #18
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Re: Heat pump size recommendation


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Originally Posted by Kemper100 View Post
Did you actually look / read the site.


Went through all of it. Even used the zip code quick calculator towards the bottom of the page. Said I need 6 tons of cooling and 120k BTU furnace for my home. Which is again, wrong.
You said-
Quote:
I never said equipment sizing was based on square footage.
But that site lists the information in the photos below.
The only thing that’s right about that site is all the way towards the bottom it gives a link to a manual J/manual D site.
But please, explain how a colorful map with sizing ranges per square foot is going to help someone size their equipment?
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Heat pump size recommendation-68308a52-039f-44b2-adec-488911b6d76e.jpeg   Heat pump size recommendation-dc19c50a-e727-44dc-bce3-3c41b3d485c9.jpeg  
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Old 05-31-2020, 09:45 AM   #19
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Re: Heat pump size recommendation


thanks everyone's input.
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Old 05-31-2020, 10:18 AM   #20
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Re: Heat pump size recommendation


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Originally Posted by SeniorSitizen View Post
In the theory of sizing it seems the known fact that -- moisture is removed first -- has been lost, then the air temperature changes.
You have to cool the air below dewpoint before moisture condenses - both happen but the ratio changes as humidity is removed.

decent sizing tools include the latent load.
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Old 05-31-2020, 11:26 AM   #21
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Re: Heat pump size recommendation


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You have to cool the air below dewpoint before moisture condenses - both happen but the ratio changes as humidity is removed.

decent sizing tools include the latent load.
We don't need to cool the air below dew point. To remove moisture we need the evap coils to be below dew point. This is where size matters. The larger the coil the more moisture removal.
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Old 05-31-2020, 12:23 PM   #22
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Re: Heat pump size recommendation


The air that actually contacts the coil fins gets cooled below the dewpoint, not all of it does, it mixes.

A larger coil doesn't necessarily improve dehumidification, it can do the opposite because it takes longer at the beginning of each cycle to get cold enough to start condensing moisture.
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Old 05-31-2020, 12:49 PM   #23
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Re: Heat pump size recommendation


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A larger coil doesn't necessarily improve dehumidification, it can do the opposite because it takes longer at the beginning of each cycle to get cold enough to start condensing moisture.
How long does it take, a few seconds?
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Old 05-31-2020, 12:51 PM   #24
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Re: Heat pump size recommendation


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How long does it take, a few seconds?
15-20 minutes in some cases.
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Old 05-31-2020, 12:54 PM   #25
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Re: Heat pump size recommendation


Having a fan that starts slow and ramps up can speed it up.

built into the programming of most variable speed blowers.
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Old 05-31-2020, 12:54 PM   #26
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Re: Heat pump size recommendation


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15-20 minutes in some cases.
That's nonsense and you should realize that. Better get a new unit because there is something out of order with that one. Your car or truck better do it in seconds or you'll be looking for another one.
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Old 05-31-2020, 01:08 PM   #27
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Re: Heat pump size recommendation


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That's nonsense and you should realize that. Better get a new unit because there is something out of order with that one. Your car or truck better do it in seconds or you'll be looking for another one.
To fully start a system, get it to stabilize and get 100% capacity out of it takes time. Absolute minimum 10-15 minutes. Most are 15-20.
To suggest that it can be done in seconds is completely unrealistic.
And your car or truck doesn’t do it in seconds.
It’s a proven fact that newer “high efficiency” systems are less efficient at removing moisture then older low SEER R-22 systems. Due to many various reasons including the sheer size and mass of the evaporator.
This is one of the reasons oversized systems have such difficulty removing moisture and cause the space to feel like a cave.

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Old 05-31-2020, 02:57 PM   #28
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Re: Heat pump size recommendation


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That's nonsense and you should realize that. Better get a new unit because there is something out of order with that one. Your car or truck better do it in seconds or you'll be looking for another one.
i don'y know if you've ever seen a system with gauges hooked up but it easily takes at least 10 minutes for the pressure and temp readings to stabilize.

the new units are worse, the lower the efficiency the faster steady state is reached due to smaller coils and a higher capacity compressor. (car a/c has small coils relative to capacity)

the cooling may start almost right away but most of the evap coil generally needs to be well below dewpoint to really start condensing moisture effectively.

it takes time not only for the low side pressure to drop but also for the evap to be mostly liquid.
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Old 05-31-2020, 04:17 PM   #29
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Re: Heat pump size recommendation


On these 2 maps where would you expect de-humidification to even be a factor and the evaporator coils to ever be cold enough for condensation to form today at this time?
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Old 05-31-2020, 05:14 PM   #30
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Re: Heat pump size recommendation


It's only mayand this weekend has been cool at least on the east side on the continent. Outdoor dewpoints are not very high now.

When the outdoor dew point is in the 60s, particularly 65+, dehumidification becomes very important.

Mild but humid weather is the most problematic.

Need a 55F indoor dewpoint inside for 50% rh at 75f so most of the coil better be at 45 or under.
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