2 HVAC systems, 2 outlet temps

[beenthere]

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[udarrell]

The return is 72 discharge 68 (only a 4-F drop?) outside temp 82F.

about 1300 sq ft 4 second floor bedrooms, 2 BR, hallway, 2 story entryway

(It seems to cool off fine and may be oversized thus not running long enough to dehumidify - I wonder if I reverse DIP 7 and 8 yielding -15% cfm if that would help)

I can measure the pressures but was afraid I'd violate the DIY rules.

Okay, it took a while to find the 16-SEER 2.5-Ton single stage Goodman but here it is: using 85F outdoors; @ 850-CFM; 24,100-Btuh
70F IDB; 59F-IWB or, 52.47% RH; 19F indoor temp-drop, Not 4F, Coil is NOT cold enough to dehumidify.
HI PR 279-psig; Lo PR 124-psig; 2.06-KW; 6.3-amps

If it feels way too humid: @ 1350-CFM 63-IWB 68% RH; 13F temp-drop a lot lower due in large part to increase in humidity latent load; total of 28,000-Btuh.

There are major problems that need addressing; first get a CFM airflow check & get it down to 1000 or even 850-CFM so it dehumidifies.

[marcushvac]

Air handler appears to be set for 1020 CFM.

I'll knock it down -15% and see how it changes.

If that is not enough decrease in air flow and assuming for now the charge is proper, would changing the filter to a MERV 13 from a MERV 8 help? My reading through the forums seems to indicate you folks favor the MERV 8. (Unfortunately this system only has provision for 1" filters 16x20)

[teddy bear]

Air handler appears to be set for 1020 CFM.

I'll knock it down -15% and see how it changes.

If that is not enough decrease in air flow and assuming for now the charge is proper, would changing the filter to a MERV 13 from a MERV 8 help? My reading through the forums seems to indicate you folks favor the MERV 8. (Unfortunately this system only has provision for 1" filters 16x20)

Using a higher merv filter will slow air flow. Enough????
Regards TB

[marcushvac]

Using a higher merv filter will slow air flow. Enough????
Regards TB

83 outside.

I dropped the CFM by 15% using the DIP switches on the control board. Outlet Temp went from 68 down to 59 --
73 inlet

Swapped the MERV 8 for MERV 13 Outlet down to 56 - still moving alot of air. We'll give it some time and see how the humidity does.

My thanks to all those that responded and may continue to respond.

[udarrell]

Air handler appears to be set for 1020 CFM.

I'll knock it down -15% and see how it changes.

If that is not enough decrease in air flow and assuming for now the charge is proper, would changing the filter to a MERV 13 from a MERV 8 help? My reading through the forums seems to indicate you folks favor the MERV 8. (Unfortunately this system only has provision for 1" filters 16x20)

Well, if U were using a cheap fiberglass throwaway filter the velocity would be around 665-FPM; when initial velocity, according to manual D, through a clean throwaway filter ought to be 300-FPM.

If possible, just go to a lower speed setting.

[udarrell]

83 outside.

I dropped the CFM by 15% using the DIP switches on the control board. Outlet Temp went from 68 down to 59 --
73 inlet

Swapped the MERV 8 for MERV 13 Outlet down to 56 - still moving a lot of air. We'll give it some time and see how the humidity does.
My thanks to all those that responded and may continue to respond.

Well, U got the temp-drop to 14F; with a high humidity latent load that could be okay; under normal conditions 18 to 19F would be normal.

However, a 2.5-Ton 16-SEER; 85-F outdoor temp; 1350-CFM; @75-IDB; 67-IWB, about 67% RH; indoor temp-split would only be 13F...you're at 73F RA temp verses 75F; 83 outdoor verses 85F; we don't know what the actual %humidity is.

With the higher pressure-drop filter; not best option; the drop went to 17F.
If U get the air flow right; low enough; it should begin to dehumidify.

[marcushvac]

Well, U got the temp-drop to 14F; with a high humidity latent load that could be okay; under normal conditions 18 to 19F would be normal.

However, a 2.5-Ton 16-SEER; 85-F outdoor temp; 1350-CFM; @75-IDB; 67-IWB, about 67% RH; indoor temp-split would only be 13F...you're at 73F RA temp verses 75F; 83 outdoor verses 85F; we don't know what the actual %humidity is.

With the higher pressure-drop filter; not best option; the drop went to 17F.
If U get the air flow right; low enough; it should begin to dehumidify.

OK it's been a few hours having changed -15% CFM from 1020CFM orig setting and a MERV 13 in place.
Return temp is 72 as is the room temp, Indoor Humidity reads 63% (First floor is 74 and humidity is 52%) Outdoor temp is 92

[motoguy128]

Raise the thermostat up 1F and set the fan to "ON" for 30 minutes. Humidity should only go up 2-3%RH... and temperature maybe 1F... unless it's pulling in a lot of attic air. IF when running the fan only you can "smell the attic", then that may answer your question.

[teddy bear]

Raise the thermostat up 1F and set the fan to "ON" for 30 minutes. Humidity should only go up 2-3%RH... and temperature maybe 1F... unless it's pulling in a lot of attic air. IF when running the fan only you can "smell the attic", then that may answer your question.

Consider that there is 1 lb. of moisture per ton of coil retained on the coil at the end of the cooling cycle. The moisture on the coil will evaporate back to the home is 30-45 mins. with the fan "on". 2-3 lbs. of moisture into 1,800 sqft. of space will raise the indoor %RH 8-10%.
Regards TB

[marcushvac]

Consider that there is 1 lb. of moisture per ton of coil retained on the coil at the end of the cooling cycle. The moisture on the coil will evaporate back to the home is 30-45 mins. with the fan "on". 2-3 lbs. of moisture into 1,800 sqft. of space will raise the indoor %RH 8-10%.
Regards TB

Thanks. Not an experiment I care to do.

[marcushvac]

So it's been about a week and the humidity is down to 59% temperature outside 85, return 72, outlet 58.

Looking through the manual, there doesn't appear to be anything else I can do to lower the blower speed. -15% CFM DIP switch setting in place and a 1" MERV 13 from Filtersfast.com

Any further suggestions would be appreciated. Thanks guys.

[budman21901]

At the moment you have a 4 degree split, and that is a major issue! It's time to call a tech out to your home. Regardless of what you think is going on. The system must work correctly before you can fix the other issues.