New Three Ton Payne Condenser
I Installed a NEW 3 ton Payne Condenser with driers. Charged the system.
Low side line is sweating good, high side line luke warm. Temp coming out of vents are 69 degrees.
I removed the entire inside system outside and cleaned the coils with evap cleaner. cleaned Blower Motor and Squirrel cage.
Replaced it.
Evacuated the system and re-charged system.
Low side would not rise above 70 lbs pressure, but high side continued to climb to 350 lbs pressure still not cooling sufficiently.
Check ducting for leaks, all looks good.
Do you have any Idea what it could be. Rodger Touchette
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Copy the data chart in the prior post, & fill out as much as you can.
NEED: Outdoor temp; indoor temp & Relative humidity.
Approximate airflow.
A shot in the dark, it sounds like a partial restriction somewhere in he refrigerant circuit.
I more information to make any meaningful judgments.
No actual data, only a shot in the dark guesses.
A liquid line, including metering device, restriction would show high head & low suction pressure.
If there is a liquid line restriction somewhere you may have overcharged the system causing the high head pressure.
- udarrell
October 25th, 2008 at 1:43 pm
I have been purposely waiting so other techs would respond to these questions; they didn’t.
It appears you did not install a new evaporator coil that matches the new SEER & EER of the condenser; Mismatched systems do not work.
What refrigerant does the new unit call for, & is the evaporator & its refrigerant control rated for the same refrigerant? The problem may be at the refrigerant control.
If it is R22 the coil temp would be around 41ºF, if R410A it is only 15ºF; on the high-side 350ºF is 108ºF using R410A, or around 142ºF if R-22. With either refrigerant the high-side is way out of line with the low-side!
It appears there could be a restriction somewhere in the high-side of the refrigerant system.
Make sure the indoor blower is moving close to the correct 1200-CFM for a 3-Ton unit.
Check the condenser discharge air temperature compared to the outdoor temperature & the SEER Rating of your unit.
I am very sorry, I should have responded while the weather was warm.
You should have filled out the trouble shooting data in my other post!
- Darrell
February 27th, 2009 at 4:57 pm
Greetings,
we went way green and had the 2 part spray in foam installed in our new 8400 sq ft home. We’ve recently found water intrusions and subsequent mold issues. In the investigations, Engineers were question the size of the HVAC which is 2 five ton Tranes and a 2.5 ton Trane. We have 3 floors [one is a daylight basement] and many windows. We’re in the Carolinas and face east with the big windows and west with smaller windows with overhangs. The house is very tight, the windows have very high r factors and even the underside of the roofing is sprayed. Do you think this sounds like a reasonable size? We’re trying to get a mechanical engr but it’s so hard to find an independent one that does residential. Any thoughts?
Many Thanks!
freckles
February 27th, 2009 at 7:35 pm
That is a little less than 675-sf per ton of cooling, which should handle a well insulated low heat-gain home. I hope they weren’t inferring that the A/C’s weren’t big enough.
I have a “half-ton” window A/C that handles over 800-sf (First Floor) in 104F Heat Index, that is over 1600-sf per ton. It’s an old 1937 farm home with a lot of old leaky windows & insufficient insulation & very little shade.
You need someone to find the source of the moisture. If the moisture is penetrating from the exterior or a source within the wall, the A/C won’;t have access to that area.
If you have very cold air hitting a wall that could cause the interior portion to get below the dew point. Check the temperatures out of the supply diffusers. If it is too cold, increase the CFM to raise the air temperature, the increased CFM will cool just as fast, but the walls won’t get as cold.
Concerning the air conditioners, the important factors are: sufficiently long runtime cycles & CFM between 350 & 400-CFM of airflow per ton of cooling BTUH on each system.
You don’t have a water pipe in a wall with a very slow drip leak?
Get someone out there that can test for sources of moisture! - udarrell
March 7th, 2009 at 7:12 pm
Hello, I’ve just bought a 5 ton package air/heater. The SA is 16X18 and same with RA. I’d read on your site and recommend to have 2 (two) 25 X 25 air filters. I am confused. so the ducts for SA and RA should be greater than 288 inches square? Wouldn’t that compromise the air velocity? Would you recommend size for ducts and how many drops for that 5 ton unit?
I’ll greatly appreciated. Sorry for my poor English.
Sonny
March 8th, 2009 at 4:46 pm
Hello, I’ve just bought a 5 ton package air/heater. The SA is 16X18 and same with RA.
I’d read on your site and recommend to have 2 (two) 25 X 25 air filters. I am confused. so the [5-Ton SA Main 22”dia. Rd duct 380- SQ.INS 758-FPM VEL] ducts for SA and 24-SQ.IN rd duct or Return Air (RA) 452-SQ.INS 637-FPM VEL. should be greater than 288 inches square?
Wouldn’t that compromise the air velocity? Yes, at 288-SQ.INS
Would you recommend size for ducts and how many drops for that 5 ton unit?
Size them according to the BTUH of cooling required for each room or area.
A room requiring 4,000-BTUH / 26.66 = 150-cfm | Chart 150-cfm = 8″ round metal duct or 50 Sq.Ins., Square duct.
I would use an 8″ duct, or a 50 sq.ins., duct. Using 425-cfm per ton 12,000-BTUH 4,000-BTUH is a third of 12,000-BTUH.
Therefore, 4,000-BTUH room requirement, using 450-cfm per ton (airflow 1/3 of a ton) X’s .3333 = 150-cfm or 8″ duct | Vel. 430-FPM FR 0.05″
Formula for finding CFM Airflow from Velocity in FPM
If you can measure the air velocity coming from a known size duct or open area of a SA register, here is a rough ballpark formula to get the CFM:
CFM = (velocity in (FPM) Feet per Minute times the Square Footage of the duct area). To convert sq.ins., multiply by 0.00694 for sq.ft., or divide sq.ins. by 144.
Converting square duct inches to round duct size, Figuring the Square Inches of Round Ducts, an 8″ x 8″ duct = 64-sq.ins. x .7854 = 50.26 sq. ins. You round off to 50 sq. ins. for an 8″ duct.
Or, simply getting the square inches of round ducts: a 7″ duct; 7″ x 7″ = 49 x .7854 = 38.48-sq.ins., or divide / by 144 = .2672222-sq.ft. X’s a velocity of 500-fpm = 133.6-cubic feet per minute delivered to the room; 133.6-cfm x 30 = 4,008-BTUH.
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Greatly appreciated. Sorry for my poor English. Sonny
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Duct system sizing depends on many factors.
First, I would do everything you can to reduce the heat-gain heat-loss; then they should have performed a load calc & sized the A/C equipment accordingly.
Solving for Available Static Pressure (ASP) - When Designing or Redesigning Duct Systems, Finding TEL, FR:
Total Equivalent Length (TEL) Find the Total Return length, then find the longest Supply Equivalent Length (EL) by finding the longest measuring duct length, number of EL in the turning elbows, trunk take-offs, boots, etc.
Once you have all the correct Device Pressure Losses (DPLs) on the longest Supply Air run, evaporator coil, diffuser, etc.
Use the manufacturer’s nameplate pressure (IWC) or .5″ ESP and subtract all airstream device pressure losses in the longest TEL duct run (supply diffuser, damper, wet coil, etc. all available in manual D) from that given value. That will leave the “Available Static Pressure” - ASP for duct & blower design purposes.
You can figure the Total Equivalent Length (TEL) by using the Manual D length additives for the various fittings; then use your Duct Designer ductulator to properly size the duct system to meet the required CFM, velocities, Friction Rate (FR) as required in respect to the blower’s Nameplate ESP. Normally, 0.5″ ESP and its performance graph in relationship to the remaining (ASP) Available Static Pressure.
There are charts available to determine what the total pressure drop will be then when you figure the “Total Equivalent Length” run of the longest Supply duct runs; ALL lengths of duct and ALL fittings trunk duct take-offs, etc., to get the Effective Length (EL) additive to that duct run for the ‘Total Effective or (TEL) Total Equivalent Length.’
Subtract the total Device Pressure Losses (DPL) from the AH equipment’s “Available Static Pressure,” usually .5” ESP because most furnaces are designed for .5″ ESP to achieve the desired high speed CFM for cooling mode, if needed, you can always use a lower blower speed.
Then get a total equivalent length of your ductwork most ductulators have this on the back of them. Friction Rate = Available Static Pressure times X’s 100; divided by the TEL, that is the friction rate per 100 ft of SA &/or RA ducting.
Hope that helps
I am NOT Responsible for what you & your contractors decide to do!
- Darrell Udelhoven
March 16th, 2009 at 12:20 pm
Greatings,
Thank you! I would now go on this blog every day!
Thank you
Robor
March 25th, 2009 at 6:38 pm
Thank You, Robor.
Learn all you can, we need to conserve on energy use & lower our utility bills!
http://www.udarrell.com/proper_cfm_btuh_duct_sizing_air_conditioning_systems.html
- udarrell