#1398 2025-SFam: Prescriptive Refrigerant Charge

[Scott Criswell]

Update rules to require Refrigerant Charge for Heat Pumps across ALL climate zones (except for homes <= 500 ft2). (T24RClimateZoneCodeBaselines table still accurate for AC => req'd in CZs 2 & 8-15)
Confirm changes to defaults and standard design HPs.

[Scott Criswell]

mods implementing this new prescriptive refrig charge standard design change checked into SVN @ r2554

[Thao Chau]

For additions/alterations:

1. HPs: Refrigerant charge verification is required for all CZs except for additions/alterations with less than 500 ft2.
2. ACs: Refrigerant charge verification is required in CZ 1 and 8 – 15 except for additions/alterations with 500 ft2 or less.

[Scott Criswell]

@ThaoChau - Re: Alteration requirement adjustments - is the check on '> 500 ft2' on just the Added (new) area, or the total home Cond area (or perhaps total area served by the new/altered HVAC system)?

[Scott Criswell]

final mods addressing latest comments checked into SVN @ r2570

• ensuring refrigerant charge not verified for standard design of small new additions or altered homes (<= 500 SF)

[Trevor Thomas]

SVN 2570: I'm seeing refrigerant charge being triggered for heat pumps under all conditions even when <= 500 sqft. The default value in the GUI is also 'verified'. I've attached 2 of the files I've used. In case I set the files up incorrectly, or perhaps my SVN didn't fully update.

These files are:

A new construction 500 sqft home w/ heat pump
An EAA model with a ~250 sqft addition w/ new heat pump

[Scott Criswell]

SVN 2577 -
New cons 500 sqft home in CZ 5 w/ ductless, mini-split HP - Refrig charge NOT required in CZ5 - HVAC system type not supported, so Prop=Std HVAC. Both Prop & Std CSE simulation inputs indicate Refrig Charge not verified (RSYS rsFChgH = 0.9), however -
Unrelated BUG - Proposed HVAC system should be identical to Std, but is NOT setup properly as PerfMap split HP (currently simulated as 'old style' split HP). Will fix this in association w/ tic #1379.
EAA Example - 1,665 SF cond area home incl. 225 SF addition - new split HP serving only addition, w/ refrig charge verified. Std design is Verified because for an EAA model the check for <= 500 SF is on entire conditioned area, not just addition area or area served by HVAC system. Addition area is used in check for <= 500 SF only for Addition Alone projects.

Pending review by CEC - no additional changes expected and ticket can be closed.