Photo may vary slightly — verify by model number before ordering.LG KUMXA421A 42,000 BTU Multi F MAX LGRED° 2–6 Zone Heat Pump Outdoor Unit, R32
In stock and ordered before 1pm ET, Mon–Fri? It ships the same day from our US warehouse.
Not sure it's the right unit? Send the model and serial — help@totalhvacparts.com or 302-219-4994.
Need more than 2? Ask about factory lead time — we'll give you a real date, not a guess.
Min. order: 1 unit · Weight: 239.2 lb · Truck Freight
Overview
LG KUMXA421A is a 42,000 BTU class R32 Multi F MAX LGRED° multi-zone inverter heat pump outdoor unit that runs 2 to 6 LG Multi F indoor units — wall-mount, ArtCool Mirror, ceiling cassette, low wall console or mid-static ducted — on one condenser. Rated capacity is 10,800 / 42,000 / 53,000 Btu/h cooling and 12,420 / 48,000 / 54,500 Btu/h heating (min / rated / max). It replaces the R-410A LMU421HHV.
218.3 lb net, 208 - 230V, 60, 1 power, 32.5 A MCA / 40 A MOP, 54 dB(A) sound pressure in cooling, heating operation down to -13°F outdoor, 48,000 Btu/h available at 5°F. Line set is Ø3/8 x 1 liquid × Ø3/4 x 1 vapor, 32.8 / 229.6 ft (180.4 ft pre-charged), 98.4 ft max elevation.
Pairing and installation
- Indoor units: LG Multi F R32 heads (KNUAB, KNUAK, KNMAB, KNUDB, KNUFB, KNUQB, KNUJB) — combination limits per LG's combination data manual, linked under Documentation.
- Refrigerant: R32 (A2L) — installation by a licensed contractor following the LG R32 installation manual and local code.
- Electrical: 208 - 230V, 60, 1, 32.5 A MCA, 40 A MOP; disconnect and breaker field supplied.
Installation and warranty registration by an LG-trained licensed contractor — current terms are in the LG limited warranty document under Documentation.
Compatible Units
LG approves KUMXA421A only in the combinations below (per the LG engineering manual and submittal). Mixing it with any other outdoor or indoor unit is not an AHRI-rated match. Ask the parts desk if your existing equipment isn't listed.
- LG Multi F indoor units: KNUAB, KNUAK, KNMAB, KNUDB, KNUFB, KNUQB, KNUJB (R32)
Specifications
Values in italic are not yet confirmed from OEM documentation. Ask us to verify before ordering.
Documentation
Companion Units & System Bundle
| Model | Description | Stock | ||
|---|---|---|---|---|
 |
KNMAB071ALG · Compatible indoor unit | KNMAB071A 7,000 BTU Multi F High Efficiency indoor unit | ✓ In stock | View |
 |
KNMAB151ALG · Compatible indoor unit | KNMAB151A 15,000 BTU Multi F High Efficiency indoor unit | ✓ In stock | View |
 |
KNMAB241ALG · Compatible indoor unit | KNMAB241A 24,000 BTU Multi F High Efficiency indoor unit | ✓ In stock | View |
 |
KNUAB091ALG · Compatible indoor unit | KNUAB091A 9,000 BTU High Efficiency indoor unit | ✓ In stock | View |
 |
KNUAB121ALG · Compatible indoor unit | KNUAB121A 12,000 BTU High Efficiency indoor unit | ✓ In stock | View |
 |
KNUAB181ALG · Compatible indoor unit | KNUAB181A 18,000 BTU High Efficiency indoor unit | ✓ In stock | View |
 |
KNUAK091ALG · Compatible indoor unit | KNUAK091A 9,000 BTU ArtCool Mirror indoor unit | ✓ In stock | View |
 |
KNUAK121ALG · Compatible indoor unit | KNUAK121A 12,000 BTU ArtCool Mirror indoor unit | ✓ In stock | View |
After You Order
Order number and confirmation by email the moment you check out.
Pulled from our shelf — the same live count you saw on this page. In-stock orders placed before 1pm ET, Mon–Fri, leave the same business day.
Tracking number lands in your inbox the moment it leaves the building.
Check the part number on the label against your order before installing. Wrong or damaged? Tell us — we'll sort it out.
Ask the Parts Desk
Not sure this fits? Need more than what's in stock? Send the model and serial from the unit's data plate — a real person reads it and confirms before you order.
Common Questions
What does the LG KUMXA421A pair with?
LG rates KUMXA421A only with LG Multi F indoor units: KNUAB, KNUAK, KNMAB, KNUDB, KNUFB, KNUQB, KNUJB (R32). Other combinations are not AHRI-matched and are not covered by the LG warranty.
What does the KUMXA421A replace?
KUMXA421A is LG's current R32 model in this position and replaces the discontinued LMU421HHV. R32 and R-410A equipment cannot be mixed — replace the indoor and outdoor unit together.
What power does the KUMXA421A need?
208-230V, 1-phase. Minimum circuit ampacity and maximum overcurrent protection are listed in the Specifications table above and on the LG submittal under Documentation; size the breaker and wire to those values and local code.
Is the submittal sheet and installation manual available for KUMXA421A?
Yes — the LG submittal data sheet, engineering manual, installation manual and warranty document are all linked under Documentation on this page and can be downloaded without an account.
Is the stock number on this page real?
Yes — it's the live count from our own shelf, not an availability estimate. If it says 2, that's how many are physically here. When it hits zero, this page says so.
Is this a genuine LG unit, or aftermarket?
Genuine LG OEM equipment — not an aftermarket substitute.
I see this listed under a different name on other sites. Is it the same part?
Yes — manufacturers and distributors sometimes use different brand names or legacy labels for the same part number. Part number KUMXA421A is identical across all name variations.
What's the warranty on this part?
Warranty terms vary by manufacturer. Contact us with your order number for details specific to this part.
How fast does this ship?
In-stock items ship the same business day on orders placed before 1pm ET, Monday–Friday. Standard ground delivers to most of the continental US in 2–5 business days. This part ships by LTL freight, so transit runs on the freight schedule — we'll contact you to arrange delivery.
Does everything ship UPS or FedEx Ground?
This part ships by truck freight rather than parcel — still free, included in the price shown, and we'll contact you to schedule delivery before it ships.Most orders ship UPS or FedEx Ground. A small number of large or heavy parts across the catalog ship by truck freight instead — that's still free, and we reach out to arrange a delivery window before those orders leave the warehouse.
