Two-Zone Heat Pump Installation in Arlington, WA 98223: How Eli Got Separate Control Upstairs and Downstairs

Location: 107th Avenue Northeast corridor, Arlington, WA 98223

Call Date: October 9, 2025

First Visit: October 20, 2025, 8:00 AM

Project Completion: October 22, 2025, 4:00 PM

Lead Technician: Dima, 2 years as an installer, lead installer

System Before: A single-zone system on one thermostat, installed in 2009, with a Trane air handler and electric heat kit in the basement and a Trane outdoor unit in the backyard, failing with age and expensive to run, leaving either the upstairs too warm or the downstairs too cold

System After: A two-zone Mitsubishi 3.5-ton Hyper Heat multi-zone heat pump (MXZSM42NLHZ) feeding, through a branch box, a 2-ton variable-speed electric air handler in the basement (SVZAP24NL) and a horizontal ducted unit in the attic (PEAD-AA18NL), two zones under separate control, much of the ductwork redone, and a CAP G150 filter box

Final Project Cost: $23,176.14 (after a $2,500.00 Snohomish County PUD heat pump rebate, a $1,250.00 qualifying-model discount, and a $915.05 cash discount, before tax), plus a $481.99 CAP G150 filter box add-on

In Eli's house on the 107th Avenue Northeast corridor in Arlington, one thermostat ran the whole house, and it could only be right in one place at a time. Either the upstairs got too warm or the downstairs stayed too cold. According to the county record, the house was built in 1942 and has 1,792 square feet and four bedrooms. The heating system serving it had been installed in 2009.

By October 2025 that system was failing with age, and it was expensive to run compared with a modern heat pump. Eli wanted it replaced, and he wanted the upstairs and downstairs handled separately this time.

Why Eli Wanted More Than a Replacement

Eli is a returning Product Air Heating, Cooling, and Electric customer. He called on October 9, 2025, and the job was sold by Vince. He had already talked to at least one other contractor. By our technician's account, no one else offered him multiple zones. That gap is common, and it is worth naming. When an old system fails, the default heating quote is the same system again: one outdoor unit, one indoor unit, one thermostat, sized for the house. It replaces the equipment. It does not touch the reason the house was uncomfortable, which in Eli's case was never the equipment's age. It was that one thermostat was trying to control two floors that behave differently.

What the Heat Pump Installation in Arlington, WA 98223 Actually Found

Dima led the install. He has two years as an installer and works as a lead installer, and the internal install notes and job photos are his. The equipment was in the basement and the backyard. In the basement was a Trane air handler, model 4TEC3F36B1000AA, manufactured in August 2009, with an electric heat kit installed in it. Outside was a Trane outdoor unit. All of it ran as one zone on one thermostat.

Our technician's read on the cause was age and cost. The system was failing because of its age, after 16 years in service, and it was expensive to run compared with current heat pump systems. Neither of those explained the comfort complaint on its own. The one-zone layout did.

The ductwork turned out to be the larger job. To install the new air handler, the crew had to redo a lot of the air duct system.

Why Is One Floor of My House Warmer Than the Other?

Usually because the whole house is controlled from one thermostat. A single-zone system heats and cools until the room with the thermostat is satisfied, then stops, regardless of what the other floor is doing. Warm air rises, upper floors pick up more heat, and lower floors and basements stay cooler. Set the thermostat for one floor and the other one is wrong.

The fix is zoning: giving each area its own indoor unit or its own controlled airflow, and its own control. With a multi-zone heat pump, one outdoor unit feeds a branch box, which splits refrigerant and power to two or more indoor units. Each indoor unit runs to its own setting.

Eli's house is the worked example. One thermostat had been splitting the difference between upstairs and downstairs since 2009. The new system has two indoor units, an air handler in the basement and a horizontal ducted unit in the attic, both fed from one Mitsubishi outdoor unit through a branch box. In our technician's words, it gave him two zones, two indoor systems, and full control of the climate in his house.

The Plan: Two Zones on One Outdoor Unit

The plan was built around the complaint. Eli did not like that his upstairs and downstairs could not be kept at an even temperature on one zone and one thermostat, so the new system gave each its own indoor unit. A like-for-like replacement would have left the comfort problem where it was.

He also approved a CAP G150 filter box as a separate estimate at $481.99, which is added on top of the $23,176.14 project total.

What Product Air Installed: A Two-Zone Mitsubishi Hyper Heat System

The crew removed the 2009 system and set the new Mitsubishi Smart Multi Hyper Heat outdoor unit on a pad in the backyard. In the basement they installed the 2-ton variable-speed electric air handler, with the branch box mounted on the wall beside it. In the attic they hung the horizontal ducted unit. They redid much of the duct system to suit the new equipment, using 6-inch insulated flex duct, mastic duct sealant, and duct ties.

Refrigerant runs, from the installer's notes: 34 feet of 5/8- and 3/8-inch line from the heat pump to the branch box, 8 feet of 5/8- and 3/8-inch line from the branch box to the air handler, and 65 feet of 1/2- and 1/4-inch line from the branch box to the attic unit. Before charging, the system was evacuated, and the micron gauge photo from the job shows 155 microns, a deep vacuum that pulls moisture and air out of the lines before the system is charged. The work ran under a Snohomish County mechanical permit and a Washington State L&I electrical permit. It is a heat pump installation designed around zones rather than around the old equipment. Because the home is in unincorporated Snohomish County, the mechanical permit came from the county.

Three Days on 107th Avenue Northeast, and a Lot More Ductwork Than Planned

The job was booked as three days for two HVAC installers plus four hours for two electricians. The crew was at the house on the 107th Avenue Northeast corridor from 8:00 AM to 4:00 PM on October 20, 2025, again from 8:00 AM to 4:00 PM on October 21 with a second appointment that day from 8:00 AM to 1:00 PM, and from 8:00 AM to 4:00 PM on October 22, when the job was finished. Three days, start to finish.

The non-standard part was the ductwork. Fitting the new air handler meant redoing a lot of the existing air duct system, well beyond what a straight equipment swap would need. That is the work that does not show in the equipment list and is easy to underestimate, and on this job it ran well past what the price allowed for.

Warranty

The Mitsubishi equipment comes with a 12-year manufacturer warranty, subject to the manufacturer’s eligibility and registration requirements. That warranty applies to the Mitsubishi equipment only. Product Air Heating, Cooling, and Electric also provides a five-year labor warranty on its installations, with the option to extend labor coverage if the company continues maintaining the equipment after the initial five years.

The Real Number: $23,176.14, After Rebate and Discounts

The two-zone system, ductwork, thermostat, permits, and electrical work came to $23,176.14. That total reflects three reductions on the invoice: a $2,500.00 Snohomish County PUD heat pump rebate, a $1,250.00 discount for a qualifying model (the MXZSM42NLHZ is on the list), and a $915.05 cash discount. It is the final amount after all three and before tax. The $481.99 CAP G150 filter box was an add-on on top of this total.

The PUD rebate applied because the home was electrically heated. Snohomish County PUD pays $2,500 for a ducted, inverter-driven heat pump rated at least 8.5 HSPF2, and its program requires electric heat to be a primary heating source. A home heated by gas would not have qualified.

One more thing a reader pricing a similar job should know: we would rather say it here than surprise anyone later. The ductwork took far more than the price allowed for. The quote our salesperson gave did not fully cover it, and we honored the quoted price. A comparable job should run about 20% higher than this one did.

What It Means for Eli Going Forward

Eli's complaint was that one floor was always wrong. He now has two zones and two indoor systems, one in the basement and one in the attic, each with its own control, so the upstairs and the downstairs no longer share a single setting. The 2009 equipment that was failing and expensive to run is gone.

By our technician's account, Eli was happy enough with the result to call us for maintenance this fall, and he is, in our technician's words, a customer for life.

FAQ

Why is one floor of my house warmer than the other?

Most often because one thermostat controls the whole house. A single-zone system runs until the thermostat's room is satisfied, and since warm air rises, upper floors tend to run warm while lower floors and basements stay cool. In a 1942 Arlington home, one zone and one thermostat meant either the upstairs was too warm or the downstairs too cold, and the fix in October 2025 was a two-zone Mitsubishi heat pump with a separate indoor unit for each area.

Can one heat pump heat two floors separately?

Yes. A multi-zone heat pump uses one outdoor unit and a branch box that splits refrigerant and power to two or more indoor units, each running to its own setting. In Arlington in October 2025, a Mitsubishi 3.5-ton Hyper Heat multi-zone outdoor unit (MXZSM42NLHZ) was connected through a branch box to a 2-ton air handler in the basement and a horizontal ducted unit in the attic, giving the homeowner two zones with separate control.

How much does a two-zone heat pump cost in Arlington?

It depends heavily on the ductwork. One real Arlington job in October 2025, a two-zone Mitsubishi Hyper Heat system with a basement air handler, an attic ducted unit, permits, electrical work, and substantial duct rework, came to $23,176.14 before tax, after a $2,500.00 PUD rebate, a $1,250.00 qualifying-model discount, and a $915.05 cash discount. A CAP G150 filter box added $481.99 on top. The ductwork took more than the price allowed for, and a comparable job should run about 20% higher.

Does Snohomish County PUD give a rebate for a heat pump?

Yes, for electrically heated homes. The PUD pays $1,800 for a ducted conversion heat pump rated at least 7.5 HSPF2 and $2,500 for a ducted inverter-driven heat pump rated at least 8.5 HSPF2, installed by a PUD-registered contractor, and electric heat must be a primary heating source. An Arlington home with a 2009 air handler and electric heat kit received the $2,500.00 rebate on its October 2025 invoice for a two-zone Mitsubishi Hyper Heat system.

Why would a heat pump replacement need new ductwork?

Because the new indoor equipment does not always fit the old duct connections, and a zoned system may need ducts routed to a second indoor unit. Old ducts can also be undersized, damaged, or poorly sealed. In a 1942 Arlington home in October 2025, installing a new air handler and an attic ducted unit meant redoing a lot of the duct system with 6-inch insulated flex duct and mastic sealant, which was the largest and least predictable part of the job.

Key Takeaways

• An upstairs that runs warm and a downstairs that runs cold is usually a one-thermostat problem, not an equipment-size problem.
• A multi-zone heat pump feeds two or more indoor units from one outdoor unit through a branch box, each with its own control.
• Snohomish County PUD's $2,500 ducted inverter heat pump rebate applies to electrically heated homes, not gas-heated ones.
• Ductwork is the part of a replacement most likely to run over; on this Arlington job it did, and a comparable job should run about 20% higher than its $23,176.14 total.

Eli wanted his upstairs and downstairs to stop fighting over one thermostat. None of the other contractors he talked to offered him multiple zones. He got two zones, and he called us back this fall for maintenance.

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Serg Nikolin, Co-Founder, Product Air Heating, Cooling, and Electric

Marysville · Issaquah · Seattle · Western Washington