Case Study · Riccarton, Christchurch
Two-Zone Ducted Heat Pump Upgrade in Riccarton, Christchurch
Upgrading a character villa with 3.3m lath-and-plaster ceilings from four individual split units to two independent Mitsubishi Electric ducted systems.
Project Overview
Two systems engineered for a character villa
An older character villa in Riccarton, Christchurch, with approximately 3.3 m high lath-and-plaster ceilings previously relied on four individual split heat pumps. One unit was no longer working, and another was suspected of having a refrigerant issue.
Rather than replacing the individual wall units, Heat Pump Upgrade Co designed an engineered solution using two separate Mitsubishi Electric ducted systems — creating two independently controlled areas of the home tailored to the high ceiling volumes and heritage structure.
System Specifications
Project details at a glance
Equipment Selection
Two independent systems for living and bedrooms
Rather than installing one large central system, Heat Pump Upgrade Co selected two dedicated Mitsubishi Electric ducted units: a PEAD-M71JAA dedicated to the kitchen, dining and living spaces, and a PEAD-M125JAA dedicated to the four bedrooms.
This two-system strategy allows the living areas and bedroom wing to be operated independently with their own schedules and setpoints. Each system features a Mitsubishi Electric PAR-41MAA wired wall controller alongside Wi-Fi control for remote operation.
Comfort that fits your routine
Both ducted systems include Mitsubishi Electric Wi-Fi Control, allowing the living areas and bedrooms to be managed independently from the same smartphone app.
The homeowners can turn either system on or off, adjust temperatures and operating modes, and set separate schedules to suit their routine. They can warm the living areas before arriving home or schedule the bedroom system ahead of bedtime.
Each system also has its own Mitsubishi Electric PAR-41MAA wired wall controller for convenient control at home.
Remote app access requires an internet connection.
The four bedrooms operate together as one zone, with their own temperature setting and schedule, independently of the kitchen, dining and living system.
Duct & Airflow Strategy
Downjet diffusers for 3.3 m ceilings
Villas with 3.3 m high ceilings present a clear airflow challenge: warm air naturally rises and stratifies near the ceiling. To ensure comfortable temperatures reach the occupied living zone at floor level, the system uses a combination of 200 mm and 250 mm Downjet diffusers.
Downjet diffusers project conditioned air downward rather than spreading it horizontally across the ceiling surface, helping drive warm air down where occupants live. Three large 750 × 400 mm hinged filter return-air grilles provide generous return pathing while allowing easy filter access for ongoing maintenance.
Workmanship & Installation Care
Precision care in lath-and-plaster ceilings
Cutting into older lath-and-plaster ceilings requires exceptional care. Aged plaster can crumble easily and fine dust spreads rapidly throughout the home. The installation team used vacuum cleaners, respirators and protective suits, taking time to ensure every ceiling opening held together cleanly without damaging the surrounding heritage fabric.
The openings created for the three 750 × 400 mm return-air grilles also served a critical dual purpose: providing the necessary access to lift the indoor units into the roof space. In the roof cavity, the PEAD-M125JAA bedroom indoor unit was positioned above the hallway with the aim of reducing sound levels near the bedrooms.
System Layout
Two-zone system design plan
The initial design plan mapped out the two separate ducted systems, identifying proposed unit locations, duct runs, supply diffusers and return-air positions across the villa's living areas and bedrooms.
Client Feedback
What the client said
“The entire experience of getting our ducted system installed was excellent. From planning through to installation and post-installation support, it was clear that the team was committed to getting it right.
I initially wondered how well the system would perform in an old villa with high lath-and-plaster ceilings, but the design and installation were thoughtfully tailored to accommodate those factors.
The team’s workmanship and work ethic were outstanding, and we are now reaping the rewards of their effort.”
Project Investment
Project investment: NZ$25,000–$27,000 including GST
Replacement of four individual heat pumps with two Mitsubishi Electric ducted systems, providing independent control of the living areas and bedrooms. The installation included Wi-Fi control and air distribution designed for the villa's high ceilings.
This investment range reflects the completed project. Pricing for your home will depend on the system design, scope and installation conditions.
Related Solutions
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