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A Tacoma homeowner asked GreenBuildingAdvisor whether a proposed $39,550 air-to-water heat pump system can replace a nearly 20-year-old leaking gas boiler and provide both home heating and domestic hot water. The published question gives the proposed equipment and installation scope, but does not include an expert answer confirming the design, sizing or expected performance.
A Tacoma homeowner is weighing a $39,550 air-to-water heat pump proposal to replace a nearly 20-year-old gas boiler that is slowly leaking, and wants to know whether the system can provide both space heating and domestic hot water. The homeowner’s question, published by GreenBuildingAdvisor, describes the proposed equipment and work but does not include an expert answer confirming that the design will meet the house’s needs.
The house is described as a 1,750-square-foot home built in the 1950s, fairly well insulated and located in Tacoma, Washington. It is occupied by two or three people and currently has hydronic heating: staple-up piping serves the main areas, while radiators heat four bedrooms. The homeowner says the existing Triangle boiler is nearly 20 years old and leaking slowly.
The favored bid specifies a three-ton Spacepak Solstice CC32-40, described in the question as a variable-speed heat pump combi water heater using R-32 refrigerant. The $39,550 proposal includes removing the boiler, installing the heat pump, adding a buffer tank and pump, running insulated lines to the outdoor unit, electrical work, a new expansion tank, water-line connections, system purging, commissioning, a permit and first-year maintenance. The listed warranty is 10 years on the compressor, five years on parts and one year on labor.
The homeowner says the current system’s design calls for 140-degree water when it is 20 degrees outdoors, with an indoor temperature of 68 degrees. They also cite local electricity at about nine cents per unit and hydroelectric power as reasons for considering a move away from natural gas. Those details are the homeowner’s account; the source does not provide utility records, a heat-loss calculation or a contractor’s engineering documents.
Replacing Gas Without Losing Heat
The proposal puts a practical question facing owners of aging hydronic systems into focus: whether a heat pump can take over existing heating and hot-water duties without requiring a separate water heater or major changes to the distribution system. For this homeowner, the decision is time-sensitive because the boiler is already leaking, while waiting for it to fail could limit the time available to compare designs and contractors.
Whether the quoted system is a sound replacement cannot be judged from the equipment name and price alone. Heat output at cold outdoor temperatures, the water temperature required by the house, domestic hot-water demand and the compatibility of the existing piping and radiators all affect performance. The homeowner’s stated electricity price and hydroelectric supply may shape operating-cost and emissions considerations, but the source contains no comparative cost or emissions estimate.
air to water heat pump for home heating
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The Existing Hydronic System
The proposed replacement is intended to preserve the home’s water-based distribution: heated water would continue to serve the staple-up floor heating and bedroom radiators. An air-to-water heat pump draws heat from outdoor air and transfers it to water; a combi system is designed to serve space heating and domestic hot water. That general description does not confirm that this particular bid will deliver sufficient heat or hot water under the property’s conditions.
The homeowner says most local HVAC contractors and plumbers do not install these systems, and has received several bids. The source does not identify the other proposals or say how their scope and equipment compare. It also does not include the home’s measured heat loss, room-by-room loads, radiator output, floor-loop details or the heat pump’s output at the relevant outdoor and water temperatures.
“I’d like to get off of natural gas … and would love air to water heat pump.”
— The homeowner, in a question published by GreenBuildingAdvisor
domestic hot water heat pump system
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Design Details Still Missing
The available report does not include a contractor response, independent technical review or completed installation. It is therefore not confirmed whether the three-ton unit is correctly sized, whether it can meet the home’s heating load at cold temperatures, or whether it can reliably supply domestic hot water alongside space heating.
Other unanswered questions include the heat pump’s capacity and efficiency at the home’s required water temperature, the size and role of the buffer tank, the controls and backup-heating plan, and whether the quoted scope covers any changes needed to existing radiators or floor loops. The source also does not explain how the bid’s price compares with the other offers, whether rebates or operating-cost calculations were considered, or when the proposed work would take place.
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Checks Before Signing the Bid
Before accepting the proposal, the homeowner could ask the contractor for a written heat-loss calculation and equipment performance data at the local design temperature and the stated 140-degree water requirement. The bid should also clarify how the system will prioritize and supply domestic hot water, what happens during peak demand or very cold weather, and which components and modifications are included in the price.
Because the homeowner is unsure whether the design and contractor can deliver, a review by a professional experienced with air-to-water heat pumps and hydronic systems could help test the proposal against the home’s actual loads and distribution equipment. The next confirmed development would be an expert response, a revised or accepted bid, or a report of installation and operating results; none is provided in the source material.
air source heat pump for boiler replacement
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Key Questions
Can an air-to-water heat pump provide both home heating and hot water?
The proposed equipment is described as a combi water heater intended for both uses, but the source does not confirm that this model and design will meet this home’s heating and hot-water demand. Capacity, controls and the installation design need to be verified.
Is the proposed three-ton unit confirmed to be the right size?
No. The source gives the proposed three-ton capacity but does not provide a heat-loss calculation or equipment output data for Tacoma’s cold-weather conditions. The appropriate size cannot be established from the question alone.
What does the $39,550 bid include?
The homeowner says it includes the heat pump, boiler removal, a buffer tank and pump, plumbing and electrical work, an expansion tank, system purging, commissioning, a permit and first-year maintenance. The proposal lists a 10-year compressor, five-year parts and one-year labor warranty.
What should the homeowner verify before accepting the bid?
Ask for documented heat-loss and equipment-capacity calculations, performance at the required water temperature, and a clear explanation of hot-water delivery, cold-weather backup, controls and any changes to the existing hydronic system. The source does not include those details or an expert review.
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