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Available Technology There are several manufacturers of packaged heat pump systems including Magic-pak, Amana, General Electric, Frigidaire, and others. Current offerings are somewhat specific to the size of the wall penetration and available cabinet space, but most common sizes and layouts will have a heat pump offering for retrofit. Third party control systems can take input from the packaged heat pumps for monitoring and occupancy sensing remote control. However, manufacturers differ on the sophistication of controls for other building system integration purposes. The control system of most packaged heat pumps needs optimization to maximize runtime in heat pump mode instead of reverting to electric resistance backup. Many packaged heat pump solutions now have the capability to integrate remote thermostats and controls that can help optimize performance, but the on-board controls typically result in poor efficiency. Implications to Cooling and DHW Systems Packaged heat pump systems can provide both heating and cooling for each room, so both systems are replaced with this retrofit. The system capacity should be designed for the larger load in each room to ensure that both heating and cooling needs can be met for the specific climate that the building is in. Domestic hot water can’t be produced by a packaged heat pump unit, so the two mechanical systems remain unlinked. In buildings with gas room heaters, the DHW is produced separately already, so this is not a departure for the typology. When: Opportunities for Phased Retrofit Each room heater can be replaced with the packaged heat pump solution when necessary, so this retrofit can be phased to coincide with normal equipment replacement cycles. This is especially true for buildings where no additional masonry or wall opening modifications are necessary. If the packaged heat pumps can be directly installed with no other modifications, then the building can simply start ordering the new part number and install/replace worn out units normally. Existing packaged room heaters are typically replaced at a rate of 5- 10% per year, so following a normal replacement schedule would have nearly all units replaced after 10 years. Gas infrastructure needs to be carefully decommissioned as gas heaters are replaced with electric units. Barriers to Consider As with all heat pumps, the cost of electricity relative to fuel should be fully analyzed. Buildings using packaged gas heaters likely operate at relatively high efficiency since there are no heating distribution losses. Additionally, each room already has a thermostatic control, so overheating is not an issue. These factors add up to a low baseline energy cost, making an electrification retrofit less financially appealing. The biggest barrier to the widespread use of packaged heat pumps is a technological one: there isn’t a product on the market that can operate in heat pump mode in cold climates such as Mixed-humid and Cold/Very Cold, where buildings use the most heating energy. Current products will work in mild climates, but once temperatures get close to freezing and lower, packaged heat pumps mostly revert to electric resistance heating, destroying the efficiency, economics, and environmental argument for electrification. There are initiatives to develop better hardware based on the latest in mini-split system technology, but it appears that there will not be a viable cold-climate PTHP for the next 2-3 years. Since most packaged gas room heaters are located in Cold/Very Cold climates, the inability of current PTHPs to perform in cold climates makes this retrofit a non-starter. Steven Winter Associates,Inc. 37PDF Image | HEAT PUMP RETROFIT STRATEGIES FOR MULTIFAMILY BUILDINGS
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