I'm looking for rules of thumb on sizing of backup resistance heaters for heat pump systems. All the plant knows is their requirements. For example, variable speed is better than a single speed because it dehumidifies better and with less energy used. Pumps don't have a fixed GPM, it depends on the head pressure. One rule of thumb estimates the average heat loss or gain based on the square footage of the structure. For example, a 20-in. One system approach that has successfully been used in practice is shown in Figure 1a. Other problems that may occur as a result are: To size a heat pump for any home, the HVAC industry follows a standard sizing method known as Manual J, established by the Air Conditioning Contractors of America. If you’re not comfortable in your own home, does it really feel like home at all? Carrier only wants the heat mode pressure chart used as a guideline, not as a charging tool. As per the advice of professionals the system should not be sized to provide all the heat required by a house, it is better to meet the heating loads between 80 % and 90% and provide not more than 125% of the cooling load – as suggested by Manual S. The balance point should be between 32 F and 23 F. It is even better to choose a two-stage heat pump as it can meet the heating and cooling loads when on low speed while the high heating loads can be met when the unit is on high speed. Cool, dude! For example, the builder may decide that it takes 1 ton (12,000 BTU) of air conditioning for each 800 square feet of space. But you have to be careful and avoid what most of so-called expert do; they make calculations based on the home floor space (area) or the old HVAC system. Blower Motor Type: Fixed Speed, Multi-Speed, Variable Speed. The building piping loop serves as a heat source (heating mode) or sink (cooling mode) for each heat pump and is connected to the ground loop in a primary-secondary piping arrangement. In humid climates if the unit is not sized properly, short cycling occurs, which leads to lower humidity control, comfort and due to its often stops and starts, the unit can be exposed to frequent failures and shorter lifespan. Heat loss calculation and radiator sizing for heat pump systems Calculation of the heat loss for each room forms the basis for the design and sizing of a heating system. Hi. This rule of thumb states that the MAX heating capacity required for your comfort cooling application is 1.7 x the cooling load. In order to properly heat and cool your home, there are a number of factors that go into sizing your unit. Not cool, dude. ©2019 Unique Indoor Comfort. For a 20F peak delta-T, you need just under 1gpm through the boiler per 10,000BTU of peak heat load. The higher the rating, the more efficient the unit. An undersized unit will work at its maximum capacity for as long as it is needed, in order to meet the set temperature, or even non-stop if it cannot keep up with the thermostat demand, leading to discomfort and potential failure of the compressor. Pump sizing Pump sizing involves matching the flow and pressure rating of a pump with the flowrate and pressure required for the process. Regarding ducts, for example, Forgot to mention another rule of thumb: Heating load in the Southeast is approximently 2.5 times cooling load. If you see a yellow bar under your address bar you must click it to allow scripts. The house was built with 24x24 and 12x12 returns which meet at the base of the air handler, for a total of 720 sq.in. Energy Efficiency Ratings: SEER and HSPF. Manual J is used to determine the heating and cooling loads (capacities) based on the house structure, size, number of doors and windows and the type, insulation, duct leakage, winter and summer conditions and other factors. The rule of thumb for GPM they have given you makes no sense to me. These describe the type of blower motor and will affect how efficient the heat pump works and its ability to provide comfort. In the simplest of terms, the rule of thumb states – for every 500 square feet of air-conditioned floor area install an AC of one-tonne capacity. Copyright © 2021-2022. This means the size of heat pump in tons is just a short hand measurement of the capacity of the system as a whole. Increased on-and-off cycling (resulting in increased stress on the motor blower), Uncomfortable, drastic temperature differences. A Manual J may seem a little complex for homeowners who aren’t heating or cooling professionals. The recommended way for sizing the heat pump, such as the air-to-air type, in North America, is using the Manual J and Manual S procedure, which are recommended by the Air Conditioning Contractor’s Association of America (ACCA). That is unless you enjoy paying higher utility costs and extra repair fees. Does it really matter if your heat pump isn’t quite the right size? The local climate and how many days a year you need active heating and cooling2. And since most sizes of heat pumps are determined by BTU (or British Thermal Unit), you’ll also need to know that each ton is worth 12.000 BTU. For example, for the mild climates use the 5 kW heating elements for the heat pump of 1.5-2 tons or 10 Kw for up to 5.0 tons heat pumps. Carrier supplies many heat pump condensing units with a pressure guideline chart. If the heat pump is oversized or undersized As the air-to-air heat pump is capable to provide both heating and cooling, it often happens, especially in central and northern parts of North America that a heat pump is sized to provide most of the heat required by a house, because the heating load is larger than cooling loads. When sizing a heat pump for your home we begin by determining the required cooling capacity just as we would with any air conditioning system. Click here for even more home heating systems comparisons. For example, if the cooling required is 30 tons (360,000 btus), then the MAX heating capacity required would be 612,000 btus (1.7 x 360,000). System components You and your contractor should discuss options that will help improve your home's comfort and the economy of your heat pump. If 5.6kW of heating capacity is required to heat a room, a heat pump that is rated at 5.6kW heating will not deliver 5.6kW at 0°C outdoor ambient temperature! 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