dual-fuel heat pump
Dual-fuel heat pump. Image credit: Crawford Electric.
A dual-fuel heat pump is a heating appliance that combines an electric heat pump and a gas furnace. Dual-fuel heat pumps are effective in regions where the winter temperature is usually above freezing (allowing the heat pump to be used much of the time) but can occasionally drop below freezing, when the gas furnace provides heat more economically. Combining the two, offers the benefits of both systems. However, you need to make sure that the system is set up so that the heat pump is used whenever possible as it will generally run at a fraction of the cost of the gas furnace.
How a dual-fuel heat pump works
Heat pumps work in winter by moving heat from the atmosphere outside to the air inside the home. Because they move heat rather than create it, they're much more efficient than systems that burn fossil fuel. Heat pumps can work effectively just by moving heat providing the outside temperature stays above about 35°F (1.7°C). At lower temperatures, heat pumps depend on auxiliary heating to make sure the home stays comfortably warm. In the case of most heat pump systems, this supplemental heat comes from electric resistance heat. However, a dual-fuel heat pump uses a gas furnace – hence the name "dual-fuel".
Because there are advantages and disadvantages to both a heat pump and gas furnace based on the outdoor temperature, the dual-fuel solution offers the best of both worlds. It's the most comfortable heating system at any outdoor temperature, as well as one of the most efficient, versatile, and economical heating-and-cooling systems you can buy.
Using a dual-fuel heat pump cost-effectively
Typically, in a dual-fuel heat pump, the heat pump's compressor does about 85% of the work and the gas furnace heats around 15% of the time. In an ideal scenario, each fuel is used when it's most efficient.
It's important to get good advice, especially with the cost of natural and propane gas having risen so much in recent years. For example, some homeowners may be told to switch off the heat pump completely during the winter by moving the thermostat to the emergency heat setting. But this can prove very costly because they end up running the furnace exclusively at the very time when the cost of gas tends to be at its peak. It also means they're losing the benefit of half the heating system they have paid for.
The only time any heat pump, electric or dual-fuel, should be set on emergency heat is when the outdoor unit fails. Emergency heat is designed to provide minimal heating until the repairman arrives.
A similar problem happens when the dual fuel heat pump's outdoor thermostat is improperly set. The job of the outdoor thermostat is to determine when the heat pump switches from electricity to gas. If it's set too high, the system switches from electricity to gas too early. This means the homeowner misses out on some of the economical electric heating.
A good heating and air contractor will calculate the optimum outdoor temperature for the dual heat pump to switch from electricity to gas. This temperature, called the balance point, is usually around the 30s for a properly designed system. Setting the outdoor thermostat higher than the balance point means less-than-optimum use of the dual fuel system and higher energy bills.
A dual-fuel unit costs about $600 to $1,000 more than conventional heating and cooling systems because you're getting essentially two systems in one. But the amount you'll save in the next two to three years from lower heating costs will more than make up the difference you'll spend on a better system.
Choosing a system
There are several different brands and models to choose from. The most noticeable differences between them will be the price, and whether they'll be installed inside or outside your home. There are fewer packaged models available on the market. These systems are also more expensive than split systems.
Dual-mafuta pampu ya joto Picha: Crawford Electric. Pampu ya joto ya mafuta mawili ni kifaa cha joto ambacho huchanganya pampu ya joto ya umeme na tanuru ya gesi. Dual-mafuta pampu ya joto ni ufanisi katika mikoa ambapo joto majira ya baridi ni kawaida juu ya kufungia (kuruhusu pampu ya joto kutumika zaidi ya muda), lakini inaweza mara kwa mara kushuka chini ya kufungia, wakati tanuru gesi hutoa joto zaidi kiuchumi. Kuchanganya mbili, inatoa faida ya mifumo yote miwili. Hata hivyo, unahitaji kuhakikisha kwamba mfumo ni kuanzisha hivyo kwamba pampu ya joto ni kutumika wakati wowote inawezekana kama itakuwa kwa ujumla kukimbia katika sehemu ndogo ya gharama ya tanuru gesi. Pampu ya joto ya mafuta ya joto hufanya kazi wakati wa baridi kali kwa kuhamisha joto kutoka kwa hewa ya nje hadi hewa ya ndani ya nyumba. Kwa sababu wao kuhamisha joto badala ya kuunda ni, wao ni ufanisi zaidi kuliko mifumo ambayo kuchoma mafuta ya visukuku. Pampu za joto zinaweza kufanya kazi kwa ufanisi kwa kuhamisha joto tu ikiwa joto la nje linabaki juu ya 35 ° F (1.7 ° C). Katika joto la chini, pampu za joto hutegemea joto la ziada ili kuhakikisha kwamba nyumba inabaki yenye joto la starehe. Katika kesi ya mifumo mingi ya pampu ya joto, joto hili la ziada linatokana na joto la upinzani wa umeme. Hata hivyo, pampu ya joto ya mafuta mawili hutumia tanuru ya gesi <unk> kwa hiyo jina "mafuta mawili". Kwa sababu kuna faida na hasara kwa wote pampu ya joto na tanuru gesi kulingana na joto nje, dual-mafuta ufumbuzi inatoa bora ya ulimwengu wote. Ni mfumo wa joto wa hali ya juu zaidi katika hali yoyote ya joto ya nje, na pia moja ya mifumo ya joto na baridi ya ufanisi zaidi, ya kila aina, na ya kiuchumi ambayo unaweza kununua. Kwa kawaida, katika pampu ya joto ya mafuta mawili, compressor ya pampu ya joto hufanya karibu 85% ya kazi na tanuru ya gesi inapokanzwa karibu 15% ya wakati. Katika hali bora, kila mafuta hutumiwa wakati inapoweza kufanya kazi vizuri zaidi. Ni muhimu kupata ushauri mzuri, hasa kwa gharama ya gesi ya asili na propane kuwa imeongezeka sana katika miaka ya hivi karibuni. Kwa mfano, baadhi ya wamiliki wa nyumba wanaweza kuambiwa kuzima pampu ya joto kabisa wakati wa majira ya baridi kali kwa kuhamisha thermostat kwenye hali ya dharura ya joto. Lakini hii inaweza kuthibitisha gharama kubwa sana kwa sababu wao kuishia kuendesha tanuru peke wakati wakati gharama ya gesi huwa katika kilele chake. Pia inamaanisha kuwa wanapoteza faida ya nusu ya mfumo wa joto ambao wamelipa. Wakati pekee yoyote pampu ya joto, umeme au mbili-mafuta, lazima kuweka juu ya joto dharura ni wakati kitengo nje kushindwa. Joto la dharura limebuniwa ili kutoa joto la chini hadi fundi wa kurekebisha atakapofika. Tatizo kama hilo hutokea wakati thermostat ya nje ya pampu ya joto ya mafuta mawili imewekwa vibaya. Kazi ya thermostat ya nje ni kuamua wakati pampu ya joto hubadilisha kutoka umeme kwa gesi. Ikiwa imewekwa juu sana, mfumo hubadilisha kutoka umeme hadi gesi mapema mno. Hilo lamaanisha kwamba mwenye nyumba anapoteza sehemu fulani ya umeme wa kupasha joto. Mfanyakazi mzuri wa joto na hewa atahesabu joto bora la nje kwa pampu ya joto mbili kubadili kutoka umeme hadi gesi. Joto la joto la joto, linaloitwa kiwango cha usawa, ni karibu na 30 ° C kwa mfumo ulioundwa vizuri. Kuweka thermostat ya nje juu ya uhakika wa usawa ina maana chini ya matumizi bora ya mfumo wa mafuta mbili na bili za nishati za juu. Kwa mfano, mfumo wa mafuta ya mbili unagharimu karibu $ 600 hadi $ 1,000 zaidi kuliko mfumo wa kawaida wa joto na baridi, kwa sababu unapata mfumo wa mbili katika moja. Lakini kiasi utakachopunguza katika miaka miwili hadi mitatu ijayo kutokana na gharama za chini za joto itakuwa zaidi ya kufanya tofauti utakayotumia kwenye mfumo bora. Kuchagua mfumo Kuna bidhaa kadhaa tofauti na mifano ya kuchagua kutoka. Tofauti kubwa kati ya hizi ni bei na ikiwa itawekwa ndani au nje ya nyumba. Kuna mifano michache iliyopangwa inayopatikana sokoni. Mifumo hii pia ni ghali zaidi kuliko mifumo ya kugawanyika.