Oil prices, being what they are, have focused many homeowners on opportunities to reduce heating costs. One way to do that is to incorporate a heat pump system for the homeowner, particularly if that homeowner plans on staying at the property for a few years.
While heat pump systems have an upfront cost, they can generate a return on investment in energy savings in less than 10 years, and can make sense for homes heated by propane and gas as well as oil.
Heating oil dealers with an HVAC operation might consider diversifying the product and service offerings to include heat pumps. In many ways it’s a natural fit, but in others it requires some specialized training and experience. In colder climates a heat pump will typically serve as a compliment to oil, gas or propane heating.
Heat pumps basically work by exchanging heat through a liquid in order to heat or cool a space or ‘ with a reversible system ‘ do either as needed. The concept is generally similar to air-conditioning. The process requires some energy input either from electricity (a compressor and pumps) or gas/propane with a heat generator. The technology supports both forced air applications and radiant heating. For a simple overview, there are three common types of heat pumps on the market.
An air source heat pump is the similar to an air conditioner incorporating a compressor, condenser, evaporator, and refrigerant all in a similar form factor. An air source heat pump can deliver one-and-a-half to three times more heat energy to a home than the electrical energy it consumes according to the Department of Energy. However, as temperatures drop below 40°F they begin to lose effectiveness, though they are typically capable of functioning down to about 0°F. However, newer innovations push the technology’s efficiency to even higher levels allowing for efficient use in even colder climates.
Another type of air source heat pump is the ductless minisplit. These are basically up to four small indoor units linked to an outdoor unit that can provide efficient zone heating and cooling in homes where ductwork is not available or where the homeowner wants more finite control.
Ground or geothermal heat pumps place the heat exchanger underground in either a deep vertical shaft or a horizontal field at a shallower depth. Geothermal is typically the most expensive up front (well digging costs being a notable factor), but it has its advantages.
‘The difference between geothermal and air source is in the efficiency,” said Tim Cutler, president of TJ’s Heating & Plumbing which serves the Boston area. TJ’s is a full-service plumbing, heating, air conditioning service company specializing in alternative energy that includes solar, geothermal and pellet boilers among other technologies. His solutions include those from Bosch. ‘Efficiencies can be a lot higher with geothermal (compared to air source) because we’re working with 50°F steady Earth temperature where air source is dealing with temperatures that can plummet as low as -10°. When temperature drops, your efficiency plummets as well. However, if a house is really well insulated you can pretty much use an air source heat pump and almost do as well as geothermal depending upon the manufacturer you pick.”
Cutler noted a recent job on the south-end of Boston in a four-story brownstone with buildings on the right and left and the only exposure being on the front, back and roof. The layout of the job site was ideal for air source heat pumps and the ones chosen provided good efficiency down to -10°F. While geothermal is more expensive to install (depending upon soil condition, etc.), Cutler noted a system can pay for itself within eight to 10 years.
An absorption heat pump is an attractive option for propane dealers or for customers that simply must convert to gas. It is similar to an air source heat pump, but uses a generator (natural gas or propane burner) to boil the ammonia out of an ammonia/water refrigerant instead of using a compressor to generate a pressure cycle.
‘The beauty of a gas absorption heat pump is that instead of using a compressor for the refrigeration cycle you are using a gas flame,” said Clark Peters, vice president at E.W. Leonard, a manufacturer’s representative agency based in Moodus, Conn., which serves New England. Its heat pump offerings are manufactured by Robur. ‘Basically, we’ve created gaseous refrigerant, but we’re left with a pot of hot water. During the heating season, we can put that usable energy into your building. So the worst case, when we get below -20°F, we are getting a 95,500 BTU gas input and we are netting out at 86 percent, so we are always getting heat. Our BTU rating will go down, but we will always be able to give you the selected water temperature, just at lower flows. So that gives us a great deal of leeway. Our maximum temperature is 140°F, but we really have about 134°F. As long as you design within the temperature ranges of the machine as far as output temperatures, the beauty is that your creativity or your customer’s creativity is only limited by imagination.”
From a skill set standpoint, a heat pump can be a natural addition to a product and service offering. However, there are specific requirements for effectively implementing these systems.
With geothermal, the well-digging aspect can be problematic.
‘Challenges with geothermal include how close you are to water, can I get a drill rig in there ‘ that type of thing,” Cutler said. ‘That is always a variable especially near a city. In a geothermal system you could go horizontal eight to 10 feet deep if you really wanted to, but in the Northeast there is too much rock. So I pretty much do a vertical bore anywhere between 300 feet and 600 feet. We just finished a project with two 510-foot holes.”
Cutler also noted that it’s important to find the right well digging partners. They should have solid experience drilling geothermal wells and have quality crews. They should also be certified well drillers with the Geothermal Association to make sure they have a solid knowledge base of the concepts involved.
Peters stated that a major consideration for an absorption or geothermal system is thermal mass. ‘You have to do primary and secondary pumping and you must have a thermal mass tank that is equivalent to the unit’s R5 ton on the cooling load so you need something like a 40 gallon thermal mass tank and what most people do is just use that mass tank as your low-loss header,” he said. ‘When you get into the heat pump business, every pump that handles water has to have a thermal mass to stop short cycling. That prolongs the machine and we all know that short cycling drives your fuel costs berserk. I would guarantee failure if you do not put thermal mass and you do not use primary and secondary pumping. You just have to follow the rules. But the oil guys are not too bad this.”
Fine tuning the system at the control end is also important. ‘Another thing you have to understand is how controls work,” Cutler said. ‘You have multiple stages of equipment. Let’s just say were doing a 12,000 ft.² house and you have a boiler for backup and hot water. So what are the criteria to bring on the boiler? In a lot of instances, we’ve had to go in and repair systems where geothermal Stage I runs, then geothermal Stage II runs and the boiler fires up. The problem is once the boiler fires up it stays in the high range and the geothermal thinks it’s satisfied and the boiler takes over and never drops out. So understanding the control logic is key.”
He also noted that an oil-fired furnace produces 140°F air while an air source or geothermal system might produce 115°F or 120°F so the system needs to run longer to heat the space.
What should someone looking to get involved in heat pump systems know going in? Cutler offers the following advice. ‘I would make sure to get certified by a reputable agency, first,” he said. ‘And the key to the whole thing is not just understanding the geothermal system, but understanding the home envelope. If the house is really loose I am not going to do it because it is going to cost the client a lot of money and we’re going to get a hassle in return. A lot of customers don’t understand that, and if they want to go to somebody else, that’s fine. If they do not want to enhance the envelope of their house, I’m not interested. There is no gray area.”