Understanding Heat Pumps | Future House | Ask This Old House

In this video, Ask This Old House building technology professional Ross Tretheway explains everything you need to know about heat pumps

How Heat Pumps Work
Heat pumps work by finding and moving heat in and out of a building. A heat pump will take heat from within the home during the summer and let it dissipate outside, allowing the air conditioning system to work more efficiently. In the winter, a heat pump can scavenge heat from the outdoors (even in temperatures as low as zero degrees) and pump it into the home for comfort. The only requirement? Enough electricity to run the compressors.

Different Types of Heat Pumps
Heat pumps are becoming more and more advanced, but there are four basic types: water to water, water to air, air to air, and air to water.

Water to Water
This type of heat pump requires geothermal drilling, which means drilling into the earth to tap into its heat. The water travels below the surface, comes back up, and travels through a heat exchanger. In the heat exchanger, the source water heats the load water. The load side water then travels through the heating system just as it would a force hot water system.

Water to Air
Water to air systems require geothermal drilling to source the heat in the earth's surface. Then, the hot water runs through a coil in a duct. When air blows across that coil, it heats up, just as it would with a furnace.

Air to Air
In an air to air system, the heat pump sources heat from the air on the load side, which is then transferred to a refrigerant. This refrigerant then travels through a coil inside the ductwork, where load side air blows across it, similar to a furnace. These are the most common heat pumps.

Air to Water
An air to water system sources heat from the air on the source side and transfers it to a refrigerant. This refrigerant then cycles through a heat exchanger where it can heat the load side water to be pumped through the house.

Once in the house, this water can serve several purposes. It can be pumped to a zone manifold for hydronic heat, cycled through a heat exchanger for domestic hot water, or even pumped through a coil to supply a ducted system. In the summer, this system can remove heat from the home, cool the refrigerant, and supply the home with cooling.

There are a ton of advantages to this system over the others. First, no drilling is required. Second, you get the efficiency of hydronics. In some cases, homeowners relying on older heating systems can expect to save thousands of dollars each year on heating costs, as well.

Where to find it?
Ross explored four different types of heat pump systems: water-to-air, water-to-water, air-to-air, and air-to-water. These heat pumps can usually be sourced through a local HVAC technician or sales representative.

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From the makers of This Old House, America’s first and most trusted home improvement show, Ask This Old House answers the steady stream of home improvement questions asked by viewers across the United States. Covering topics from landscaping to electrical to HVAC and plumbing to painting and more. Ask This Old House features the experts from This Old House, including general contractor Tom Silva, plumbing and heating expert Richard Trethewey, landscape contractor Jenn Nawada, master carpenter Norm Abram, and host Kevin O’Connor. Ask This Old House helps you protect and preserve your greatest investment—your home.

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Understanding Heat Pumps | Future House | Ask This Old House

[nicklk]

I've watched 100's of episodes of TOH and had no clue Russ was Richard's kid :o

[martinroncetti]

That air-to-water system looks amazing. The vendor/installer mentioned that the homeowner (in this case) would be saving ~$2K/yr in costs. I would like to know roughly what the homeowner costs were (& therefore, the payback period) and if/how could solar hot water panels could be tied in to further reduce costs. I am aware of at least one hot water tank provider/producer that has a "dual-fuel" source hot water tank. Regardless, the air-to-water looks like a great way ahead.

[sailorjerry]

great video, would love a more updated one with comparisons of multiple heat pump systems.

[paulutato]

This system is phenomenal and perfect for retrofits like mine where I want to transition to hydronic radiant from gas-fired forced air. Worth highlighting the manifold, at 6:35, allowing expansion to radiant in the future. Hoping Enertech can find contractors in my area.

[ilovetotri]

Awesome! Not sure it fits my situation, but I have learned a ton. Thanks.

[mking]

That air to water system is sweet, I'd like to know more about it, for a future project, thanks

[kevinremsen]

What an amazing technology. Thanks for the video!

[jeremyjedynak]

In the air-to-water system shown, during summer months when heat is removed from the house to cool the living space, is that heat directly transferred to the domestic hot water, or instead is the heat directly transferred to the outdoor air, and then when the system needs to heat dhw the does the system then pause from cooling the house to heating dhw?

[b_uppy]

Think that NY heat exchanger needs to be a lot higher. There are those years where it can get deep.

[trailguy]

i live in virginia lowlands, near DC, and my heat pump is 20 years old. i use A/C in the summer and use wood almost exclusively in the winter, 6 cords. I might run heat a total of 3 days. my question is how much longer will my heat pump last if it's getting almost no wear from heating? is there a way of an inspection to determine longevity?

[briangc]

As a licensed HVAC contractor, I always compare cost benefits and ROI on every system we sell. The biggest benefit of these systems is space savings. Their Achilles heel is that WHEN, not IF, they break, you lose all 3 systems at once. Cold shower, no heat, etc on Saturday morning in A far more economical solution is separates, with redundancy. A heat pump water heater with electric backup is better. A Carrier/Bryant 2 stage air to air heat pump for heating and cooling is more efficient and dependable than the system shown in the video. The total cost is less for separates due to the economy of scale in production. Service is never an issue since the separate units use industry standard components that 90+% of the time I have on my service trucks as standard stock parts because over 90% of the HVAC units use these same parts.
TOH has a history of showcasing new tech that never survives to grow into old tech. Been watching the show since the 70's and seen many many of these unicorns come and go.

[SRK-vm]

This looks cool. How much does this cost roughly?

[Bournechris]

Can your air to water heat pump be used on a dryer he says the high cost of a heat pump dryer

[sharpshooter]

1st time seeing this guy & as soon as i saw him, i knew who his dad was. Lol

[RangeRov]

I'm in upstate NY; better raise that heat pump up higher than that!

[malikdigger]

Definitely important to know how newest water pump technology the older ones will split within 10-15 years.

[Bournechris]

Can you add a self running motor generator unit to you air to water heat pump the runs continuously If you lose electricity from a weather event and are there rebates

[ulicrammond]

I would need a second house for all this equipment.

[RRaucina]

I have a year round non freezing creek. Can I make this my heat source? Seems awfully simple compared to miles of pipe.

[OzziePara]

All these systems, solar, geo thermal, etc sound really good at saving the homeowner(s) on energy costs. But what they never tell you is how expensive these types of systems cost and how it will take a LONG period of time before the homeowner(s) get to the point of breaking even. Trust me, I've been there done that.