The whole loop. Not just one box out of it.
- Free sizing by in-house hydronic engineers — before you buy
- Parts stocked and shipped from New Jersey
- 7-year compressor warranty · 3 years on parts
Shop the whole loop.
A hydronic system has five jobs: make the heat, move the water, deliver the heat into the room, store what the building isn't using yet, and decide when all of that happens. Aquacoils supplies every one of them, so the parts arrive matched instead of assembled from four suppliers.
Heat Sources
The machine that makes hot or chilled water. Everything downstream is sized around what this unit can deliver, and at what water temperature.
Distribution
The plumbing that moves water from the heat source to the rooms, and splits it into zones.
Emitters
Where the heat leaves the water and enters the room. This is the single choice that most affects running cost.
A note on radiant floors: Aquacoils supplies the manifolds and PEX that make a radiant floor work. Fan coils are what you add when you also want cooling, because a floor cannot dehumidify.
Storage
Water the building has not used yet. Storage is what keeps the compressor from short-cycling and what lets one machine do two jobs.
Five reasons this loop will still be running in fifteen years.
1. Engineers size it. Then you buy it.
Most online sellers hand you a filter and wish you luck. Aquacoils has an in-house team of hydronic specialists who do the heat loss calculation, pick the model, choose the water temperature, size the buffer tank, and lay out the zones. You get a system, not a cart full of parts that happen to fit together.
Open the cabinet. You'll recognize what's in there.
A heat pump is three components and a lot of sheet metal. These are the three.
Panasonic compressor
The compressor is the heart of the refrigerant circuit. It raises the pressure and temperature of the refrigerant so heat can be pushed into your water loop. It runs more hours than anything else in the system, and when it fails, the unit stops. That is why it is the first component we specify and the one covered for 7 years.
Carel controller
The controller decides how hard the compressor works, when the unit defrosts, and what temperature the water leaves at. Good control logic is what turns a variable-speed compressor into long, steady, efficient cycles instead of constant starts and stops. Poor control logic wears out good hardware.
Grundfos circulator pump
The circulator moves water through the loop. Under-pump the system and the heat pump sees low flow and faults; over-pump it and you pay for the noise and the electricity every hour of the season. A properly matched circulator is the difference between a system you hear and one you don't.
Named on every spec sheet · Covered by the 3-year parts warranty · Replacement parts stocked in New Jersey
Hydronics, explained.
Water has carried heat around buildings for a century. In most of the US, forced air won the market instead, so hydronic systems are unfamiliar here even though they are ordinary in Europe and Asia. Nine questions, answered plainly. Skim it in a minute or read it in six.
What is a hydronic heating and cooling system?
A hydronic system moves heat around a building using water instead of air. A heat source warms or chills water, pumps push that water through pipe, and emitters release it into each room. Aquacoils supplies every part of that loop. The advantage is physical: water carries far more heat per unit of volume than air does.
Because water is that much denser a carrier, the pipe that serves a room is roughly the diameter of your thumb instead of a duct the size of a chair. That changes the building. You lose the chases, the soffits and the dropped ceilings that ducts demand. You also lose duct leakage, which in a typical US house wastes a meaningful share of what the equipment produced before it ever reaches a room. Water pipe running through a wall cavity does not leak heat into an attic.
It is also quieter. Moving heat with water means moving a small volume slowly. Moving heat with air means moving a large volume quickly, and air moving quickly is the noise you hear from a supply register.
What does an air-to-water heat pump do, and how is it different from a mini-split or a boiler?
An air-to-water heat pump takes heat out of outdoor air and puts it into water. That water then heats your building, your domestic hot water, or both. A mini-split puts that heat straight into refrigerant coils mounted in each room. A gas boiler burns fuel to make the heat. The heat pump moves heat that already exists.
The difference from a mini-split matters for two reasons. First, a mini-split needs refrigerant lines run to every indoor head; the Aquacoils AQ Series is monobloc, meaning the entire refrigerant circuit is sealed inside the outdoor cabinet at the factory and only water pipe crosses into the building. Nothing about the refrigerant circuit is field-assembled. Second, water lets one machine serve radiant floors, fan coils, radiators and a hot water tank at the same time. Refrigerant does not.
The difference from a boiler is efficiency. A boiler converts fuel to heat, and it can never produce more heat energy than the fuel contained. A heat pump collects heat from outside and moves it in, so the heat it delivers is a multiple of the electricity it consumes. Whether that is cheaper to run than your current system depends on your existing equipment, your local electricity rate, and your local fuel price. It is a calculation, not a slogan.
Where does the heat actually go? Radiant floors, radiators, fan coils and hot water.
One water loop can feed several kinds of emitter at once. Radiant floors take the lowest water temperature, typically 86 to 95°F supply. Hydronic fan coils take 104 to 113°F. Panel radiators take 122 to 131°F. A domestic hot water tank taps the same loop through its own coil. Aquacoils supplies all four connection points.
Fan coils do something the other emitters cannot: they cool. Run chilled water through a fan coil and it removes both heat and humidity, with the condensate going to a drain. That is why most Aquacoils residential systems pair a radiant floor for winter comfort with fan coils for summer cooling. One heat pump, one pipe network, two seasons.
The FP Series fan coils come in wall-mounted, ducted, cassette and console formats, so the emitter can be chosen room by room. A finished basement takes a ducted unit; a retrofit bedroom takes a wall unit; an open commercial space takes a four-way cassette.
Why does a buffer tank exist, and what happens without one?
A buffer tank is an insulated water tank sitting between the heat pump and the building. It adds volume to the loop. Without enough volume, a heat pump satisfies a small zone in a couple of minutes, shuts off, and restarts a few minutes later. That pattern is called short cycling, and it is the most common way a good compressor is worn out early.
The problem is worst in zoned systems. When five of six zones are satisfied and one small bathroom loop calls for heat, the water in that loop holds only a few gallons. The heat pump's minimum output can overwhelm it almost instantly. A buffer tank gives the machine somewhere to put that heat, so it runs a long steady cycle instead of a burst.
Long cycles are also more efficient cycles. A compressor at steady state is doing useful work; a compressor starting up is not. Sizing the buffer correctly is part of what the Aquacoils engineering team does with every system design.
What do manifolds and PEX actually buy me?
A manifold is the fitting where one supply pipe splits into many separate loops, each with its own balancing valve and its own actuator. PEX is the flexible tubing that runs those loops. Together they are what makes true room-by-room zoning possible, because every loop can be shut off, opened, or throttled on its own.
Zoning is not a luxury feature. It is how you stop heating the guest room you use twice a year, and how you keep a south-facing room with a wall of glass from overheating at three in the afternoon while the north bedroom is still cold. In a forced-air house, zoning means dampers and a lot of compromise. In a hydronic house, zoning is the default state of the system.
Every loop also comes back to one place. When something needs balancing five years from now, a technician opens one cabinet instead of chasing pipe through a ceiling.
R-290 or R-32? What the refrigerant actually changes.
R-290 is propane. R-32 is a fluorinated refrigerant. R-290 has a very low global warming potential and reaches high water temperatures well, which makes it strong for retrofits onto existing radiators. R-290 is also flammable, which is why every Aquacoils R-290 unit is monobloc and lives entirely outdoors.
Here is the honest trade-off. R-290's flammability is a real property, not a marketing footnote, and it is the reason the AQ Series has no indoor refrigerant charge to assess: the compressor, both heat exchangers and the expansion device are sealed in the outdoor cabinet at the factory, and only water pipe crosses the building envelope. That makes the safety question an outdoor siting question rather than an indoor plant-room calculation. It does mean the outdoor unit needs correct clearances, and we will specify them for your site.
R-32 carries a higher global warming potential than R-290 but is classified in a lower flammability category. Some projects, some owners and some jurisdictions prefer that. Both are legitimate engineering choices. The decision table further down lays them side by side.
When does geothermal earn its cost, and when does it not?
A geothermal heat pump draws heat from the ground instead of the outdoor air. Ground temperature barely moves across the year, so a geothermal unit does not lose capacity on the coldest night the way an air-source unit does. The trade is the ground loop itself: drilling or trenching is a significant, permanent, site-dependent cost.
Geothermal tends to earn its money on large heating loads, long heating seasons, sites with land or drilling access, and buildings the owner intends to hold for a long time. It also earns its money where an outdoor unit is not acceptable: noise ordinances, historic districts, exposed rooftops.
It tends not to earn its money on small loads, mild climates, tight urban lots, or projects where the owner will sell in a few years. An air-to-water unit with published capacity down to −13°F outdoor air covers a great deal of the US without a borehole. We will tell you honestly which side of that line your project falls on.
COP, and why your emitter choice matters more than you'd think
COP is coefficient of performance: heat delivered divided by electricity consumed. A COP of 3 means three units of heat for one unit of electricity. COP is not a fixed property of a machine. It changes with outdoor temperature and, critically, with the temperature of the water the heat pump is asked to produce.
The rule is simple: the lower the water temperature, the higher the COP. Asking a heat pump for 95°F water is far less work than asking it for 140°F water, and the efficiency difference across that range is large. This is why emitter selection is an efficiency decision, not just a comfort decision.
Which is why a radiant floor at 86 to 95°F supply is the most efficient emitter you can pair with a heat pump, a fan coil at 104 to 113°F is close behind, and existing high-temperature radiators are the hardest case. If you are keeping old radiators, the fix is often to add emitter surface so the loop can run cooler, and that is exactly the kind of call the Aquacoils engineering team makes on a design review.
Four things people believe about hydronics that aren't true
“Heat pumps don't work in cold climates.” The AQ Series has published capacity data down to −13°F outdoor air. At 5°F outdoor with 95°F leaving water, the AQ-060 produces 35,500 Btu/h. Capacity does fall as it gets colder. That is physics, and it is why we size against your actual design temperature rather than a nominal rating.
“Radiant can't cool.” Correct, and that is why nobody asks it to. Cooling is done with hydronic fan coils on the same water loop, because a fan coil removes humidity and a floor cannot. One heat pump, one pipe network, radiant in winter and fan coils in summer.
“It's only for new construction.” Retrofits are a large share of hydronic work. If a building already has radiators and pipe, much of the distribution exists. The design question is water temperature: whether the existing emitters can run cool enough for a heat pump to be efficient, or whether emitter surface needs to be added. That is a calculation, and we do it for free.
“It's exotic and nobody can service it.” A hydronic system is a pump, a tank, some pipe and a compressor. Any competent plumber can work on the water side, and any refrigeration technician can work on a sealed monobloc. Aquacoils stocks the parts in New Jersey so that service call does not stall.
Two loops, start to finish.
Here is what a complete Aquacoils system looks like on paper. Both examples are sized using the same method our engineering team uses on your project.
Residential: a 2,000 sq ft house
The building. 2,000 sq ft conditioned, good envelope, 19°F design temperature. Radiant floor throughout the main level, fan coils upstairs for cooling, and domestic hot water off the same machine.
The load. At 19 Btu/h per sq ft for a well-insulated envelope, the design heating load is 38,000 Btu/h.
1 — Heat source. An AQ-060 air-to-water heat pump. At 19°F outdoor air and 95°F leaving water, it produces 43,700 Btu/h, which covers the 38,000 Btu/h load with margin and stays inside our 0 to 15% oversizing target. Monobloc, so it sits outside and only water pipe comes into the house.
2 — Buffer tank. A stainless buffer tank between the heat pump and the zones, so the compressor runs long steady cycles even when only the bathroom loop is calling.
3 — Circulator. A Grundfos circulator matched to the flow the AQ-060 needs and the head the pipe network imposes.
4 — Distribution. A manifold in a central cabinet, one loop per zone, each with a balancing valve and an actuator. PEX from the manifold to every loop.
5 — Emitters, winter. Radiant floor loops on the main level, supplied at 86 to 95°F. The lowest water temperature in the house, which is also the highest efficiency.
6 — Emitters, summer. FP Series wall-mounted fan coils in the upstairs bedrooms. Chilled water in, heat and humidity out, condensate to a drain. 3/4" NPT connections, 120V/60Hz, 34 to 44 dB(A) on low.
7 — Domestic hot water. A stainless DHW tank with its own heat pump coil, magnesium anode rod and electric element. A three-way valve diverts the heat pump to the tank when hot water is called for, then returns to space heating.
8 — Controls. A room thermostat per zone, wired to the zone actuators and the fan coils.
Every numbered item above is an Aquacoils product. That is the point of the section.
Light commercial: a multi-zone building
The building. An office, clinic or small multi-family building with a load beyond a single residential unit, a mix of open floor plate and private rooms, and a real cooling requirement.
1 — Heat source. Multiple AQ Series units in cascade, staged so the plant modulates across the whole load band instead of one large machine cycling at part load. Up to eight units run on a single cascade bus.
2 — Buffer tank. Sized for the cascade, not for one unit. On a staged plant the buffer is also what gives the control sequence somewhere to put heat while it brings the next compressor on.
3 — Circulators. Primary circulation on the plant side, secondary circulation on the building side, so the heat pumps always see their required flow regardless of how many zones are open.
4 — Distribution. Manifolds per floor or per tenant, so zones are commissioned, balanced and billed in logical groups.
5 — Emitters. FP Series in the format each space needs: four-way cassettes in the open plate, ducted units above corridors and back-of-house, wall or console units in private offices. Nine sizes from 200 to 1,400 CFM, so the emitter matches the room instead of the room accommodating the emitter.
6 — Domestic hot water. Indirect DHW tank, sized for the building's simultaneous demand rather than its daily total.
7 — Controls. Zone controls per space, with the plant sequence handled at the heat pump controller.
On a commercial job, submittal data and a design review come from the same Aquacoils engineers who size the plant. Send drawings, get a plant schematic and a submittal package back.
Send us the building. We'll send back the system.
Every Aquacoils system design is done by our in-house hydronic team at no charge, whether you are a homeowner with one house or a contractor with a bid due Friday. There is no obligation to buy from us afterward, and we would rather tell you that a project is a poor fit than sell you the wrong machine.
1
You send us the building
Floor plans or a sketch with dimensions. Square footage and ceiling height. Construction type and insulation, as best you know it. Project ZIP code. What is heating and cooling the building today, and what you want to keep. Whether you need domestic hot water. If you have drawings, send drawings.
2
We calculate and select
We run the heat loss against your local 99% heating design temperature, not a national average. We pick the water temperature the emitters can live with, because that is what sets the efficiency. Then we select the heat pump, size the buffer tank, lay out the zones, and check flow and connection sizes across the whole loop.
3
You get a system, in writing
A one-page system schematic. An equipment schedule listing every component with its model number. The design water temperatures and flow rates. A priced cart you can edit or check out directly. On commercial projects, submittal data for the specifying engineer.
Turnaround: One business day.
No cost. No obligation. A real engineer reads it, not a chatbot. Prefer to talk? Call +1 332-245-2701.
What happens after it's installed.
7-year compressor warranty, 3 years on parts
Every Aquacoils heat pump carries a 7-year warranty on the compressor and 3 years on parts. Registration within 180 days of delivery is required to keep coverage active. Full terms are on the warranty page, linked from every product page, and we will not surprise you with a condition that isn't written there.
Parts stocked in New Jersey
We hold parts inventory in a New Jersey distribution facility. A controller, a circulator, a sensor or a valve ships domestically, so a unit in the field is not waiting on a container. Orders placed in the morning, Eastern time, ship the same day.
A hydronics engineer on the phone
Commissioning question, a fault code you haven't seen, or a design call at 4pm on a Friday. You reach the same team that sized the system, not a script. Call +1 332-245-2701, 9am to 6pm Eastern.
Domestic shipping from New Jersey · Spec sheets on every product page · Support from the engineers who sized it
R-290, R-32 or geothermal?
Three ways to make hot and chilled water. None of them is universally correct. Here is the honest comparison, and then the one-line version of each.
| Air-to-water, R-290 | Air-to-water, R-32 | Geothermal | |
|---|---|---|---|
| Heat source | Outdoor air | Outdoor air | Ground loop |
| Refrigerant | Propane. Very low global warming potential. | Fluorinated refrigerant. Higher global warming potential than R-290. | R-32. |
| Flammability | Flammable. Managed by design: monobloc, sealed at the factory, entirely outdoors. | Lower flammability category than R-290. | Not an outdoor-siting factor in the same way |
| Water temperature | Reaches high leaving water temperatures, which is what makes existing radiators workable. Published capacity data from 86°F to 167°F water. | Not currently stocked | Leaving water temperature from 59°F to 131°F. |
| On the coldest day | Capacity falls as outdoor air falls. Published data down to −13°F outdoor air. | Not currently stocked | Ground temperature barely moves, so capacity holds through winter. |
| What it takes to install | Outdoor pad or brackets, clearances, water pipe into the building. No indoor refrigerant work. | Outdoor pad or brackets, clearances, water pipe into the building. | Drilling or trenching for the ground loop, plus the unit indoors. Site access decides feasibility. |
| Aquacoils range | AQ Series, 20,500 to 61,400 Btu/h, cascadable for larger loads | Not currently stocked | One model, 4 ton nominal, 48,000 Btu/h. |
| Best for | Retrofits onto existing radiators, low-GWP priorities, most US residential and light-commercial jobs | Projects that prefer a lower flammability class | Large loads, long heating seasons, sites with land and a long ownership horizon |
Choose R-290 if
You want the lowest global warming potential available, you need high water temperatures because the building already has radiators, or you simply want the most capable air-source option. The monobloc design keeps every bit of refrigerant outside the building. This is the right answer for most US houses and most light-commercial jobs, and it is where our deepest model range and parts stock sit.
Choose R-32 if
Your owner, your specification or your local authority prefers a lower flammability class, and you are willing to accept a higher global warming potential to get it. It is a legitimate engineering trade, made deliberately. We are not stocking R-32 units yet, so tell us about the project and we will advise honestly on whether to wait or specify R-290 instead.
Choose geothermal if
The heating load is large, the season is long, the site has room for a ground loop, and the owner is holding the building. Also choose it when an outdoor unit is not acceptable at all: a noise ordinance, a historic district, or a roof with nowhere to put a machine. If none of those describe your project, an air-to-water unit will almost certainly be the better economics.
Frequently asked questions
What is an air-to-water heat pump?
An air-to-water heat pump takes heat out of the outdoor air and transfers it into water, which then heats a building through radiant floors, fan coils or radiators, and can also heat domestic hot water. Aquacoils air-to-water heat pumps are monobloc, so the entire refrigerant circuit is sealed inside the outdoor unit and only water pipe enters the building.
Does an air-to-water heat pump work in a cold climate?
Yes. Aquacoils AQ Series air-to-water heat pumps have published capacity data down to −13°F outdoor air temperature. Capacity does decrease as outdoor temperature falls, which is why Aquacoils sizes every system against the actual 99% heating design temperature for your project location rather than a nominal rating taken at mild conditions.
Can a hydronic system provide cooling as well as heating?
Yes. A hydronic system cools by circulating chilled water through fan coil units, which remove both heat and humidity and drain the condensate away. Radiant floors cannot cool, because they cannot dehumidify. Aquacoils systems commonly pair radiant floors for winter heating with hydronic fan coils for summer cooling on the same water loop.
Do I need a buffer tank with a heat pump?
In most zoned systems, yes. A buffer tank adds water volume so the heat pump runs long, steady cycles instead of starting and stopping every few minutes, which is called short cycling and is a leading cause of early compressor wear. Aquacoils sizes the buffer tank as part of every free system design.
Can I use my existing radiators with a heat pump?
Often, yes. Aquacoils R-290 air-to-water heat pumps have published capacity data at water temperatures up to 167°F, which covers many existing radiator systems. The real question is efficiency: lower water temperature means higher efficiency, so adding emitter surface to let the loop run cooler is frequently worth the cost. Aquacoils calculates this for you.
What is the difference between R-290 and R-32?
R-290 is propane, with a very low global warming potential and strong high-temperature water capability, but it is flammable, so Aquacoils R-290 units are monobloc and sit entirely outdoors. R-32 is a fluorinated refrigerant with a higher global warming potential but a lower flammability classification. Both are legitimate choices, decided by project priorities.
Does Aquacoils size and design the system for me?
Yes, at no charge. Aquacoils has an in-house team of hydronic specialists who calculate the heat loss, select the heat pump model, set the design water temperature, size the buffer tank and lay out the zones. You send floor plans, square footage, construction details and your project ZIP code, and receive a system schematic and equipment schedule.
What does the Aquacoils warranty cover?
Aquacoils heat pumps carry a 7-year warranty on the compressor and 3 years on parts. The compressor runs the most hours and costs the most to replace, which is why Aquacoils covers it longest. Registration within 180 days of delivery is required. Full terms are on the Aquacoils warranty page.
Can I buy directly from Aquacoils, or do I need a contractor?
You can buy directly. Prices are listed and every product can be added to the cart and ordered online, whether you are a homeowner, a contractor or a specifying engineer. Installation still requires a qualified installer for the plumbing and electrical work, and Aquacoils provides the system design and commissioning support at no additional cost.
Are Aquacoils parts stocked in the United States?
Yes. Aquacoils holds parts inventory in a New Jersey distribution facility and ships domestically, so a unit in the field is not waiting months on an overseas shipment for a controller, circulator, sensor or valve. This US parts stock is a deliberate part of how Aquacoils supports equipment after installation, not an afterthought.
Can one heat pump handle both space heating and domestic hot water?
Yes. A three-way valve diverts the heat pump to an indirect domestic hot water tank when hot water is called for, then returns it to space heating. Aquacoils supplies stainless DHW tanks with a dedicated heat pump coil, magnesium anode rod and an electric element, sized alongside the heat pump in the same free system design.
Is geothermal worth it compared with an air-to-water heat pump?
Geothermal earns its higher installed cost on large heating loads, long heating seasons, sites with room to drill or trench, and buildings the owner intends to hold for a long time. For most US houses and light-commercial projects, an air-to-water heat pump with published capacity down to −13°F is the better economics. Aquacoils will tell you which applies.
Buy the system. Or have us design it first.
Every product is priced and in the cart. Every system design is free and done by a hydronic engineer. Most people do both, in that order or the other one.
Questions? +1 332-245-2701