Heat pumps: Monoblock or split?

Before we delve into the different designs, it's important to understand the working principle of a heat pump. No matter which type you choose, heat pumps are efficient heating systems that harness free environmental heat by using a small amount of electricity.

For more information, please visit our website.

Heat pumps operate much like an inverted refrigerator, extracting thermal energy from the surrounding environment and transferring it to the building's heating system. This energy can be utilized for domestic hot water (DHW) heating and/or central heating backup. Common sources of primary energy in the private sector include ambient air, groundwater, and geothermal heat.

Given the higher initial investment required for water-to-water and geothermal heat pumps, many building owners opt for air-to-water heat pumps. They offer many advantages, especially in terms of flexible installation, which can be crucial when renovating existing buildings.

INTRODUCTION

Electricity prices have risen significantly in many Canadian provinces and U.S. states. This trend of increasing utility rates is expected to continue as federal and local governments push for greater energy efficiency by tightening building codes. This presents a major challenge for homeowners, designers, contractors, and equipment suppliers who must develop new products to meet these higher sustainability standards.

With many Canadians spending more time at home due to long winters, the COVID-19 pandemic, and an aging population, there is a growing demand for natural light in indoor spaces. More natural light involves larger fenestrated building envelopes, which in turn require more energy to maintain comfortable indoor living standards. Given the rising energy prices, stricter environmental regulations, and evolving living conditions, air-to-water heat pumps (also known as mini air-cooled chillers in Europe) are a cost-effective solution. These HVAC devices produce chilled/hot water (or a water/glycol mixture) for space heating and cooling as well as domestic hot water (DHW) heating. Equipped with a DC Inverter Compressor and EVI (Enhanced Vapor Injection) technology, split configurations of ATW heat pumps can operate in temperatures ranging from -25°C to 45°C.

MONOBLOCK AIR TO WATER HEAT PUMP

The Monoblock ATW heat pump is a single-piece unit installed outdoors. In areas where winter temperatures drop below 0°C (32°F), a propylene glycol/water mixture is used as a heat transfer fluid to prevent freezing. The glycol concentration depends on the lowest winter temperatures, with major Canadian cities typically using a 50% water/propylene glycol mixture. This heat pump requires an external pump for circulating the heat transfer fluid. During winter, the unit switches to cooling mode to defrost the ice on its evaporator, necessitating an external heat source for defrosting. The pump's speed is controlled by a PWM (Pulse Width Modulation) signal, allowing for modulating speed pumps.

SPLIT AIR TO WATER HEAT PUMP

A Split ATW heat pump consists of two units: one outdoor and one indoor. Unlike the Monoblock, it doesn't require a water/glycol mixture because the refrigerant used in the copper lines between the indoor and outdoor units doesn't freeze. The controller features a PWM signal to regulate pump speed, enhancing energy efficiency and summer performance when the system is in humidity control mode. Like the Monoblock, the split unit also switches to cooling mode in winter for defrosting and requires an external heat source.

ATW CONFIGURATIONS COST ANALYSIS

Air-to-water heat pumps can provide either chilled or hot water and pre-heated DHW. The price difference is largely driven by individual costs of the machines, glycol, pumps, and manpower.

HEATING OR COOLING WITH DHW PRE-HEATING

SIMULTANEOUS HEATING AND COOLING WITH DHW PRE-HEATING

The above schematics show the two most common installations of air-to-water heat pumps. In the setup on the left, one tank with an indirect coil preheats DHW to up to 130°F (55°C), while the other tank is used for either space heating or cooling. On the right, one indirect tank is used for both DHW pre-heating and space heating, and the other is dedicated to chilled water. In properties with significant fenestration, especially those with southern and northern exposures, different areas can have varying heating and cooling demands even in mid-winter.

Item

OUTES provides professional and honest service.

Monoblock HSS030V2LM

SPLIT HSS030V2LS

Heat Pump Selling Price

5,235

7,521

50% Glycol - 16 Pails - Selling Price (required to fill 2 x 40 US Gallons Tanks)

3,840

Manhours Cost for the Installation of Refrigerant Copper Lines Between Indoor and Outdoor Unit

480

Total Cost (CAD $)

9,075

8,001

CONCLUSION

Despite the lower initial cost of Monoblock heat pumps, the total installation cost of a Split ATW heat pump is often cheaper for customers. When water is used for heat transfer in split systems, costs associated with high-quality glycol and circulation pumps make the overall installation of Monoblock heat pumps more expensive. Monoblock heat pumps are popular among DIY enthusiasts for their perceived lower cost and ease of installation. However, Split ATW heat pumps require professional installation, particularly for refrigerant copper lines, which can deter some DIY customers.

Contact us to discuss your requirements for a Monobloc Heat Pump. Our experienced sales team can help you identify the options that best suit your needs.