Climate Control

HVACR Tech Tip: Everything You Want to Know About 3-Way Heat Reclaim Valve Applications

HVACR Tech Tip: Everything You Want to Know About 3-Way Heat Reclaim Valve Applications - Parker Sporlan 3-Way Heat Reclaim Valve Type 8D

Today more and more applications are utilizing “heat reclaim” as a means of providing a supplementary or even a primary heat source. Heat reclaim can significantly lower energy costs. Heat reclaim is best described as the process of reclaiming heat that would normally be rejected by an outdoor condenser. Typically, the refrigerant is diverted to an air handler in an area that requires heat. One of the older applications of heat reclaim is in a supermarket since a supermarket has a constant supply of heat removed from the many refrigerated display fixtures and coolers. Today there are many cost-effective applications of heat reclaim in refrigeration, air conditioning, dehumidification, and heat pump systems.

While the most popular application of heat reclaim is air, water heating is popular in supermarkets, convenience stores, and restaurants, which all use considerable amounts of hot water. Essentially any application that requires heat can recover the heat from a refrigeration or air conditioning system. The energy efficiency of recovered heat will almost always be more efficient than any other purchased heat source. The common sense question is “Why reject heat to the outdoors when additional heat is required in any other moderate temperature application within the system or building?” 3-Way refrigerant heat reclaim valves make it convenient to recover rejected or waste heat.

 

Application

Valves may be installed in either a horizontal or vertical position. However, it should not be mounted with the coil housing below the valve body.

Series Versus Parallel Piping Schematics

Figures 2 & 3 show typical piping schematics for the two basic types of piping arrangements, series and parallel condensers. The selection of the piping arrangement will depend on the sizing of the reclaim coil and the control scheme of the system.

If the parallel piping arrangement is used, the reclaim condenser must be sized to handle 100% of the rejected heat at the conditions and time at which the reclaim coil is being utilized.

If the series piping arrangement is used, care and safety measures should be taken to prevent the mixing of subcooled refrigerant with hot gas vapors. These safety measures could include pressure or temperature lockout controls and time delay relays.

For both parallel and series piping, when the idle condenser is pumped down to suction pressure, a small solenoid valve can be used to pressurize the idle condenser prior to the 3-way valve shifting. This may reduce the potential for stress and fatigue failure of the refrigerant piping.

HVACR Tech Tip: Everything You Want to Know About 3-Way Heat Reclaim Valve Applications - Parker Sporlan Type B Reclaim Valve Condenser Pump Out

Heat reclaim with or without a bleed port

3-Way Heat Reclaim Valves with 3-way pilot valves are available in a variety of different sizes. These valves are available with an optional “bleed” port, see Figure 1. The bleed port allows the refrigerant to be removed from the heat reclaim coil or heat exchanger when it is not being used. There are two reasons why the refrigerant is removed from the heat reclaim coil. One is to maintain a proper balance of refrigerant in the system (i.e., refrigerant left in the reclaim coil could result in the remainder of the system operating short of charge). A second reason is to eliminate the potential of having condensed refrigerant in an idle coil. When an idle reclaim coil has condensed or even subcooled liquid refrigerant sitting in the tubes there is a potential for a problem. When refrigerant liquid, either saturated or subcooled, is mixed with hot gas refrigerant, the reaction of the mixing can cause severe liquid hammer. Hot gas mixed with liquid can create thousands of pounds of force and has the potential of breaking refrigerant lines and valves.

An alternate method of removing the refrigerant from a heat reclaim coil is to use a separate normally open solenoid valve and an optional fixed metering device, see Figures 2 & 3. The separate solenoid valve allows the flexibility of pumping out the reclaim heat exchanger as a liquid instead of a vapor. There are two benefits to pumping out the reclaim coil as a liquid: (1) Removal of any oil that may be present in the reclaim heat exchanger. (2) The refrigerating effect of the liquid can be used to lower the superheat of vapor entering the compressor, instead of cooling the heat reclaim heat exchanger. Sporlan recommends that recognized piping references be consulted for assistance in piping procedures. Sporlan is not responsible for system design, any damage resulting from system design, or for misapplication of its products.

Note: A check valve should be installed in the heat reclaim pump out or bleed line whenever the reclaim heat exchanger is exposed to temperatures lower than the saturated suction temperature of the system. This will prevent migration of refrigerant to the coldest location in the system.

HVACR Tech Tip: Everything You Want to Know About 3-Way Heat Reclaim Valve Applications - Series Condenser Typical Piping Schematic

Series condenser typical piping schematic

  1. Use optional solenoid valve and piping if pump out is required and “C” model Heat Reclaim Valve is used, see Note 4. It is optional to omit this solenoid valve and piping on systems using “B” model Heat Reclaim Valve.

  2. Restrictor, Part #2449-004, may be required to control pump out rate on an inactive condenser.

  3. The pilot suction line must be open to common suction whether or not Heat Reclaim Coil is installed at the time of installation and regardless of Heat Reclaim Valve model/type.

  4. Proper support of heat reclaim valves is essential. Concentrated stresses resulting from thermal expansion or compressor vibrations can cause fatigue failure of tubing, elbows and valve fittings. Fatigue failures can also result from vapor propelled liquid slugging and condensation induced shock. The use of piping brackets close to each of the 3-Way valve fittings is recommended.

HVACR Tech Tip: Everything You Want to Know About 3-Way Heat Reclaim Valve Applications - Parallel Condenser Typical Piping Schematic

Parallel condenser typical piping schematic

  1. Use optional solenoid valve and piping if pump out is required and “C” model Heat Reclaim Valve is used, see Note 4. It is optional to omit this solenoid valve and piping on systems using “B” model Heat Reclaim Valve.

  2. This check valve is required if lowest operating ambient temperature is lower than evaporator temperature.

  3. Restrictor, Part #2449-004, may be required to control pump out rate on inactive condenser.

  4. Pilot suction line must be open to common suction whether or not Heat Reclaim Coil is installed at time of installation and regardless of Heat Reclaim Valve model/type.

  5. Proper support of heat reclaim valves is essential. Concentrated stresses resulting from thermal expansion or compressor vibrations can cause fatigue failure of tubing, elbows and valve fittings. Fatigue failures can also result from vapor propelled liquid slugging, and condensation induced shock. The use of piping brackets close to each of the 3-Way valve fittings is recommended.

For additional information on 3-Way Heat Reclaim Valves download Parker Sporlan Bulletin 30-20 or visit the product page here.

 

HVACR Tech Tip: Everything You Want to Know About 3-Way Heat Reclaim Valve Applications - Jim Eckelkamp, Parker Sporlan

HVACR Tech Tip Article contributed by Jim Eckelkamp, senior application engineer,  Sporlan Division of Parker Hannifin

 

 

 

 

 

 

Additional resources:

HVACR Tech Tip: Using Bi-Directional Solenoid Valves for Heat Pumps

HVACR Tech Tip: 12 Solutions for Fixing Common TEV Problems

HVACR Tech Tip: How to Determine Total Refrigerant System Charge When Using Head Pressure Control

 

 

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