LG Multi F HVAC Minimum Load Operation Owner’s Manual
- June 12, 2024
- LG
Table of Contents
LG Multi F HVAC Minimum Load Operation
Product Information
LG Multi F HVAC
The LG Multi F HVAC is a versatile heating, ventilation, and air conditioning system designed to provide efficient climate control for various spaces. It offers a combination of indoor and outdoor units that work together to deliver customized comfort.
This system is equipped with advanced features and technologies to ensure optimal performance and energy efficiency. It is suitable for both residential and commercial applications, offering flexibility in system design and equipment selection.
Minimum Load Operation
The LG Multi F HVAC is capable of operating at low or minimum capability, allowing it to efficiently handle spaces with varying load requirements. This feature ensures that the system adjusts its performance based on the specific needs of each space, maximizing energy savings and comfort.
When designing a project using the LG Multi F HVAC, it is important to consider the combination capacity range. The project designer should evaluate the system design and equipment selection, especially when individual indoor units (IDUs) are oversized for the load of the space they serve.
Example:
Let’s consider an example to better understand the product operation at low
or minimum capability:
- Outdoor Unit Model: LMU480HHV
- Total Connected Capacity: 36,000 Btu/h
- Indoor Units (IDUs):
- (3) 7,000 Btu/h IDUs
- (1) 15,000 Btu/h IDU
In this example, the 7,000 Btu/h IDUs have a space load requirement of 5,000 Btu/h each, while the 15,000 Btu/h IDU has a space load requirement of 13,000 Btu/h.
Product Usage Instructions
Follow these instructions to effectively use the LG Multi F HVAC system:
- Properly install the outdoor unit (LMU480HHV) and connect it to the indoor units (IDUs) according to the provided installation guide.
- Ensure that the combination capacity range for your specific project is within the recommended limits. Evaluate the system design and equipment selection, considering the load requirements of each individual indoor unit.
- When connecting multiple IDUs, distribute them strategically to match the space load requirements. Take into account the cooling or heating capacity of each IDU and assign them accordingly.
- Refer to the LG RLC Applications Guide for detailed information on system design and equipment selection.
- Regularly maintain and clean both the outdoor and indoor units to ensure optimal performance and longevity of the system.
- For additional assistance or troubleshooting, refer to the comprehensive user manual provided with the LG Multi F HVAC system.
By following these usage instructions, you can effectively utilize the LG Multi F HVAC system, enjoying efficient climate control and energy savings in your space.
Disclaimer
This white paper is a design-and-analysis guide to help designers optimize LG Residential Light Commercial system design based on product capacity. For the design and/or installation and service of LG HVAC products, please utilize or consult with the appropriate software, Engineering, Installation or Service manuals. Equipment selection and software modeling accuracy is highly dependent on user-supplied data. It is the user’s responsibility to understand how the data referenced or entered in software affects determination/program output, and to understand that any predefined libraries are to be used only as guidelines for entering project-based data. Calculation results and software reports described by this guide are meant to aid the system designer and are not a substitute for design services, judgment, or experience. The most current equipment data may be accessed on the LGhvac.com website.
Proper understanding of equipment capability is important to ensure successful design, installation, and operation. It also helps with setting appropriate expectations. While inverter components can adjust across a range of operation, the equipment’s capability may not be appropriate for every designed load. Statements like “it’s an inverter, it will ramp down to match the load” are common throughout the industry, though may not be true depending on the particular application of the product. In addition to consideration of equipment operation at design conditions, it’s essential for designers to evaluate the capability for equipment to “ramp down” and operate at low or minimum output.
First, it’s important to understand the overall capacity range that’s represented by the “Min~Rated~Max” capacity values cited in applicable product literature. The LG Residential Light Commercial Applications Guide (hyperlink embedded for convenience) includes a section that details equipment Min~Rated~Max capacity. Two main take-aways when reviewing the product’s capacity, should be that the cited values are based on AHRI rated conditions (cited on the equipment AHRI certificate) and that “Min” represents the minimum capacity output while “Max” represents the maximum (full-load) capacity output. So, a design taking into consideration more favorable or severe temperature conditions, when compared with the AHRI conditions could result in a variance from cited Min and Max capacity values, just as the capacity based on design conditions may be different than the AHRI “rated” capacity, or the published nominal capacity. Additionally, it is worth noting that the LG RLC Applications Guide includes other helpful information that should be reviewed such as a section that includes considerations to avoid equipment oversizing.
In addition to the content published in the LG RLC Applications Guide, the following examples provide additional details that should help improve understanding of product operation at low or minimum capability.
For a single zone HVAC system, the Min~Rated~Max capacity range simply correlates to the equipment capacity range. A cited Min or Max capacity is based on the matching indoor unit (IDU) and outdoor unit (ODU) – so any variance between cited values and expected output would only be due to external factors, such as project design temperatures and applicable pipe derate. For example, a 24k Btu/h Long Pipe system cited with Min capacity of 3,070 Btu/h at AHRI conditions could have a slightly diffe rent Min capacity when compared to actual project design conditions (such as 100F outdoor temp, 77/64 indoor temp). Before accounting for any pipe derate, the capacity in this instance, based on project design conditions, would be 20,790 Btu/h compared to the AHRI conditions capacity of 22k Btu/h. This is an important factor that must be taken into consideration since the Min~Rated~Max capacity range is based on AHRI temperatures and other physical system variable defined in the AHRI Standard, but the project design capacity is 5.5% less than the AHRI Rated capacity. Although it may appear at first glance that a designer might correlate a similar 5.5% reduction to the AHRI rated Min capacity if evaluating equipment minimum operation (or similarly the maximum operation), this assumption may not be true.
Table 2: Sinale Zone Extended Piping Wall Mounted Specifications
Cooling Capacity Table for LS243HLV3 (LSU243HLV3 + LSN243HLV3)
Table 11: LSN243HLV3 / LSU243HLV3 Cooling Capacities.
For example, consider a multi-zone product where the minimum capacity cited for a unit (c/o the Min~Rated~Max capacity cited in literature such as the Engineering Manual example below) may not be consistent with a specific project’s combination. The LMU480HHV has a cited Min~Max capacity range of 10,800~58,000 Btu/h: the minimum 10,800 Btu/h capacity corresponds to the minimum possible combination for that outdoor unit (which is 18k Btu/h of connected indoor units/capacity). Similarly, the maximum 58,000 Btu/h capacity corresponds to the maximum possible combination for that outdoor unit (which is 65k Btu/h of connected indoor units/capacity). In this example, a Multi F unit designed to accommodate the minimum 18k Btu/h combination will not be able to demand the ODU’s full-load Max capacity, and a Multi F unit designed to accommodate the maximum 65k Btu/h combination will not be able to unload to reach the Min capacity due to the capacity of the IDUs connected.
Table 17: Multi F MAX with LGRED Outdoor Unit Specifications.
INSTALLATION
To properly evaluate an outdoor unit’s minimum or maximum operation, it’s
important to first determine the appropriate minimum or maximum capacity
associated with the specific project’s IDU combination.
In the Multi F ODU Combination Data Manual Table 27 shown below, a unit with
36k Btu/h of connected indoor units/capacity has a specific and different
“Min~Rated~Max” capacity range compared to the “overall” capacity range cited
for the ODU. For example, a LMU480HHV with 36k Btu/h connection has a
Min~Rated~Max capacity range of 21,600~36,000~39,686 Btu/h.
Table 27: Non-Ducted Indoor Units ~ Rated Cooling Combination Table
The specified combination capacity range for a specific project is what the project designer should evaluate with respect to system design and equipment selection, especially if IDUs are each individually oversized for the load of the space load each serves.
Example: LMU480HHV with 36k Btu/h connected capacity from a combination of (3) 7k Btu/h IDUs and (1) 15k Btu/h IDU Consider that the 7k Btu/h IDUs have a space load requirement of 5k Btu/h each while the 15k Btu/h IDU has a space load requirement of 13k Btu/h.
In the above example scenario, if minimum required demand were evaluated only
for (2) of the 7k Btu/h IDUs – a total space load requirement of 10k Btu/h,
the project designer could mistakenly presume that the LMU480HHV “overall” Min
capacity of 10,800 Btu/h is adequate to satisfy the combined 10k Btu/h minimum
space load for the (2) 7k Btu/h IDUs. However, due to the overall
combination’s 36k Btu/h connected capacity, the actual Min capacity of the ODU
would be 21,600 Btu/h – more than twice the required space load (resulting in
more than twice the capacity required in each space). With no bypass
capability in the ODU for excess capacity and because the Branch Distribution
Unit EEVs are sized to accommodate up to a 24k Btu/h IDU1, the EEVs for the
(2) 7k Btu/h IDUs would pulse open wider than required to simply satisfy IDU
capacity, to accommodate the refrigerant flow from the compressor in order to
maintain target suction pressure… in this example, half of 21,600 Btu/h Min
capacity would go to each of the 7k Btu/h IDUs – 10,800 Btu/h each. Like the
single zone example above, the Min or Max capacity obtained from Multi F ODU
combination tables is based on AHRI temperatures, so at design conditions
there may be a slight variance that can be evaluated similarly using Multi F
ODU performance tables for the applicable combination.
Whether the Min~Max capacity range is determined by equipment limitation
(required minimum refrigerant mass flow through the compressor or the
compressor’s full-speed maximum capacity) or determined by logic based on
equipment combination (connected IDUs in a Multi F system that may be large
enough the compressor-based minimum is less than the connected combination
minimum capacity, or maybe small enough that the compressor-based maximum is
more than the connected combination maximum capacity), it’s important that the
designer understand how to determine and take into account which of these two
conditions will determine the corrected Min or Max capacity based on the
project’s equipment selection and local weather conditions. An accurate
representation of product operation must be evaluated so that proper design
adjustments can be made if necessary. For example, if small space loads drive
the oversizing of IDUs (and the ODU), it may be advantageous to combine space
loads so that they are accommodated by a single right-sized (ducted) IDU
instead of multiple oversized IDUs. With low static, high static, and VAHU
options there should be a solution available provided there is space to
accommodate ductwork.
Port D on PMBD3641 accommodates a 36k Btu/h IDU; IDU connections on single-fan Multi F ODUs accommodate up to 24k Btu/h; RLC IDUs do not contain EEVs – they are in the ODU or BDU vs VRF IDUs that have an integrated EEV sized for that IDU
Due to our policy of continuous product innovation, some specifications may
change without notification.
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