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Friday, November 22, 2024
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Mini Split Air Conditioner

MEP Academy Instructor
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Mini Split Air Conditioner

We’ll cover single and multi-zone split systems air conditioners and the requirements for piping, electrical, and controls.  We’ll show you three different system configurations using a single zone layout, and two different multi zone layouts. There are many different styles of ductless indoor units that we’ll present in this article.

If you prefer to watch the Video of this presentation, then scroll to the bottom or click on the following link. Mini Split Air Conditioners

Single Zone Air Conditioner

The use of a single zone air conditioner is good for one room. The single zone mini split system has two main components. One is the condenser which will be located outdoors on a pad or attached to the wall with a bracket, and the other one of many different indoor fan coils.

Mini Split System Air Conditioner - Single Zone System
Mini Split System Air Conditioner – Single Zone System

Here we show a wall mounted indoor fan coil which houses the evaporator, fan, and filter. The indoor unit attaches to the wall using a bracket that comes with the unit. Just locate a stud in the wall to mount the bracket for proper support of the unit.

Refrigerant Piping

Insulated copper line sets will be installed from the outdoor unit to the indoor fan coil. There are some line sets that come per-charged with refrigerant. They work for some applications where the distance is 25 feet or less between the outdoor and indoor unit. If a line set doesn’t work then standard lengths of ACR refrigerant piping will need to be installed. This could involve cutting pipe to length, possibly brazing at some locations, and/or new flares installed on the ends. 

ACR Copper Tubing and Line Sets for mini split system air conditioners and heat pumps
ACR Copper Tubing and Line Sets

After making the connection between the outdoor and indoor unit, the non-pre-charged refrigerant line set should be pressure tested to ensure no leaks. Next, a vacuum will be pulled on the piping before opening the valve on the outdoor unit. The outdoor unit can hold a predetermined amount of refrigerant based on system capacity.

Checkout These Mini Split Air Conditioners

Electrical Power

Electrical power will need to be provided to the outdoor unit through some form of disconnect. There are two options for powering up the indoor fan coil depending on model and make. One is that the outdoor unit can provide the electrical power directly to the indoor unit along with the communication wire, or the indoor unit can be separately connected to a power source. 

Condensate

Since the fan coil produces condensate in cooling mode, there needs to be a drainpipe installed to an approved drain receptor like the tailpipe of a sink or to the outdoors. Condensate occurs when moisture in the air condenses when drawn over the cold indoor coil.  The indoor fan coil units have the option for a condensate pump. Condensate may need to be pumped upward before connecting with a drainpipe.

If you have more than one zone or room needing air conditioning, then a multi zone air conditioning system is available in various configurations.

Multi Zone Air Conditioner

With a multi zone system you’ll need an outdoor unit with an inverter compressor. That’s a compressor that can vary the volume of refrigerant to match the current load. There are many different styles of indoor fan coils that you can use such as floor mounted, wall mounted, and a ceiling cassette. There are also ducted versions that can be concealed out of view.

Indoor Unit Types for Multi Zone

Some manufacturers allow up to nine indoor units for every one outdoor unit. 

In this example, this multi zone mini split air conditioning system has three zones. As you can see it requires that you run a set of separate copper refrigerant lines for each indoor fan coil. Each zone feeds a different room, and they each have their own controller. Two rooms could be in cooling mode, while the other one is off. 

Multi Zone Split System Air Conditioner (3 Zones)
Multi Zone Split System Air Conditioner (3 Zones)

Inverter Compressor

With the inverter compressor the reduced demand is not a problem, as the compressor reduces its flow of refrigerant to meet the demand. The old school central air conditioner will cycle on or off to meet demand. Without an inverter compressor and zoning there was no way to reduce energy usage when demand was reduced.

Multi Zone Split System Air Conditioner (8 Zones)
Multi Zone Split System Air Conditioner (8 Zones)

If you need more zones, then there are some manufacturers that allow up to 9 indoor units. Here we show a large home requiring 8 zones. Of course, this is just an example of what’s possible, it’s unlikely this would be the best design for this home.

Refrigerant Piping

Copper tubing carrying the refrigerant will need to be installed starting at the outdoor unit where the compressor is located. The compressor is the pump that pushes and pulls the refrigerant through the system.

The first length of tubing runs from the outdoor unit to a special tee fitting (RefNet) that allows for the refrigerant to go in two directions. The refrigerant piping continues to the next tee fitting, and then to the a branch control box. 

Multi Zone split system air conditioner zone branch controller box and refNet fitting
Branch Controller for Zone Control and a RefNet type Tee Fitting.

There are two copper tubes entering the control box from the compressor, and two copper tubes leaving for each fan coil unit, one liquid line and the other gas. 

A one-ton fan coil will have approximately a 1/4” liquid line and a 3/8” gas line. A two-ton indoor unit may need a 1/4” liquid refrigerant line and a 5/8” refrigerant gas line. 

Branch Controller Box

The branch control box on the upper floor of this home has three zones attached to it. So, there will be six copper tubes leaving the box, two for each fan coil.

This system uses a branch control boxes between the outdoor unit and the indoor units. The control box contains electronic expansion valves to control the amount of refrigerant directed to each indoor fan coil based on demand.

This system allows for a maximum of 3 indoor units per control box. A maximum of eight indoor fan coils for one outdoor unit. If you needed more zones, you could add another outdoor unit. 

Checkout These Mini Split Air Conditioners

Electrical Power

Each component of the system will need electrical power, starting with power coming from the electrical panel to feed the outdoor unit. The power will run to a disconnect switch before entering the compressor. This allows a quick method of disconnecting the power when the unit is being serviced or replaced.

208/230-volt power is run to the first branch control box, then it’s daisy chained to the other two control boxes. The fan coil receives its power directly from the control box.

Summary

These are just three examples of mini split systems, but there are many variations on this. Commercial buildings need to consider ASHRAE 62.1 ventilation during design. See our videos on “Demand Controlled Ventilation” and “Dedicated Outside Air Systems”.

Note that each indoor unit in a ductless mini-split system can be controlled independently, allowing for different temperature settings and personalized comfort in various zones or rooms. This zoning capability is one of the significant advantages of these systems.

Overall, ductless mini-split systems provide efficient and customizable cooling and heating solutions, offering flexibility and energy savings compared to traditional central air conditioning systems. See How Split Systems Work.

Mini Split Air Conditioner

Construction RFI

MEP Academy Instructor
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Construction RFI

Submitting a Request for Information (RFI) is an important communication tool used in construction projects to seek clarification or obtain additional information about project specifications, plans, or any other project-related matters. The use of an RFI can occur during the bidding process or during construction for clarification. 

If you prefer to watch the video of this presentation, then scroll to the bottom or click on the following link. Construction RFI

MEP Academy construction RFI
MEP Academy Construction RFI (Upper Portion)

Here are the steps for submitting a Construction RFI:

Get a copy of this RFI and RFI Log here. RFI and RFI Log

Identify the Information Gap

Identify the specific area or aspect of the project where additional information or clarification is needed. It could be related to design, specifications, materials, installation methods, coordination, or any other relevant issue. Keep each RFI to one area of inquiry and submit additional RFI’s for other aspects needing clarification. This simplifies your RFI process by avoiding multiple issues in one RFI. You can insert multiple questions into one RFI if they are related, and then gather the details.

Gather Details

Gather all relevant details about the issue or question you want to address in the RFI. This includes specific references to drawings, specifications, contract documents, or any other supporting information that provides context to your inquiry, and make sure the RFI is formatted correctly.

Format the RFI Document

Prepare the RFI document using the required format or template, if provided by the project owner, general contractor, or construction management team. Include a clear and concise description of the issue, along with any relevant background information that can help the recipient understand the context. Address the RFI.

Address the RFI to the Appropriate Party 

Identify the appropriate recipient for the RFI. This could be the project owner, architect, engineer, design team, or the general contractor, depending on the nature of the inquiry and the project’s communication protocols. Follow the established channels for submitting RFIs to ensure the information reaches the right person or team, and provide any supporting documentation.

Provide Supporting Documentation

Include any supporting documents, such as marked-up drawings, sketches, photographs, or other visuals that help illustrate the issue or question. Attach these documents to the RFI to provide clear and specific references to aid in the response.

Clearly State the Deadline 

Specify the desired response deadline in the RFI document. This helps ensure timely feedback and enables effective planning and decision-making in the project. Coordinate with the project schedule and any critical milestones to determine an appropriate response timeline.

Review and Proofread

Review the RFI document for accuracy, clarity, and completeness. Proofread the document to correct any grammatical or spelling errors. Ensure that the inquiry is articulated clearly and concisely to facilitate a better understanding by the recipient.

Submit the RFI 

Send the RFI document to the designated recipient through the established communication channels. This can be done via email, online project management systems, or any other method specified by the project team. Retain a copy of the RFI for your records.

Follow Up 

Track the progress of the RFI and follow up with the recipient if a response is not received within the specified timeline. Effective communication and timely responses are essential to keep the project moving smoothly and address any potential delays or issues promptly.

Review and Evaluate the Response 

Once you receive a response to the RFI, review it carefully to ensure that it adequately addresses your inquiry. Evaluate the information provided and assess its impact on the project. If further clarification or action is required, communicate it promptly.

Cost or Schedule Impacts

Review the RFI response for any impacts that it might have on the cost of the project and the duration of the schedule. If either of these are impacted, then notification of the impact must be addressed immediately to comply with any timely notice clauses of the contract, and to protect your company from the impact. 

MEP Academy Construction RFI Log
MEP Academy Construction RFI Log available in link below

RFI Log

The RFI log helps ensure that all RFI’s are recorded in a central location, making it easier for team members to communicate and collaborate on addressing questions and concerns. An RFI log serves as a historical record of project-related questions, clarifications, and decisions.

The RFI log also provides a comprehensive audit trail that can be referred to in the future for accountability, disputes, or to understand the rationale behind decisions made during construction or bidding process.

An RFI log assigns responsibility for each RFI to specific individuals or companies. This helps ensure that RFI are tracked, addressed, and resolved in a timely manner.

Summary

Remember that with a plan and specifications delivery method, the design team is responsible for providing sufficient information for the contractor to build the project. With the information lacking in some respect or needing clarification, then an RFI can help assist with any decisions that need to be made to keep the project moving.

Remember, effective RFIs are clear, specific, and focused on obtaining the necessary information or clarification. Well-crafted RFIs help ensure that all project participants are on the same page and can proceed with their work without unnecessary delays or confusion.

Get a copy of this RFI and RFI Log here. RFI and RFI Log

Construction RFI and RFI Log

HVAC Equipment Budgeting and Purchasing Database

MEP Academy Instructor
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HVAC Equipment Budgeting and Purchasing Database

HVAC Equipment Budgeting and Purchasing Database. Tracking historical HVAC equipment costs can significantly save you time and money on future estimates and purchases, by providing valuable insights on cost, and easy to read comparable data like cost per ton, or cost per CFM.

If you prefer to watch the video of this presentation, then scroll top the bottom or click on this link: HVAC Equipment Budgeting and Purchasing Database

Here’s how and why tracking is important for estimators and purchasing agents:

Accurate Cost Estimates and Informed Budgeting 

With a database of historical equipment costs, you can accurately estimate the budget required for future HVAC projects based on past purchases or vendor quotes. Historical cost data allows you to create more realistic and well-informed budgets.

MEP Academy HVAC Equipment Cost Database

This can be accomplished with the use of a tracking spreadsheet, such as that created by the MEP Academy for this purpose. The spreadsheet tracks the cost of 36 different types of HVAC equipment, from Air Conditioners to VRF Systems.

Looking at the Air Conditioners there are parameters that let us know immediately how much per ton was spent or quoted for a particular AC unit. The information is sortable to allow for quick retrieval of any type of AC unit.

Coils of various types, such as DX, chilled water and heating hot water are easily sorted to determine how much should be paid per coil type, per square feet.

Condenser are tracked for their cost per ton.

36 different types of HVAC equipment are easily tracked and used for budgeting new projects or for purchasing negotiations. Get a copy of this spreadsheet here HVAC Equipment Database.

Vendor Negotiations

Armed with historical cost information, you can negotiate better deals with HVAC equipment suppliers. You have a reference point to discuss pricing and ensure you’re getting fair rates.

Based on previous purchases or supplier quotes, you can quickly know what you should be paying based on what you paid for similar equipment and avoid overpaying for new purchases.

Without historical data, you might unknowingly pay more than necessary for HVAC equipment. Comparing current prices to historical averages prevents overpaying for similar equipment.

Comparative Analysis 

Analyzing historical data helps you identify trends in equipment costs over time. This information allows you to make informed decisions about the best times to make purchases, taking advantage of lower-cost periods.

Total Cost of Ownership (TCO) Consideration

Recording both purchase costs and other associated expenses (installation, maintenance, repairs, energy consumption) enables you to calculate the TCO accurately. This comprehensive view guides you in choosing cost-effective equipment that provides long-term savings.

Selecting Optimal Equipment 

Historical data can reveal which equipment models and brands have been more cost-effective in the long run. This helps you choose equipment with proven reliability and lower maintenance costs.

Project Planning

When planning new construction or renovations involving HVAC systems, historical cost data helps you project expenses more accurately. This prevents unexpected financial challenges during project execution.

Reduced Decision Time

Instead of researching and estimating costs from scratch for each new HVAC project, you can rely on your historical data. This accelerates decision-making and project initiation.

Minimized Risk of Surprises 

Historical data reduces the risk of unexpected cost surprises during a project. You can anticipate potential expenses based on past experiences, ensuring smoother project execution.

Resource Allocation 

Accurate historical cost data helps allocate resources more effectively, ensuring that you prioritize projects that align with your budget and financial goals.

Improved Planning

The ability to project expenses accurately leads to better overall project planning. You can schedule maintenance, replacements, and upgrades strategically, optimizing operational efficiency.

Long-Term Savings 

Making well-informed decisions based on historical data often leads to choosing more energy-efficient equipment and avoiding costly mistakes, resulting in significant long-term savings.

In essence, tracking historical HVAC equipment costs empowers you to make more informed, efficient, and cost-effective decisions for your HVAC projects. It eliminates guesswork, reduces risks, and helps you plan and budget with confidence. Click on the following link to get a copy of this spreadsheet and start saving time and money.

HVAC Equipment Cost Database

HVAC Equipment Budgeting and Purchasing Cost Database

Spiral vs Flexible Duct

MEP Academy Instructor
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Spiral vs Flexible Duct

Spiral vs Flexible Duct. In this presentation we’ll look at the advantages and disadvantages of spiral versus flexible ductwork. Ducts are used to provide a path for air to travel from one place to another. There are important factors to consider when designing the layout of a duct system which we’ll cover here.

If you prefer to watch the Video of this presentation, then scroll to the bottom or click on the following link. Spiral vs Flexible Duct

Pressure Drop in Spiral and Flexible Duct

The first consideration which has an impact on the fan energy is the pressure drop difference between spiral and flexible ductwork. Spiral ductwork is rigid and has mostly a smooth interior which is good for air flow. Flexible ductwork is not as smooth as spiral which creates a higher resistance to airflow and increased pressure drop. Additional static pressure is added to the system fan when using flexible ductwork.

Spiral vs Flexible Duct - Pressure Drop Chart Comparison
Spiral vs Flexible Duct – Pressure Drop Chart Comparison

For example, a 12” spiral duct at 800 feet per minute has a pressure drop of 0.15”/100 feet. The same size flexible duct at the same velocity would have a pressure drop of 0.30” per 100 feet, which is twice the amount.

Checkout these Flexible Ducts here

Ease of Installation

Flexible ducts are more flexible and lightweight, making them easier to install, especially in tight or hard-to-reach places. They can be easily bent and adjusted to fit various configurations, which can simplify installation in complex layouts. Because spiral ducts are rigid, they may require a more unobstructed path, and additional space.

Hanger Spacing

Flexible ductwork will require more hangers per code. For example, a 12” flexible duct may require a hanger every 4 feet, while spiral can require one every 12 feet maximum. Also, flexible ductwork is restricted on how much sag can occur between hangers.

Flexible Duct Hanger Spacing Between 4 to 5 Feet.
Flexible Duct Hanger Spacing Between 4 to 5 Feet.

Durability of Spiral vs Flexible Duct

Spiral ducts are rigid and maintain their shape, which can lead to better airflow and minimize pressure loss. Flexible ducts are more prone to damage from sharp objects or rough handling. They can collapse or kink, leading to reduced airflow efficiency. Flexible ducts have a shorter lifespan compared to rigid spiral ducts, especially in commercial or high-traffic environments.

Checkout these Flexible Ducts here

Cost of Spiral vs Flexible Duct

Flexible ducts are generally less expensive to purchase and install compared to rigid spiral ducts. Flexible ductwork comes prefabricated wrapped in insulation, while most spiral will need to be insulated after installation including fittings. Flexible duct can avoid some fittings by its ability to flex to achieve various angles, while rigid spiral would need a sheet metal fitting.

Spiral versus Flexible Duct
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