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How to Calculate Cooling Capacity for a DOAS unit

This is an easy calculation if you know the cfm (airflow to be conditioned) and have a psychrometric chart handy.  The formula for calculating total cooling is: Qt = cfm x (Hf-Hi) x 4.5 Where: Qt = Total capacity in btu/h Hf = Enthalpy of the leaving air Hi = Enthalpy of the entering air 4.5 = constant 
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HVAC Rules of Thumb

If you’ve been in the HVAC industry for a while, you probably have some “Rules of Thumb” that you use throughout your day. Here are a few that you may not have used before and could prove to be useful!  The 1.7X rule This rule of thumb states that the MAX heating capacity required for
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How to design a DOAS unit as sole source heating and cooling

When possible, it makes life easy to have a separate DOAS system from the space HVAC system. In this case, each system has one specific job: -The DOAS’s job is to bring in 100% Outside Air, when the space is occupied, and delivers neutral temperature air. -The main heating & cooling system can be (in most cases) 100%
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DYK York doesn’t require suction traps for R410a?

When an HVAC system uses POE (Polyolester) oil, which is typical of current R410a systems, suction oil traps are not required* because POE is miscible in R410a in all phases (liquid, saturated liquid and vapor).Just be careful sizing the suction line and make sure the velocity is > 1,000 FPM minimum on any vertical riser. That
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Fan Types- Centrifugal, Axial, Forward Curve, Airfoil. What does it all mean?

The cfm Distributors Inc Applied Systems Group meets every other Monday at 8am for training. This training covers a plethora of topics, but a portion of this training is on HVAC design and application. Last month we were discussing fan types and we thought it would be fun to create a document that explains the
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How to use Fan Laws for design/build retrofits

If you’ve ever had a situation where your HVAC unit had less airflow than expected, you’ve officially had a run-in with the FAN LAWS. The biggest takeaway from this article should be that sizing your ductwork is extremely critical, because if it is undersized it can be very expensive to fix!Here are the 3 Fan
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How to Avoid a VRF Piping Nightmare

Refrigerant copper piping isn’t new. It’s been in use for years and has stood the test of time. What you might not know is how important the insulation can be. Check out this article to make sure you’re following code and not sidestepping potential problems.

How to Avoid a VRF Refrigerant Nightmare

If you haven’t designed a VRF system yet, you need to be aware of what code violations can get you into the most trouble. Check out this article to learn about ASHRAE Standard 15 and how to avoid a VRF refrigerant nightmare.

How to Avoid a VRF Zoning Nightmare

One of the biggest benefits of VRF is the built-in zoning that is available. But if you don’t design the system properly you can run into major problems. Check out this article to learn how to avoid a VRF zoning nightmare.

The 35% Rebate that no one is talking about

In case you missed it, effective January 1, 2018, via the Tax Cuts and Jobs Act Section 179, all components of an HVAC system can be expensed immediately instead of being depreciated over 39 years. Qualified applicable property includes heating, ventilation, and air-conditioning property.Previously the maximum deduction was $500,000 depreciated over 39 years. Now the maximum deduction
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