TDSHS Ventilation Standards and Guidelines

Presented by: Aric Murray December 12, 2014 TDSHS Ventilation and Psychrometrics Agenda 1. What are the TDSHS ventilation requirements? 2. Pressure relationships. 3. What are the air change requirements and how do you calculate them? 4. Why are air change requirements important? 5. Exhaust requirements. 6. Recirculating Units. 7. Temperature/Humidity Requirements 8. FGI /ASHRAE ventilation tables TDSHS Ventilation and Psychrometrics 2012 TDSHS Ventilation Table TDSHS Ventilation and Psychrometrics

2012 TDSHS Ventilation Table TDSHS Ventilation and Psychrometrics 2012 TDSHS Ventilation Table TDSHS Ventilation and Psychrometrics 2012 TDSHS Ventilation Table TDSHS Ventilation and Psychrometrics 2012 TDSHS Ventilation Table

This means that if your air handling units that serve your patient rooms receive all of their outside air from 100% outside air pre-treat units then you can reduce your total minimum air changes supplied to patient rooms to 4 air changes instead of 6. (Minimum VAV box setting) TDSHS has confirmed that under the above scenario a VAV box with a re-heat coil is considered a supplemental heating system. NOTE: This does not apply to ICU rooms.

ENERGY SAVINGS AVAILABLE!! TDSHS Ventilation and Psychrometrics Calculating Air Changes per Hour One Air change per X minutes where X =

Room Volume in Cubic Feet (length x width x height) Air Delivered to Room (Cubic Feet per Minute or CFM)

Air Changes per Hour (ACH) =

60 minutes X

For example: 30 foot wide by 25 foot long operating room with a 9 foot ceiling height is receiving 2000 CFM of air to the room. How many air changes per hour is this OR receiving? Does this room meet the TDSHS requirement for an OR?

Answer: 17.78 ACH Answer: NO TDSHS Ventilation and Psychrometrics

2012 TDSHS Ventilation Table

Example: How much exhaust airflow do I need to meet the minimum requirements for an isolation room that is 12 feet wide by 25 feet long with a 9 foot ceiling? Answer: 540 CFM TDSHS Ventilation and Psychrometrics 2012 TDSHS Ventilation Table Why are air change rates important?

Code compliance for TDSHS inspections

Pass Joint Commission and/or DNV inspections

Reduce risk of hospital acquired infections

Protect the patient! Improve patient health, patient comfort, patient recovery, etc. TDSHS Ventilation and Psychrometrics 2012 TDSHS Ventilation Table TDSHS Ventilation and Psychrometrics 2012 TDSHS Ventilation Table TDSHS Ventilation and Psychrometrics 2012 TDSHS Ventilation Table TDSHS Ventilation and Psychrometrics 2012 TDSHS Ventilation Table

20% TDSHS Ventilation and Psychrometrics 2012 TDSHS Ventilation Table TDSHS Ventilation and Psychrometrics ASHRAE/FGI TABLES TDSHS Ventilation and Psychrometrics

The Basics of Psychrometrics

Presented by: Aric Murray December 12, 2014 TDSHS Ventilation and Psychrometrics Agenda 1. The Basics of reading a Psychrometric Chart 2. Example problems

3. Why use a Psychrometric Chart?

4. Practical example of using a Psychrometric Chart to determine Operating Room temperature and Relative Humidity TDSHS Ventilation and Psychrometrics

Basics of Psychrometrics

How do you determine wet bulb temperature?

Sling Psychrometer TDSHS Ventilation and Psychrometrics

Example: What is the wet bulb temperature for a room temperature of 75 degrees and 45% relative humidity?

Answer: 61 Degrees F TDSHS Ventilation and Psychrometrics

Example: What is the dew point temperature at the same room conditions?

Answer: 52.2 degrees F TDSHS Ventilation and Psychrometrics

Why is this important ???? How could this be useful ????

Consider the following real world example: An air handling unit brings in outside air through an uninsulated duct through a mechanical room that is kept at 68 degrees F. During the summer months this outside air duct sweats on the inside bringing moisture into the air handler.

Why does this happen?

What could we do to fix the problem? TDSHS Ventilation and Psychrometrics

What is the dew point of the outside air travelling through the uninsulated duct?

Use the design summer outside air conditions for Houston at 96 Degrees F dry bulb and 80 degrees F wet bulb. TDSHS Ventilation and Psychrometrics

Answer: 74.6 degrees F TDSHS Ventilation and Psychrometrics

Why is this happening?

The cold metal of the uninsulated outside air duct (68 degrees F) is below the dewpoint of the outside air (74.6 degrees F) causing the moisture in the outside air to condense on the cold surface. TDSHS Ventilation and Psychrometrics

What can we do to fix the problem? 1. We could insulate the outside air duct which will keep the metal surface warmer than the room temperature of 68 degrees and above the dewpoint of the outside air. This option will cost $$$

2. Raise the mechanical room temperature to 78 degrees to make sure the room and the uninsulated duct sheetmetal stay above the dewpoint of the outside air, 74.6 degrees F. This will solve the problem and save $$$ in operating costs. TDSHS Ventilation and Psychrometrics

Let’s look at another real world example:

What is the coldest temperature an Operating Room can achieve when it receives supply air at 52 degrees F while still keeping the Operating Room relative humidity below the code required 60% RH?

Assume the 52 degree air is coming from a standard cooling coil and not a desiccant wheel.

What do we need to know? We need to know the sensible heat ratio of the Operating Room. TDSHS Ventilation and Psychrometrics Sensible Heat Ratio Sensible Heat Ratio =

Sensible Heat Load in the Room Total Heat Load in the Room

For an Operating Room the sensible heat ratio can be assumed to be around 0.86 , which means 86% of the heat produced in the room is sensible heat and 14% is latent heat.

What does this mean Psychrometrically? TDSHS Ventilation and Psychrometrics

Air coming off the cooling coil will be saturated with moisture at 90% relative humidity.

Answer: 65 Degrees F Minimum TDSHS Ventilation and Psychrometrics

Coil Entering: 80dB/67wB 31.5 BTU/lb

Coil Leaving: 55dB/90% RH 22.2 BTU/lb TDSHS Ventilation and Psychrometrics

Total Cooling (BTUH) = CFM * 4.5 * Change in Enthalpy 20,000 CFM Air Handling Unit Total Cooling (BTUH) = 20000 * 4.5 * (31.5-22.2)

Total Cooling (BTUH) = 837,000 BTUH

12,000 BTUH per Ton

Tons of Cooling = 837,000 BTUH / 12,000 BTUH per Ton

Tons of Cooling = 69.75 Tons

GPM = BTUH /500/ (Leav Water Temp – Ent Water Temp) GPM = 837,000 BTUH /500/ (54 – 42 degrees F)

GPM = 139.5 TDSHS Ventilation and Psychrometrics Questions?