Archive for the ‘Mechanical’ Category

Condensate Discharge for City Multi VRV Fan Coils

Tuesday, September 28th, 2010
The City Multi fan coils have three condensate drain systems.  The primary drain is the gravity drain at the bottom of the drain pan.  The second is an optional pumped condensate outlet up high above the gravity drain.  The third is the overflow drain that operated only when the normal drains fail.  This first photo shows the lower gravity drain connected to the copper drain pipe through the patented Mitsubishi horizontal trap.  Someday I will cut one of these traps open to see how it works, but for the moment I’m just happy to say it does not require additional vertical space that a normal trap requires. 
Above shows the pumped condensate outlet.  It is a bluish color plastic. 
And finally, this photo shows the overflow drain connection on the opposite side of the drain pan. 
This photo shows the tailpiece connection of the condensate drain at a nearby lav.  The pipe is the black hose. 
In this photo the overflow drain outlet is shown above the shower.  If water comes out of this pipe, it is time to clean the normal drain.
Just a note of warning.  The City Multi fan coils come with the pumped condensate units as a standard feature and they are energized.  If you use the gravity drain and not the pumped drain, then the pump needs to be disabled.  Otherwise, the pump will come on and dump water on the floor.  (Ask me why I know this if we ever meet.:)  To give credit where credit is due, Lonny Potter, hotel engineer, was the person who discovered this issue and shared the details with me.  Lonny is seen below admiring his evaporative cooler for the kitchen make-up air unit.

Mitsubishi City Multi goes into Ontario Airport

Wednesday, September 22nd, 2010

Embassy Suites, California

The new Embassy Suites hotel located at the Ontario airport in California will have guestrooms served by a VRV system by Mitsubishi.  This is following the Embassy Suites in Palmdale with the identical system completed in early 2010. 

Here are a series of photos taken during construction to showing how this system is constructed in the corridors and guestrooms.


This photo shows a typical guestroom fan coil unit located above the guestroom entry soffit.  The units are very compact. 


This shows a closer view of the fan coil unit.  The ductwork to the guestroom space is flex duct.  The two black pipes in the foreground are insulated refrigerant pipes.   The white PVC pipe is the condensate drain.  The strange grey tube with corrugations between the PVC and the fan coil is the proprietary Mitsubishi condensate trap.  It solves the problem of the P-trap which otherwise requires additional ceiling cavity height to accommodate.  Note that the electrical J-box is in the upper left corner of the photo.  All connections are on one side of the fan coil.


This photo shows the BC controller located in the corridor ceiling cavity.  Note the refrigerant piping connected to the left side with the brass fittings.  There are two pipes per guestroom and each pair of pipes is stacked vertically.  There are thirteen rooms connected to this BC controller.  For a typical hotel floor with about 26 guestrooms per floor, two BC controllers are provided.


This is another view of the BC controller with the condensate piping and main refrigerant connections shown on the end of the unit.


This shows the BC controller nestled amongst the other systems in the corriodor including the ventilation supply duct nearest the wall.


This photo shows the refrigerant piping as it splays out to the guestrooms along the corridor.  As we move further from the BC controller, the congestion becomes less and less as refrigerant pipes “drop off” to the guestrooms. 


This shows a small bundle of refrigerant pipes near the most remote guestrooms.  Note that the ceiling space becomes very comfortable at this point. (If we could only rent out this unused space. J)


This photo shows an electrical J-Box with the access panel framed in.  I have included it just so my electrical engineers do not feel left out.

Corridor Guestroom Supply Systems

Wednesday, September 22nd, 2010

Both Hilton and Marriott now require ducted ventilation air to guestrooms.  This means that outside air openings at each guestroom via PTAC or VTAC is no longer acceptable.  Likewise, operable windows are not acceptable.  In response to this requirement, designers are now providing central HVAC units to supply corridor ventilation that also includes ductwork along the corridor with branch ducts to each guestroom. 

The photo below shows the ductwork on each side of the corridor with sprinkler pipes and electrical routed in the center above the drop ceiling. 


This is a typical condition along most of the corridor.  However, the conditions become much more crowded where the main supply duct first enters the corridor as seen in this photo:

Here the duct must exit the vertical shaft and cross the corridor as it splits into the two branches extending the length of the corridor.

You might ask why two ducts and not just one, and the answer is that the small duct into each guestroom would have to cross over (through) the sprinkler piping in the center.  Here is a photo of the duct into a typical guestroom:

In most states there is no requirement for a fire / smoke damper.  However, California is one state where a fire/smoke damper is required at the duct penetration to each guestroom.  Here is a photo of  a typical fire/smoke damper:

Terminating the ventilation air inside the guestroom can be done in three different ways.  One approach is to run the duct to a diffuser on the other side.  The second is to connect the duct to the return side of the guestroom fan coil unit.  The third method is to terminate the duct inside the return air plenum of the ceiling space where the guestroom fan coil unit is located.

The advantage of this approach is that the return grille for the plenum can also function as the access panel for the fire/smoke damper.  This is the configuration shown in this photo as taken through the ceiling opening for the return grille.  The fire/smoke damper is seen as accessible from this opening. 


It should be noted that the return air plenum concept can only be used in a non-combustible building construction.  Also, any wiring routed through this plenum must comply with plenum rating requirements.  Therefore, no smurf tube in the plenum.

The New Look of Green for Hotels

Saturday, March 28th, 2009

Summary: I am embarking on a personal campaign to make the new wall mounted VRV air conditioning units for guestrooms the new “look of green” for hotels.

Studies show that green conscious buyers of electric cars want their cars to look green as well as be green.

So why not apply that same marketing strategy to hotel guestroom air conditioning units?

What is the chance that the VRV wall mounted unit below could become the desirable “look of green” of the modern hotel guestroom? If that could be accomplished, hotel developers would have an economic solution to costly, high-end HVAC systems. These VRV systems are low cost, energy efficient, and exhibit “five star” comfort and quiet to guests.

So I challenge hotel designers to make this look the “look of green” in hotel design.


As seen in the photo above, use of these systems is not completely original for hotels.  However, I am not aware of any major brand prototypes that include this as an option.  Concealed VRV units are being installed, but the construction cost savings are not being fully realized.  The challenge is to incorporate the exposed unit into designs that look good.

Please contact me if you wish to discuss ideas for incorporating this concept into your hotel projects.

Check out this website for more information on VRV systems:
Mitsubishi City-Multi

Marriott Mid-Rise vs. Code High-Rise

Monday, February 23rd, 2009

Summary: Comparison of a Marriott mid-rise smoke control and building construction requirements compared to a Marriott under full IBC code high-rise smoke control and building construction requirements.

Marriott construction guidelines define a mid-rise hotel as any hotel more than six stories and less than 75 feet tall.  For this mid-rise classification, Marriott requires certain aspects of a high-rise building to be included in the design.  The following is a comparison of the these requirements relative to what is required by the IBC for a fully  classified high rise hotel.

As is often the case, when a local jurisdiction is informed that a mid-rise hotel is going to be designed per the Marriott criteria, full high-rise criteria is imposed.  Check with your local jurisdiction regarding this issue at the start of your project to avoid surprises.

Emergency Generator Stair Fans Only All Fans
Smoke Report and
Rationale Analysis
Third Party Testing of
Smoke Control
Fire-Fighter’s Control
Fire Command Center X X
Exit Stair Pressurization X X
Mechanical Smoke Exhaust
for Corridors
Mechanical Smoke Exhaust
for Public
Elevator Pressurization X
Full Smoke Control
System per Section
Fire Alarm Speaker
System for Zoned
Secondary Water Supply
for Sprinkler
Emergency voice/alarm
Automatic Fire Detection
Two hour protection for
control and
power wiring (907.2.12.1)
Fire Department
Communication System
Vestibule at Exit Stairs
on Each Floor
Exhaust Fans Rated for

Hotel Mitsubishi City-Multi VRV Installed at Sheraton Carlsbad Resort & Spa

Saturday, February 7th, 2009

Summary: Here is a photo tour of a successful VRV installation in an operational hotel.

VRV HVAC systems are making their way onto the American scene.  Although the VRV technology is common in Europe and Japan, it is a newcomer to America.  As such, there are few installations for engineers to observe.  At the Sheraton Carlsbad Resort & Spa, California,  the Mitsubishi City-Multi VRV system has been successfully installed.  I visited the site and was impressed by the equipment and performance.  Most notably, the guestroom unit is almost completely silent.  This photo tour was made possible by Bruce Zelenka who enthusiastically allowed me to see all the pieces of the system from the roof to the guestrooms.

Bruce Zelenka was instrumental in getting the Mitsubishi City-Multi VRV system installed in the Sheraton Carlsbad Resort & Spa.


The condensers are modular and can be placed like soldiers shoulder to shoulder.  Here they are about six inches apart, but if space is at a premium, they can be shoved completely together.

A custom curb is used to create a platform to support the condensers.

The refrigerant piping is light weight and can be routed above the roof membrane on off-the-shelf supports.  Here is an example of the piping stacked two layers high.

Here is an overall view of the piping neatly racked across the roof.  The electrical is extended through roof jacks from disconnect switches mounted on the wall of the parapet.  Alternatively, the disconnects could be located at the roof penetration, but this is a cleaner installation.

The piping transition from the roof to a shaft down the building is shown here.  Typically, refrigerant piping penetrates a roof with a roof jack, but with this large number of pipes, it is more efficient to create a roof hatch that handles a bundle of pipes.  Also, the risk of a roof leak is very low with this detail.

The BC Controller is what Mitsubishi calls the unit which manifolds the refrigerant lines to the guestroom units.  The best analogy to describe it is an electrical branch panel.  Only one pair of refrigerant lines extend to the roof like a panel feeder, and each guestroom unit is separately served by refrigerant lines like branch circuits.

Looking up at the ceiling of the corridor, the refrigerant piping can be seen routed horizontally.


In a guestroom the fan coils are mounted in ceiling spaces near the corridor.  This is no different than a four-pipe fan coil installation.

In this installation, the air filter is mounted behind the return grille to simplify filter replacement.

This is the standard Mitsubishi thermostat.  This thermostat is under review by Marriott and Hilton for acceptance in their hotel brands.

Mitsubishi has a fantastic design, but there is still no magic to deal with condensate.  Here the condensate from the fan coil unit in the ceiling is piped to the bathroom lav trap.

Mitsubishi offers a variety of fan coil unit styles.  Here is a four-way cassette unit suitable for a kitchen or work area.  This unit is installed without a ceiling, but as the trim would indicate, it is intended for a ceiling installation.

Mitsubishi has a special condensate trap that does not require a vertical loop.  This simplifies installation in ceiling cavities with limited clearance.

This wall mounted style of fan coil is an economical alternative to a built-in type for a guestroom.  Although this installation made no attempt to conceal the electrical power or the condensate drain, these units can be installed in guestrooms with a clean look not too different than a PTAC.  However with this unit, it is mounted high on the wall and does not require any floor space near the outside wall.  I have seen these units successfully applied to a college dormitory.

Hotel Elevator Hoistway Venting

Monday, December 15th, 2008

Summary:The IBC requires the top of all elevators to be vented to the outside. The size of this vent is important because in many cases it is routed through the elevator machine room.

The IBC requires the top of all elevator hoistways to be vented to the outside.  Since almost all hotels have  elevators, this is a feature the architect will ask the mechanical engineer for help sizing.  Therefore, this article is intended to be a quick reference.  The purpose of the vent is to allow smoke removal from the shaft in the event of a fire.   As an aside, I have also heard the argument that the vent provides relief from the piston effect of the elevator, but I have not seen this reason confirmed in writing anywhere.  Of course, if the piston effect reason was actually true, then there should be a corresponding relief opening at the bottom of the shaft, and the code does not address a vent at the bottom.
The vent size is determined by IBC Section 3004.3, which requires the area of the vents be not less than 3.5% of the area of the hoistway, but not less than 3 square feet for each elevator car. Dumbwaiters hoistways are also included in this requirement with a minimum of 0.5 square feet per dumbwaiter.
For hydraulic type elevators, the top of the elevator shaft is generally at or above the roof and providing this vent is simple. However, for elevators with machine rooms at the top, access to the outside is often through the machine room. This is accomplished done by routing a duct through the machine room in a rated enclosure. Routing of the duct and shaft involves close coordination with the elevator machine equipment layout and the associated working clearances.
The code allows up to 2/3 of the area of the opening covered with annealed glass. In mild climates, this is not generally required. However, in extreme cold climates, the glass can reduce the heat loss from cold air coming into the hoistway.
The table below shows typical vent sizes required for elevator shafts with one, two, and three cars. Obviously, there is no single size for an elevator. However, the table below can be useful during schematic design to quickly assess vent sizing requirements. Note that for two and three car banks with a common hoistway, the sizing criteria is dominated by 3 sf per car rule rather than the 3.5% rule. Therefore, estimating for multiple car hoistways is quite easy.
Shaft Size (Ft2) Number of Cars Vent Size Free Area (Ft2) Louver size (in) with 50% free area (nominal)
80 1 3 30X30
90 1 3 30X30
100 1 3.5 36×30
110 1 3.85 36×36
120 2 6 48×36
130 2 6 48×36
140 2 6 48×36
150 2 6 48×36
160 2 6 48×36
170 3 9 48×60 (close to 48×48)
180 3 9 48×60
190 3 9 48×60
200 3 9 48×60



  • 3004.1 Vents Required

Hoistways of elevators and dumbwaiters penetrating more than three stories shall be provided with a means for venting smoke and hot gases to the outer air in case of fire.

  • 3004.2

Vents shall be located at the top of the hoistway and shall open either directly to the outer air or through noncombustible ducts to the outer air. Noncombustible ducts shall be permitted to pass through the elevator machine room, providing that portions of the ducts located outside the hoistway or machine room are enclosed by construction having not less than the fire protection rating required for the hoistway. Holes in the machine room floors for the passage of ropes, cables, or other moving elevator equipment shall be limited so as not to provide greater than 2 inches (51mm) of clearance on all sides.

  • 3004.3 Area of vents.

Except as provided for in section 3004.3.1, the area of the vents shall not be less than 3.5% of the area of the hoistway not less than 3 square feet(0.28 m2) for each elevator car and not less than 3.5% not less than 0.5 square feet (.047 m2) for each dumbwaiter car in the hoistway, whichever is greater. Of the total required vent area, not less than one-third shall be permanently open. Closed portions of the required vent area shall consist of openings glazed with annealed glass not greater than 0.125 in (3.2 mm) in thickness.


ASHRAE 62.1 LEED Credits for Hotels

Tuesday, December 9th, 2008

Summary: Example of how to apply ASHRAE 62 to achieve a LEED credit. 

Applying ASHRAE 62 to a hotel to get LEED credits is very easy to do because hotel spaces generally have separate air handlers serving each type of space.  Therefore, to achieve ASHRAE 62 ventilation is as simple as setting the air handler minimum outside air to the ventilation requirements for the respective zones computed according to the ASHRAE 62 method.  This includes an area factor and a occupancy factor, of course.  The only situation that truly challenges the designer is where a single outside air unit is used to serve several air handlers each serving zones with different ventilation requirements.  For those cases, the ventilation minimum outside air setting must be computed according to the involved formulas.  ASHRAE has a spreadsheet available to help with these calculations, or you can use a design program such as Design Master which has this feature integrated into the load calculations.

Below is an example of an ASHRAE 62 computation performed for a simple building with diverse zones served by common air handlers.  The example is offered to assist in understanding what is involved.  The computations are performed using the ASHRAE 62 spreadsheet and Design Master for comparison.

Sample Analysis:

ASHRAE 62 ventilation concept is a method for setting the minimum outside air for an air handler, which serves rooms that have different percentage outside air requirements.

The building consists of five zones, each zone served by a separate HVAC unit. Within each zone are a number of rooms ranging from one room to eight rooms. The single room zones are a trivial case of the ASHRAE 62 concept. For those zones, the minimum outside air setting is simply the ventilation rate prescribed by the ASHRAE 62 ventilation amount based on occupancy and room area.

For the zones with more than one room per zone, there are three possible methods of calculating ventilation rates that could be used, each with a different effect on air quality and energy consumption. The first method is to simply add up the individual room ventilation rates and set the HVAC unit to a minimum outside air based on that sum. This results in an amount of outside air at the low end of the spectrum. This is the most energy efficient selection, since this minimizes the outside air heating and cooling load on the system. However, it may not provide sufficient ventilation for the room, which requires a higher percentage of outside air compared to other rooms in the zone. For example, if a conference room and an office are both served by the same HVAC unit, and the conference room requires 50% outside air and the office requires 20% outside air, then the office will not receive sufficient ventilation based on this method.

One method to absolutely guarantee that every room receives the required ventilation is to set the outside air at the HVAC unit to the percentage matching the room with the highest percentage ventilation requirement. The drawback to this approach, however, is that the rooms such as offices compared to conference rooms would receive far more ventilation than necessary. Thus, energy would be wasted.

The ASHRAE 62 approach is to find a middle amount of ventilation between the two extremes described above. Based on extensive research and analysis, the ASHRAE approach gives credit to the mixing effect of return air from one room to another. For example, if an office needs 20% outside air, but it is being served with 25% outside air, then a portion of the air returned to the HVAC unit is still “fresh” and could be counted as outside air when recirculated. The trick is to determine just how to translate this general concept into actual usable outside air values. This is what the formulas of ASHRAE 62 accomplish. ASHRAE 62 computations result in a setting for the outside air that is a proper compromise between the most efficient energy setting, and the maximum case ventilation setting.

The following table shows the five zones, the supply air for each room, and the amount of ventilation required for each room within the zones. In the least ventilation amount case, the sum of the room ventilation cfms is shown for each zone. In the maximum ventilation amount case, the ventilation for each room is computed based on the percentage of ventilation of the worst case room applied to all the other rooms. This percentage is then applied to the zone to show the worst case outside air setting. The column between the least and the worst-case ventilation rates is the ASHRAE 62 rate as computed using the ASHRAE 62 formulas. Note that this amount is between the two extremes in all cases except the cases where the zone has only one room. In those cases, the ventilation rate simply matches the minimum amount required for the room.

The ASHRAE 62 calculations were performed using Design Master HVAC software, which combines load calculations, ductwork design, and the ASHRAE 62 calculations. As a further check of this method of computing the AHSHAE 62 values, the official ASHRAE spreadsheet was used. The values matched and confirmed the correctness of the solutions. 

 The following exhibits are included for reference:

  1. Floor plans showing the five zones and rooms. Each room is labeled with the occupancy and ventilation requirement: LINK
  2. Summary of the outside air settings recommended for each HVAC unit. Note, this is the minimum setting and any economizer cooling operation may and should increase these values during economizer operation: LINK
  3. Design Master printouts showing the ASHRAE 62 results: LINK
  4. ASHRAE 62 spreadsheet showing a comparison analysis: LINK

Ducted Ventilation to Guestrooms from Corridors

Wednesday, November 26th, 2008

Summary: The new codes now allow ducted guestroom ventilation for hotels in the west coast states which have now moved from the Uniform Building Code to the International Building Code.

Discussion:  The following code analysis is presented to document the conclusions stated in the summary above.  This topic requires a step-by-step analysis of the code and there is really no short cut to what appears below.  Just to be clear, the question is: Are fire/smoke dampers required at the penetration of the duct into the guestroom at the corridor wall?

Code Analysis:

1.    The code defines four relevant types of separation that must be addressed as part of the code analysis.  Those types are: Fire Barriers, Fire Partitions, Smoke Barriers, and Smoke Partitions.

2.    Addressing each type of separation, we find the following:

a.    Section 706 Fire Barriers: This applies to the hotel corridors.
b.    Section 708 Fire Partitions: This applies to the separation of hotel sleeping units (guestrooms)
c.    Section 709 Smoke Barriers:  This section does not define where smoke partitions are required. It is silent regarding where the section is applied.
d.    Section 710 Smoke Partitions: This section does not define where smoke partitions are required. It calls upon other sections to provide that definition.

3.    Are smoke barriers and smoke partitions involved with guestrooms?

a.    Section 419 Group I-1, R-1, R-2, R-3:  This section applies to guestrooms and states that walls separating sleeping units shall comply with Section 708.  That means the walls between guestrooms are Fire Partitions.  It does not elaborate and extend the rating to Fire Barrier, Smoke Barrier, or Smoke Partition.

4.    Section 706 requires ducts and air transfer openings comply with Section 716.

5.    Section 708 requires ducts and air transfer openings comply with Section 716.

6.    Section 716 addresses duct and air transfer openings of all types.  Paragraph 716.6 Where Required defines where fire dampers, smoke dampers, and combination fire/smoke dampers are required for each type of separation. There are then two cases to analyze the hotel guestrooms. The first case is a duct routed in the corridor with taps to each guestroom through the corridor wall. This case involves crossing a Fire Barrier. The second case is a duct routed from guestroom to guestroom which involves crossing a Fire Partition. These two cases are analyzed below.

7.     Duct Routed in Corridor: Since we know from above that guestroom separation from the corridor is a Fire Barrier, then the applicable sub-paragraph is 716.5.2 Fire Barriers:

a.    This code requires fire dampers except where the duct system is constructed of 26 gage steel and the ductwork is continuous from the air handling equipment to the air outlets in the guestrooms.
b.    Conclusion: The 2006 IBC allows air supply to guestrooms from a common duct in the corridor without fire dampers or smoke dampers as described above.

8.    Duct Routed in Guestrooms: Since we know from above that guestroom separation is only a Fire Partition, then the application sub-paragraph is 716.5.4 Fire Partitions:

a.    716.5.4 Fire Partitions:  This sub-paragraph requires fire dampers in ducts and air transfer openings except when all of the following conditions are met:
i.    Building is sprinklered.
ii.    Duct penetration is less than 100 square inches.
iii.    Duct is 26 gage steel.
iv.    No openings communicated to corridor.
v.    Duct installed above a ceiling.
vi.    Duct not terminated at the corridor wall.
vii.    A 12 inch steel sleeve through the corridor wall is provided for the duct.
b.    Conclusion:  The 2006 IBC allows an air supply to guestrooms from a common duct in the corridor without fire dampers or smoke dampers if the conditions of 716.5.4 are met.  The following is a review of those conditions:
i.    Sprinklers:  No problem.
ii.    Duct less than 100 square inches:  We need 30 cfm of air per guestroom, therefore, a 4″ diameter duct is sufficient for a guestroom.  A 4″ duct has an area of 12.5 square inches and meets this criteria.
iii.    26 gage steel is standard.
iv.    The duct would have no openings to the corridor since the corridor air system would be a separate system.
v.    A ceiling would be provided for the corridor.  This is not always the case, but would be necessary (and desirable) under these conditions.
vi.    The duct could not be terminated at the corridor wall of the guestroom.  This requires some form of soffit in the guestroom, which is easily accomplished.  The grille can then be installed at the wall of the soffit.
vii.    A 12 inch sleeve through the corridor wall is easily provided.  The requirements for this sleeve are detailed further in the code.


Proper Sizing for Hotel Guestroom Units

Monday, November 24th, 2008

Summary: Reduce noise with proper sizing of guestroom units.  But be careful with undersizing the heating capacity.

One of the big temptations for designers of hotels is to oversize the guestroom units.  This is especially true of the cooling mode.  My observation has always been that the most important time for a guestroom to perform properly is at night, and at night there is no solar load.  So by oversizing a unit for peak solar load plus all other extreme assumptions about the load in the room, the result is a unit is far over sized for the night.  This always translates into excessive noise. 

The only caution is to make sure the units are sized adequately for heating at night in cold climates.  At night there is no heat gain from such things as lights and the television once the guest goes to bed.  The in-room refrigerator is the one exception that produces heat all night long, but it is not significant. 

If you are using heat pumps, make sure the supplemental strip heat is large enough.  In the case of hydronic systems, make sure the boilers can maintain water temperature in the extreme cold conditions with ample spare capacity for the very extreme cold.  Unlike cooling, guests have no tolerance for an occasional cold night.  An occasional hot day is expected, but not a cold night.