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

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.

8 Responses to “Hotel Mitsubishi City-Multi VRV Installed at Sheraton Carlsbad Resort & Spa”

  1. Armando Dela Cruz Says:

    1. Is this VRV unit certified by california T-24 as approved appliances for calif installation.

    2. How do you handle economizer control and CO2 requirements.

    3. How many fan coils can you connect to one Outdoor unit. Where is the inverter?

    4.How can get catalog and manuals.


  2. Mark Says:

    1. They have efficiency ratings that are posted and can be used for T-24 analysis. However, the last time I checked, Energy Pro did not yet have the units included in their model, but that was being worked on. Check with Energy Pro for their latest status.
    2. Guestrooms generally have their own form of outside air and economizer is not a factor.
    3. You can connect up to about 16 units depending on tonage. I typically connect about 12 for best optiminzation of performance and cost.
    4. Just type in Mitsubishi City-Multi in the web and you should get to their site for a catalog.

  3. Karen J. Laracuente Says:

    Hi… Great installation. FYI here you can access the latest MEHVAC CITY MULTI Catalog. And, yes.. .EnergyPro was updated recently.

    We are Mitsubishi Electric Authorized Distributors and installers in Puerto Rico and we are trying to get some CITY MULTI into some hotels as well. Have you install or design any college or university? Have you incorporated the loosney as fresh air or what fresh air device have you use?


  4. marco torrontegui Says:

    hi do u have more pictures of another installation in a mall by example? thxs

  5. p.p.gunawardana Says:

    I would like to know more about vrv systems, working pressures ,gas ,& compressor types

  6. Bruce Zelenka Says:

    The is the first time I have seen Mark’s blog at length. It’s me in some of the pics. Revolutionary system is all I can say. It makes no sense this system is not wide spread already.

    FYI…The coils not dressed up in the pictures like the cassette and the wall-mount unit are in the Maintenance Shop and a Telecom Room. The City-Multi System at the Sheraton Carlsbad Resort & Spa is still a great example of VRFZ systems. I know the system in my sleep.

    Fresh air intake to a ‘hotel room’ is accomplished simply by the use of a sliding glass door or operable window. The slider provides enough fresh air intake per code in combination with 55cfm of bathroom exhaust without any fresh air intake ducting of any kind up to a certain square feet of room (I think it is up around 600sf per code…not sure off the top of my head but I can find the answer if you ever need it). I can tell you that the standard room at the Sheraton Carlsbad Resort & Spa is 428sf, they all have 4-ft sliding glass doors and do not have any special fresh air intake assembly.

    Better late than never,

    Bruce Zelenka
    Corporate Director
    Grand Pacific Resorts, Inc.

  7. Kelly Says:

    We did a condo that required fresh air, Mitsubshi makes a losnay unit that incorporates into the system quite nicely, although it is large, sometimes hard to find space for it.
    Mark, when I went to Mistubishi school, they repeatedly harped about “NO TRAPS” which in some cases is imposible. I noticed between the outdoor units and the roof penetration you have them all traped right out of the box, is this an issue at all?
    Very nice looking job, having the challenge currently of trying to correct a dissasterous install (by others) on a three tower, seven story building I really appreciate seeing good work….kudos!

  8. Paul O'Connor Says:


    Quite an interesting installation technique.

    Given the hotel application and depending on the number of heads, the AG150 master controller is an excellent option for the entire building. With expansion cards, it allows for connection of up to 150 fan coil units throughout the building, to one main colour touch screen.

    This is particularly useful in hotels where it enables management at reception to manage each room individually as a patron checks in,adjusting start/stop, temperature etc, without the need for a full blown BMCS system, or indeed waiting for the client to reach his/her hotel room to bring conditions to an acceptable level. This enhances the energy rating of the facility with specific management of AC operating times.

    The applications thereafter are numerous for lots of various commercial applications. I have managed at least 15 major installations of this type. Some with 170 + fan coil units.

    Additionally, the AG150 can be linked directly to a BMCS for a commercial office space via a BACnet module, with high level link on Cat 6 cable. I find it ideal to mount the AG150 directly onto the face of the Mechanical switchboard, as a monitoring point of all the VRF, without the need to interrogate the BMCS head end during routine maintenance.

    Im guessing in this instance, you installed the heat recovery VRF rather than the heat pump system, with the fresh air make up to the unit dependent on whether it be natural (ie. openable windows), or forced (ie. a fully sealed hotel room).

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