Author: Kyle C. Mackenzie, P.E.
Date: November 3, 2021
The following is a case study regarding engineering services rendered at the ACE NY Hotel at 20 West 29th Street, NY NY.
Hotel ownership, GFI reached out to Polise Consulting Engineers to discuss options for improving efficiency and the functionality of the HVAC system.
In lieu of replacing the existing guestroom fan coils at the hotel as recommended by the HVAC contractor, this office determined that the guestroom fan coils could be operated more efficiently and worked with a controls vendor and a HVAC maintenance contractor to commission/ reprogram the existing guestroom HVAC systems thereby saving Hotel ownership over $1,500,000.00. The hotels heating and cooling system includes (2) Modular Climacool Electric Centrifugal Chillers totaling over 400-tons of capacity and 4 gas fired Hydronic Boilers from Raypak. Guestrooms are served by dual temp 2 pipe IEC Fan coils with an integrated electric heating coil to accommodate the swing seasons.
The Hotel includes 287 guestrooms, a full-service restaurant, event and meeting space and retail including Stumptown, Black Seed Bagel, Milk Bar, Le Labo and Rudy’s Barbershop.
The mechanical contractor gave several options for new equipment as a proposal to rectify the heating and cooling issues including:
- Replacing the existing fan coils with water source heat pumps
- Replacing the existing fan coils with water cooled VRV units
- Replacing the existing fan coils with combination fan coil/ heat pumps with the heat pump portion sized for the swing seasons.
The only viable option from a cost and hotel disruption perspective was the combination fan coil/ heat pump as the heat pump option would require re-building the piping infrastructure to allow for common area fan coils to be utilized at different water temperatures then the guestrooms and the VRV option would require a centralized condenser to be installed on each floor.
The combination fan coil/heat pump option can run as a fan coil unit as well as heat or cool with a built-in compressor. The unit has 6 operating modes. Fan coil cooling, Fan coil heating, Fan coil cooling + AC supplement, Fan coil heating + heat pump supplement, Heat pump heating with chilled water loop, and Air conditioning with hot water loop. This would allow the building to retain its existing system without any modification and provide for heating or cooling selection as needed in each guest room during the swing seasons (fall and spring). Preliminary pricing from the mechanical contractor indicated an installed cost of $7,500.00 per unit or $2,152,000.00 for all guestrooms.
Polise Consulting Engineers visited the hotel to verify the feasibility of the combination fan coil/heat pump option and perhaps take on the responsibility of designing and filing the system. The visit was conducted January of 2021. We noted the following during the visit:
- Hotel guests had complained about either being too hot or too cold during the spring and fall seasons.
- Hotel staff indicated that during the change over each of the inncom thermostats in each guestroom would be re-wired from heating to cooling and vice versa.
- The heating mode automatic control valves associated with the guestroom 2 pipe fan coil were not closing and the fans were not turning off. As such the boiler plant water setpoint was set to 115 degrees F to mitigate overheating complaints from guests. It was noted during our walkthrough that several guestrooms were untenably hot. A subsequent phone conversation with the building HVAC maintenance vendor clarified that not all guestroom fan coils were being controlled in heating mode, several units’ valves would close, and fans would shut down when commanded to do so by room thermostat setpoint. In addition, several of the automatic control valves had been failing and that several of the service calls were related to failed control valves (the valves would fail open which would cause space heating issues).
- Hotel Staff and Central HVAC Services indicated that none of the 1 kW electric heating coils were operational.
- Hotel staff indicated that guestroom fan coils would not operate until the associated hotel guest enters the room and there had been a few complaints regarding the rooms not being hot or cold enough at the time of initial entry.
- This office viewed the operating information on the BMS workstation in the cellar of the hotel and verified that the boiler plant was running at 115 degrees F Hot water supply temperature.
- The hotel utilized a property management system however it was not connected to the HVAC controls of the guestrooms
It was clear from the site visit that the issue was not the original system design but instead how the system was being utilized from a controls and operational perspective leading to the aforementioned thermal comfort issues. As such in lieu of providing a proposal to design and file a combination heat pump/ fan coil system Polise and GFI structured a Construction Administration agreement to facilitate the modifications to the guestroom and hotel controls necessary to have the system operate as was originally designed. As part of this scope of work Polise coordinated with and provided direction to the building BMS vendor, the building HVAC vendor, the guestroom thermostat vendor, and the property management system vendor as required.
The following design/ construction administration work was performed:
- Polise performed load calculations to verify that the originally designed fan coils and integrated 1 kW electric heating elements were acceptable to accommodate the guestrooms.
- Polise coordinated with the building BMS vendor (who was hired to re-wire and re-program the guestroom controls) and the guestroom thermostat vendor to configure the controls to engage the integral electric heating element when the dual temperature system was in cooling mode, but the system required heating (during swing season months) and have the inncom stats automatically switch over from heating to cooling mode through aquastats mounted on the dual temperature piping.
- Polise coordinated with the guestroom thermostat vendor and the property management vendor to re-program the existing interface infrastructure so that when guests arrive at the hotel the fan coils activate to bring the space to the required temperature.
- Polise coordinated with the building BMS vendor to increase the hot water set point to 140 degrees as per the original design
- The HVAC maintenance company and the BMS vendor replaced failed control valves, failed fan decks, and failed thermostats as required to meet the original sequences of operation and the design directions from Polise.
- The HVAC maintenance company is also in the process of cleaning all the fan coil unit coils and re-insulating the dual temperature piping at the connections to the fan coils.
As a result of the work indicated above there has been a significant drop in guest thermal comfort complaints. In addition, GFI has since hired Polise Consulting Engineers to investigate thermal comfort issues throughout the hotel including administrative offices and amenity space areas.
Maintaining the existing systems resulted in a very significant cost savings over installing new equipment as follows:
BMS Vendor- 159,877$
HVAC Maintenance Company- $40,263
Guestroom Thermostat Vendor- $6,507
HVAC Maintenance Coil Cleaning- $150,000
Client Cost Savings- $2,152,000-$356,647 = $1,795,353.00