VRF Systems in Mechanical Rooms and ASHRAE 15-2013
VRF Systems in Mechanical Rooms and ASHRAE 15-2013
(OP)
Hi Everyone,
I am working on a large 40-story condo tower that is looking at using water-source VRF systems on each floor. The heat pump/condensing unit for each VRF system will be located in a small mechanical room on every floor. ASHRAE 15 requires a dedicated MUA/ventilation system for mechanical rooms. To dedicate a single system for all 40 floors would be very expensive to do. We have looked at possibly using a wall vent between the mechanical space and the hallway to essentially increase the total area the refrigerant could disperse to if the entire 30-35lbs of charge were to leak. We haven't had luck getting confirmation from a code official that this would be ok.
Does anyone else have any suggestions? I have heard of other high-rise buildings using water source VRF where they put the heatpump/condensing units in a small closet in the corridor that is not actually occupiable. The closet has large double doors that open up to the equipment, but you cant actually fit in the space with the doors closed. This may be a way to get around the ASHRAE 15 requirement of a 26 RCL for an occupiable space, but does it get around the mechanical room ventilation requirement?
Thanks for the help!!!
Tyler
I am working on a large 40-story condo tower that is looking at using water-source VRF systems on each floor. The heat pump/condensing unit for each VRF system will be located in a small mechanical room on every floor. ASHRAE 15 requires a dedicated MUA/ventilation system for mechanical rooms. To dedicate a single system for all 40 floors would be very expensive to do. We have looked at possibly using a wall vent between the mechanical space and the hallway to essentially increase the total area the refrigerant could disperse to if the entire 30-35lbs of charge were to leak. We haven't had luck getting confirmation from a code official that this would be ok.
Does anyone else have any suggestions? I have heard of other high-rise buildings using water source VRF where they put the heatpump/condensing units in a small closet in the corridor that is not actually occupiable. The closet has large double doors that open up to the equipment, but you cant actually fit in the space with the doors closed. This may be a way to get around the ASHRAE 15 requirement of a 26 RCL for an occupiable space, but does it get around the mechanical room ventilation requirement?
Thanks for the help!!!
Tyler





RE: VRF Systems in Mechanical Rooms and ASHRAE 15-2013
ASHRAE is a pretty good design guide.
RE: VRF Systems in Mechanical Rooms and ASHRAE 15-2013
As in one fan pulling air from all 40 floors? Yeah, I could see that being a challenge. What about one fan and inlet louver for each floor?
Per ASHRAE 15 8.11.2.1, you need a detector that will sound an alarm and actuate mechanical ventilation. It's not like the fan would have to be on continuously, only when a leak is detected and concentrations levels are sufficiently high.
The requirement is there for a reason, you don't want a maintenance person to open a door or enter a space with too much leaked refrigerant, you will suffocate him.
RE: VRF Systems in Mechanical Rooms and ASHRAE 15-2013
The VRF system is an alternative to a WSHP system. With the heat pumps you obviously don't run into this issue. The owner is very interested in using VRF, but we are concerned the dedicated ventilation system for 40 floors of small mechanical rooms could possible price out that option.
RE: VRF Systems in Mechanical Rooms and ASHRAE 15-2013
RE: VRF Systems in Mechanical Rooms and ASHRAE 15-2013
Cheapest is an open fire for heating and a block of ice and a fan for cooling.
RE: VRF Systems in Mechanical Rooms and ASHRAE 15-2013
This project has been well thought out and engineered up to this point. The VRF system with heat recovery has been modeled to be 30-40% more efficient that a four pipe system. Each floor has a total refrigerant charge in each VRF system of less than 30lbs, well below the RCL limits set by ASHRAE for occupied spaces. If you for one minute think refrigeration systems will ever be phased out in the next 100 years you are off your rocker. At this point the US has zero plans to phase out R410-a.
@Willard3 - Awesome contribution to the conversation, thank you for your input.
I came here because we have designed this VRF system option per the owners request. One of the last remaining issues that we have not dealt with previously was many small mechanical rooms and if there was any other way than a dedicated ventilation system to those rooms. My original thought of using a transfer grill to the hallways/core, which have a dedicated ventilation system, was what I had hoped the discussion would have been focused around. If anyone with any actual helpful advice has something to say, please do.
Thanks
RE: VRF Systems in Mechanical Rooms and ASHRAE 15-2013
RE: VRF Systems in Mechanical Rooms and ASHRAE 15-2013
Bad experience will also cause an owner to prefer one type of system over another.
My concern for this option would be the possibility that the door vent would eventually get removed, either with a new door or blocking on the louver itself. "It looks bad" or "sound of the heat pump is keeping people up at night". People can be funny about things like this.