Heat Pump

[Fayaz]

Hello all,
I am designing a hotel. Owner has insisted to use Heat pumps throughout the building. Hotel has many conference rooms, banquet-halls, and large kitchens.
I don't have much ceiling space to use multiple small heat pumps. I never used large (20-ton) heat pumps. Have you applied heat pumps in these type of occupancies? What design problems should be considered?
I will appreciate your input

Sincerely,

Fayaz

 

[joken]

Contact Trane

 

[CarolinaPE]

We have used some larger heat pumps but they are big. I would think above the ceiling is not a good application for these units. A check at the manufacturers website for the size of the unit and required clearances will tell you if it is even possible. If they won't work above the ceiling the best bet would be to tell the owner to go with heat pumps will require him giving you some space for a mechanical room for the air handler.

 

[stanlsimon]

Heat pumps could work well in this application. Hotel banquet rooms are often subdivided with moveable partitions. In order to maintain control in these smaller subdivisions you can provide one heat pump for each.

Another option is to use VAV heatpumps with VAV boxes.

You can fit a five ton vertical heat pump in a fairly small closet. The door to the closet can serve as the access to the piping, and controls.

You are right about ramming heat pumps up into ceilings. They require maintenance such as filter changing, drain pan cleaning, compressor replacement, etc.. This is done sometimes but the maintenance people will curse you daily.

 

[willard3]

Heat pumps, either air-to-air or water-to-air come with two-row coils which are poor at removing moisture from the air.

In any conference room, you are going to have high latent loads (moisture) from the people and the outside air (OA). How much latent from OA you will have will depend upon climete, but there will be some.

Two-row coils will not remove much moisture and room conditions will get humid in the meeting rooms, causing complaints. Heat pumps are a poor choice for conference rooms.

 

[designbuild]

willard3 has a very good point. One way to overcome this problem would be to have a central outdoor air unit that provides room neutral, or even preconditioned, outside air to the individual units. This is common in the schools in my area. It is very much a $$ game, is it cheaper to do a central system vs. increasing unit capacity and getting specialized units with deeper coils and hot gas bypass to handle higher outside air loads. If you have several units in a central location it can make sense to pretreat the outside air. If the units are spread out the increased installation costs can add up very quickly. Also, this centralized approach will minimize building penetrations, something that most architects and owners like.

All of this completely ingnores the energy usage side of the equation. Units that are properly sized to handle a large portion of outside air that end up running on a single circuit with hot gas bypass 80% of the time is a very good way to run up an energy bill.

To truly address your first question. Sized properly they will work great. You will need to take an extra look at the heating side. You will really need to pay attention to the sizing of your electric heat (and make a determination is this emergency heat or supplemental, it makes a difference).

 

[stanlsimon]

Point well taken on the outside air. Large heat pump buildings should have a centralized outside air system. This takes the humidity out, before it gets to the space.

Heat pump manufacturers are offering a dehumidification mode as an option. Basically it slows down the supply fan so that the supply air temperature is low enough to dehumidify.

 

[willard3]

If you don't want coil frosting with a two-row heat-pump coil, you will have to run hot gas bypass....a lousy solution.

Probably the best solution is a dedicated OA unit with a deep enough coil so saturated suction temp stays up if you must use DX.