HVAC Design for Indoor Swim Spa

Most "normal, nothing special" HVAC units have one thermostat. Your pool is a HUGE thermal mass. I would think it is impossible to do what you need without two thermostats. I don't know much about HVAC units but I would easily accept the idea that two HVAC units would be more cost effective than one larger unit with all the computer controlled this-and-that required to properly service two very different zones.

pool room is 364sf and the pool is 13'-6" X 25'. The Pool is a package system in the room and does not require chemical as it has a internal cleaning system utilizing ozone, UV-C light and CuZn filtration system. Tipically water is recharged New water once a month. Source of the water is our well water so no chlorine to start with.

https://www.aaon.com/Documents/Sales/WSHP_Rooftop_161114_online.pdf

You stated pool size is 337 1/2 sqft , and the stated room square footage is 364...You don't seem to have room to even walk around the pool, there should be at least 3 - 5ft on all sides...that would be 605 - 823 square feet...

My mistake. The pool is 8' X 15' (120sf) the room interior is 13'-6" X 25' (337.5) with 10' ceilings (3,375cuft) conditioned space. there are windows along the 3 sides and forth is connected to the house.

I think I would put an exhaust fan on the roof or high on the wall with a fresh air intake with flaps on an opposite wall, and about a 1 ton A/C and heat unit.... You could probably get by with just the exhaust fan running most of the time...The water temperature in an indoor pool tends to stay colder than an outdoor pool so you don't want cold air hitting you when you get out of the pool, so the pool area is kept much warmer than the house would be...

Maybe 2 of these for wide control of airflow...or a larger one with variable speed.. 100 - 400 cfm range would be optimal...

Exhaust fan

...or something like this...

It's also nice to have a heatpump to manage the water temperature, this eliminates a lot of the need for the A/C unit...

Hey Carl. Yes your best bet will be to separate the rooms as the heat and humidity in the spa room is going to effect the house unless you keep it separate. In florida it is common practice when installing such structures as ambient heat humidity is hard enough to deal with. Plus you just might find you want that room a different temp than the rest of the house.

Get a geothermal system with separate zones. You may even be able to use the heat mass of the pool itself as part of the system. I put my geothermal system in 20 years ago. It cost more up front but my system paid for itself within 4 years. I'm in coastal Virginia..lots of humidity but I don't have a pool.

You are going to have significant differences in the heating/cooling requirements for the main house and for the pool room. Anyone in your area that has taken the manufacturers certification course for HVAC design and is selling design services in your area should be able to design the two systems you should be putting in.

The humidity will certainly be a problem.

I recommend a separate dehumidifier for the pool room in addition to a separate A/C unit.

When it comes to A/C, bigger is not always better.

It is called Air Conditioning for a reason:It conditions the air by removing moisture,as well as cooling the air.

If a unit is too large,it will cycle too quickly to lower the room humidity and the thermostat will have to be set lower to feel comfortable.(Sensible heat).

The newer VFD units are more efficient,using only enough energy to meet demand.

My $.02 cents worth.

..."If a unit is too large, it will cycle too quickly to lower the room humidity..."

....an oversized unit will raise the humidity causing a dank uncomfortable environment, and other associated problems that come with high humidity in an enclosed environment...Though this is not likely to be a problem due to the low humidity ambient environment in that location...This is why a staged unit with variable speed blower and fresh air supply would be a good tool for controlling the humidity as well as the temperature...

I agree, a unit that is too large will cycle too frequently to lower the humidity.

(Shortcycling).

I also agree with adding a high vent and fresh air intake,and a variable (VFD) heat pump that varies output according to the need.