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Pool equipment puzzle

I did an inspection today of a mid-90s house with an indoor pool. The mechanical equipment looks to be a pretty good puzzle. Here are some photos: http://bailerhill.com/pool Most of this equipment no longer works, and the owner is pondering how to replace it.
Heating and cooling of the pool room is by a heat pump / air handler with ductwork. When I looked at the outdoor unit, I noticed a second set of piping entering below the refrigerant lines. Both of these pipes are 1/2". The owner took the side cover off for a look at what's inside. To me, the connections look like a hack by the installer, not a factory-supplied configuration, although the stuff inside the box looks manufactured.
In the mechanical room, there are a couple of oddities. First, there's a bunch of copper piping with a couple of circulators. It was once piped into the pool pump/filter loop, but has been disconnected. That piping connects to a wall-mounted heat exchanger using the larger diameter connections. The smaller diameter connections are the same 1/2" piping that connects to the heat pump. There is a second heat exchanger in the supply airflow, shown in the last photo?
Not shown is a fairly recent propane pool heater and a bunch of new-ish PVC piping for it.
With me so far? This was a quick visit, and I didn't have time to do more than snap some photos.
It looks to me like the installer was trying to heat the pool water with the same heat pump that heats (or cools) the room. I'm gonna go out on a limb here and say that the installer went into mad-scientist mode, bought a bunch of stuff from the supply house, put it together, and tried to make it work. Is this even a remotely feasible idea? Any other interpretations as to what the intent of this set-up is?
For the record, I advised the owner that he needs to identify and hire a competent mechanical designer to evaluate the building and come up with a system that will provide heating, cooling, and humidity control.


  • Wow! I think your out on a limb is right were the installer went. Piggy back the water warmer by pulling extra heat from a heat pump.
    The problem with an indoor pool is not heating the water, it is controlling the humidity in the room. The heat pump is probably not a bad idea for the room enclosing the pool in your neck of the woods.
    Not many refrigeration units will keep up with the humidity a pool creates. So you have to exhaust the majority of it out.
    I would also wonder about and be prepared to deal with some mold somewhere. The disuse of the pool in the past may have removed the moisture source, and the hidden mold may have become inactive. The original owner may have cleaned up any black stuff visible etc. Who knows???
  • Based on a review of the manual for this unit, the bottom copper piping inside the outdoor unit is definitely a addition to the original equipment. Regarding heat exchanger 1, this looks to be just inside where the pipes enter the home. This is probably to switch between a glycol loop within the outdoor unit to a straight water system inside the home. I feel that that exchanger is sadly lacking and a oversized plate exchanger is what is typically used and required in this configuration. Per John Siegenthaler, you want the liquid on each side of the exchanger to be at or less 5ºF difference. Cannot help with the rest of your question.
  • David ButlerDavid Butler Posts: 3,889
    Sounds like a site-installed desuperheater (DSH). The connection at the heat pump is (was) a refrigerant loop tap. The pump on the water side of the wall-mount HX circulated pool water through the HX.
    In theory, a DSH can maintain a pool at comfort levels but it can't handle pickup loads so no surprise a propane heater was added. In any case, site-installed DSH's went by the wayside after the switch to R410a. And they made more sense in areas with a long cooling season.
    The inline duct coil was likely an attempt to use the hot gas (via the DSH) for reheat so the A/C could operate as a dehumidifier when there's no sensible cooling load. The controls required to make this work are not trivial. And if the pool has chlorine, the DSH, reheat coil and air handler would corrode fairly quickly.
    Putting a pool inside a building, especially a home , is a complex endeavor on many levels. Most folks are surprised that the mechanical systems end up costing more than the swimming pool.
  • David ButlerDavid Butler Posts: 3,889
    Opps, I didn't scroll down past the top photo. Wow. That is not a manufacturered DSH but rather it's site-configured, requiring even more custom controls. That black loop appears to be a hot-gas (refrigerant)-to-water heat exchanger, but as Sean said, too small to do much good.
    There's zero chance any of this can be salvaged (or worth salvaging), except perhaps the ducts.
    Indoor pools are typically maintained around 80F with air temp slightly higher. Without a pool cover, the dehumidification load goes up dramatically, so a tight fitting cover is essential for any residential indoor pool (typically motorized, and in place 95% of the time). Air distribution, warm-side vapor barriers, and negative pressure when the pool is uncovered are all critical ingredients to maintain comfort and protect building components.
  • There are several companies that specialize in this field. I'd suggest calling a minimum of three for quotes. There are several technologies, especially dealing with heat recovery, fresh air and humidity, that should be evaluated for your locale. I would also recommend service contracts that include on-line monitoring. I does not take very long for a system component in need of repair to cause damage. Checking building pressure after new equipment install should be on the checklist since excessive positive or negative can effect building damage and operating costs. Scrap the existing system completely.