Upon further study:

https://en.m.wikipedia.org/wiki/Radiant_cooling

I think that I could use the buried outside loop to cool the downstairs slab (1440ft2) using the Pex loops designed for heating (7” OC)

Only needed about 4 weeks a year.

Climate is dry so this might work, I would need to avoid condensation.

It would be easy to tie into the radiant slab loops with a flat plate heat exchanger & pump the buried loop controlled by a greatroom thermostat and a dew point controller.

The reason for the flat plate HX is: the buried 450’ loop of 1” pex is open to Oxygen permiation,
& the house heating system is closed O2 barrier pex.

The buried pipe can hold about 13.5 gallons so I need to put about 7 gallons of propylene glycol in it?

Some of it goes under a window well & is only about 16” below bottom, so cold Winter air could freeze it if no glycol.

I bought a Honeywell dew point controller & a line voltage cooling only thermostat.

I plan to pump the buried loop through the flat plate HX (rated at 50,000 BTU,s)
with a Grundfos SS Alpha ECM pump,
Under 10 Watts on low.

Safe and Sanitary Hot Water Delivery Systems

https://www.caleffi.com/sites/defaul...nics_22_na.pdf

Caleffi has a series of these great free learning tutorials.


Planning my Domestic hot water recirculation system.

My 79 gallon Viessmann dual coil indirect water heater acts as a buffer tank between the boiler and the heated floor system. The bulk 79 gallons is used for Domestic hot water to fixtures, deep soaking tub etc.

This tank has an aquastat that is mounted in a well (thermal grease) that has a 30*F Delta-T
This aquastat controls the boiler fire cycles.

In winter I will set it to 140-170* & Summer I will set it to 120-150* TBD

At top of tank where DHW exits, I will not have the normal ASSE1017 thermostatic mixing valve (TMV)

Full tank temperature hot water will go through the insulated 3/4” red pex-a distribution/recirculation line.

This 3/4” pex line will run as close as possible to each fixture that requires hot water.
A short stub of 1/2” pex-a will tee off the 3/4” line.
At each fixture I will install an ASME1070 point of use TMV.

The Recirculation pump is a small Grundfos made for this purpose, it has a sensor & several modes of operation that I need to study.

The insulated recirculation return line will be 1/2” pex-a and enter the tank at the bottom through the drain port, this is to mix the bottom.