Antifreeze Recommendations for Non Pressurized System

Yes, but only because you indicated your system is open to surrounding air. Most are capped.

I imagine you lose some water along the same lines.

 

Sorry to continue this thread with my own questions but they relate directly with Bent's.

I also have a 3 ton unit w/desuperheat, 3 loops at ~600' per loop and a non-pressurized flow center with cast iron circulation pumps. My original intention was to use Methanol as an anti-freeze but after hearing about a co-worker’s corrosion problem, reading about Methanol/cast iron corrosion issues on the web (http://hvacrdistributionbusiness.com/ma ... ndex1.html[/url]) and the fact that Methanol is toxic (my desuperheat circuit is potable water on one side and I’m concerned about an undetected anti-freeze leak) I have decided to go with polypropylene glycol. Does anybody have any input on Dowfrost vs. Cryo-Tek 100 vs. Camco boiler anti-freeze vs. other with regards to cost vs. performance vs. lifespan?

A general question on the desuperheat circuit. Is the desuperheat heat exchanger on most heatpumps a single wall design or a double wall design? I know in my location for indirect water heaters fed from a boiler, we are required to have a double wall water heater design for protection of potable water from the boiler heating fluid. I have not seen any such requirements (or references) for the desuperheat circuit on heat pumps but I would assume they would also be required to be double wall for the same reason.

Thanks.

 

It may be 3 years later:

The Grundfos Techs in the 90'd said they wanted atleast 5 ft TDH water column for non-pressurized, on the inlet of the geo-piping described pump set ups.
Net Positive Suction Head NPSH was important with 18% to 22% Methanol.

Methanol by the way has been safe and fine for since the 1980's... Pond loops to 28%... 52 deg zones 5 and 6... just fine.

The slime or layer of whatever on the fluid that is too all inside the system is thinly traping methanol reduction.

Systems have not been below 18% meth solution in over 10 years at a stretch, tested... so we depend on the limits of the HYDRO-TEMP AR OEM Systems anyway and safeties of other systems as they do work for freeze protection.