Hello all, newbie here... I am trying to decide what percentage glycol to use in my hydronic radiant heat system?

I am in central Virginia, have two Chiltrix air to water heat pumps, indirect DWH, 20 gallon buffer tank for the radiant supply.

We have 2200 sq ft of concrete on a slab and the same in an upper level, both with 1/2" pex throughout.

Is there a formula that should be used for calculating the percentage glycol? Should I consider not using glycol?

And, any thoughts as to the best place within a 100 miles or so of Richmond to get it?

fyi... in the event of a power outage in the winter, I would fire up the generator... but if for some reason the generator would not start, I would be stuck and would not be able to circulate the water. I have a great fireplace that is capable of heating the entire house, new build that is very tight... but the Chiltrix are still in the elements...and would freeze.

Thanks,

Dean

https://www.chiltrix.com/documents/CX34-IOM-3.pdf. Page 11 has glycol %. Would love to hear your experience with the Chilltrix HP's.

It is best to avoid using glycol altogether and it really should only be used when you have a significant risk of freezing the PEX. You should only use propylene glycol and you should never use ethylene glycol. Glycol reduces the heat transfer which will require increasing the supply temp in order to generate the design heat gain. Glycol also increases the required pumping head to achieve the required circuit design flow rates which may require a different pump setting or pump to accomplish this. 25-30% is usually recommended to provide burst protection but this can be refined based on the expected outdoor temp.

https://www.hpacmag.com/features/how-to-match-glycol-levels-to-various-systems/