Radiant cooling/heating

Gta

Hi all , well I finally ditched my 26 kw electric boiler and replaced it with a cold climate heat pump ! . I currently have it set to cooling and it works well . It’s  a hydron air ev1 unit . As it’s set to provide 57f water I do have a question about condensation. The pex lines were installed on top of a suspended wood floor then covered by concrete. Will the lines sweat in there and eventually cause rot? 

Gta

Pic for ya 

Gta

This is a steep learning curve… it has a 30 gallon mass tank with a 12 kw back up boiler for really cold days …. It’s my only heat/ cooling source …. It’s supposed to work very well down to -30-35 c 

GroundUp

What are you doing for dehumidification? There is a VERY fine line with humidity controls and dewpoint to prevent any condensation. Not saying it can't work because it can, but simply switching out the hot water for chilled water isn't the answer. And 57 degree water doesn't do a whole lot of cooling.

Gta

Hi 👋, it actually cool’s very well , my humidity control is just a air exchange and a few dehumidifiers… keeps things round 50 percent 

EBEBRATT-Ed

You would need the indoor coil below 50 deg to get 50% RH

Gta

Could you explain that a bit better ? 

Jamie Hall

Gta said:

Could you explain that a bit better ? 

I'll try. Probably won't succeed. Relative humidity is only a measure of the difference between the dewpoint -- the temperature at which the water vapour in the air will condense -- and the actual air temperature. In order to remove water vapour from the air, you need to cool it below the dewpoint. Then, for comfort, it needs to be warmed up again -- either by mixing with warmer but dry air, or with actual reheat. For example, to achieve a relative humidity of 50% at 70F air temperature, the dewpoint -- and hence the temperature of what ever is doing the condensing, like your AC coil, must be below 50F. If the target air temperature is higher, the dewpoint is higher too, for a given relative humidity.

Interestingly, you can cool air by evaporating water into it, if the dewpoint of the incoming air is low enough. This is how "swamp coolers" or those cheerful little coolers which big box stores sell work, and why water sprays can cool the air in outdoor venues in Phoenix, for instance. The air is cooled by the evaporating water. The relative humidity rises, of course, but if you started at 10% you can, in theory, actually get the air temperature below freezing!