Question about a Viesmann

John_108

I have a customer with a Viesmann Vitola 200 & Vitocell V100 indirect tank. The house is radiant in the first floor/basement and baseboard heat on the other two floors.

The problem they have is that in the summer the first floor/basement floor which is marble will actually start to form condensation. We are working on humidity removal with the HVAC systems but this is in a coastal area with many high humidity/low temp days.

Customer asked if there was a way to cycle on the radiant zone (humidity sensor) to temper the floor to stop the condensation with out heating the space up.

Any ideas would be great.

Steve Ebels_3

Hmmm

What control is the Vitola operating with? Is there a mixing valve in the system for the infloor?

joel_19

uhhuh

Yes you could run the radiant to get the floor above dewpoint. but that's not a great idea IMHO because then your condensation will just form someplace else more nasty like behind the walls and bloom mold like a pretty spring garden. Your real problem is the moisture. Sounds like a job for an ERV and SanteFe dehumidifier. Warming up the floor will only move the moisture to another spot where it can condense. I'd be alot more woried about it collecting in places i can't see than on the floor.

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Mike T., Swampeast MO

If you have condensation on the marble floors on the 1st floor I can almost guarantee there's also condensation in any insulation (especially fiberglass) installed in that floor.

This creates an ideal environment for brown mold--frequently (and inappropriately) called "dry rot". First you'll see tiny holes in the joists. After a few years you'll hear a thud instead of a ring when you hit a joist with a hammer. A few more years and the hammer will actually penetrate into the joists.

Sounds like you need some pretty hefty mechanical dehumidification in the basement (in addition to any A/C). For the floor(s) above you might really consider the Rawal APR control. I don't claim to fully understand it, but have heard from some users and it definitely works. It's a variable unloader/de-superheater. During periods of low need for air cooling the system will still run with the evaporator essentially removing only latent heat (e.g. near constant dehumidification without cooling the air significantly).