measuring MRT

jerry scharf_2

In my ongoing quest to collect more information that I could ever use, I was thinking about houw I could get a reading of the MRT of a room. I seem to remember there was a Wirsbo tstat that could do this, but I am looking for something my computer can read and log.

Anyone know of such a beast?

thanks,
jerry

Tim Doran

MRT/not that easy

Measuring true MRT is somewhat complex and I am not aware of any single component that can do this. It would essentially have to be a sphere. In most cases I would suspect that the use of multiple sensors would be required.

Mrt is an area weighted average of the heated and unheated surfaces. The traditional process involves calculating the AUST or average unheated surface temperature. The next step is calculating the average heated surface temperature. The two are then averaged. Once again, this is all area weighted.

The next step is to determine the operative or resultent temperature. This is what we realy feel or experience in the space. It is the average of the ambient temperature and MRT. Operative temperature is where the rubber hits the road and is why radiant systems can provide comfort at somewhat unconventional ambient temperatures. ASHRAE standard 55 speaks to much of this as does the ASHRAE comfort tool. Hope this helps. Nice to meet you at wetstock Jerry.

Tim D.

bob_25

Eupatheoscope

Jerry, you want to find a copy of Radiant Heating by T.Napier Adlam published by The Industrial Press. A practical treatise on American and european practices in the design and installation of systems for radiant,panel or infra-red heating. Several chapters on measuring and calculating MRT. bob

GMcD

Mean Radiant temperature sensor

There are some commercially available MRT sensors for electronic output - check Invensys, Yamatake and Seimens Europe. I think Wirsbo or Velta had one in their European line of sensors, too. You could "McGyver" one by taking a standard thermistor type element and encasing it in a round globe that is painted matte black. Think toilet tank float, the old brass kind.

Tim Doran

Genius Stat

We had a thermostat that did a pretty good job of looking at MRT but getting a pc to read it is over my head. Not to mention that the line is discontinued.

Tim D.