BIG MASS, BIG SUN and CONTROL?

Pete Millar (PM)

Yes, we're doing a BIG mass job with big solar gain(see, www.alderhill.com).

Radiant concrete floors and 2 ft thick rammed earth exterior walls. 7,000+sq ft, 8300 heating degree days, minus 10 F design temp, geothermal heat source. 7,000 ft elevation, Sierra Nevada Mountains. The view is awesome.

We're somewhere between keeping it utterly simple WRT controls and dreaming up some sort of fancy situation. I mean really, in the limit of infinite mass solar irradiance wouldn't matter would it? And overheating wouldn't be an issue.

Where IS that DYNAMIC interactive MASS/SOLAR/RADIANT model?

OR, how about experience and the human mind, instead of a computer program? Any of you hard working people out there have EXPERIENCE with radiant heating in the realm of very high mass? That is, experience you'd like to share?

And, thanks.

Mike Kraft

Pete M.......

that is one heck of a project.Good to be an American eh ;)Very very curious to see what your stradegy is!I have not expierienced a solar gain design.The article below should help some.That heating load must be in the 300K-400K range.How much will be RFH and if not all what will the other emitters be?How about the DHW load?Are you handling that or is that the plumbing?Fuel?Sounds like capacity will be important I'm just supposing @ 7000' altitude the chances of being snowed in are pretty likely......"Heres Johnny":)(The Shining)

The Geo-thermal.........have the wells been drilled?How many?How deep?Any solar voltaic cells for juice?How is the power being handled?LP generators?

Too many questions eh.........

Thanks for the link to the picture shoot.Heres the Siggy link(cut and paste)

cheese...........http://www.pmmag.com/pm/cda/articleinformation/features/bnp__features__item/0,2379,4148,00.html

Pete Millar (PM)

A Reply!

Yes, its a big one. The load calcs out at around 140K Btuh what with mass, airtightness and insulation values... did I mention there will be a sod roof? Indeed, the load calcs out at around 240K if we had medium infiltration levels.

We were going to have 8 wells @ 320 ft with enhanced grout but due to geology are now going with 10 wells and shorter bores.

The job is actually on the grid but has phenomenal solar exposure. Between the solar and wind scour, there is actually little snow build up on the south side, say 4 to 6 feet max, and that settles out pretty quickly. Snow(pack) is pretty amazing stuff in how it changes over time. I've been there.

Startup draw with heat pump compressors is very high so PV systems tend to be too pricey for the application.

We are doing evacuated solar hot water feed to storage which feeds through a whole house on-demand system for DHW. Ground source is not the best way to go for DHW supply in a heating dominated climate.

Thanks for the link and the reply, nice to hear from you!

My sense for temperature control is to go with slab sensors and let the system basically be isothermal through the diurnal swing... so much mass should? temper the room swings to an acceptable range doncha think?

Pete

Dan Peel

Big swings

Include constant flow, full reset from a blending tank and return temp targeting off your indoor sensor and taming the territory should be easier. Enjoy...Dan

To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"

Steve Ebels

Big Heat

My favorite method is to size (output from the slab) just a little on the light side. Tube spacing and/or water temp will accomplish this. Like maybe 85% of the heat load on a given day. Using full outdoor reset with an indoor RTU makes this fairly easy. Then use some other type of heat emitter (panel rads, radiant BB or standard BB depending on the HO's preference) to make up the difference during peak load times. Then when the sun come out.....Presto! the secondary, independently controlled, heat source shuts down and the over heating problems don't happen. Same deal when the opposite happens. Here in Michigan, it's nothing to see a 40* temp drop in a matter of a couple hours. A slab has a hard time dealing with this scenario also. Too much flywheel. Do yourself and the HO a favor and add something with a quick response time to help the system out.

With heat pumps you're kind of limited temp wise. When I do this scenario it's always with a boiler, thereby allowing the system to give me as high of a water temp as we need for whatever secondary heaters we're using.

JMHO

Steve

To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"

Dave_4

quick response

how about....rig up a heat exchanger or parralel pipe a shallow ground source loop to radiantly cool the slab using ....quick response, no overheating....can the floor take the thermal cycling on changeover?

Pete Millar (PM)

Good Suggestions, All!

Indeed, I appreciate the feedback and will review the options further w HOs and my own brain. Thanks, guys.