How will I get in trouble?

Mike T., Swampeast MO

While I try to avoid this in my computer program designs, am not always successful. It's all too possible to design something so subtly and tightly that even you can't recall exactly how it works...

That said, I believe it impossible to be "too picky" when conducting a heat loss calculation. Be particularly vigilant regarding ceilings--a given space may well have multiple ceiling types. The most important ability of a good calculation (to me) is determining the accurate proportion of requirement for each space. Watch out for recessed lighting--this is not the best combination with radiant UNLESS the housings are in sealed, conditioned space.

While the control and near-boiler piping is nearly pure science, there is quite a bit of art to tubing layout. Runs very similar in pressure drop are VERY desirable. I believe it preferable to use a smaller tube with a similar head loss for its length than using a shorter run of larger tube. Planning your runs back to the manifold is really important--sometimes remote manifold(s) are the best option. Interior spaces with little/no "real" heat loss (like baths/halls) can be tricky. The true masters of tube-in-slab seem to automatically vary the spacing with presumed loss, add/remove a bit of tube and use temperature drop along a tube run to advantage.

Watch out for areas on the borderline for purely radiant floor heat. Be aware that seemingly small changes in floor coverings and even furniture can change borderline to inadequate. If in doubt plan for supplemental heat--other radiant forms or TRVd panel radiators are good choices.

Control runs the gamut from a single-temperature, single-zone, digitally controlled systems to fully proportional, multi-temperature and fully zoned. Keeping everything working with a single supply temperature is desirable but not always possible. If you plan on using a lot of independent zones give high consideration to proportional control--if you use digital control micro-loading and short-cycling become a real possibility. With proportional control some heat is flowing to all zones the vast majority of the time and rarely is there a need for buffering. "Simple" is certainly a relative term--I consider proportional control to be simple--but such can become so dynamic that it causes severe distress to some engineers. The best thing about proportional control is that when applied to a reasonably balanced system it becomes inherently self-correcting.

D. Brown

I'm a retired engineer having fun building my own house including the radiant heat system. It's a total of 3500sf of slab and thin slab concrete embedded with Kitec. I've gotten a heat loss calculation and have done a lot of 'book learning'. If I'm going to have problems because of my inexperience, where will it be and therefore where should I get professional advice to protect me from myself? I want to do it all myself for the challenge, but don't want to re-do it either!

Thanks for any help!

Dana

Get Dan's books, Hydronic Radiant Heating and Primary-Secondary Pumping Made Easy, available at this site. Follow the Radiant Manufactures installation instructions. I have found that the most trouble is with the control wiring. Get a good electrician who understands controls or do what I do, wire the system yourself.

Frank_3

More books and stuff

I would add Dan's "Pumping Away" to the reading list that Dana posted. You may also want to look for "Simplified Design of HVAC Systems" by William Bobenhausen (1994, John Wiley & Sons publisher).

You say you've "gotten" a heat loss calculation. Did you do it yourself or have it done for you? I can recommend you buy a two-month license for Hvac-Calc Residential software ($39, but in online) which will allow you to do a fairly detailed heat gain and loss calculation. Since you'll undoubtedly want to cool the space in the summer, the heat gain portion will help you size the air conditioning unit and duct work.

When you have the piping design for the heating system sketched out you may want to consider posting it here for review. The folks here can be very helpful and may raise questions about your design that you hadn't thought of yourself.

Frank_3

More books and stuff

I would add Dan's "Pumping Away" to the reading list that Dana posted. You may also want to look for "Simplified Design of HVAC Systems" by William Bobenhausen (1994, John Wiley & Sons publisher).

You say you've "gotten" a heat loss calculation. Did you do it yourself or have it done for you? I can recommend you buy a two-month license for Hvac-Calc software ($39, buy it online) which will allow you to do a fairly detailed heat gain and loss calculation. Since you'll undoubtedly want to cool the space in the summer, the heat gain portion will help you size the air conditioning unit and duct work.

When you have the piping design for the heating system sketched out you may want to consider posting it here for review. The folks here can be very helpful and may raise questions about your design that you hadn't thought of yourself.

Hvac-Calc Residential

hot_rod

Also consider

getting help with the venting, combustion air, and initial set up and firing of the boiler.

Insulation and IAQ would top my list if I were building a new home. We really need to consider air changes, filtration, de and humidification, etc. I'd research and spend time planning that portion of you job also. It needs to be done early on the plan for installation space!

Lots of reading on this subject in the trade mags, most of which have online acess to articles.

If you belong to ASHRAE, their members magazine deals with IAQ issues on a regular basis.

Contact www.contractingbusiness.com and see if you can get a copy of this supplement. A well written piece on IAQ and products available.

hot rod