A friend needs to move his sharpening business to his garage and wants to have heat in the floor. His sharpening machine weighs 5000 lb. We’ve never installed in floor heat before. The existing concrete floor has several cracks.
Here’s the way we have come up to do it and I would appreciate any criticism/suggestion/counsel:
Fill the existing cracks/lay down 1 inch R board and also R board up perimeter.
Install #4 re-bar above that on chairs, 12 in each way. Attach tubing to re-bar (not sure if standard pex can be used or how close together loops should be).
Pour 5 1/2 inches of 6 bag concrete over R board.
He has the ceiling height and this would change the house side of the garage to an “L” shaped shop. The garage door would be replaced with a walk in door and the rest of the garage would remain garage, so the increased floor thickness would work and not affect the value of the house. He has the ceiling height for this.
Any suggestions? Thanks.
Edited 6/25/2008 7:10 am ET by Fonzie
Replies
"Standard" pex, 1/2" on 12" centers will be perfect for an uncovered slab. He'll need to supply water around 100 degF or so. Wisbo/Uphonor makes a great "whirley" tool and wire ties with loops on each end that is perfect for tting tubes to rebar/WWM.
Loops should be equal length, no more than 300 feet long each. To budget, figure 1LF/sq ft. for tubing.
Any plans for the heat source, zones or controls? How large is the space? Fuel source? A small modulating condensing boiler would be great for this.
A water heater would be way more than adequate & a hell of a lot cheaper.
Joe H
I keep hearing about guys using water heaters for this - do you have to use a pump or does it just go by convection? Also, if you end up with two different loop zones, how do you do that - just put them in series?
You really should do a heatloss to start with, to see how many BTU's needed to maintan temp. you require. Otherwise you would be just guessing on what size boiler/water heater you would need to carry the load.
The pex should be an oxyengen barrier type or you will corrode your pump & fittings.
Keep loops equal, much easier to balance the system for even heat in the slab.
More than 1 loops you would run off a manifold with a constant curculating pump, expantion tank, prv, air scoop, and some places by code a backflow preventer.
But your small area sound like a water heater would carry the load.
Check over on http://WWW.heatinghelp.com the guy there are as helpfull as here.
Fonzie, I downloaded an article from JLC (maybe) 10 years ago?
It was written by Bill Clinton, I remember that much and think the title was -- never mind, searched the site and found the first response references the article.
http://www.jlconline.com/cgibin/jlconline.storefront/
4863aae9095637e627170a32100a0610/UserTemplate/44
I have the article somewhere.
Joe H
Joe,water heaters can be fine heat sources in some case, but you have no idea how big this area is or what its heat load is, and so you have no basis for making heat source recommendations.Please be careful when recommending people use lower efficiency units. There are conditions where tank water heaters will outperform other units, but larger single zone slab areas are NOT typically one of them. If this is a small area, fine, but if it's a full size building, higher efficiency heat sources such as mod/con boilers are very likely to be cost effective in the not-so long run, and have been for years.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
I'm ASSuming it is a small area.
OP said a home garage.
Guess it could be a large building, but the information supplied indicates otherwise.
Joe H
then note your assumptions. I've seen some pretty big garages.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
By "standard pex" do you mean either the red and white stuff Manards sells or the tranparent or either? Do you mean the standard wire ties can be used - you can attach the pex with wire? We have never done this or even seen this first hand. I assumed you would have to use plastic ties. His heat will be fueled with natural gas. He will probably end up with 250 ft2 floor area, so you're saying that would take roughly 300 lin ft of pex. If you can only buy it in 100 ft rolls do you make a standard splice/coupling in the concrete? (we have the crimp tool)
I would find a source of one of the major PEX manufacurers like Infloor, Rehau or Uphonor, and by "standard" I meant the oxygen-barrier type that is standard in the infloor heating world. When I sold Wirsbo/Uphonor and Rehau products, all but the largest sizes came in 300 ft rolls ans 1000 ft rolls.
The plastic cable ties, zip-ties or whatever you want to call them can be used. I tied the tubes in my garage floor to the welded-wire mesh with those and they are readily available everywhere. It gets a little rough on the fingers, but for 250 sq ft, bearable. What I was refering to is short pieces (about 6" long) of metal wire with a small loop at ench end. Metal and PEX get along very well, BTW. Either way is fine.
You can create joints in the slab, but I would not recommend doing so. If I only had 100 foot lengths available, I would make that my longets loop length and keep the joints out in the open.
Another item I would suggest is the Grundfos three-speed pump. Cost the same as the red pumps or the green pumps and you get three different pump capacities built into one unit, and it happens to be a very good unit at that.
Find the necessary peices and parts to put the loop(s) under (air) presssure before during and afetr the pour, with a pressure guage to monitor any leakage. 20 to 30 psi is fine. Pressurize and leave it for a day. If it is exaclty the same pressure as when it was filled, you can pour.
Taco has 3-speed now, designed for infloor. So far, a good option.
I'd use plastic ties ... just cuz. Course you are tying it to steel, so don't know if there is a difference ... to me ... it 'just feels right' using the plastic zip ties. Not sure if the tubing manufacture (wirsbo) says what to use in their floor heating guides.
I'm no concrete expert. But I would consider 6x6wwm (flat sheet, not rolls) to tie the tubing to ... I used zip ties on mine ... worked fine. But on dobbies and you should be in business. The rebar will probably work good, too.
Sounds like you got a good plan going. If it's cold where you are, it will be sweet working in the shop.
Do you have to anchor the equipment to the floor? You might avoid tubing in those areas. When I did my house, I avoided the kitchen island, other base cabinets, etc.
Insulate the floor/perimeter base you can. The existing floor and perimeter ground will act a a giant heat sink and you will pouring on the BTU's and growing flowers around the garage in the middle of the winter.
For starters, the existing concrete floor has "several cracks".
You want to pour new concrete over something that has cracks in it now.
You want to install a 5,000 pound machine on top of new concrete poured over an existing base with cracks in it. How big of an area are those 5,000 pounds distributed over?
You want to put tubing that carries water in new concrete installed over old concrete that has shown movement already.
You have not defined the size of the existing cracks. Why are they there?
I would think real hard about this before proceeding as planned.
My thinking too, Dan. This may be an excellent time to break out the cracked floor, take care of any problems with the old baserock (add more if necessary and re-compact it), then pour a new (and level) floor.