What circulating pump to use?

[ikessky]

I'm building a 24' x 40' attached garage. The ceiling will be 9', 2x6 walls, and I'll be getting as much insulation as I can in the walls and ceiling. I believe the concrete will be 5". My plan is to run in-floor heat to keep the garage around 40 degrees or so. I'm also installing a Hot Dawg so that I can bring it up to higher temps when I want to go out and work on something. I've found a lot of info regarding the radiant heat, but I can't seem to find what to do about a circulating pump. I'm planning on running a natural gas Takagi Jr and will only have a single zone as the entire garage will be open. In all my searches, Taco pumps keep coming up, but I'm not sure what model I need. Can anyone tell me either what models I should look at or what additional info I need to calculate data to choose a model?

 

[metaldad]

need to know your reqwired flow rate, and head to size a pump. you do NOT want to oversize. you'll probably need something in the 15-30 gpm range, with a tdh of probably no more than 12. small fractional hp motor
this site has many gurus of wet heat. you may find your answer there...........
http://72.3.142.104/forum-category/76/THE-MAIN-WALL
or, here.
http://www.pexsupply.com/resources/boilerRoom

 

[KenB]

As one data point, I have a 30x40 building but I'm using the Takagi T-K3. I have a Grundfoss 52722512 three-speed pump and use the lowest speed. Works fine.

Ken

 

[ikessky]

Sorry for the newb questions, but what is the “head” that you speak of?

I’m guessing that to calculate my required flow rate, I need to know the diameter of pex and how many feet are run in the slab?

 

[Jackfre]

Any time you select a pump/circulator you need to know what its performance curve is. Every foot of pipe and every 90*, Tee or reducer has a specified "feet of head" resistance to it. If you know how many fittings, feet of pipe you add them all up to see the "total head" or friction loss if you will that your particular system develops. You take your total head and your desired flow rate in gpm and see if the circ you are looking at will give you the desired performance. A good example of this is to go to your hose bib on the side of the house and turn it on. Big water pressure and flow, right? Now, put 100' of that dinky 5/8" garden hose on it and the water will come out much less slowly and with much less pressure. Do a flow check on it to fill a 5 gal bucket. That friction loss/head is what you need your pump to accomodate.

 

[chickenhauler]

I used a little all brass Taco pump for a year with a 40 gallon water heater before I put in a boiler. It pumped fine, through around 10 loops totaling close to 1200 feet of 3/4" pex. I went ahead and kept it for my floor heating with the boiler, going on 4 years now.

I think it was this little guy:
http://www.pexsupply.com/Taco-006-B4-006-3-4-Sweat-Taco-Bronze-Circulator-1-40-HP-3797000-p

 

[BadgerBoilerMN]

First you get a professional to do a proper heat load analysis. From the heat load you determine the size and length of pipe and from this information a proper circulator can be specified. Everything else is pure speculation.

Oh, by the way, think 3 to 4 gallons per minute, depending on the heat load of course.

http://www.badgerboilerservice.com/images/SampleHeatLoadAnalysis.pdf

 

[ikessky]

Thanks for the info guys. I'm going to go back to the contractor and find out how much pex is going into the concrete and then see what things calculate out from there. In the research that I've done so far, I don't see why something like the Taco 00R wouldn't work, but I'll do the calculations before I spend the coin.