hey guys. we've decided to put a simple floor heating system in our new home (we will have forced air to supplement) the basement is 1200 sq feet with 400 sq feet garage basement also...i was going to run 6 250 foot loops off one pump and a hot water tank, expansion tank, rv, and air eliminator (closed loop) the amount of tube that i'll order will leave 500 feet, so i was thinking of running 2 more loops under the main floor in the joists with some metal backing plates....should i be thinking about doing 2 zones, or can i just keep it simple as it is only for extra comfort on the toes....i was keeping the garage on the same zone just pinching in those 2 loops to keep it more of a modest temp compared to the house basement. thanks for any advise.

forgot to mention, 1/2" tubing fed from 3/4" headerss. the pump is a 1/25th hp grunfos 3 speed pump. and the tank is just a hot water tank, havent decided exactly what im going to use yet.

Sounds like you are thinking about a single pump, single supply temp system.  This is a great way to go, but you first need to determine what the required supply temp needs to be to the circuits in each zone (i.e., so as to generate the required heat flux given the likely different heat loss and floor area of each zone) so you can ascertain whether a single supply temp will be able to get the job done.  I recommend that you visit our website and run the numbers using our free DIY software.  Please be sure to read the instructions a couple times so you fully understand the drill. I suspect that the downstairs slab-heated living space, slab-heated garage and upstairs under floor-heated living space will require significantly different supply temps, but you will find out when you run the numbers.  I would recommend that you consider having separate zones for the downstairs slab-heated living space, slab-heated garage and upstairs under floor-heated living space. Bottom line, you need to do a proper design BEFORE doing a proper installation.

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thanks for the reply. im going to just simplifiy my question.
if i add the 2 loops for the under joist heating, will this particular pump still be able to push water thru all the loops still?
thanks

While this is a simple question, there is no simple way to correctly answer it without FIRST accomplishing and finalizing the design. You really should NOT just arbitrarily select a pump and install tube without FIRST accomplishing and finalizing the design...although arguably and regrettably there are "pros" who will often do just that simply out of design ignorance or because it moves the inventory that they sell.

Each circuit requires a specific flow rate (and a specific supply temp as previously discussed) in order to generate the required heat flux for the zone. As the required circuit flow rate increases and as the circuit length increases, the circuit hydraulic friction head that the pump must overcome also increases. The pump needs to be able to provide the total flow rate and total head that is required for ALL the circuits in your system. Every pump has a specific performance curve of the flow rate and the head that it will provide.  For maximum pump efficiency, you will want to select a pump that places this total required system flow rate and total required system head close to the center of the pump performance curve. Our hydronic radiant floor design software allows you to determine this design head and design flow rate so you can select the proper pump and then also allows you to enter the actual performance curve of your selected pump into the software to determine the manifold balance valve Cv settings in advance of installation and to ensure that your actual system performance with this selected pump will indeed accomplish your design objectives.

Again, you really need to do a proper design BEFORE doing a proper installation. Failing to do this will likely cause you to have problems that will be difficult and expensive to correct after the fact.

ok, i guess im not being very clear. We have (and will have) forced air heat, gas fired high eff. furnace to heat our home. i have slate floors right now over a crawlspace (which is super cold and unconfortable to walk on) except in my bathroom and kitchen where i ran 1 zone of rad electric wire heating (at the time i was told not to run the same zone to do the bathroom and kitchen together) it works beautifully and very comfortable to walk on.....
all i want to do, is be able to walk on our floors and have them be at a relatively warmer temp than ambiant....if i can just get some warm water to flow thru these pipes i imagine i will acomplish this....
so again, willl this pump circulate water thru the previously stated loops, or do i need to get a bigger pump

http://www.pexsupply.com/Grundfos-59896341-UPS15-58FC-3-Speed-Circulator-Pump-1-25-HP-115-volt-4701000-p

Any pump that you install will circulate water at some flow rate. The real question is whether the pump that you install will supply the proper flow rate of water at your supply temp to produce the desired floor temp and associated zone heat gain.

If you have 6 circuits that are each 250 feet long being feed by a Grundfos UPS15-58FC pump at the lowest speed setting (speed 1), your flow rate in each circuit will be 0.73 GPM (or 4.36 GPM total) at 5.76 feet total head.

At the Grundfos UPS15-58FC pump middle speed setting (speed 2) your flow rate in each circuit will be 0.99 GPM (or 5.92 GPM total) at 9.83 feet total head.

At the Grundfos UPS15-58FC pump highest speed setting (speed 3) your flow rate in each circuit will be 1.13 GPM (or 6.78 GPM total) at 12.45 feet total head.

If you have 8 circuits that are each 250 feet long being feed by a Grundfos UPS15-58FC pump at the lowest speed setting (speed 1), your flow rate in each circuit will be 0.64 GPM (or 5.13 GPM total) at 4.69 feet total head.

At the Grundfos UPS15-58FC pump middle speed setting (speed 2) your flow rate in each circuit will be 0.89 GPM (or 7.10 GPM total) at 8.29 feet total head.

At the Grundfos UPS15-58FC pump highest speed setting (speed 3) your flow rate in each circuit will be 1.03 GPM (or 8.25 GPM total) at 10.79 feet total head.

BTW, PexSupply.com is one of our affiliates and a great place to buy hydronic radiant floor heating system components. We also prefer Grundfos pumps over Taco pumps too.

Happy Thanksgiving

thank you very much, looks like the extra loops wont make that big of a deal. like i said, im not looking for a perfect system, and if i need to change out things after the fact, well so be it. as long as the loops are in the cement, i think were going to be ok