Radiant floor question

hr

the boiler, pump, loops and tube space should be designed to that heat load number.

Insulation under the slab, and more importantly around the edge?

Keep in mind 1500 square feet of concrete 4 inches thick would be 18 yards and 72,000 pounds of mass to warm! That is not something that will warm up quickly, depending on the heatload, it very well could take hours. Best to run them at a steady state, no set back.

I say about 1/2 gpm per loop is realistic. Probably not going to be able to move that 120 K through 5 loops, regardless of the pump size! 300- 350 is acceptable for 1/2. Some push 400- 500 footers!

A great article on this subject "Two Certanties" in the December pmmag.com column by John Siegenthaler.

hot rod

<A HREF="http://www.heatinghelp.com/getListed.cfm?id=144&Step=30">To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"</A>

Bernie Riddle_2

Radiant Floor

I have a 1500 Sq. ft. slab in my basement that has 5 loops of 300 ft 1/2" pex. The boiler is a cast iron Crown CT35 120000 BTU. The system consists of a main boiler loop with a taco 007 circulator with taco vortec air separator/expansion tank. The floor zone is heated with a 007 pump, and taco series 5000 mixing valve to limit temp.

With the 007 pump when the zone calls for heat it takes several hours to satisfy the therostat. This causes the boiler and power vent, (very noisy as I mentioned in other thread) to cycle on and off many many times.

I tried a larger 011 pump to try to push the water through the floor quicker, but then the return water flow is too high and then boiler cant keep up.

So after all that my question is this. In a radiant system such as I have are you better off with a high capacity boiler? The CT 35 is only 4.2 gallons and I noticed some boilers hold alot more water....

If I replace this one with another would I be better off with something with higher BTU/capacity?

With the 011 I can put heat in the floor pretty quickly if I play with the water temp and limit the flow somewhat with the shutoff valve and let the boiler run constantly.......

Ragu_5

Hey DC: ....

Who put the thing in, who did the Heat Load, the specifications and the installation? What does the raw data say? That would be a good place to start. Thanks. Jack.


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

kevin coppinger_4

Dc...

you are just guessing...do the math, reverse engineer the system, and find someone to help you with this project who does the install. 300' is a long run for 1/2" tubing. What temp is the water going to the floor? Are you mixing it? kpc

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

Bernie Riddle_2

Ragu, as far as heat load and who done the install thats a long story. I dont like it when anyone tells me how to do my job so when all the calculations were done I left it up to them because, "they had done lots of systems like this" and they worked great............I thought we should use 3/4 tubing and they installed 1/2 so now what do you do jackhammer the whole floor up? Also I have asked contractors several times to look this system and nobody has ever showed up to even give me a opinion. To be honest I think when I mention radiant floor heat to them it is something most have not fooled with and dont want any part of. Especially "someone elses mess". You know how it is......

Kevin I thought 300ft runs of 1/2" were too long in the beginning also and wanted to go with the 3/4 and/or shorter loops. There is just too much heat loss in the loop and the return water temps are too low. This is why I tried a larger pump but as in my earlier post its too much of a strain on the boiler. I think the solution might be some type of constant heat source,(outdoor furnace)(really hate the thought of that) and constant circulation with a slab thermostat to keep the slab at a more consistent temp.

Bernie Riddle_2

You posted while I was typing Hotrod.:) Yes I do belive its best to maintain a constant temp in the slab as if its allowed to cool during milder days its quite a chore to put the heat back in it....

What I am thinking of is maybe a variable speed variable voltage circulator with a outdoor reset.

Ericjeeper

3/4 inch tubing

From what I have read, It will gain you nothing except more flow. The larger the id. of the tubing the thicker the wall of the tubing..
I would have made more loops of half inch/.But it will work just fine at 300 feet lengths.
Radiant is not going to ever be fast in a concrete slab. and as for constant slab temps.. That would be very uncomfortable on a warm couple of days..Just my opinion as a homeowner with 3200 feet of concrete slab. heated with a water heater, and heat exchanger. and a large solar hot water system tied in.

kevin coppinger_4

btu's are btu's

if the boiler is sized properly more volume ie a bigger boiler w/ that much mass won't gain you anything. Again how are you controlling the loops? Are you just pumpng it out and back? Is there a bypass? A mixing valve of some type?
That is too bad you can't get a reputable contractor out to work w/ you...Do you have any pictures to let us take a look at the set up? kpc

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

Bernie Riddle_2

Bernie Riddle_2

Boiler setup

Here is the way its set up. Did it up quick in paint