Pumps for in floor heat

[swvega]

Do you really need two pumps to make a simple one zone in floor heat system work? The insturctions that came with the boiler shows two pumps on system. I've got a 1800 sq ft building with 6 runs of just under 300 ft of pexs. All the floor will be at same temp to heat shop to 50-55.So why wouldn't one pump of the right size be enough.

 

[clayton]

My shop is 1600sq' with floor heat. I use one 1/8hp water pump and have not had any issues. Been in service for 8 yrs.

 

[aandpdan]

It depends on the system. Some boilers use a primary/secondary system and they do need two pumps. One for each zone and one for the boiler itself.

What model boiler? Can you post a picture?

 

[hansen1]

My boiler has an internal pump and I added one external pump. I have 8 zones under 300' each. Seems to be working fine.

 

[swvega]

The boiler I have is a menards hydro smart 170 gas.

 

[aandpdan]

Nice system.

You do need two pumps, it is a primary/secondary loop system.

The first pump moves the water through the heat exchanger while the second pump moves the water through the loops. It helps prevent thermal shock on the system due to low return water temps. It also helps with the pressure drop across the boiler. You'd need a much larger pump and also a very high flow rate with one pump.

 

[Fastback]

I figured my pump size bases on my "feet of head" and found that my runs (285' or so) did not justify much more than a taco 009 style pump running on low. Since my heat is an on demand heater designed to heat incoming ground water to really high temps I did not see the need for any type of mixing system or a second pump. If you have total control of an on-demand heaters output temp, why bother with a mixing system? Don't forget that since it has no tank it will not need to deal with condensation or temp shock due to a wide delta....

I am no pro, I'm just to cheap to pay anyone else, so take my advice as such.

 

[Highbeam]

I also have an 1800 ft floor with 6 300 foot loops. You do not need two pumps unless you choose to use a primary/secondary system. I plan to run the floor water right through the boiler so only one pump is needed.

Can't wait for the pics.

 

[swvega]

Talked to hydro smart this morning and they said I need two pumps. One at a slower speed running though the boiler and one running the floor tubes at a higher speed. Or it is hard on the boiler.

 

[Highbeam]

That makes no sense at all. You do realize that the water will be moving through all parts of the system at the same flow rate nomatter what?

Be careful that you are asking the question properly. Sounds like they are assuming a primary/secondary system with two independent water loops, one for the boiler and one for the floor. In that case you need two pumps, one for each water system.

Many systems use one reservoir of water. The water goes through the boiler and then through the floor, the same water. You only need one pump to create a system flow rate. Anything else would be redundant.

 

[aandpdan]

That makes no sense at all. You do realize that the water will be moving through all parts of the system at the same flow rate nomatter what?

Be careful that you are asking the question properly. Sounds like they are assuming a primary/secondary system with two independent water loops, one for the boiler and one for the floor. In that case you need two pumps, one for each water system.

Many systems use one reservoir of water. The water goes through the boiler and then through the floor, the same water. You only need one pump to create a system flow rate. Anything else would be redundant.

He does have a primary/secondary system. The water does move at different speeds with two pumps through the loops and boiler.

Most modcon's use this system.

 

[swvega]

Yes thats what they said I have to do. If I dont no warranty on the boiler.

 

[brewchief]

The heat exchanger in most mod/con boilers isn't designed to have all the systems flow though it. By using primary/secondary piping the proper flow rates can be achieved, piping should be done exactly per the manufacturers instructions.

 

[rburke65]

Swvega, what size of pex did you use in your floor? Thanks