Injection Mixing

woodshed

Hi -
The heat source for the radiant floor heating system is being replaced. The original boiler was about 13 years old, not modulating but condensing. The home has several zones of Quik-Trak in-floor pex, outdoor reset and variable speed injection mixing. The original boiler was not modulating and operated at a fixed setpoint but it was a condensing unit.

The heat source will be replaced with a Versa-Hydro.

Should I keep the injection mixing loop or remove it? The Versa-Hydro is modulating, condensing, has ODR. There are no low water temperature zones. The zones use valve actuators with t-stat's.

I'll be replacing the system pump which is a fixed speed unit with a Delta-P pump.

The amount of copper pipe to remove from the injecting mixing loop is minimal.

I'm wondering if the injection mixing loop is necessary or needed with the heat source upgrade.

Would you recommend removing the injection mixing loop or is there some benefit to keeping it?

Thanx, Rick

Ironman

This is a good question for Rich McGrath since he's very familiar with the Versa Hydro.
Injection mixing is the best method for operating a slab, but if you don't have another temp zone, and never will, then it would be unnecessary redundancy to me.

woodshed

Bob -

My question was regarding the need for injection mixing since the replacement heating source is a mod-con.

The current system is not heating a slab, using Quik-Trak sub-floor tubing. All zones are controlled with t-stats and valve actuators.

Since low boiler water temps are not a concern, the heat source has ODR and there are no low temp zones, is there a need for injection mixing?

hot_rod

You m ay run the radiant directly to that heater, really no need to have any mixing device unless you need multiple temperatures in excess of 15 degrees from one anothere

Rich_49

Watch your pump sizing Woodshed . Take into account the the high head loss possibility with 5/16" tubing and factor in the head oss through the flat plate at design and maybe a bit below so you don't get into trouble . At least the 5 /16" has a 20* Delta recommended .
Get rid of the injection mixing .

Ironman

woodshed said:

Bob -

My question was regarding the need for injection mixing since the replacement heating source is a mod-con.

The current system is not heating a slab, using Quik-Trak sub-floor tubing. All zones are controlled with t-stats and valve actuators.

Since low boiler water temps are not a concern, the heat source has ODR and there are no low temp zones, is there a need for injection mixing?

As you can see, we all agree that the injection mixing is unnecessary. Unless you plan on adding a supplimental heat source, such as a wood boiler or solar, then I'd remove it.

RobG

What type of flooring are you using and why do you not need low temperatures? It kind of defeats the purpose of using a modcon if you are going to use high temps. Is there insulation underneath the existing flooring? Have you done a heatloss?

woodshed

hot rod said:

You m ay run the radiant directly to that heater, really no need to have any mixing device unless you need multiple temperatures in excess of 15 degrees from one anothere

Hot Rod - I was reading idronics 7 and there was a section that discussed systems that do not require injection mixing. It seemed that my application met that criteria in idronics 7; thanx for the confirmation.

woodshed

Rich said:

Watch your pump sizing Woodshed . Take into account the the high head loss possibility with 5/16" tubing and factor in the head oss through the flat plate at design and maybe a bit below so you don't get into trouble . At least the 5 /16" has a 20* Delta recommended .
Get rid of the injection mixing .

Rich - the heat loss calculation is 35,000 btu/hr, 3.5 gpm, 4.2 ft. head; using the Versa-Hydro graph would add 1 ft. head for the heat exchanger. The manifolds use valve actuators so I was going to use a Delta-P system pump set at 5 ft.head with a 20*Delta as you stated. I'll eliminate the injection mixing.

woodshed

RobG said:

What type of flooring are you using and why do you not need low temperatures? It kind of defeats the purpose of using a modcon if you are going to use high temps. Is there insulation underneath the existing flooring? Have you done a heatloss?

RobG - The home has a wood flooring, tile flooring and carpet/pad. The first floor joists have foam joist insulation and and the second floor joist have blown fiberglass insulation. A heat loss calculation was done, 35,000 btu/hr, 3.5 gpm at 4.5 ft.head including the heat exchanger.

I was not clear in my original post about not needing low temperatures. All zones fall within a 15* spread with maximum supply water temperature of 140*.

Rich_49

The Delta is important when using Quik Trak . Might I suggest a Taco VT2218 ? Quik Trak performance cares much more about Delta than velocity . You could very well end up with an under performing floor . I am positive Uponor recommends a 20* Delta f reason , as do most manufacturers .

That Versa heat pack also is really responsive . You'll hold the burner out longer by using less of the mass at 20* also .

woodshed

Rich said:

The Delta is important when using Quik Trak . Might I suggest a Taco VT2218 ? Quik Trak performance cares much more about Delta than velocity . You could very well end up with an under performing floor . I am positive Uponor recommends a 20* Delta f reason , as do most manufacturers .

That Versa heat pack also is really responsive . You'll hold the burner out longer by using less of the mass at 20* also .

Rich - interesting suggesting on the Delta T pump; I was more concerned with a constant Delta P since I was using valve actuators, but I see your point about Delta T and Quik-Trak. If I use a Delta T pump, would that require a pressure differential valve since I'll be using valve actuators (wax element).

Are you referring to the "mass" of the Versa or ...?

Rich_49

No. You will not need a pressure differential bypass valve . It varies it's speed and flow based on supply and return sensors while maintaining the designed for Delta of the radiant panel .

Yes , You will move less of the mass in the Versa and you will also since the unit side pump will not be flowing water as fast have better thermocline in the tank . In other words water at bottom will be cooler and upon firing will have an colder temp fluid to condense a bit more . Just like a buffer tank we want those layers of varying temperature water .

Suggesting anything other than a Delta T pump when there is one capable of handling your highest head zone in any system makes no sense , in my opinion . We design systems around a Delta T and we can stay near that Delta for a good majority of the heating season by using the technology . Some say that ODR will not work with a Delta t circ . If you've had a design done for your Quik Trak you will notice that while SWTs , head and flow rates may change , the Delta never does . Why use a circ that guarantees a head that you may encounter <5% of the year while at design ?