Injection Piping Diagram

nick31

I was hoping to get some help with what will be my first time piping a system as injection pumping. I’ve been trying to read as much as possible but I’m a visual learner and looking at and drawing out a diagram will always help more than reading something. I have a small house with radiant heat for the living room, kitchen and bathroom then a baseboard loop for two bedrooms. It’s an oil boiler with a tankless coil that has to stay this way because there’s a storage tank that’s only a couple years old the customer wants to keep. I’ll post a picture of what I drew as a diagram for my understanding of the injection loop. Where I’m struggling is where in the system do I take the high temp baseboard loop from. I’m assuming from the primary loop but I haven’t seen anything to confirm. I plan on using the tekmar 356 variable speed mixing control and that manual is where I got a lot of the info and diagrams for the system.

Another question I had that I was also going to ask the guys at the supply house is what pump would be best to use in the injection loop. My thought was something like the Grundfos alpha because its pressure differential setting. If I’m understanding everything correctly I would need 4 circ pumps, one for the primary loop, one for the secondary, one in between the injection tees and one for the high temp loop.

I’ve also never seen in any diagram air elimination outside out the primary loop. What’s the best way to add air elimination closer to the radiant loop.

Any advice would be greatly appreciated, also any sources you recommend reading on it that also have visuals would be fantastic. Thank you!

ratio

Start with idronics #7: https://www.caleffi.com/en-us/education-and-resources/idronicstm

I'm sure there are others, too. Read them all!

hot_rod

Injection mixing is not as common anymore, it requires a small circ, often a dhw recir is enough and a controller. Usually a common 1/12 hp circ was used and choked way down, not ideal. The math below to size the gpm. You need to know the

BTU/hr load of the low temp

divided by 500 X the (hi-low delta)

The example below 50,000 radiant, 180 inject, 90° return = 1.1 gpm.

Another option, lower drawing, if you have just one zone of low temperature is what is called proportional mixing.

The boiler is operated on ODR outdoor reset, so it modulated the high temperature.

A manual 3 way mix valve rides along with that reset curve, so it gets the advantage of ODR without needing a second ODR control.

If you have multiple low temperature zones a 3 way thermostatic is another option, good for around 5-6 gpm flow.

In either piping adding a second air purger speeds up air removal. The expansion tank connects to the boiler air sep.

Which ever loop has the expansion tank conection is the primary loop. So depending on where the tank is connected determines the primary loop.

GroundUp

Is there a reason you're leaning toward injection compared to a simple mixing valve?

nick31

So I was originally going to go with a taco iseries mixing valve. I don’t really work on radiant but this is for a friends mother in law. It’s their 2nd home so people are rarely there in the winter so I figured it’s the perfect job to take my time and learn on. When I reached out to my supply house I get my boilers from injection is what they recommended saying it was simple piping with common components easy to work on or god forbid replace in the future.

I’m not married to a specific idea but I do like going with what they recommended. They’ve helped me in the past with different things and occasionally offer classes on some of their products.

Kaos

Look through this thread here:

https://forum.heatinghelp.com/discussion/201967/need-help-with-new-install-of-radiant-with-buderus-cast-iron-boiler

https://forum.heatinghelp.com/discussion/202046/help-setting-up-variable-speed-injection-mixing

Pretty much what you are trying to do. Injection ended up being the cheapst that gives ODR, boiler protection and low temp for radiant.

HydronicMike

I've had no problems with injection mixing, Tekmar boiler control w/odr, and a 007

hot_rod

A few other questions?

Is there a boiler in place? An oil boiler with a tankless coil may be oversized to the homes total load? What size is the boiler?

Any idea on the total home load, hi and lo temperature zones?

Does the boiler have any reset control already on it?

A small zone of radiant, will not require boiler protection, but may also cycle an over-sized boiler a lot.

Boilers with fin tube rarely need return protection either. So maybe scratch return protection that off the wish list. Any idea of the radiant load, btu/ hr?

ODR is nice to have on any system, especially with radiant to keep a consistent temperature, avoid over-shooting room temperature. Also a fuel saving device.

Manual mix valves are very affordable. Shop around, I've seen new ones on ebay for 100 bucks or less.

The question still what circ for a 1 gpm, or less, injection mix?

A 10 gpm 007 to move 1 gpm or less?? Maybe 3- 5% efficient?

Even a 1/40 hp circulator, intended for 4-5 gpm at mid curve, would need to be choked way down for injection under 2 gpm.

Some of the new ECM circs may work off a tekmar signal. At least use an efficient circ if you injection mix.

Notice ECM pump curves tend to trim away the upper and lower part of the curves, the least desirable operating conditions.

Back to a system that maximizes components :) I've done a number of thse on my own properties, simple, reliable, low tech.