3 way mixing valve vs injection

butcherpete

Having another discussion with the guy at my new job.
I mentioned to him that i wanted to raise the boiler temp but was worried about the 3 way mixing valve for the low temp loop.
He says "injection?"
I said "no, 3 way mixing valve"
He says "yeah injection"
I said "injection is not the same as a 3 way valve"
He says "they are both the same"

Please somebody tell me, i'm just old, and i missed the memo

Injection piping is not the same as a 3 way valve

hot_rod

results are or could be the same, regardless of the terminology. One uses a motor to adjust flow, the valve uses a heat sensitive cartridge to adjust flow.

SuperTech

Both are good for reducing standby loss and eliminating the risk of thermal shock and flue gas condensation.

I went with variable speed injection pumping myself and I have been quite happy with it. Just added a Caleffi Dirtmag to it. A Taco I series mixing valve would have required less Labor and piping but neither are a concern for me.

clammy

I was always of the understanding that cost wise on small jobs 3 way or with multi temperature in one system and injection for larger systems or temperature reset on say on large sub zone of the system . Way in the past we used injection piping w reset on perimeter commercial fin in small private schools that where over heating and had mucho emmiters . Injection piping is great when u want remote mainifold or zones . It’s a great trick to have in your bag for difficult jobs w issues and building constraints and where u have hi flow and and where u may have a 3 way hunt to get to set point without under r over shoot and ur loop temp during varying flow condition in which case injection may win . Usually I only see it on larger homes and most of the time there s a issue usually as I always see its bad piping practices lack of proper primary secondary or cross over piping usually always a issue w piping and not following or understand the proper piping and of course no checks and no globes valves to throttle the injection aside from to large of piping or to large a pump and or better yet not wired correctly like zone pump to injection and injection wired to zone . Usually from what I see it’s either going cheap or following a standard tech piping diagram but not understand the whys and when’s . I have a small radiant zone and I used a taco I series w outdoor reset and it mostly tracks the outdoor reset curve on my boiler but on design day my system temp is higher then my radiant so it comes into play .on another note for shuttle and large commercial jobs vs is the way but never rule out 3 ways saw a mess of them in Germany many years ago all mounted on or near the boiler they would keep the kettle warm and reset the system by mixing at the boiler outlet ridding them selfs of flue condensate issue . Everything I saw there was in the nurmberg area learned a lot and really not only opened my eyes but put a higher quality on to which I endever to carry threw on my installs Peace and good luck clammy

butcherpete

hot_rod said:

results are or could be the same, regardless of the terminology. One uses a motor to adjust flow, the valve uses a heat sensitive cartridge to adjust flow.

so, if i sent you to a job, and said fix the 3 way mixing valve, and you get there and there isnt one, but there is injection.

you would call that the same.

I didn't say the same results, i said they are not the same.

butcherpete

SuperTech said:

Both are good for reducing standby loss and eliminating the risk of thermal shock and flue gas condensation.



I went with variable speed injection pumping myself and I have been quite happy with it. Just added a Caleffi Dirtmag to it. A Taco I series mixing valve would have required less Labor and piping but neither are a concern for me.

I agree, similar results.
But are they the same.
If i sent you to fix a 3 way mixing valve, what are you going to look for once you show up?

hot_rod

butcherpete said:

hot_rod said:

results are or could be the same, regardless of the terminology. One uses a motor to adjust flow, the valve uses a heat sensitive cartridge to adjust flow.

so, if i sent you to a job, and said fix the 3 way mixing valve, and you get there and there isnt one, but there is injection.

you would call that the same.

I didn't say the same results, i said they are not the same.

Not sure I said or implied they were the same device?

An on/ off, typical 2 way zone valve is also used for injection mixing. So is it a zone valve or injection mixing valve?

Solid_Fuel_Man

Injection uses a pump.....usually controlled by some type of variable speed device.

Mixing valves can be thermostatic (purely mechanical) or motorized.

Both can be large or small scale (residential or commercial/industrial)

Both have advantages over the other as well as disadvantages. And neither can be said to be more or less reliable than the other.

butcherpete

Solid_Fuel_Man said:

Injection uses a pump.....usually controlled by some type of variable speed device.



Mixing valves can be thermostatic (purely mechanical) or motorized.



Both can be large or small scale (residential or commercial/industrial)



Both have advantages over the other as well as disadvantages. And neither can be said to be more or less reliable than the other.

I agree
Both ultimately do the same thing, by a different means.
neither being the same though.

thank you

SuperTech

To fix a mixing valve? First I'd inspect the piping, make sure everything looks correct. After that I would test operation of the valve, see what it does or doesn't do. If functional I would check settings and voltage to the valve. If not functioning then I would check to see if it's a mechanical problem with the valve or a control issue.

Are you having trouble with a mixing system?