Injection pumping

JoeP

I am installing a system with 5 radiant zones, DHW and one high temp. zone. I plan on using injection pumping. There will be 2 injection pumps, as I have 4 zones with similar design temps and one with significantly higher design temp. One of my techs prefers using 3-way mixing valves and says it's great because he "only needs 2 pumps for the whole radiant system" the way he wants to do it. Is there a significant advantage to injection pumping that justifies a system with almost 5 times as many circulators?

hydronicsmike

5 times as many?

When I count all the pumps, one for each zone, the DHW Tank and 2x Injection, I only come up with 10 Pumps total.

If you were to use a 3-way mixing valve instead of the injection, you would only have 2 pumps less if piped correctly. Then you'd have to look at the price difference between the two pumps and the two valves and thats really the only difference as far as material goes. But dont forget about the actuators either. A mixing valve needs one, a pump doesn't.

As far as operation goes, an Injection Pump can respond to load changes a lot quicker than a Mixing Valve due to the motor speed of the mixing valves actuator. I have seen actuators ranging between 60 and 200 seconds to go from fully closed to fully open. An injection pump can go from 0-100% of its output in just seconds, if that.

I don't see much difference at all, other than price. Don't even know if that is significant enough. Wouldn't think so. I mean we are talking Residential system here, not?

Injection is my preference, but everybody has their own. I sell valves, but still favor pumps, which I do not sell. Does that make sense?

I hope this helps. Others?

Mike

Alan(CaliforniaRadiant)Forbes

We used to

use mixing valves on all our radiant systems. Injection pumping was always a hot topic here on The Wall and one day, I decided to try one out. It was on a staple-up job with plates and I wanted to reduce expansion noises by using a reset system ; a lot of the tubing was touching the wood framing.

We used a tekmar 356 and a Taco 006-BC7 with an integral flow check as the injection pump. After we were finished, I vowed never to use a mixing valve again. There's something very satisfying about watching the controller's bar graph show injection percentage and listen to the pump ramp up. It's a much faster response than a mixing valve.

Alan


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hot_rod

I count 5 pumps for VS

not 5 times as many!

If the boiler is the primary loop, and you use zone valves for the 4 zones. I am also a fan of VS mixing.

But it's not for everyone:) All mix valves need a pump downstream to operate properly, even 3 ways. Also needed is a primary loop pump to handle the boiler and provide a "temperature" for the mix valves to draw from.

The VS mix should only add two additional pumps in your example.

hot rod

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Rookie

re: Taco injection

Since a lot of times we were using the Taco contol boxes, we decided to use the plug ins for injection and outdoor reset control.I was impressed. Has anyone tried them?

Wayco Wayne

Yes

I've used them on 2 jobs so far and they work fine. They're a little different than the straight Tek-mar so be aware when setting up, but they worked well. On the 3 way valves; Is there any need for protecting the boiler against cool return? A 3 way valve could be a problem there, where of course injection ususally has a boiler return sensor that will slow down the injection circ and even shut it off is the return is too cool. WW

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Jim Kelleher

re: Manifold build

I try to use the primary/secondary piping when I can sell it, I like the way it can gives the future contolling options to the customer. If I only had a person to put together manifolds ( helper) then I would use it on all boiler jobs.

Jim Kelleher

re: Primary secondary pics

This was the last job we used the taco injection and the outdoor temp control.