injection circulators

Wayco Wayne

do you guys use for your injection set ups. What is the correct way to size them. I have several jobs where I'm using a Tekmar injection control with a 15,000 heat loss. Don't think I need too much in the way of circ capacity. WW

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hot_rod

Think small

Got an aquarium pump lying around? Seems like a three way thermostatic valve might be better suited to such a small zone. I've used small DHW circulator pumps on real small injection loops like that.

You need to know the fluid (water 490), the supply temperature (180) and the return temperature from the load (80)

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Wayco Wayne

Just so I'm clear here

The .3 in your equation is GPM right? How do you size your injection line. I could get away with 1/2" pex most likely.

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Aidan (UK)

injection line size

The pressure loss through the injection loop at the maximum injection flow-rate, should be equal to the injection pump differential pressure at that flow rate, when running at maximum speed. You'd probably have to put a throttling/regulating valve into the 1/2" pipe to provide additional resistance.

That sounds about as clear as mud. John Siegenthaller explains it much better.

See
http://www.pmengineer.com/pme/cda/articleinformation/features/bnp__features__item/0,2732,7879,00.html

Aidan (UK)

injection lin

> The .3 in your equation is GPM right? How do you

> size your injection line. I could get away with

> 1/2" pex most likely.

>

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> HREF="http://www.heatinghelp.com/getListed.cfm?id=

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The pressure loss through the injection loop at the maximum injection flow-rate, should be equal to the injection pump differential pressure at that flow rate, when running at maximum speed. You'd probably have to put a throttling/regulating valve into the 1/2" pipe to provide additional resistance.

That sounds about as clear as mud. John Siegenthaller explains it much better.

See
http://www.pmengineer.com/pme/cda/articleinformation/features/bnp__features__item/0,2732,7879,00.html

Aidan (UK)

injection line size

The pressure loss through the injection loop at the maximum injection flow-rate, should be equal to the injection pump differential pressure at that flow rate, when running at maximum speed. You'd probably have to put a throttling/regulating valve into the 1/2" pipe to provide additional resistance.

That sounds about as clear as mud. John Siegenthaller explains it much better.

See
http://www.pmengineer.com/pme/cda/articleinformation/features/bnp__features__item/0,2732,7879,00.html

hot_rod

Yes, .3 gpm

You could probably use 1/4" copper tube for that flow rate. As Aidan mentioned even with 1/2" you will need a throttle valve.

hot rod

Wayco Wayne

I think

I'll use some 3/8 pex and even then I will install a throttling valve. At 180 F the head through pex is .0159 per foot. I figure 20 feet each way, to the mixxing loop and back, would give me .636 total head. .0159 x 40. Even a taco 006 is a monster at .636 at .4 GPM (My load is acutally 18000 btu's. Just checked my notes) Does Grundfos make anything smaller??

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chuck shaw

circuit setting valves

When doing an injection system, how many people use circut setting valves? Like the Esbe 2650 or the Watts CSM-61. If you do use these, what do you use for Differential Pressure Meter?

Just curious,

Chuck

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Wayco Wayne

Yeah

and how much do these cost????

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heatboy

I agree with hr.

a three way or 2 way injection valve would be more than sufficient for this. Taco just released a three way that incorporates a set point or reset control and remote sensing. It would be perfect for you. Sorry, I don't know the part number. David Sweet showed to me the other day. I have never been a big fan of thermostatic three ways, but this looks Sweet (g).

hb

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chuck shaw

the valves?

or the meters?

Chuck

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Wayco Wayne

Do tell

I was going to use the Tekmar 361 I usually go with constant circ. Also this gives me outdoor re-set and boiler protection. If I'm over controlling let me know. I'd rather put the money in my pocket. I know Danfoss has some valves that are proportional with outdoor re-set, but have no boiler protection so I would need to install a bypass valve. I'm still learning so let me know. WW

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Boilerpro_3

Wayne, are the temps in HR's calc those you are using?

This makes a big difference on injection pump sizing. Also, if you can run the boiler at only 140F to meet your other space heating loads, you may want to replace the 180F number with 140F. Running the boiler cooler will get you better efficiency and longer life. I use the 361 for boiler protection only on multiple boiler installs and reset supply water temp with a boiler control, with a tekmar zone control tied to the boiler control. Worked great this winter on the two jobs set up this way.

Boilerpro

hot_rod

make sure the boiler

return temperature stays above 140- ish range. If you have a 20 degree delta T on the control aquastat you may be able to run a 140- 160 range. If you run a 140 with a 20 degree aquastat delta T you will return at 120, much too cold for non condensing. Be careful not to chase efficiencies with the risk of flue and boiler condensing problems.

On my injection systems I have been playing with 40 degree delta T boiler controls. This greatly reduces boiler cycling, allows for small diameter boiler piping (have to agree with the mad hatter, I mean mad Russian on that point

I've done a couple cast boilers with the HTP 20 gallon buffer tank and a 40 degree delta T control. Seems to be a nice control strategy. Inject off the spare taps on the buffer tank. With some clever control (post purge) work you can purge the heat from the boiler on every cycle, shove it into a well insulated tank to store. This minimizes standby loss from the boiler. Some of the tekmar controls will handle all this and give you boiler return protection to boot!

Here is a Crown with a RTI setpoint control at 40 degree differiental, with the sensor mounted in the HTP 20 gallon buffer. The Crown also has a Taco board built in to allow DHW priority. That's a Danfoss 5 zone panel with motorized 4 way mixing for this gypcrete application.

On another job I used the Istec flowsetter with the window for viewing and setting the gpm flow rate. www.istec.com. About 40 bucks, I believe. The Taco circs were replaced with Grundfos Super Brutes with intergral checks.

hot rod

Boilerpro_3

H R 140F return temps?

I keep seeing this number come up, while for years, modern vertical section, atmospheric gas cast iron boilers have been run at with aquastats set at 140F. This is also the temp. control companies (ie Tekmar) recommend. I finally cornered Dunkirk engineers on this and thier recommended minimum return temp is 117F. Remember, the surface of the casting near the return is not at this temp while the boiler is firing, only the water inside the casting. Cast iron is a significant insulator, so the surface near the flue gases is much warmer than the water temp. I've seen a number of boilers running at 135 to 140 supply that are staying nice and clean in the combustion chamber. Now if there is a tall cold chimeny connected to this boiler, you may need higher temps to keep it warm, but I don't think the boiler needs these temps. Just some of my experience and thoughts.


Boilerpro

hot_rod

My tekmar lit.

say to keep the boiler RETURN temperature above condensing temperature. I've always been told the dewpoint for natural and LP is in the 130 degree range. For this reason the returns to the boiler should be maintained above this. But it depends on the boiler, the piping, and what you are comfortable with, I suppose.

All of Siggys articles suggest 130 return for gas fired and 150 for oil. Or, as you did, consult with the manufacture. They hold the warranty card

Certainly all boilers run below condensing temps on cold start up. I suppose it depends on how long they run below condensing temperatures, and how often. The problem generally starts in the flue pipe and does not present itself in the combustion chamber of the boiler, always. Boiler manufactures don't generally warranty flue pipe failures probably why more and more are recommending stainless flue pipe!

Checking the flue at the upper most portion will always tell if the system has been running too cold for too long! Each and every installation will have different run time and temperatures to adequately "dry out" all the components. I've seen plenty of failed B-vent liners in my days. For me it's not worth the 20 degree risk, I'll stick with the 140 return, or go condensing equipment.

hot rod

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