Primary/Secondary

Andy Morgan_2

Every now and then the question of the spacing of the tees, and the spacing between sets of tees comes up. I have another question, does it mater if the tees coming off of the header are on the same plane or not, say like in the 12 o'clock and 3 o'clock position??? Maybe I am beginning to worry to much!

Happy Fourth of July!

Andy Morgan

Steve Whitbeck

As long as they are on the same pipe without any fittings between them and they are no more than 12 inches apart then it doesn't matter. One thing you have to watch for is will the pipe going to the boiler trap air? I have installed the secondary return pipe going up off the header for the purpose of drawing off the air.

Steve Ebels

Pri/Sec

The rule is no more than 4 pipe diameters apart for the secondary tees. In other words if you have a 1 1/2" primary loop, the centers of the secondary tees should be no more than 6" apart. As far as what angle the tees are at, it doesn't make any difference.

The effect you are trying to achieve with primary secondary is to eliminate the pressure loss between the two tees. From that statement you can see that the closer they are, the better that effect will be accomplished.

Don't forget the flow-checks in your secondary loops!!

Josh M.

Bottom line... Heat rises put em at 3o'clock when possible.

Doug Oest

Are Flow Checks Necessary in P/S?

Hey- I just saw the one fellow saying you should use flow checks in P/S. The other guy said if your spaced no more than 4 pipe diameters apart, the pressure drop across that point will be minimal- which is what you're after.

My question is, do most guys do a belt and suspenders kind of thing with the max of 4 pipe diameters, PLUS the flow checks? I've seen that in all of Tekmar's mechanical application piping diagrams. In theory, you shouldn't need the checks because of the closely spaced tee's but I wonder if guys have been having some trouble with this.

Anybody?

Floyd_3

Some will....

some won't... the checks are a CYA deal.... as I see it.... why take the chance?????

I hate call backs... it affects my ability to sleep at night and screws with my customers confidence in my abilities...

for an extra fews bucks I don't have to wory about either....

Steve Ebels

Flow checks

I use them in just about all installations and situations. The exception would be a loop with a positive shutoff, like a zone valve. It's just so much easier to put them in at the time you're piping the system than the alternative. What you're dealing with is not pressure induced flow, but flow that is caused by temp differential. It's amazing how much flow you can induce by creating a large temp difference in the water of a secondary loop...... any loop for that matter. Use 'em and save the call back. It's cheaper!!

Doug Oest

Amen

I hear ya!!! Thanks!!

Doug Oest

Thanks

Yep- I agree with that... temperature induced flow.

Had that happen to me on another job- it wasn't P/S but the baseboard zone was very close to the boiler. We had a flow check on the supply to the zone but nothing on the return. The customer called and said the zone was getting hot and he had the thermostat off. We went back and sure enough, the hot water was creeping back up the return. We put in another flow check on the return side and that did it.

But, yea, it's amazing how that ghost flow works. Well, that's how they survived before pumps came along!

Thanks for the help.

doug_10

Check Valves

I have heard of many people using check valves in Injectin Systems.

There are a couple of possible issues that you should be aware. Not that they will occur, but it wouldn't be the first time that I have heard of any of the following complaints:

1.) If a Swing Check Valve is used:

Under low speeds (Injection Pump), I have heard complaints about chattering (like) noises. The flab keeps on knocking on the seat. (Thats the best explanation I could think of at the time )

2.) If a Spring Loaded Check Valve is used:

Under slow speeds (Injection Pump), I have heard complaints about continuous ramping up and down of the Pump. At very low speeds, the pump may not be able to provide enough pressure to pop the check valve open, so the pump increases its output as there is no increase of temperature seen on the mixed side by the control. It has to increase its output so much, that all of the sudden the Check Valve pops open and the pump introduces a large amount of hot water into the system, which may cause the Control to slow this pump back down. Of course, the Check Valve will eventually (or right away) pull itself shut.

3.) Check Valves built into pumps, like Grundfos and Taco have them.

No problems heard as of today.


tekmar never has recommended using Check Valves, but it has been done. Thermal Heat Transfer can be dealt with by using a Check Valve. However, I generally suggest to people to run the boiler loop around the ceiling and then drop down with the injection loop by at least 1 ft, if not more, into the system loop thats at about 4-5 ft off the ground. Never had any thermal heat transfer problems when doing that. It is important to get this drop in. tekmars literature references 1ft, but if you can make it more than that, that would be better. Then you shouldn't need a check valve.

Just my input and feedback from installers in the field.
Thanks for the other feedback on this topic. It's great that you guys teach me (and thousands of others that come on here)so much, every day.......

Thanks,


Mike


PS.: Doug, how come I can't see your name on the Wetstock 3 attendee list? Burnahm should be there!