Primary secondary piping.

cubbydog

I’m trying to find out if I need flow check on the secondary circ in a primary secondary system?
Does anyone have any diagrams showing circuit piping including boiler in the primary and them secondary feeding all the zones? I would like to see a complete diagram, they seem to be elusive on the internet and in Dan’s books.

Ironman

It's generally a good idea to use them to prevent ghost flow. I'm referring to the ones that go in a circulator or in some brands of isolation flanges, not cast iron ones. They can easily be changed if necessary.

STEVEusaPA

Here's tons of info and diagrams. If you can't find it here, your piping is probably wrong.
https://www.caleffi.com/usa/en-us/technical-magazine

I'd start with Issue #19:
https://www.caleffi.com/sites/default/files/coll_attach_file/idronics_19_na.pdf

You can also check with a K-type thermocouple on a meter to see if heat is migrating more than desired.

Might be easier to show a pic of your boiler piping for comments.

hot_rod

There are a number of ways to pipe a primary secondary. With a separate loop method fig 5-8 Use a a check on both supply and return if they go up vertically from the loop. Vertical piping seems to encourage thermo-siphon or ghost flow.

Fig 7-2b is another way to pipe primary secondary, eliminating that loop pump. It also seems to eliminates ghost flow up the returns as they are on a cold return leg, so just check the supply side.

The checks in the circulators work ok as Bob mentioned. Ideally the check should be 6" or so away from the circulator discharge.
Use only spring checks designed for hydronic use, conical, soft seat type checks, plenty brands available.

This journals shows good piping practices, and the ones with X thru them, not so good


https://www.caleffi.com/sites/default/files/coll_attach_file/idronics_19_na.pdf

cubbydog

Any comments? Is it possible to get ghost flow without internal check? Will I be able to adequately purge the system the way I have it?

hot_rod

The purge cock needs to be upstream of the shut off valve
Flow goes up from circ stops at valve to purge

I would have a check on supply and return to assure no ghosts in the machine

SuperTech

When piping a supply manifold in primary secondary systems I like to pipe my zone branches downward from the manifold to prevent ghost flow. I believe I got this idea from one of Dan's books or Siggys articles.

cubbydog

The cir has a internal check, what would you use on the return.

SuperTech

Caleffi makes a wonderful check valve that uses the same thing as the flow check circulators, it's built into a union and is a breeze to install. I can't remember the part number at the moment.

cubbydog

I’m guessing hotrod knows the check part number.

cubbydog

I recently installed the caleffi thermomix valve with the 140, also bought temp Thermometer probes. The valve opens at about 140 as advertised but it appears the mixed water after it opens is far to low. Acourding to the probe thermometer it’s as low as 110 degrees. This is exactly what I was trying to prevent.
Anyone have any ideas?

icy78

What's your boiler supply temp?
Does it have outdoor reset?

hot_rod

Where are you measuring the return temperature?

Zman

Are you desiring a significantly lower temp on the second set of tees (bottom right)?
With that piping arrangement, the second set of tees will get whatever heat is left. This may be exaggerated when the boiler is in bypass and the flows are lower in the loop to the right.

hot_rod

Curious on what controls the boiler/ primary circulator? Also what controls the boiler? a heat call?

For a P/S piping to work, when any secondary calls, the loop needs flow. Also any time the burner is on you need flow, even if there is not a heat call.

The 280 is only looking to maintain temperature returning to the boiler.

Usually you would pump away from a mix valve as shown in the drawings, pumping into the boiler. I have not tried one with the circulator on the boiler outlet, I think it should still flow properly.

Peter_26

I have the same valve. The mixed return is steady at 128-130 and that's with a system return of 87 degrees. That's not a cold start, but I don't see that it would make much of a difference since the valve starts opening at 140 anyway.

Hot Rod - Does the valve maintain the blended water temp at around what I measured on mine or can it really get as low as 110? I never checked that at a cold start so I'm curious now.

Is it piped correctly? Pictures?

hot_rod

It should work as you describe, temperature may vary as you have some lag in the gauges and the thermostatic element needs some time to respond It also depends on how and where you are measuring. Ideally the gauge is in the fluid for best numbers.

No it should not allow 110 to the boiler ever.

It is possible to get crud stuck between the valve and seat that could prevent accurate operation

Peter_26

I measured my temps about 1' from the valve with individual thermocouples strapped to the pipes.

Maybe the OPs valve has some crud in it like you said hot_rod.

cubbydog

The bottom left thermometer is the temp that concerns me.
The primary circulator is controlled by hydrostat 3250 plus, it turns the primary on when the boiler reaches 125 degrees. The secondary circulates are controlled Taco 504 controller that turns on a Circulator when there is a call for heat.
The outside reset is in the off position until I get the bugs ironed out.
I really don’t know how the cir pushing rather than pulling could effect the thermomix? Stranger things have happened and I will move the primary cir if nothing else works

Peter_26

Pictures of the near boiler piping and components? Did you consider what hot_rod commented about the possibility of some debris lodged between the valve and seat?

Thanks

hot_rod

Let me get some other opinions. Traditionally with any mixing valves we pull through the valve, pump away from the mixed port to get an accurate blend of H&C.

Is the low temperature just for a short period? Or does it continue too run low return temperatures for minutes or hours?

Is there a Y strainer our dirt separator on the system? It is always a good idea to have one of the two when you have control valves of any sort that are sensitive to even small dirt particles.

It does disassemble easily to clean, either by removing the valve on the unions, or dropping the internals out. There is a spring with tension on mix valves when you remove the lid. It is fairly simple inside.

Zman

If you temporarily disable the system circulators, does the boiler temp rise and does the valve stabilize?
What are the 2 zones? It sounds like at least one is high mass radiant.

hot_rod

Remember when it sees a cold return it is possible for the lower left (return) port to close 100%, so you do not have a flowing primary loop in that case. Flow is from the boiler, directly back to the boiler. The secondary circs can run and flow via the closely spaced tees, but no heat energy is available.

With a 140° cartridge and 110 flow from the boiler the return should be 100% closed.

If the boiler/ primary circ only runs when the boiler is at 125° or higher that would help, is that the pump logic?

That port does modulate, starts to open as it sees the temperature increase as the boiler SWT can blend up the return adequately to maintain the safe return temperature.

The valve is usually connected to a single circulator or to a buffer tank, so there is always a flow path.

Back up and take a pic, the drawing shows the valve piped wrong, I think. The "branch" should be facing up or towards boiler supply. Can't see enough piping to see if it is installed according to the arrows on then valve?

cubbydog

I’m quite sure the piping is correct except the cir is pumping away from the point no pressure change rather than on the other side of the thermomix.

cubbydog

I will put a thermometer inside the mixed water and take the a valve apart and clean the debris and see what happens.
I just can’t believe the valve is effected by where the cir is.

cubbydog

Z man I don’t know how to address individuals separately on this forum. Yes with the secondary circ off it Will stabilize

Zman

If you type @cubbydog, the person gets notified that you mentioned them. If you click on the person's handle there is a tab that allows a private message.

I am thinking it is time to disassemble and clean the valve. There is either debris in there or you got a bad one. It happens sometimes with any brand.

hot_rod

I would leave the piping as is, disassemble and check the valve next. It looks like you have good isolation to work on it.
As you can see in the cut away view, that spool or piston needs to be able to move freely.

Warm and cool the copper “pill” to see if it strokes.

With all that threaded pipe it could have pipe dope or metal chips stuck inside. Put a bucket under it when you pull it apart.

cubbydog

I have TRV’s throughout the house and think your suggestion of installing a wye strainer is a good idea. I will relocate the cir at the same time and put a well and thermometer to closely monitor the return water. When I’m done I want this system to run like it was designed to.
Are all wye strainers created equal? Thank you I really appreciate it.

hot_rod

I would highly recommend a dirt separator, not a Y strainer. It works faster and takes down to a 5 micron particle. The particles removed do not plug or slow the flow like a Y strainer does as it collects.
Get a version with a magnet function for even better performance.

You are correct TRVs are sensitive to dirty fluid also.

colinbarry

Cubbydog based on your second picture I don’t think you have adequate hydraulic separation. There are supposed to be straight lengths of pipe between each of your secondary circuits, as well as a length of straight pipe between the crossover and secondary circuits. I think that it is possible that the pump for the “first” secondary circuit could be disrupting the flow through the thermomix.

colinbarry

Here are the requirements for the straight lengths I’m talking about.

hot_rod

Agreed they are a bit close. The critical dimension is between the pairs of tees. As long as that is close you should not induce flow in the primary loop via the secondary circulator. The spacing between the sets of tees helps eliminate turbulent conditions assures stable flow to the next set of takeoffs.

Assuming the primary loop is sized large enough to handle the entire flow?

If the return temperature regulation is not correct with all the secondaries turned off, that would confirm the valve is not functioning properly.

cubbydog

I’m doing another system but doing it differently!

hot_rod

Embrace the hydroSeps, get rid of all those separate components!

cubbydog

Why do they always put the dirtmag on the return side? I would be more concerned the components on the supply side.
PS I bought a dirtmag yesterday,it’s very nice.

hot_rod

Yes, it will work anywhere in the system. Upstream of the boiler and circulator has the best chance of getting crud before it enters either.

It is a multiples device, it takes 20 or so passes of the fluid to pull the tiniest particle.

cubbydog

Is the hydrocal made in 1 1/4 IPT? will definitely try one if they are.

hot_rod

We have hydroseparators from 1" to 14" pipe size, with or without magnetic function.

The 549 Sep 4 sales have pretty much taken over our separator sales. That magnetic function is a game changer for ECM circulator protection.

cubbydog

I moved the cir added the filter and thermometer and cleaned the thermomix. The first time from cold start it did not maintain the 140 on the return side, I waited a day and tried it again and it performed flawlessly. Hopefully it’s healed!!
Does anyone know if caleffi sells replacement check for 1 inch sweat Inline flow check valve?

hot_rod

Do you have the brass or stainless steel check valve?