Is a check valve a must?

cloudd

In a simple closed loop 1 manifold (equal loop lengths) radiant system with 1 auto adjusting circulation pump is a check valve required? 

Jamie Hall

Probably not.

hot_rod

Maybe, you could get a small amount of ghost flow if the tubing is above the boiler via thermo siphon. Some DHW recirculation systems work without circulators, and thermo siphon solar also.

The small checks come with most all circs now, may as well use it.

cloudd

hot_rod said:

Maybe, you could get a small amount of ghost flow if the tubing is above the boiler via thermo siphon. Some DHW recirculation systems work without circulators, and thermo siphon solar also. The small checks come with most all circs now, may as well use it.

The reason I asked is because I finally got my system configured with all of my actuators/Uponor Smatrix Pulse controller.

In my closed loop radiant loop my plumber connected the Grundfos circulation pump (with the check valve installed) between my Combi and the expansion tank. I think because of space on my wall and I did not notice that it might cause a problem at the time (obviously he didn’t notice). I believe the circulation pump (with check valve) should be installed after the expansion tank between the expansion tank and manifold.

I think this is causing the pressure in the system to slowly drop to almost nothing on the primary loop/combi side over 1-2 hours if all the actuators are left closed.

Once the pressure has dropped like this, If I manually open any actuator on the manifold the pressure immediately jumps back to where it was before the drop. 

If you can’t follow what I mean by the circulation pump (with check valve inside) placement. I’ll draw a picture. I’m just leaving for a few days at the moment.

I was thinking if I remove the check valve from the circulation pump it would solve the problem? If not I’d have to move the circulation pump to be between the expansion tank and manifold.

Jamie Hall

The expansion tank should be located on the INLET pipe to the circulator. Whether that will solve your problem or not I can't say. The check valve, however, is NOT the problem. Leave it.

hot_rod

Got a pic of the piping? If you have actuators on the manifold a check would not be as crucial. The actuators are 100% shut off.

There may be a simple way to get the expansion tank upstream of the circ. Pumping at the tank can drop pressure on the return side. If the gauge drops when the pump starts then comes back up when it is off, that is a good indication.`

In some cases based on piping, pump, etc you can drop to sub atmospheric, 0 gauge pressure, when pumping at and expansion tank. That can cause air issues, noise, air lock, inadequate heat transfer...

cloudd

Thanks hot_rod,

It took a long time to respond as I did not want to waste everyone's time since it was not cold outside and the system was not operational 24/7. I also had deal with some medical issues that caused me to drop everything for a few months.


I took the check valve out of the circulation pump and even though the circulation pump is installed on the wrong side of the expansion tank the problem was fixed immediately.