ᐅ Subsidy Amount for Circulation Pump and Overflow Valve

I am currently planning to remove the bypass valve from my heat pump system with underfloor heating, but a friend of mine who works as a heating engineer has made me uncertain. He said that this would be nonsense and that I should keep both the bypass valve and the ERR valve installed.

Here are the details of the system:

Maximum nominal flow rate of the heat pump:
at 5K = 540 l/h (1.4 gal/h)

Underfloor heating hydraulics calculated at ~ 850 l/h (2.2 gal/h) with a pressure loss of 100 mbar (1.45 psi)

Maximum bypass valve opening pressure ~ 300 mbar (4.35 psi)

Lowest pump head of the heating pump is 400 mbar (5.8 psi) at ~ 1000 l/h (2.6 gal/h); only from around 1000 l/h does the pump head drop to about 380 mbar (5.5 psi).

If I open all heating circuits fully without throttling anything, I can achieve a maximum of 700 liters per hour in the heating circuit. If I then throttle at least some of the shorter heating circuits, the pump flow stabilizes around 610 l/h (1.6 gal/h).

Therefore, I believe the minimum pump head of the heat pump is high enough that despite the pressure loss in the heating circuit, the bypass valve always opens. As a result, I never reach the maximum possible flow rate in the heating circuit or the manifold.

The pump can deliver up to nearly 1000 l/h:
400 mbar (5.8 psi) pump head minus 100 mbar (1.45 psi) pressure loss for the worst heating circuit leaves 300 mbar (4.35 psi) up to 1000 l/h. However, the bypass valve opens at 300 mbar.

According to my friend, this theory is nonsense and unnecessary. He says my system is already running so optimally that trying to tweak the smallest adjustments now would be “over-optimizing” the system to death.

Am I on the wrong track, or is there some truth to my reasoning? Or has my friend rightly made me uncertain? Otherwise, I was planning to disable the bypass valve during the holiday break.

Usually, the bypass valve can be adjusted, including being fully closed. If the heat pump then gets enough flow during defrosting (minimum amount specified in the manual), you can remove it. Of course, the prerequisite is that the ERR do not start shutting off entire rooms, so remove those first. That is always possible.

The ERR is not working. I don't think I can fully close the pressure relief valve; I believe it always opens as soon as the maximum pressure of 300 mbar (4.35 psi) is exceeded.

This is a Watts pressure relief valve 16L

What exactly is the question?

I find it surprising that anyone still wants to install a differential pressure valve (DPV) nowadays.

An electronically controlled circulator pump (UWP) with pressure difference regulation takes care of this function on its own. And if too many radiators are turned off, the pump simply reduces its output by itself. These pumps now cost less than €200 (Wilo or Danfoss).

Or what is this actually about?

The head pressure has no influence here. The pump is only supposed to circulate the water, not generate any significant head pressure.

The issue is that the pump does not circulate enough water. (The house is still warm.) Approximately 850 liters per hour (about 225 gallons per hour) are supposed to flow continuously when hydraulically balanced, but a maximum of only 700 liters per hour (about 185 gallons per hour) flows through when unbalanced.

Therefore, I thought the often-criticized balancing valve might be to blame—unless the calculation is incorrect.

Oh, I thought you were worried that too much flow would pass by the heating circuit through the balancing valve. The balancing valve can’t be responsible for a too low total flow; that’s not what it’s for.

@Deliverer There are also balancing valves that can only be set for maximum response pressure. Unfortunately, I have one like that too.