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.
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.
If I had to check tomorrow, theoretically I can query various values (compressor modulation, electrical power consumption, cooling capacity—which should basically correspond to the current heating capacity) and combine or base them on each other to get a value.
In general, regarding the internal heating circulation pump (HCP), I can only adjust the residual head from a minimum of 250 mbar to a maximum of 900 mbar. According to Vaillant, 900 mbar corresponds to 100% pump output. But no matter what I set, whether 250 or 900 mbar, the HCP always shows a performance between 55-65%, which it supposedly operates at.
I just don’t know how to query or simulate 100% performance of the heat pump, except perhaps by increasing the heating curve from the current 0.20 up to the maximum of about 1.xx?
The internal HCP is probably a Grundfos UPM3 OEM version, which is available in many different models. In my system, it should be one with PWM, which automatically adjusts flow rate and changing pressure conditions based on the operation of the modulating valves (ERR). But since I no longer have active ERR, nothing changes because there are no actuators opening or closing.
In general, regarding the internal heating circulation pump (HCP), I can only adjust the residual head from a minimum of 250 mbar to a maximum of 900 mbar. According to Vaillant, 900 mbar corresponds to 100% pump output. But no matter what I set, whether 250 or 900 mbar, the HCP always shows a performance between 55-65%, which it supposedly operates at.
I just don’t know how to query or simulate 100% performance of the heat pump, except perhaps by increasing the heating curve from the current 0.20 up to the maximum of about 1.xx?
The internal HCP is probably a Grundfos UPM3 OEM version, which is available in many different models. In my system, it should be one with PWM, which automatically adjusts flow rate and changing pressure conditions based on the operation of the modulating valves (ERR). But since I no longer have active ERR, nothing changes because there are no actuators opening or closing.
Damn, time window for editing closed:
Snapshot:
Outdoor temperature -1°C (30°F)
Air intake outdoor unit -3.7°C (26.7°F)
Supply temperature 27.4°C (81.3°F)
Return temperature 24.2°C (75.6°F)
Temperature difference 3.2 K (3.2 K)
Flow rate building circuit 610 l/h (2.7 gpm)
Heat pump performance 56%
Electrical power consumption 0.4 kW
Cooling capacity 1.5 kW
Therefore: 610 l/h (2.7 gpm) x 3.2 K x 1.16 = 2264 watts
Snapshot:
Outdoor temperature -1°C (30°F)
Air intake outdoor unit -3.7°C (26.7°F)
Supply temperature 27.4°C (81.3°F)
Return temperature 24.2°C (75.6°F)
Temperature difference 3.2 K (3.2 K)
Flow rate building circuit 610 l/h (2.7 gpm)
Heat pump performance 56%
Electrical power consumption 0.4 kW
Cooling capacity 1.5 kW
Therefore: 610 l/h (2.7 gpm) x 3.2 K x 1.16 = 2264 watts
D
Daniel-Sp25 Dec 2021 22:28Well, the current heating capacity and volume flow result in a temperature difference of 3.2K. The house is warm, and the heat pump is operating without any faults, so everything is fine. Why do you want more volume flow in the heating circuit? That only reduces the temperature difference, increases pump electricity consumption, and doesn’t improve anything.
There should be an option somewhere in the menu to run the heat pump at 100%, otherwise, how would you perform the hydraulic balancing?
There should be an option somewhere in the menu to run the heat pump at 100%, otherwise, how would you perform the hydraulic balancing?
Then I must have misunderstood. I thought the system always had to operate at the design flow rate of approximately 850 liters per hour (3.7 gallons per hour) in the heating circuit and only adjusted the temperature difference depending on the outside temperature. Learned something new again.
Similar topics