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.
Hmm, there’s not much more to say about the old pump that is inside the indoor unit. No matter what settings I adjust, the flow rate only shows the above-mentioned liter values. What surprises me is that the pump seems to run at only around 60% of its capacity. In hot water mode, it circulates about 1100 liters (290 gallons) through the system.
D
Daniel-Sp25 Dec 2021 11:17Merry Christmas to everyone.
Can you tell if the heat pump control actually demands the full capacity from the circulation pump?
Does the heat pump heat directly into the heating circuit and is switched to domestic hot water using a three-way valve?
What kind of heat pump do you have, does it modulate its output?
Can you tell if the heat pump control actually demands the full capacity from the circulation pump?
Does the heat pump heat directly into the heating circuit and is switched to domestic hot water using a three-way valve?
What kind of heat pump do you have, does it modulate its output?
Air-to-water heat pump Vaillant Arotherm-Split with indoor unit, 3.5 kW heating capacity. The system runs directly into the underfloor heating but has the mentioned overflow valve installed and an 18-liter (4.8 gallons) series buffer tank. Connected is the heating circuit distributor (14 heating circuits) with 28 mm (1.1 inches) copper pipes, pipe spacing everywhere VA 10. ERR except function or disconnected.
D
Daniel-Sp25 Dec 2021 14:51Modulating?
What pipe size do the heating coils have?
What pipe size do the heating coils have?
Yes, the air-to-water heat pump modulates, and the heating circuits have been installed with 16mm (5/8 inch) PEX pipes.
The calculated heat load is 3.2 kW at -12°C (10°F), designed for underfloor heating with a supply temperature of 30°C (86°F) and a return temperature of 25°C (77°F). Of the 3.2 kW, approximately 750 watts account for ventilation losses, and the controlled ventilation system has not been considered in this 750 watts. Therefore, the actual heat load should be only 2.8 kW if the controlled ventilation system’s heat recovery with an efficiency of 50% is taken into account.
The calculated heat load is 3.2 kW at -12°C (10°F), designed for underfloor heating with a supply temperature of 30°C (86°F) and a return temperature of 25°C (77°F). Of the 3.2 kW, approximately 750 watts account for ventilation losses, and the controlled ventilation system has not been considered in this 750 watts. Therefore, the actual heat load should be only 2.8 kW if the controlled ventilation system’s heat recovery with an efficiency of 50% is taken into account.
D
Daniel-Sp25 Dec 2021 16:24At what "percentage" output is the circulation pump (HUP) controlled by the heat pump?
Can you manually set it to 100%?
My heat pump also adjusts the circulation pump’s output to achieve the optimal temperature difference for best efficiency at the current heating load. Usually, it requires only 600 liters per hour (about 260 gallons per hour), and at the beginning of a heating cycle, when the load is higher, it increases to around 900–1000 liters per hour (about 400–440 gallons per hour).
At 100% circulation pump output, I would expect around 1800 liters per hour (about 790 gallons per hour). I calculated 1200 liters per hour (about 530 gallons per hour) based on the manufacturer’s specifications, using a 17 mm (0.67 inch) pipe.
I’m not familiar with the Vaillant control system, but I imagine that here, too, the circulation pump’s output is adjusted according to the current heating load.
Can you manually set it to 100%?
My heat pump also adjusts the circulation pump’s output to achieve the optimal temperature difference for best efficiency at the current heating load. Usually, it requires only 600 liters per hour (about 260 gallons per hour), and at the beginning of a heating cycle, when the load is higher, it increases to around 900–1000 liters per hour (about 400–440 gallons per hour).
At 100% circulation pump output, I would expect around 1800 liters per hour (about 790 gallons per hour). I calculated 1200 liters per hour (about 530 gallons per hour) based on the manufacturer’s specifications, using a 17 mm (0.67 inch) pipe.
I’m not familiar with the Vaillant control system, but I imagine that here, too, the circulation pump’s output is adjusted according to the current heating load.
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