I am new to UFH and ASHP and have been adjusting with the flow settings to maintain consistent room temperatures. I do have the companies design for the system, but it’s not clear what pump setting I should use. Currently on 2 and Constant Pressure. The pump is a Grundfos UPM3 auto. There is also a 50 litre buffer tank. The head is approx 1m. Unfortunately I am unable to translate the Grundfos UPM3 flow tables to what setting I should be using. I can see on the drawing that 1.1m cubed per hr is the designed flow rate.
I appreciate that the UFH design is just a guide to setting the system up.
Each UFH zone should have a design flow rate which can be set by adjusting the flow setters on the manifold and would recommend you initially balance the system to match these figures and can then be readjusted to fine tune, especially if running open circuit without stats/zone actuators.
Set the pump on the lowest setting to achieve the design/desired flow when all zones are open - static head/hight difference dose not matter on a closed circuit, the pump only needs to overcome the frictional pressure drop of the pipes etc of the index circuit (the circuit with the most resistance) at total system flow rate.
Ideally if you have (need) a buffer you would try to match the flow rates across the primary and secondary circuits, but can be tricky and inconsistent, especially with stat zoned secondary. A better solution is to consider if you really need a buffer - which can make the system less efficient, over complicate things and cost more to install/maintain.
In many cases you won’t need a buffer and secondary pumps etc - they are generally only required if the primary pump is insufficient, or using third party stats/zone control on most of the circuits, which could limit flow/available system volume. The simplest and most efficient solution is to just supply the UFH directly with the heat pump primary pump and use weather compensation - maybe ask your installer why they fitted a buffer and get them back to balance the UHF!
Tony. Thank you. So I will set the pump speed to min and adjust the flow adjusters to achieve the desired flow rates. If this is not possible then the pump speed will need to be increased to the next setting. This now seems logical.
As for the need for buffers and secondary pumps, it’s a bit beyond me at the moment as I am still learning about UFH and ASHP.
