Question: What are the steps for setting up the different inputs in multi-pump function control on a Grundfos CRE-DP?
Answer: For the different inputs in multi-pump function, the pump should be installed as shown below:
For “Alternating” and “Backup” then the installer has to be aware that on site two pot.-free-contacts for start/stop and two analog-outputs 0-10V is needed for correct control.
In the cascade function, the two output relays shows the two pumps configuration identically on both relays. So if a error will appear on the master pump, then the error will also be shown on the slaves output relay, even if the pump is “ready”.
*There is different settings for the analog input: The temperature sensor, which is used for the heat energy meter: There should only be fitted one sensor to the master pump. (And the heat energy meter should be activated on this pump)
-The heat energy meter will always use the total flow in the twin pump as a reference for the accumuluted heat energy, which the system of the two pumps is using.
So only connect one sensor to the master and activate the heat energy meter on this one, then the master heat energy meter will represent the heat energy for the twin pump. If the however is connected a sensor input to both the master and the slave pump, then be aware that there will be a difference between the accumulated heat energy date, described below:
The difference between the heat energy shown on the master and the slave pump is simply that the must is using the average temperature between the two pumps, and the slave is only using its own measured temperature. So it will be most correct to use the heat energy meter data from the master pump. Setpoint influence from a external signal: Can be connected to the master only.
Additional operating modes for multi-pump setup.
The multi-pump function enables the control of single-head pumps connected in parallel and twin-head pumps without the use of external controllers. The pumps in a multi-pump system communicate with each other via the wireless GENIair connection.
A multi-pump system is set up via a selected pump, i.e. the master pump (first selected pump). All Grundfos pumps with a wireless GENIair connection can be connected to the multi-pump system. The multi-pump functions are described in the following sections.
Alternating Operation – Only one pump is operating at a time. The change from one pump to the other depends on time or energy. If a pump fails, the other pump will take over automatically
Back-up Operation – One pump is operating continuously. The back-up pump is operated at intervals to prevent seizing up. If the duty pump stops due to a fault, the back-up pump will start automatically.
Cascade Operation – Cascade operation ensures that the pump performance is automatically adapted to the consumption by switching pumps on or off. The system thus runs as energy-efficiently as possible with a constant pressure and a limited number of pumps.
The back-up of a twin-head pump will start at 90 % and stop at 30 % performance when operating in constant pressure mode. It can be advantageous to choose a twin-head pump, as the back-up pump will start for a short period in peak-load situations.
If an oversized single-head pump is chosen, it may run outside its best efficiency range most of the time.
All pumps in operation will run at equal speed. Pump changeover is automatic and depends on speed, operating hours and fault.
One pump is operating continuously. The back-up pump is operated at intervals to prevent seizing up. If the duty pump stops due to a fault, the back-up pump will start automatically.