controller vs pressure switch
If the only issue is starting and stopping the pump, a mechanical pressure switch does that job for less money.
Comparison table
| Subject | Mechanical pressure switch | HYDROSET PM821 controller |
|---|---|---|
| Pressure setting | By spring, approximate | Numeric, F1 and F2 on the display |
| Pump start | Abrupt | Soft, over the F11 time |
| Pump stop | Abrupt | Soft, over the F12 time |
| Dry running | Not detected | Detected by current (F4) or pressure (F10) |
| Over current | No protection | Stops above the F3 current |
| Over temperature | No protection | Stops, then returns automatically |
| Status display | None | Four-digit display with fault codes |
| Retry | None | Automatic, every F6 minutes |
Which one to choose?
If the only issue is starting and stopping the pump, a mechanical pressure switch does that job for less money. If pressure swings, water hammer in the pipework, or a pump burning out from dry running are also in play, HYDROSET PM821 covers all three, because it reads the pump current and the unit temperature as well as the pressure.
Model selection guide
| Pump current | Pump power | Model | Typical use |
|---|---|---|---|
| up to 8 A | up to 1.5 kW | PM821-8 | 1–4 floors, homes and shops |
| 8 – 16 A | up to 3 kW | PM821-16 | 5–10 floors, booster sets |
| up to 25 A | up to 4 hp | PM821-25 | Residential, commercial and agricultural |
The current on the pump nameplate decides the model, nothing else.
Frequently asked questions
Which one to choose?
If the only issue is starting and stopping the pump, a mechanical pressure switch does that job for less money. If pressure swings, water hammer in the pipework, or a pump burning out from dry running are also in play, HYDROSET PM821 covers all three, because it reads the pump current and the unit temperature as well as the pressure.
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