Caleffi 527 EST safety relief valve

How to read the code

The fourth digit gives the size: 4 = 1/2" × 3/4", 5 = 3/4" × 1", 6 = 1" × 1 1/4", 7 = 1 1/4" × 1 1/2". The last two digits are the set pressure: 22 = 2.25 bar, 25 = 2.5 bar, 27 = 2.7 bar, 30 = 3 bar and so on up to 60 = 6 bar; 54 means 5.4 bar. Example: 527530 EST is 3/4" × 1" at 3 bar.

How to choose

• Choose a set pressure that does not exceed the permitted working pressure of the most pressure-sensitive component in the system (boiler, expansion vessel, radiators).
• The valve opens fully at 10% above the set value and recloses when pressure falls 20% below it; keep normal operating pressure below this closing band.
• Choose the inlet size to match the safety outlet of the boiler or equipment; the outlet is always one size larger, and the discharge pipe should continue at that size.

How to write it in a quote

Write size and set pressure together: "Caleffi 527430 EST safety relief valve 1/2" × 3/4", 3 bar, PN 10". Do not drop the "EST" suffix from the code; a missing size or pressure can lead to the wrong product being supplied.