Filling and water quality
Fill the UNI 60 with water below 2 ppm hardness, vent the system, and pressure-test to no more than 50 psi. Scale damage is not covered by warranty.
Fill the boiler with clean, transparent water of no more than 2 ppm hardness — scale damage is explicitly excluded from the warranty. This is the cheapest step in the whole installation to get right and one of the most expensive to get wrong.
Never fire a dry or frozen boiler
Do not start the boiler in the absence of water, or if the water in it is frozen. Do not operate the boiler without water or only partially filled.
Water quality
When filling the heating system with water, check that it is clean and transparent, without impurities or aggressive substances, with hardness of not more than 2 ppm.
Hard water causes scale on the heat transfer surfaces, which:
- reduces heat exchange and therefore efficiency;
- can cause premature failure of the boiler.
1 mm of scale deposit reduces heat transfer from the metal to the water by 10 %.
If the water hardness does not meet the required parameters, the water should be treated before filling.
Not covered by warranty
Damage to the boiler due to the formation of scale is not covered by warranty.
Filling procedure
Check ambient temperature
Do not leave the boiler with water in it at an ambient temperature below +41 °F / +5 °C. If the room can freeze, do not fill until that is resolved.
Test and treat the fill water
Measure hardness. Treat if it is above 2 ppm.
Fill slowly from the lowest point
Filling from the bottom pushes air up and out rather than trapping it in the emitters.
Fill to working pressure
Fill at a pressure not exceeding the maximum working boiler pressure. Normal operating pressure must not exceed 15 psi.
Vent every high point
Work through the automatic and manual vents, the emitters and the boiler itself.
Pressure-test
Maximum test pressure is 50 psi. Hold and inspect every joint, then release to working pressure.
Check the relief valve discharge
Confirm the discharge is piped to a safe location and is not obstructed or valved.
Air in the first weeks
Air must be removed during the first weeks of operation. Dissolved air comes out of solution as the system heats for the first time, and it collects at the high points.
Throughout the heating season, monitor the pressure in the system — a falling pressure means a leak or a failing expansion tank; a rising pressure with heat means the expansion tank is undersized, waterlogged, or the fill valve is passing.
Quick reference
| Parameter | Value |
|---|---|
| Maximum water hardness | 2 ppm |
| Effect of 1 mm scale | −10 % heat transfer |
| Maximum operating pressure | 15 psi |
| Never exceed | 36 psi |
| Maximum test pressure | 50 psi |
| Maximum water temperature | 185 °F / 85 °C |
| Minimum ambient temperature, filled | +41 °F / +5 °C |
Power, grounding, the boiler sensor, the STB safety chain and the exhaust probe.
Frequently asked questions
Hydronic piping
Pipe the UNI 60 — 2 in supply and return, mandatory safety relief valve, expansion tank, drain and return-temperature protection to stop condensation corrosion.
Electrical and sensors
Wire the TIS Tronic 260U — 230 V supply, grounding, boiler sensor in the immersion well, STB safety thermostat on I1, and the optional PT1000 exhaust probe.