WaterBoost Package Heating Systems
WaterBoost Mikrofill 3 Pro + 2 × HWB-INT-300LV Pressurisation Kit
- Established 1975
- Trusted by thousands of customers
Mikrofill 3 PRO pressurisation unit + 2 × GWS HeatWave HWB-INT-300LV expansion vessels + 1¼” service valve, for heat pump systems up to 11,590 litres.
A complete set for keeping a large sealed heating system at pressure. The Mikrofill 3 PRO is a pumpless, direct-type unit. It connects straight to the mains, fills the system from empty and tops it up automatically, with WRAS-approved Category 4 backflow protection built in. Two HeatWave HWB-INT-300LV vessels share the expansion as the water heats, and the lockable service valve lets them be isolated and drained for checks.
Wall-mounted unit, colour display, leak detection, MODBUS RTU and 4 BMS outputs. Two floor-standing vessels on legs, 10 bar rated, each with an exchangeable membrane. For closed-loop heating and chilled water systems. 2-year warranty on the Mikrofill unit.
More about this product
What’s in the kit
The WaterBoost Mikrofill 3 Pro + 2 × HWB-INT-300LV Pressurisation Kit brings together four components, matched to heat pump systems up to 11,590 litres:
Why the Mikrofill 3 PRO
How it’s installed
The two vessels stand side by side on their legs, teed together, and connect to the heating return through the service valve, which is locked open in use. The unit’s system hose connects into the return near the vessels, and its inlet hose takes the mains or boosted cold supply. Mikrofill’s schematic shows a pressure reducing valve on the incoming supply.
The unit’s 22 mm tundish drain goes to a visible discharge point. The safety valve stays on the heat source. Power is 230 V from a 3 A fused spur. Leave 100 mm clear to the left and top, 170 mm to the right, and 750 mm in front of the unit.
Specifications
| Kit | |
| Application | Sealed heating and chilled water systems (closed loop) |
| System volume — heat pump | Up to 11,590 L (60 °C flow) |
| System volume — boiler | Up to 6,470 L (82 °C flow) |
| Total vessel volume | 600 L (2 × 300 L) |
| Sizing basis | 3 bar safety valve, 1.5 bar vessel pre-charge |
| Max working pressure | 9 bar (set by the unit) |
| Max system water temperature | 85 °C (set by the unit) |
| Service valve | 1¼”, lockable, with drain |
| Mikrofill 3 PRO (72846) | |
| Type | Pumpless, direct type |
| Max inlet pressure | 9 bar |
| Max cold fill pressure | 8.7 bar |
| Max operating pressure | 9 bar |
| Max flow rate | 12 l/min |
| Low inlet pressure cut-out | 0.3 bar |
| Backflow protection | WRAS Category 4 (2307805), Kiwa Regulation 4 |
| Display | 3.95″ backlit colour LCD |
| Pressure setting resolution | ±0.1 bar |
| Communication | MODBUS RTU, 4 BMS outputs (5 A max) |
| Connections | Inlet 15 mm compression; system 15 mm compression; drain 22 mm compression |
| Supplied with | 2 × braided hoses with integrated isolation valves; backplate (fixings not included) |
| Electrical | 230 V / 1 ph / 50 Hz, 3 A fuse |
| IP rating | IP55 |
| Ambient / inlet / system water temperature | 5–45 °C / 5–23 °C / 5–85 °C |
| Max relative humidity | 70% non-condensing |
| Dimensions (W × D × H) | 250 × 155 × 290 mm (386 mm to bottom of tundish) |
| Weight | 5.3 kg (without hoses) |
| Warranty | 2 years |
| GWS HeatWave HWB-INT-300LV (× 2) | |
| Quantity | 2 |
| Nominal volume | 300 L each |
| Type | Vertical on legs, exchangeable membrane |
| Connection | 1¼” BSPT |
| Max operating pressure | 10 bar |
| Operating temperature | −10 to 99 °C |
| Factory pre-charge | 1.5 bar |
| Membrane | Exchangeable, high-grade butyl |
| Dimensions (H × Ø) | 1,238 × 680 mm each |
| Weight | 44.5 kg each |
FAQs
How do I know 11,590 litres covers my system?
Add up the water in the heat source, buffer tanks, cylinder coils, emitters and pipework. The 11,590 L figure is based on 60 °C flow, a 3 bar safety valve and the vessels’ 1.5 bar pre-charge. This is the largest kit in the range. For bigger systems, get in touch.
Why two vessels instead of one large one?
The largest single HeatWave vessel is 500 L, so two 300 L vessels give more expansion capacity than any one vessel in the range. At 1,238 mm tall and 44.5 kg each, they are also easier to move into a plant room than one very large vessel.
Can I use it on a boiler system?
Yes, up to 6,470 L at 82 °C flow. A boiler runs hotter, so the water expands more and the same vessels cover less.
What does the exchangeable membrane mean?
The membrane inside each vessel can be replaced if it ever fails, so the steel vessel stays in place rather than being scrapped.
What fill pressure can it reach?
Up to 8.7 bar, but never more than your incoming supply. The 3 PRO has no pump, so it uses the pressure already in the mains or boosted supply, and it cuts out if the inlet drops below 0.3 bar. In practice the fill pressure is set well below the heat source’s safety valve.
What’s the service valve for?
It isolates the vessels from the system and drains their water side, so the pre-charge can be checked or a vessel swapped without draining the system. It must be locked open in normal use.
Can I use glycol?
Yes, propylene glycol up to a 50% mix. Don’t use ethylene glycol.
Can this go on a hot water cylinder or a potable system?
No. HeatWave vessels are for closed-loop systems only. For potable hot water, use a GWS ThermoWave vessel.
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Mikrofill 3 Pro PDFDownload
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Data Sheet PDFDownload
Standard delivery:
Standard delivery is free on most orders. Some items may incur a delivery charge depending on weight, size or value. Any applicable charge will be displayed at checkout.
Deliveries will typically be made between 7am and 6pm, Monday to Friday (excluding public holidays).
Next day delivery:
Next working day delivery is available for a £16.50 + VAT delivery charge.
Orders must be placed before 12 noon to qualify for next working day delivery. Orders placed after 12 noon on Thursday but before noon on Friday will be delivered the following Monday. Orders placed after 12 noon on Friday will be delivered on Tuesday.
Pallet/Large/Difficult items:
Some large, heavy or difficult to transport items may incur an additional delivery charge. Please contact us for a delivery quote before ordering.
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