Sun: two hundred and ten watts per square metre
A dark water surface absorbs nearly all the solar radiation landing on it. For a 400-litre tub with 0.88 square metres of surface, full midday sun adds about 185 watts on top of a base load of 516 — a 36 per cent increase that runs for four or five hours of every clear day. On a 700-litre tub the figure rises to around 270 watts. That is why we ask for a photograph of your garden at two in the afternoon rather than the flattering one taken at breakfast.
There are two legitimate answers and we will quote either. A canvas canopy removes almost all of it and costs about Rp 6.5 million installed. Or let the 2 HP unit work longer: on a 400-litre tub it still holds 5 degrees under full sun, but daily consumption rises from 4.9 to 6.5 kWh, about Rp 66,000 a month, and the compressor accumulates far more running hours. What you cannot do is step up cheaply: after 2 HP the next size is 4 HP and another Rp 43 million, six times the price of the canopy.
Rain: the problem is chemistry, not volume
An open 0.88 square metre tub collects about 26 litres of rain during a wet month in Bogor at 300 millimetres of rainfall. The volume is irrelevant because the overflow deals with it. What matters is that rainwater arrives at pH 5.2 to 5.8 carrying nothing at all, so it dilutes residual ozone and pulls the pH down. On tubs in daily use we have watched pH drop from 7.4 to 6.6 over a fortnight of continuous rain. A lid that actually gets used outside bathing hours solves ninety per cent of this, which is why ours is split and light enough to lift with one hand.
Base load, 400 L covered, Jakarta516 W
Full midday sun, 400 Ladds about 185 W
Holding load in full sun, lid on700 W
Chiller, shaded or not2 HP
Rain collected, 300 mm monthabout 26 litres
pH drift without a lid, two wet weeks7.4 down to 6.6
Outdoor lid60 mm foam, UV-stable skin
The condenser in an open garden
A chiller standing outside faces two enemies: dry leaves drawn into the fins, and driving rain soaking the electrical enclosure. We use blue epoxy-coated fins, the same coating specified for coastal air-conditioning, with 316 fixings and frame, an IP65 enclosure with a rain hood, and a dedicated 30 milliamp earth-leakage breaker on the chiller circuit. The unit stands on a 250-millimetre plinth so a heavy downpour cannot pond around its base, and it faces at least 60 centimetres of clear air. Full comparison of the two chiller lines is on ice bath chillers.
| Garden condition | Chiller for 400 L | Shade | Condenser fin wash |
|---|
| Tree shade all afternoon | 2 HP, 516 W load | not needed | every 3 months, heavy leaf fall |
| Morning sun only | 2 HP, 516 W load | optional | every 6 months |
| Full sun 10:00-15:00 | 2 HP, 700 W load | strongly advised | every 6 months |
| Coastal, salt wind | 2 HP, coated fins | helps | every 3 months |
Leaves, insects and the wet patch underneath
- A 2-millimetre trap basket sits ahead of the pump. Under a rain tree or a ketapang it needs emptying twice a week during leaf fall.
- Water pooling in a fold of the lid breeds mosquitoes within seven days. Our lid is domed by three degrees so it drains, and that is the only reason its profile is not flat.
- A tub standing on grass or soil always leaves a damp patch beneath it. We lay a concrete or paved base falling 1.5 per cent away from the tub rather than setting it straight onto the ground.
- Do not aim garden lighting down onto the water. Night insects gather there and end up in the filter cartridge; light the surround instead.
Wind: the load nobody budgets for
A steady three metres per second across an open water surface raises evaporation by about 40 per cent compared with still air. On an uncovered 400-litre tub that is roughly 75 extra watts, all day. Gardens beside rice fields, rooftops and beachfront sites live with this permanently. The answer is not a bigger chiller but a baffle at rim height on the windward side — a timber screen, dense planting, or a low wall — that breaks the flow right at the water surface. A 60-centimetre screen a metre away removes most of the effect for far less than the difference between two chiller sizes.
When an open-air tub is a bad ideaIf your garden takes full sun all day and there is nowhere to put shade, we will tell you plainly that holding 3 degrees there needs one chiller size more and about Rp 60,000 to 90,000 a month extra, permanently. If there is a mango or ketapang overhead, think again about the position: mango sap stains pale terrazzo and does not come out. A tub under a terrace roof is always cheaper to run, and that is an honest comparison even though we sell both.
Price and what is in the outdoor package
The range is Rp 47-86 million for a 300 to 700-litre body with the full outdoor specification: UV-stable lid, leaf trap, IP65 electrics, condenser plinth and adjustable feet. Canopy and timber decking are quoted separately. To estimate the chiller for your city and your particular garden, the chiller calculator has a direct-sun option; every shell material is compared on the pricing page, and what our crew does on installation day is set out under installation and cold test.
Does an outdoor tub need its water changed more often?
Yes, roughly a third more often. Dust, pollen and rain all accelerate it. With ozone and a cartridge, an outdoor tub runs three to five weeks against four to eight weeks indoors.
What happens in a storm power cut?
A covered 400-litre tub warms about 1.1 degrees an hour with the chiller off, so a six-hour outage leaves the water near 11 degrees and it recovers within three hours. What actually needs protecting is the voltage when the supply returns, so every outdoor chiller circuit gets a voltage protector.
Can the chiller live in a shed?
Only if the shed has at least half a square metre of inlet and the same again of outlet. Without that the condenser breathes its own hot air and loses up to 30 per cent of capacity. Hose run stays under six metres on standard insulated hose.
Is the lid strong enough to stand on?
It carries a momentary load of about 80 kilograms in the centre, which is enough for a child who climbs on by accident, but it is not a structural cover. Where small children play we fit a locking lid on an aluminium frame, add Rp 2.9 million.
Which shell survives outdoors best?
Terrazzo and granite, both without qualification. Teak works under shade with regular oiling, acrylic is a poor choice, and onyx must not go outside at all. Service lives for each material are compared on the pricing page.
