Alde Compact 4000 D / 4000 D Plus

The technician may have left the circulation pump in continuous mode, which is meant for testing and stops the hot water cylinder getting enough heat. Resetting the Alde control panel to its factory defaults is usually the simplest fix - see your heater's operating instructions.

The circulation pump may still be on speed 5, which technicians use to push air out of the system. Turn it back down to speed 2-3 for a touring caravan or a B- or C-class motorhome, or to just below speed 4 for an A-class. If the heating fluid was replaced, there may also be air trapped in the system - see your heater's operating instructions.

Yes - use it exactly as you normally would. The hot water cylinder has no heating elements that could burn out, so it does no harm.

In the UK, the products meeting Alde Approval 40X0 2024 are: Comma Xstream G40; Fuchs Fricofin DP; Volkswagen Group G12evo; and Alde's own Protective Premium in G12++ and G12evo versions. (Alde stopped selling its G13 products at the end of 2023.) All come ready-mixed with deionised water, are magenta, can be mixed with each other, and give frost protection down to -37°C plus 5 years' corrosion protection - but always check the label. North America has its own, chemically different, approved list.

Ideally the same antifreeze that's already in it. Magenta fluid almost certainly means an Alde-approved antifreeze, so top up with any approved product - they can all be mixed. If the fluid isn't magenta, the safest option is to add just one or two cups of deionised water - you lose a little frost, corrosion and bacteria protection, but mixing incompatible antifreezes risks worse damage.

Then have the fluid replaced with an Alde-approved antifreeze as soon as you reasonably can.

Turn on all the electric and gas/diesel heating you have available - this actually uses less energy overall. Set the thermostat to a comfortable temperature rather than turning it right up when you feel cold, or you'll overshoot and end up opening windows; a jumper and a setting a couple of degrees lower saves more. If you don't need hot water overnight, tell the system not to heat it then.

Each season, bleed any air out of the heating fluid, and keep the vents at the top and bottom of cupboards and lockers clear.

On 12V DC, how much it takes from the leisure battery varies a lot. It peaks at ignition - about 2 A for gas heating, about 20 A for diesel. For off-grid planning, allow roughly 1 A while gas heating is running and about 4 A for diesel; switched off, the standby drain is around 80 mA. On mains: UK mains is nominally 230V but usually nearer 240V in practice, so expect roughly 4.8 A at 1 kW, 9.5 A at 2 kW and 14.3 A at 3 kW.

That depends on how the vehicle is built and insulated, how cold it is outside, and how much power you can give the heater - more power means more heat. Most manufacturers now aim for around an hour from cold to a comfortable temperature.

You can heat the vehicle through the winter, though if nobody's staying in it you may decide it isn't worth the running cost. On mains hook-up at home, for example, you could set 10°C with 2 kW of electric heating. Check inside regularly for condensation and signs of rodents, and bear in mind some lockers and compartments probably won't be protected from frost.

The heating fluid needs replacing once its corrosion protection runs out - Alde-approved antifreezes (magenta) last 5 years. Bleeding air from the fluid now and then improves efficiency. Each season, check the boiler flue: the hose should be secure and undamaged, and the outlet free of blockages. After 10 or more days staying in the vehicle, top up the boiler's air cushion.

Before any frost, drain the fresh water - and while you do, make sure the red breather valve hasn't scaled up. See your heater's operating instructions for details. An annual service may be a legal requirement, particularly if the vehicle serves as an annex to a house, is hired out, or is somewhere people work.

Set the room temperature on the control panel to around 15°C. In summer that's low enough that the central heating will rarely circulate, day or night, while hot water is not affected.

That's down to whoever installed it - ideally an Alde-approved antifreeze, which is magenta. Alde advises against any antifreeze it hasn't approved.

With the system cold, about 1 cm higher than the Min mark. As the fluid heats up it expands towards the Max mark.

Roughly 10-15 litres in a touring caravan or a B- or C-class motorhome, and 20-25 litres in an A-class motorhome or a boat.

After 10 days' use, the Alde system prompts you to top up the air cushion in the hot water cylinder, which keeps it running smoothly. If there's been water in the system: turn off the water pump, open all the taps and the shower fully, open the safety drain valve for 5-10 seconds and then close it, and refill the water system as usual. If the system has been dry, you can ignore the reminder.

By law, stored hot water has to be kept hot enough to scald, to stop legionella - a potentially deadly bacteria - from growing. The Alde TMV3, an aftermarket accessory, limits the temperature of the water reaching your taps and shower.

Expect roughly a 4-5 minute shower every half-hour. The aftermarket Alde TMV3 can cut down on hot water wasted in the shower, and the Alde Flow gives continuous hot water - it can be retrofitted to any Alde-equipped vehicle from the 2018 model year on, and in the UK is sold only through Moosewerks.

Only water that's pleasant to drink. Some sites in Spain, Portugal and North Africa supply water heavy in bleach or salt, which corrodes stainless steel. Even if a tap is labelled as drinking water, don't put it through the Alde system if you couldn't bear to drink it - unless your vehicle has a reverse-osmosis water filter of at least 4 stages.

Anything the label says is safe for a stainless steel water cylinder. Clean Tabs make a range of suitable products that are easy to find.

Yes. A vehicle can be designed to winterise itself, but very few on sale are.

Yes, and Alde recommends it. You can also set the system to favour one source over the other - for example, whichever is cheaper.

As a rough guide, a 6 kg propane cylinder should last a weekend of gas heating - though in freezing weather it will go considerably faster.

Propane. Butane isn't suitable below 13°C (BS 5482 Part 1).

Yes.

Alde advises against it. A crash sensor on the bulkhead regulator doesn't change the main risk: drive onto a fuel forecourt with the gas heater running and fumes could be pulled straight into its combustion chamber - effectively the same as carrying a lit camping stove across the forecourt. You'd need to pull over and switch gas heating off before every fuel stop, and forgetting just once could be disastrous.

No need to worry - it does no harm in the short term, though B10 or stronger biodiesel shortens the burner's life if used long-term. Carry on using the diesel heating normally until you can top up with at least half a tank of a compatible fuel, and try not to repeat it.

Alde's diesel models - the Compact 4000 D and the 4000 D Plus - run on B7 diesel (EN 590) and XTL diesel (EN 15940). If you use agricultural or marine diesel, HVO meeting EN 15940 is also compatible.

Alde doesn't recommend it. It's technically possible, but if you forget to switch the diesel heating off before stopping to refuel it won't go down well with staff or other customers - and fumes could be drawn straight into the combustion chamber. An Alde engine heat exchanger is the better option for heat on the move.

It depends on how much the boiler compartment and diesel tank need reworking. The Compact 4000 D isn't a straight swap for a Compact 3030, for instance, and not every diesel tank has an accessible sender or a spare fuel pick-up. The cost may well rule it out - Alde puts such a job at probably over £5,000.

Yes - both the Compact 4000 D and the 4000 D Plus run on diesel. The Compact 3030 and 3030 Plus can't heat on diesel themselves, but an Alde-equipped motorhome can have the engine heat exchanger fitted to use the engine's waste heat.

No. Even caravans and motorhomes built to the top BS EN 1645 grade aren't insulated like a house, so underfloor heating would have to run too hot to walk on to warm the whole vehicle by itself.

No - it's an open-vented system, which keeps the weight down and reduces the draw on the leisure battery.

No. The controls run on 12V DC, but the electric heating elements need 230V AC mains. Away from hook-up, you'll need to heat with gas or diesel. Run from a leisure battery, the electric heating would produce only around 9 W - roughly a tenth of the heat your own body gives off.

When filled, it's about 10 kg heavier than a combi heater. Separate space and water heaters are generally less powerful these days, so they aren't a like-for-like comparison.

No. Alde Compact boilers have aluminium surfaces inside the glycol cylinder, and any copper particles circulating into it would set up galvanic corrosion.