Descaling the boiler

Jul 18, 2017
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We had the water filter removed from our caravan in 2017. Would using a filter stop scale build up in the hot water boiler on an ALDE system as the it works in a jacket for the hot water heating? If scale has built up in the boiler, how would you know when the boiler would require descaling?
 
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We had the water filter removed from our caravan in 2017. Would using a filter stop scale build up in the hot water boiler on an ALDE system as the it works in a jacket for the hot water heating? If scale has built up in the boiler, how would you know when the boiler would require descaling?
I removed the filter from my caravan too and I don't think many new caravans have fit water filters fitted at all.
I believe the water filter was there to catch dirt and large particles along with bacteria from entering the water system. I don't think it reduces the amount of limescale build-up though. Check your electric kettle, if you use one and check the element. If it's furred up then there's a good chance the element in the boiler is too. I use Elsan Fresh Water Tank Cleaner a couple of times a year to treat the hot and cold water system. Elsan recommends you leave this product in the system for at least 24 hours before flushing.
I also found this from another caravan owner who contacted Truma directly and got this response so, I'm sure the same would apply to Alde boilers;

“For hygienic reasons, you should decalcify the water container occasionally. Use special decalcification products from camping specialists or conventional vinegar essence or citric acid, for example. Fill the decalcifying product in the recommended ratio into the appliance via the water system, allow it to work and then rinse the Combi heater thoroughly with fresh water.

Instructions for descaling the Truma water heater:
Dilute 2 litres of white wine vinegar into 10/12 litres of fresh water, and introduce it into your water system via your water inlet, (removing the filter if one is fitted for this process).
The recommended ratio if using citric acid is 1 tablespoon of citric acid to 1 litre of water”.

Open all the taps to pull through to the heater and then leave the solution in the heater for 4 to 5 hours and then flush through thoroughly with fresh water".



I hope this helps.
 
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I don't think the ALDE boiler has a "normal" element system. As er the ALDE owner's manual;

The boiler’s internal heat exchanger consists of three concentric cylinders; the combustion chamber, the central heating cylinder and the hot water cylinder.

The combustion chamber is made from aluminium, and is divided into two halves by a baffle plate, with the burner head located in the top half, and the flue gases venting through the bottom half.

The combustion assembly is fixed to the end of the internal heat exchanger. It consists of the burner, combustion fan, gas valve, air intake and exhaust ducts, and gas line.

Two electric heating elements are sealed inside the central heating cylinder, one for 1 kW, one for 2 kW. The room thermostat is integrated intothe touchscreen control panel and connected to the boiler by a Registered Jack (RJ) cable.
 
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I don't think the ALDE boiler has a "normal" element system. As er the ALDE owner's manual;

The boiler’s internal heat exchanger consists of three concentric cylinders; the combustion chamber, the central heating cylinder and the hot water cylinder.

The combustion chamber is made from aluminium, and is divided into two halves by a baffle plate, with the burner head located in the top half, and the flue gases venting through the bottom half.

The combustion assembly is fixed to the end of the internal heat exchanger. It consists of the burner, combustion fan, gas valve, air intake and exhaust ducts, and gas line.

Two electric heating elements are sealed inside the central heating cylinder, one for 1 kW, one for 2 kW. The room thermostat is integrated intothe touchscreen control panel and connected to the boiler by a Registered Jack (RJ) cable.
Descaling as Paullus describes would work just as well. I think I will find the Elsen stuff and do mine, as it is 10 years old.
 
Jun 6, 2006
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I found this on the Alde website. I must admit I had read about renewing the air cushion but forgot about it and haven't done it. On the other hand, I haven't experienced any problems as a result.

This would normally only come into play into play if the boiler has been filled and not drained for 3-4 weeks as in constant use, if it is drained each trip it should never be an issue
 
Jun 20, 2005
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If it’s working ok why fix it? It all depends where you have been using the system. Parts of Wales and Devon and indeed the Midlands are soft water. Where I am is the hardest water you could ever dream of!
The best and gentlest on the metal work is spirit white vinegar. You can use it undiluted without damaging the metals.
Is there a problem with yours?
 
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Our previous caravan had a Carver Cascade 2 water heater - in my ignorance I descaled it using malt vinegar instead of wine/spirit/white vinegar - whether it did any good I don't know but it didn't seem to come to any harm.
 
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Yet in the video, Alde recommends renewing the air cushion every ten days.
The owner's manual states;

When the hot water cylinder is in continuous use, it should be drained and refilled once a month. This recreates the air cushion in the hot water cylinder that absorbs pressure surges.

Confusing as website says one thing and the manual something else? Many of us spend more than 10 days on a site without moving.

TIP!
If continuously using the hot water cylinder in a hard water area, fit an inline scale inhibitor to minimise the effects of limescale.
 
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Some caravans are fitted with a pressure damper in the water system - does this do the same job?
Not as far as I am aware, the damper just gives equal pressure when you open a tap.

The air cushion in the boiler takes the expansion and contraction, once gone you get hammering, this is where the water heater has no choice but to expand and contract thus weakening the structure. It’s equivalent to ullage space in gas bottles etc
 
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Not as far as I am aware, the damper just gives equal pressure when you open a tap.

The air cushion in the boiler takes the expansion and contraction, once gone you get hammering, this is where the water heater has no choice but to expand and contract thus weakening the structure. It’s equivalent to ullage space in gas bottles etc
Surely, as the pressure increases in the hot water cylinder, the damper will absorb that increase - as there's no valves/taps between the damper and the boiler.
 
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Surely, as the pressure increases in the hot water cylinder, the damper will absorb that increase - as there's no valves/taps between the damper and the boiler.


It’s called a surge damper it helps to provide a smooth water flow in your caravan, motorhome or boat, by reducing pulsation and system noise.

Not to be confused with the air cushion in the boiler
 
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It’s called a surge damper it helps to provide a smooth water flow in your caravan, motorhome or boat, by reducing pulsation and system noise.

Not to be confused with the air cushion in the boiler
Don't they both achieve the same thing, regardless of their names.
 
Mar 14, 2005
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Some caravans are fitted with a pressure damper in the water system - does this do the same job?
Yes and no... The pressure or surge damper is connected to cold water side, and it's purpose is to smooth out the cold water pressure and flow changes when the pump switches on or off in a pressure switch controlled system.
of the cold water. It mimics the action of the air cap in the hot cylinder, and helps to prevent the water temperature at mixer taps from fluctuating too much.
 
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Yes and no... The pressure or surge damper is connected to cold water side, and it's purpose is to smooth out the cold water pressure and flow changes when the pump switches on or off in a pressure switch controlled system.
of the cold water. It mimics the action of the air cap in the hot cylinder, and helps to prevent the water temperature at mixer taps from fluctuating too much.
The hot and cold pressures will be the same with or without air cushion or surge damper - the hot side is fed by the cold supply with no valving in between so the pressure will equalise.
 
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The hot and cold pressures will be the same with or without air cushion or surge damper - the hot side is fed by the cold supply with no valving in between so the pressure will equalise.
But the air cushion in the boiler stops hammering in the boiler as I said earlier.

The surge damper is basically a tube of air that puts a constant pressure on the cold feed.

Also as mentioned earlier is ullage space, this is in the majority of liquid containers and why there is an air gap left as in the example of the gas bottle, this takes the excess pressure of the container.

I should have added not all vans are fitted with surge dampers either.
 
Mar 14, 2005
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The hot and cold pressures will be the same with or without air cushion or surge damper - the hot side is fed by the cold supply with no valving in between so the pressure will equalise.
Hmmm. then what is the none return valve on the cold water inlet to the heater?

In a pressure switch controlled system the cold water pump delivers water to both cold and hot systems at the same pressure. But the water that enters the heater passes through the NRV on the inlet to the heater. When the taps are closed the pump continues to deliver water that begins to compress the air cap in the hot tank until the pressure switch is satisfied and the pump

As the water in the heater rises in temperature it expands into the air cap raising it's pressure. The pressure does not equalise into the cold system because of NRV.

When a true mixer tap is opened, the raised hot water pressure will overcome the lower pressure cold water and deliver from the hot tank because the ultra compressed air cap provides the flow, untill the pressure has reduced to match the cold supply pressure, at which point the cold will begin to flow due to the resilience of the plastic hoses, as the pressure continues to drop a few moments later the pressure switch detects the drop and starts to pump.

Often with showers the pump can actually deliver mor water than the shower can pass, so as the pump operates it can start to raise the pressure in the pipework and the water heater. As the pressure rises the air cap in the hot tank also compresses. If the pump is strong enough, it can add enough pressure to retrip the pressure switch, which stops the cold flow, but the recompressed air cap in the hot tank can continue to deliver hot water.

This results in repeating pulses of hot and warm water synchronised with the pump pulsing.

To largely overcome this problem, fitting a similar sized air cap to the cold water pipes (a surge or pressure damper) provides the cold water system with a similar pressure resilience as the hot system, and crucially prevents such wide short term water temperature variations and improving comfort and control.
 
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Hmmm. then what is the none return valve on the cold water inlet to the heater?

In a pressure switch controlled system the cold water pump delivers water to both cold and hot systems at the same pressure. But the water that enters the heater passes through the NRV on the inlet to the heater. When the taps are closed the pump continues to deliver water that begins to compress the air cap in the hot tank until the pressure switch is satisfied and the pump

As the water in the heater rises in temperature it expands into the air cap raising it's pressure. The pressure does not equalise into the cold system because of NRV.

When a true mixer tap is opened, the raised hot water pressure will overcome the lower pressure cold water and deliver from the hot tank because the ultra compressed air cap provides the flow, untill the pressure has reduced to match the cold supply pressure, at which point the cold will begin to flow due to the resilience of the plastic hoses, as the pressure continues to drop a few moments later the pressure switch detects the drop and starts to pump.

Often with showers the pump can actually deliver mor water than the shower can pass, so as the pump operates it can start to raise the pressure in the pipework and the water heater. As the pressure rises the air cap in the hot tank also compresses. If the pump is strong enough, it can add enough pressure to retrip the pressure switch, which stops the cold flow, but the recompressed air cap in the hot tank can continue to deliver hot water.

This results in repeating pulses of hot and warm water synchronised with the pump pulsing.

To largely overcome this problem, fitting a similar sized air cap to the cold water pipes (a surge or pressure damper) provides the cold water system with a similar pressure resilience as the hot system, and crucially prevents such wide short term water temperature variations and improving comfort and control.
It's not on the cold inlet to the heater, it's on the cold inlet into the caravan - with the hot supply taken off after that - at least that's the way it is on my Lunar with a Truma inlet.
 
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If there isn't an NRV on the cold inlet to a storage water heater, then any stored hot water might find it's way into the cold pipes and partially empty the heater which could be damaging to the appliance.

I would be very surprised if your heater doesn't have an NRV on it cold water inlet

Most Truma models use a combined NRV and pressure relief/drain valve fitted just before the heater

Carver Cascade 2s had one screwed into the casting as the cold water inlet Fulham, and the MK1 Cascades had one fitted inside the cold water inlet pipe.

Edit..For the same reasons I would expect all tourer storage water heaters to have some form of NRV on their input.
 
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