Wet central heating

[CampinGazz]

I'm thinking very hard about replacing the current heating system in my.. erm, boat that dosent float (ok it's got wheels and you cruise down a tarmack river

 

At the moment i've got what's almost standard for motorhomes, a truma gas fired space heater, basicaly it's a 3kw heat exchanger, with a fan on the back and blown air ducts around the van.

 

And for water heating it's a carver cascade water heater, storage tank type heater, onlt holds 9 litres of hot water, gas fired again.

 

I'm thinking of selling the truma space heater and the carver water heater, and replacing them with an eberspacher hydronic type system.

 

Wet central heating is not that common in motorhomes, but is very common on boats... hence me asking here.

 

I can't afford to buy a new eberspacher, and looking around there's a few second hand D5W eberspachers about for a half decent price,

but there are also hundereds of webasto thermo top C units about (they both output 5KW on high, and 2 and a bit on low), i'm looking in germany as they are more plentiful over there, and it seems there's a big flood of these webasto units that come out of accident dammaged cars, where they are fitted as standard for parking heaters (as they call them) there's also a law in germ,any that the heat exchangers must be replaced every 10 years, so a lot of 10 year old heaters are about.

 

But i am guessing that with so many webasto heaters about that means they aren't as good as the eberspachers, there's a few places selling a brand new webasto thermo top C, diesel fired water heater for about 500 euro's, but they are sold as car specific kits, most have a timer controler, but mention a 60 minute max heat time.. as that's all you'd want in a car when your using the starter battery for power.

 

should i not even consider the webasto for the heat source? or anyone know where i can get an eberspacher D5W second hand for a decent price?

 

I know i'll need a calorifier, looking at about a 22 litre one with twin coils, that'll more than double my hot water capacity, allow me to heat the water off the engine when driving and so on.

 

So the eberspacher or webasto runs the 2nd coil in the calorifier, that gives hot water when stationary, how does the eberspachers run when used say in summer just to heat up the water in the cylinder, i read they start up on high, then go to low heat, going back up to high if needed, but it seems they dont shut off unless you turn them off at the switch, is this the case? or is there a different controler that monitors the calorifier temperature, and when it's upto temp it shuts the heater down?

 

For heating the van, i want to use domestic style radiators (small ones) and would use a diverter valve to divert the hot water from the calorifier coil to the radiators when heating is wanted, if i can get a 12 volt powered valve like used on home centeral heating systems that'd be great, heard them mentioned on here, but never found a source.

 

Am i on the right track with these ideas? or way off, what's the best thing to do,

 

At the moment with my 2 seperate units, i turn the water heater on when i park up, and it takes care of it's self, light up and heats the water, shuts down when it's reached 80 degrees C, then when the temp in the cylinder drops to about 70, it lights up again and brings the temp back up... it fires for about a minute every half hour... the insulation on the carvers tank is just a polystyrene slip on jacket, so heat loss is bad.

 

For space heating, i turn the heater on as and when i want it, set the temperature, and it adjusts the flame accordingly to keep the temp stable in the van,

 

Can something like that be done with a eberspacher system?

[DHutch]

If you use the search feature (top right of every page) you will fine theres a lot of threads abouth the webasto and eberspacher systems.

 

 

Daniel

[Smelly]

there's a fella on ebay selling recond eberspacher units for 600 quid... that's more than 500 euro's but still pretty cheap!

[CampinGazz]

had a good search through the posts but didn't find all the info i'm after, i guess most people already have a central heating system installed, hence most of the questions relate to when it goes wrong as opposed to fitting one in something that's never had anything like that before.

 

Think i've decided on going the eberspacher route, too many bad reports about the webasto thermo heaters, hence why i find so many for sale cheap.

 

I've had eberspacher air heaters before, so i know they are very expensive to fix, but i also know that certian common items that go can be substituted for a non eberspacher version... i.e. my D3L heater blew it's combustion chamber temp sensor, eberspacher wanted over 40 quid for a new one, luckily a few days before i'd fixed an electric shower where the overheat temp sensor had failed... and the eberspacher heat sensor was exactly the same thing,

 

So i bought a shower over heat sensor for £1.49 from RS components, and it worked in the heater for the rest of the time i had it.

 

Anyway, i imagine i'm on the right track with... eberspacher hydronic heater, plumbed into a calorifier of about 22 litres capacity, (twin coil calorifier so i can utilize engine heat for hot water when touring)

 

Then is it best to divert the flow of water from the calorifier coil to the radiators and by pass the calorifier when central heating is needed, or add the radiators in line with the calorifier coil... before or after the rads,

 

I'm thinking about using a servo valve like used on home hot water cylinders to select heating or hot water,

can anyone tell me where to get a 12 volt servo/motorised 3 way valve from, dont really want to have to power the inverter just to change the radiators in and out of the circuit.

 

I plan to use small domestic style radiators, with thermostatic rad valves.. is this ok on this kind of system, and how the best way to plumb the rads into the heating pipes to avoid the water bypassing the rads further down the system when the first one is fully on?

 

Sorry for all the questions, i've been searching for web sites that detail boat heating systems and instlations, but all i've found so far is people who have fitted the air heaters, which is very simple.. but that may because i've done a blown air heating system 3 times now, but never a wet heating system.

 

Now i just have to sell my 1 year old convection and blown air heater from the van to fund the purchase of the eberspacher.

[dor]

Have you considered an Alde?

 

Popular on boats and very reliable. True you need to lug a propane cylinder around, but a couple of 6kg ones wouldn't be too difficult. Perhaps you are already carrying them for cooking anyway (better flame than butane).