D5W Z

[rob2]

I have acquired am Eberspacher D5W Z - originally a pre-heater on a Transit van. I wonder if anyone might advise me what load would be required to use it as a CH boiler on my boat (and how to calculate it)? In many ways, I'd prefer an air heater, but looking at the joinery in the boat it would be much easier to thread a couple of hoses along the hull than find room for an air duct! Unfortunately, I don't have the tankage to make a HW system and calorifier an option.

Rob.

 

[Steve_N]

Hi Rob,
I have a D5WZ used just to heat the hot water via the calorifier.
Sorry, probably my fault but I don't understand exactly what you're asking? If you can elaborate I may be able to help.

 

[David2452]

Just a boiler like any other, all you will need is a circuit and radiators or heater matrix.

 

[rob2]

I appreciate that an Eber water heater can be used as a boiler, but surely there is a maximum and minimum load in the circuit for it to run happily? I'm looking to find out how to calculate what radiators and heater matrices it can handle and how many it needs to keep it loaded - as said, I don't have the option of using a calorifier which would have put a base level load onto the system whether other heat exchangers are on or off.

I've made some preliminary searches threough the Eber literature and, so far, have found it rather confusing. All the manuals assume that the heater will be used to pre-heat your car under arctic conditions and it isn't clear what controllers are suitable or what functions they perform. Being somewhat strapped for cash I can't afford to start a project and end up with a controller that doesn't work or building a system that cokes up the boiler before the cabin has warmed up.

Rob.

 

[David2452]

There is little point in working out what you need as you already have the boiler so must work from there, it's 5kw so I would load it with about 6kw to reduce cycling (that's what Webo recommend for a TTC of similar output) much less and it will cycle, much more and it will under perform, when working out the load remember that most kw designations for matrix are quoted at much higher temperature than the D5W will produce.

 

[David2452]

Also, just remembered, I believe the "Z" designation makes it an additional heater not a parking heater so you will need a circulation pump of the correct spec, also if it is of the type (as a number are) which is controlled by the vehicle bus then you may have issues getting it to work outside of that vehicle.

 

[rob2]

OK, have read the manuals for similar variants several times. Not a good read as it is very much a translation of the original German and riddled with references to their automotive regulations. However, the detail of options and applications finally seem to make sense (although one component on mine is not readily identified). It is indeed an additional heater, so many of the usual control options are not available. The wiring seems to be quite simple as the vehicle specific loom has a spur to the dosing pump and a 6 way connector. The wires at the connector include the +ve & -ve power (25A fused supply) and three others. One is for dianostics, a second requires a postive supply to switch on/off (originally taken from the alternator so that it only runs when the engine is on) and the third is for a simple on/off switch. the unidentified component seems to be a thermistor for outside air temperature. I believe this is to confine the use of the heater to very low temperatures in its original application.

The plan for test of concept is to fit a cheap ebay 12v timer as the on/off switch (also feeding the water pump) and see if I can fire it up and heat a bowl of water. First I have to calibrate the thermistor to find a suitable resistor to fool it! I guess ice, room temp and steam should give a good idea. If that works, I shall be after some matrix units - if not, the timer must have other uses on board...?

Rob.

 

[David2452]

the unidentified component seems to be a thermistor for outside air temperature. I believe this is to confine the use of the heater to very low temperatures in its original application. Rob.

Indeed, identical to the Webasto Thermo Top when used as an additional heater, usually fixed to operate only when outside temperature is < 5c I will have a look for the value, it will be a starting point at least.

 

[rob2]

Thanks for that. My plan was to measure the resistance in icewater and steam and replace with a resistor to fool it it was below freezing. I'm hoping that once that's done I can simply experiment with which combination of positive feeds gets it running.

Rob.