Eberspacher Hot Water Minimal Plumbing Setup

[Patrick_C]

When I moved onto the boat I inherited a certain amount of 'creative' plumbing.   There's a double coil calorifier heated from the engine and an Eberspacher 4 hydronic (it has an immersion as well). The Eberpacher used to feed a run of radiators the length of the boat as well as the calorifier. There's a header tank too and a mass of old capped polypipe, strange little t-junctions and spurs that don't seem to lead anywhere and so on.  It looks like it was put in by Central Services from 'Brazil' on a bad day.

Well, I finally got fed up with the superfluous radiators and ripped them out (the stove does a much better job of space heating) but I'd like to keep the Eberspacher to just heat the water in the calorifier from time to time - so I don't have to run the engine when I'm moored up. Also I've got a timer on it so I can heat up a tank of water for early morning use.

Does anyone have a clear illustration of the minimal, safe arrangement of pipes and valves that I'd need to just use the Ebbie to heat the calorifier without short-cycling, tripping out etc?  I assume a balancing valve on the way in (and out?) and the header tank still included.  Most of the diagrams I can find (including on manufacturer sites) either show loads of radiators, bypass circuits etc or are alarmingly vague about valves etc. (i.e. don't show any).

Thanks in advance.

Patrick

[NMEA]

You should at least give it a chance by including a bathroom towel radiator. Then take great care in the length of time it runs for so as to prevent cycling as much as possible. Main problem you will encounter is with cold water it will rip thermo from the coolant and the heater will run normally but as it increases and removes few therms from the coolant so the returning temperature will increase quickly due to the above mentioned factor excasobated by the low coolant volume. So in short, keep the running time as short as possible and expect more frequent decokes.

[Chewbacka]

If you have a radiator or two in the bathroom on the return from the calorifier it will give you a bit of cooling so the return water going back into the ebber will be cool enough to reduce some of the cycling.  You will have a nice warm bathroom as well.  -  Now this is just a guess, but the coil in your calorifier will dissipate a couple  of kW when cold, and if your ebber is say 4kW then it will be getting hot water back from the calorifier and so will cycle a lot. 

[OldGoat]

Echo all of the above.

I have a vey large (by boat standards) cylinder and a run of radiators.

If I just want hot water without going cruising, I shut off all the rads: except the bathroom and run the mikuni-splutter UNTIL it starts to cycle, then I turn it off. It takes about 1 1/2 hours to get to that stage. I've not had to decoke in n years..... 

[smileypete]

Could put the eber on the engine side, then use 1 coil for engine (less 'overcooling') and both coils for eber, plus a couple of non return valves to stop backflow through eber or engine.

Saves having a separate coolant circuit for the eber, which would need header tank or expansion vessel. I guess the eber is in the engine room/bay  already.

Sometimes simplicity and effectiveness don't go together... but complexity doesn't guarantee effectiveness either.

Edited May 16, 2017 by smileypete

[Patrick_C]

Thanks for advice.  Though the double coil idea is intriguing i think a towel rail or drying rack type set up is the best bet then. I just have to decide whether to run a length of pipe most of the length of the boat to the bathroom  or do something close by the eber (reverse layout agh).