New member
19 Jan 2005
Starting to think about the heating plan for our Schooner. We have an 80 hp Ford Dover with a heat exchanger, a 5.5 Kw Gen Set with a heat exchanger, a solid fuel cabin heater with a back burner and will have a Dickinson stpve with a double coil water heater. All of these can and will provide a lot of heat. On the heat out side we will be running four "Bus" radiators, a 10 gallon calorifier, and two heatex blown hot air matrixes.

Now the idea is to have all of this on a single circuit. Driven by a standard Grundfos household central heating pump (will run off a 150 watt inverter) Water can be heated by any or all of the engines / stoves, and pumped round the boat. Each rediator will have its own thermostats and each heating unit (engine etc) will have three shut off valves (one to close the water in, one to close the water out and one to open a relief pipe so that water can still flow around the circuit.
THe circuit will be off 22mm flexible plastic pipe using push fit connectors. This is so that any repairs can be made quickley and safely, 22 mm pipe should move enough water to keep every think cool enough to run safley. THis systen will also give a huge reseviour of cooling water for the two engines.

THis will give multiple backups, and no single point of failure, what do you think? Or am I nuts!!



New member
11 May 2004
That 'push-fit' connector stuff is a pain. There are a couple of types, and the HeP type is terrible! You need a special tool to get a connection off, and more often than not end up cutting it out and putting a new section in, using *more* connectors.

Why not use a Bolin pump to circulate the water, runs off 12V and only uses 0.15A? Kuranda in the UK stock them.


New member
5 May 2004
Sounds like a great idea. Having 3 valves per heat source sounds pretty complicated though - could anyone understand it and get the sequence right? I'm sure this could be automated with bypass valves.

My limited experience with push fit plumbing has been more than satisfactory. As long as you depressurise the system, I found the fittings will come apart easy. An adjustable spanner adjusted to size, will release them with a light tap or an even pull. Copper to plastic worked a treat too, in all sizes. The proper release tool is cheap to buy too. I would question the need for 22mm - many home systems will work fine with 15mm or even the microbore 10mm.

With central heating systems, there are automatic relief valves available that should be across the radiator supply pipes before any shut off valves. This ensures there is always a path for the water to flow, even when someone has accidentaly shut a supply valve off, or all thermo regulators happen to close at the same time.

However you do need some control though to prevent pressure build up from happening. A regular boiler is thermostaticaally controlled and when the bypass opens, the water heats up very quick and shuts the boiler down, until the temp drops below the setpoint.

Consider all radiator valves being closed on your proposed system, for whatever reason, and your stove merrily boiling a small amount of water away.......

I'm sure theres probably a heating engineer on the forum who can advise you, and will probably know a way around that.

BTW Got all my stuff from Screw fix, inc the relief valve. Recommended.



Or am I nuts!!

[/ QUOTE ]No! It's what I would have gone for myself if I had been starting from scratch and if I had needed to be completely independent of shore supplies for long periods of cold weather. However, we never intend to be away from marinas and shore power for very long when the weather is as cold as winter in the UK and North Europe and electricity is cheaper than burning diesel - red or road fuel. So we have a 5kW Eberspacher and use portable electric heaters most of the time in marinas. Like you, we have a large generator but it isn't cost-effective against marina electricity at 4.5p per kWh.


Well-known member
30 Jun 2002
Sounds OK in general. Wish my catamaran would take the weight of this lot and I would have something similar! I would however dump the domestic grundfos pump in favour of a 12v one as inverted power is pretty inefficient. I would also consider an eberspacher water heater too... Expensive perhaps but they give mega heat for little fuel when you are not running anything else.


New member
16 May 2001
By the Sea
NM You're nuts - Oops sorry mate.

I had a multiple system in a house, pumped by a danfoss, a woodburner and a rayburn, I spent my life turning valves on and off until one day I forgot to turn on the valve when I lit the rayburn. Lots of steam blew out of the boiler with a massive bang. The pressure was a problem in normal operation, the headertank would steam the system would creak and bubble and groan, it was horrible.

Throw this lot into a boat and as you know, you can treble the problems.

Good luck though...I'd love to see it when you're done!

Ian (SB)


New member
26 Feb 2002
Sounds complicated to me. Would a system that employs a second caolorfier as a heat sink work better?

Get a four coul calorifer knocked up with coils from engine, genset, backboiler and the dickinson in and pump water through that to the second calorlfier for domestic hot water then on round your central heating circuit.
A second coil in the domestic hot water supply calorfier from the genset (or whatever you will run the most might be an idea.

Then each system is self contained and a melt down in one won't bugger the rest?

Course you will need more pumps and separate headers for te Dickinsons and backboiler and lots more pipework so ummm forget about it!