Fitting a heater in a Sun Kiss 47

[Sea Change]

We're heading up to Nova Scotia this summer and I'd like to install a blown air diesel heater. I'm familiar enough with these units and have installed two on previous boats, and helped a friend install his.
I'm aware of the limitations on ducting length, exhaust length, and I'm aware of how hot the exhaust can get.

In an ideal world I'd fit the heater in the engine room or in a stern locker, and run the ducts forward. However my boat's layout doesn't lend itself to that. In typical 80s French fashion, the aft heads/shower is under the bridge deck, between the aft cabins. The aft cabin berths both have tanks underneath them.
So there's no obvious way to get a 70/90mm insulated duct run from the engine room past these obstacles, without building some sort of trunking, which would be a bit of a pain.
I could run the ducting higher up along the side of one aft cabin, possibly sacrificing the storage shelf to do so.

The other idea I had was to abandon the transom mounted exhaust, and run the exhaust up to a metal mushroom vent on deck. But then I started thinking about the downsides of that... you'd have to watch you didn't melt any halyard tails, you'd need to shut it if you expected any water over the deck, and of course open it again if using the heater.

Any thoughts? Any other ways of approaching this?

 

[Minerva]

Could you exit the exhaust on the hull side? Our old CC moody has her heater exhaust just outside the cockpit locker, around 2/3rds of the way back from the bow. Never had an issue with water / wave ingress.

Also at 47ft, are you perhaps at a point where having two, smaller systems, might work? One for the aft cabins and one for the saloon / v berth?

 

[Minerva]

Of course the Gucci option is small blown air heaters for over night in the sleeping cabins and a drip heater fire in the main saloon…

 

[Sea Change]

All valid points, but this needs to be a cheap and cheerful solution, possibly a temporary one.
One of the aft cabins is full of Victron gear so I don't want to heat that space.
A long term, more effective, solution would depend on whether we decide to do a few years of Scandinavian cruising in the future.

 

[AngusMcDoon]

A hydronic one may be more appropriate for that size of boat, especially now that Chinaspatcher have started making them. Bigger burner, but much easier pipes to run, and longer lengths possible allowing you to get heat all the way from the engine room to the front cabin. Forced air radiator units or passive radiators needed which is more of a faff than just a hot air outlet. Another advantage is it's separate way to heat domestic water with a twin coil tank. A summer valve can direct heat just to the domestic water if it's hot weather.

 

[Sea Change]

A hydronic one may be more appropriate for that size of boat, especially now that Chinaspatcher have started making them. Bigger burner, but much easier pipes to run, and longer lengths possible allowing you to get heat all the way from the engine room to the front cabin. Forced air radiator units or passive radiators needed which is more of a faff than just a hot air outlet. Another advantage is a it's separate way to heat domestic water with a twin coil tank. A summer valve can direct heat just to the domestic water if it's hot weather.

That's a compelling argument. We don't have hot water either, and whilst like to fit it. But it's no longer a ~£150 job that can be done in a weekend...

 

[AngusMcDoon]

That's a compelling argument. We don't have hot water either, and whilst like to fit it. But it's no longer a ~£150 job that can be done in a weekend...

You could do it in stages. You can always add more forced air matrix outlets and a dual coil tank later. The system is easy to extend once the boiler is in. The kits come with some circuit pipe and a circulation pump, but no outlets. Here's a 4kW outlet...

Siroco Water Heater Matrix Tenere 2 (Grill) Low Noise 3 Speed Blower 12v 4.2kw Black, Night Heater Kits, Eberspacher, Webasto, Mikuni, Durite

Fitting the boiler and a single matrix output should be doable in a weekend if access is ok. Once the boiler is in the circuit pipes are easy as they are flexible rubber things with Jubilee clip joints. They are pretty bendy so can be poked around and behind things - easier than an air duct. A simple small header tank at the high point is needed like an engine coolant tank.

You can also get single matrix multiple output units that are fitted to trucks where you attach ducts to the outlets to pipe to different areas.

 

[geem]

We have a Webasto hydronic heater. I swapped our old tired calorifier for a nice new highly insulated one with twin coils.
Its great for hot water but the heating side of it was a bit of a let down. The fan coil units are noisy and demand quite a bit of fan power if you are running 4 of them like me. Also, there is a lot of pipework, tees, hose clamps, elbows, wiring, control panel to fit. Its not a cheap job. The old Eberspacher fan blow heater was far quieter and pretty adequate. It just didn't do hot water. The ductwork was a pain to route and insulate and my ducts rotted out after a few years. I had lovely hot bilges but not so much in the cabin.
No option is ideal but the water based system might be easier to fit. Just make sure you over size the fan coil units or install ore of them

 

[Sea Change]

This hydronic idea does seem to make a lot of sense. I've been reading up about them and I think I understand the gist of it.

Bearing in mind the boat currently has no heating or hot water system, I'll need:

- a twin coil calorifier
- a hydronic unit (looking at a Chinese one most likely)
- a header tank
- piping
- either fan coils or plain old radiators

Do I have that right?

The boat did actually have hot water originally; at some point in the past the tank was removed to install a second holding tank. So I have the plumbing in place for hot water to all the taps.

I take it the exhaust on a hydronic is basically the same as the blown air heaters?

Seeing as I'm starting from scratch, I think I'd spec dual voltage immersion as well, so that I can heat directly from 12v.

Choosing the size of calorifier presumably it's dictated mostly by where it's going to live. The bigger the better?

 

[AngusMcDoon]

This hydronic idea does seem to make a lot of sense. I've been reading up about them and I think I understand the gist of it.

Bearing in mind the boat currently has no heating or hot water system, I'll need:

- a twin coil calorifier
- a hydronic unit (looking at a Chinese one most likely)
- a header tank
- piping
- either fan coils or plain old radiators

Do I have that right?

The boat did actually have hot water originally; at some point in the past the tank was removed to install a second holding tank. So I have the plumbing in place for hot water to all the taps.

I take it the exhaust on a hydronic is basically the same as the blown air heaters?

Seeing as I'm starting from scratch, I think I'd spec dual voltage immersion as well, so that I can heat directly from 12v.

Choosing the size of calorifier presumably it's dictated mostly by where it's going to live. The bigger the better?

Twin coil tank only if you are going to have the engine also heat the water (either now or planned in the future), otherwise a single coil.

A towel rail type radiator is sometimes used in heads compartments, otherwise forced air matrix is more common and quicker, but noisier and use electrical power. Check the electrical consumption of the outlets before you commit to a system.

Exhaust is the same. You'll need a skin fitting and maybe some lagging. The silencer that comes with the Chinese kits is not suitable for boat use. Either buy a better one of leave it out. I've never had one. One can always be fitted later.

Calorifier size will be space you have, up to a certain point.

A summer valve may be useful if you are somewhere warm, but it's not essential. This is a valve that allows you to send the heated circuit water only to the calorifier and not the rest of the system in warm weather. The forced air matrix outlets even when the fan is not on still give out some heat. It's not necessary though, and can always be added later if it's felt it's needed. I've never had one.

 

[Sea Change]

It seems sensible to go twin coil if I'm starting from scratch. No point wasting that free heat from the engine (especially at current diesel prices!)

I presume the reason that matrices are used is because most boats don't have the free wall space for radiators?

Have I missed out anything that I'll need- accumulator? Circulating pump?

 

[AngusMcDoon]

It seems sensible to go twin coil if I'm starting from scratch. No point wasting that free heat from the engine (especially at current diesel prices!)

I presume the reason that matrices are used is because most boats don't have the free wall space for radiators?

Have I missed out anything that I'll need- accumulator? Circulating pump?

If you get a twin coil tank there's no harm leaving one of the coils not connected to anything for now and plumb it into the engine at a later date.

Radiators may be cumbersome to fit in a boat. It depends on the space.

The Chinese boilers + fitting kits I've seen on ebay for about £200 look like they have a circulation pump included, but not a header tank. The lengths of pipe and wires I expect will be too short for your install so you'll have to source and budget extras.

The circulation water doesn't need an expansion tank - it expands into the header tank like an engine. For the domestic hot water whether an expansion tank and accumulator is needed is no different on a hydronic heated system than an engine heated one. Others here will know more about that than me. When I had a hydronic system I don't think mine had them. I would get a small dribble out of the calorifier pressure release valve which went into a strategically placed pop bottle that I emptied once a month.

 

[fredrussell]

…Also at 47ft, are you perhaps at a point where having two, smaller systems, might work? One for the aft cabins and one for the saloon / v berth?

I think this is your answer. Chinaspachers are pretty much free at the moment - the last 5kw one I recently bought and fitted for a mate cost £60 !!

47ft boat = lots of invasive ducting runs as you say. Easier surely to put a heater near each area to be heated. My exhaust is just below gunwale on a boat with low freeboard- no problems caused by seawater getting in (I have a swan neck type arrangement on exhaust pipe)

 

[Sea Change]

I think this is your answer. Chinaspachers are pretty much free at the moment - the last 5kw one I recently bought and fitted for a mate cost £60 !!

47ft boat = lots of invasive ducting runs as you say. Easier surely to put a heater near each area to be heated. My exhaust is just below gunwale on a boat with low freeboard- no problems caused by seawater getting in (I have a swan neck type arrangement on exhaust pipe)

Valid point. I'm a bit wary of putting the exhaust on the side of the hull, we don't have the freeboard of a modern boat. But I'll look at the space and think about it.

At the moment I'm actually wondering if I should just do a portable/temporary cockpit mounted heater with a duct running through a plywood washboard. Just to get us through this season. Then when we get the boat back home next year do it properly and fit a hydronic system.

 

[Sea Change]

For example, one of these:
https://www.amazon.com/GEARLASSO-Co...efix=parking+heater,aps,408&sr=8-4&th=1&psc=1

I've already got a spare 60Ah lithium battery to power it with. So all I really need is to make up a board with a hole for the duct.