Boat Heating System Design

[CanalRetentive]

Just a quick sketch but are there any problems with this design?

 

The idea is to have 12v solenoids/isolators connected to the control panel so they are easy to operate. One controls the circuit between the engine cooling system and a heat exchanger connected to the radiators, allowing them to be heated by the engine when wanted. The other controls the circuit between the back burner and calorifier, allowing the radiators to get the full effect from the stoves back burner if heating is a priority and hot water isn't.

 

Thanks in advance, feel free to call me a moron if it applies ?

 

[Tracy D'arth]

Using a solid fueled heat source with motorised valves or solenoids on a pumped  system, safely,  is very complicated as getting sufficient fast control of the heat output is almost impossible, especially on a boat with finite electrical power capability

[Jen-in-Wellies]

The engine to skin tank to calorifier circuit is wrong. The hoses between engine and skin tank are typically 1.25" to 1.5" diameter. The hoses to the cauliflower are typically much smaller, 5/8", going to hose tails and in to 1/2" BSP fittings on the calorifier. Trying to run the main engine cooling through the calorifier will be too restrictive and probably end up with the engine overheating. The most common engines have a separate small diameter cooling circuit from the thermostat housing, before the thermostat, out to the calorifier, then back to the water pump. This typically isn't affected by thermstat position. What engine are you going to use?

 

It isn't common to heat radiators with the engine, as it only works with the engine on, which is typically in the day. It is colder at night, when the engine is usually off. You have no return from the heat exchanger to the engine cooling loop.

What is the current drawn by the valves? What make/model of solonoid valve do you plan to use? A small current for a long time will drain batteries badly. Having the ability to bypass the calorifier to heat the boat quickly from the stove is a good idea, but is probably easiest with hand operated valves. Only any use when you arrive at a cold boat. KISS principle is best for boats.

Jen

Edited May 30, 2021 by Jen-in-Wellies

[CanalRetentive]

6 minutes ago, Tracy D'arth said:

Using a solid fueled heat source with motorised valves or solenoids on a pumped  system, safely,  is very complicated as getting sufficient fast control of the heat output is almost impossible, especially on a boat with finite electrical power capability

 

Ok, I assumed there was a reason you don't see this done more often I guess that's why then ?
 

2 minutes ago, Jen-in-Wellies said:

The engine to skin tank to calorifier circuit is wrong. The hoses between engine and skin tank are typically 1.25" to 1.5" diameter. The hoses to the cauliflower are typically much smaller, 5/8", going to hose tails and in to 1/2" BSP fittings on the calorifier. Trying to run the main engine cooling through the calorifier will be too restrictive and probably end up with the engine overheating. The most common engines have a separate small diameter cooling circuit from the thermostat housing, before the thermostat, out to the calorifier, then back to the water pump. This typically isn't affected by thermstat position. What engine are you going to use.

 

It isn't common to heat radiators with the engine, as it only works with the engine on, which is typically in the day. It is colder at night, when the engine is usually off.

What is the current drawn by the valves? What make/model of solonoid valve do you plan to use? A small current for a long time will drain batteries badly. Having the ability to bypass the calorifier to heat the boat quickly from the stove is a good idea, but is probably easiest with hand operated valves. Only any use when you arrive at a cold boat. KISS principle is best for boats.

Jen

Yeah I've noticed the numerous mistakes after I posted it too, probs far more I haven't noticed too ?  Just in the early planning stage atm and throwing ideas out there, was thinking it would be nice to have the option for the sake of a couple of solenoids and a bit of extra plumbing. Have the radiators nice and hot when cruising in winter, let the stove do the water and radiators or just radiators. Looks like it's more complicated than that though, it always is!

[Jen-in-Wellies]

If you possibly can, have the stove back boiler circulate by gravity with no pump. A pump, or electrical failure will cause boiling and possible danger. @Tracy D'arth has a real downer on pumped back boiler systems and I can see why. This needs careful layout, with big diameter copper pipes and minimal bends and strict attention to heights, but works very well if done right. No noise either. A constantly running circulation pump can be annoyingly loud after a while! I'd fit a single hand operated valve bypass to the cauliflower. Don't have one on my boat and occasionally it would be useful when arriving at the boat after time away when it is cold. Just never got around to doing it.

Gravity circulation may be harder to make compatible with a heat exchanger from the engine. Need to make sure it is not too restrictive as the pumping force from the relative density of hot and cooler water is tiny. Also needs to be at the lowest point of the system.

 

Stoves tend to be run 24/7 when you are on board in winter. They take a long while to go out. If it is still warm when you get up in the morning, then the stove is likely still lit. A shovel of coal will keep it ticking over till the evening, when you'll stoke it up again. I'm not convinced an extra heat exchanger and complications to the plumbing is worth it to use heat from the engine too.

Jen

[frahkn]

It is possible to overestimate the amount of heating needed. There are no radiators in my 70' boat, the cabin (about 35' long) is heated by a Refleks diesel stove while there is a traditional solid fuel stove in the (more or less traditional) back cabin, which I rarely light at all. The engine room is next to the bathroom and as I need to run the engine to heat the water, the bathroom is always warm when needed.

[Tacet]

Heating the rads via a engine heat exchange works well for a cruising boat.  The boat should be pleasantly warm when you tie-up on a chilly day; naturally there are other ways to heat the boat - but free is good.

 

It is usually achieved by putting a 12v centrifugal pump in the heating circuit rather than valves.  Chances are that the system will not circulate without the pump, which means it is an effective control.  And a centrifugal pump should not offer any resistance to gravity circulation from the back boiler.  The engine will be heating the back boiler - which will send its heat up the chimney but probably a lesser evil than valves.