Hot Water with Brazed Plate Heat Exchanger

[patprice]

Standard practice to provide hot water in a yacht for the bathroom or galley is to install a hot water heat exchanger. Like this one.

Whereas my engine is cooled by a heat exchanger and therefore suitable for one of these units, they are not cheap and in particular are big.

See below is a "Brazed Plate Heat Exchanger".


Does anyone know if they can be installed tp provide hot water in my bathroom for a shower. Obviously the engine would need to be running and hot.
These units are cheap and small.

Would appreciate any comments please.

[AndyEss]

I think you would need an insulated storage tank to make use of this heat exchanger. The exchanger itself stores very little hot water, and during a shower the pass through time of more water against the 200 deg F engine coolant side would result in very little temperature rise.

[patprice]

Originally Posted by AndyEss

I think you would need an insulated storage tank to make use of this heat exchanger. The exchanger itself stores very little hot water, and during a shower the pass through time of more water against the 200 deg F engine coolant side would result in very little temperature rise.

Yes I see your point. Obviously it depends on the shower water volume. A storage tank would presumably require a pump to circulate water.

[AndyEss]

With a clever design you might be able to get it to thermosyphon without a pump. Actually your question and a refrigeration thread has me thinking about using my water cooled fridge as a source of pre-heat for my shower. I have a brazed unit like the one in your photo in my boat project storage unit.
I’m just not sure I want to devote the space for the hot water storage tank on my boat to squeeze out the last couple of calories of waste heat. I live on a 38 ft boat and am hoping to cross to the Marquesas or Tuotamoto’s in the spring. I can think of a million things better to store than hot water.
Don’t tell Dockhead, but I use an instant propane hot water heater and it works great

[patprice]

Thermosyphon would be slow and the issue here is the engine would be running.
The boat in question is my Australian boat here in Tasmania. A 36 ft Swanson. We have travelled extensively in the Western Pacific and not needed hot water. A swim with hair shampoo, which lathers in salt water, then a litre of water to wash of the salt.
But we are in Tasmania. Sea water swimming is mostly a very activity for most of the year.
I hear you with the gas installation. Some yachts put them on deck.
I recently installed a diesel cabin heater. Maybe I can use the very hot exhaust, windings of small diameter copper tube. But a long way from the bathroom.
You have a nice yacht, I know them well. Will you extend to the Western Pacific?

[AndyEss]

I like the coil/exhaust idea.
I don’t want to circumnavigate, so French Polynesia, north to Hawaii, Alta California and back to La Paz.
The exterior mount for the propane instant heater takes care of some problems, which I suspect is a solution looking for a problem.
I have a propane Force10 cook stove. I bet it is probably more dangerous than the propane hot water heater. I have propane sensors in the galley and head. The carbon monoxide concern can’t be any different between the unvented stove, and the vented HWH.
I liked my engine cooling loop/electric tank heater, but the coolant loop sprung a leak, and I can’t see any reason to spend the $$ to replace it - and I have the extra space it used to occupy.
I would have probably enjoyed visiting New Zealand in my boat - previous owners crossed from North America to NZ and then shipped her back.
Maybe in another lifetime.

[Ivansgarage]

https://www.amazon.com/Camplux-Porta...0587818&sr=8-9

[Culwatty]

I used one for years on my landrover via a hose lock connections, showered every day with it without an issue and had to fit a thermostatic valve as it produced some serious hot water!

[Jdavidcooper]

Yes, I have used one like this: https://www.amazon.co.uk/gp/product/B002OQYEFU
for several years now. It works extremely well and is fairly cheap (approx. GBP30). Mine is powered by a Kabola KB20 boiler that is used for central heating - the hot output from the boiler goes through one side of the plate and a cold water feed goes into the other side.
Years ago this type of plate exchanger was expensive and difficult to find since they were mostly designed for the food processing industry but the advent of domestic combi boilers has made them cheap, compact and widely available.
A caveat though - the temperature of the hot water output to the shower etc. from the exchanger depends on the flow rate you need and the temperature of the cold water input so you may need to experiment a bit. As a guide, my Kabola boiler output is about 55C and easily provides 30-35C at the shower head (normal size not power shower type).
Let me know if you want any further information.

[redog]

I run my engine coolant water through an external heat exchanger, then run the shower or fresh water through the other side of the exchanger. Storage tank is an 80 litre 240 v household.

Water is circulated via a 240v solar system pump and shut off with a 240v solenoid water valve. Both of these turn on via the engine key to stop natural convection when stopped. I'm sure 12v would be available. Only downside I have found here is with hot water in tank and a cold engine start it cools the hot water, until engine temperature gets back up. Temperature sensor controlling the water valve and pump maybe a solution to this.

Hot water (engine running temperature) within 15 minutes of getting engine under load. Idling engine not so effective. This turns on every time the engine is running. With the solar pump and shut off valve no worries about positioning of each unit.

Continuous hot water when running the engine or generator. 80 litres storage holds quite well in the engine room.

Cheers Dave