On demand gas hot water

[Neeves]

We don't have calorifiers, we generate hot water, for showers, from a Bosch boiler. The boiler has been great but technology may have moved forward from 20 years ago. We don't use the engines for water as if you are anchored for a few days - you don't use the engines. In winter cold showers do not appeal - in winter Oz is not the exotic land with unlimited sunshine - so black poly bags do not appeal.

As our Bosch unit is getting old I'm exploring options for the future. What are the modern replacements or more important, recommendations, for instant, on demand, hot water using gas to heat the water. For those that worry - our existing boiler is vented into the cockpit, it works off a pilot light but we turn the gas off when not in use.

Jonathan

 

[rotrax]

Very popular on Kiwi boats are 'Califonts' a simple gas hot water heater, often without a flue.

We had one. It had just a heatshield above it and the burner vented into the galley. It supplied instant - well instantish - hot water to the heads sink and shower as well as the galley sink.

When in use for a shower I opened the hatch. For just a bowl of hot water the CO buildup was not significant, it was less than a minute in operation.

It was old, but there are still plenty of newer types on offer as they are popular in less developed countries, the Islands for example.

If you insist on a vented flue type, no doubt they would be available.

 

[Neeves]

Very popular on Kiwi boats are 'Califonts' a simple gas hot water heater, often without a flue.

We had one. It had just a heatshield above it and the burner vented into the galley. It supplied instant - well instantish - hot water to the heads sink and shower as well as the galley sink.

When in use for a shower I opened the hatch. For just a bowl of hot water the CO buildup was not significant, it was less than a minute in operation.

It was old, but there are still plenty of newer types on offer as they are popular in less developed countries, the Islands for example.

If you insist on a vented flue type, no doubt they would be available.

Thanks,

I'm not insisting on a vented flue - but I did not want the thread to cover the dangers of unvented gas appliances - been there done that.

I need to get out more - I was unaware of Califonts.

At the back of my mind was the idea that I thought I had seen small instant gas heaters. Our Bosch unit sits about 1m high and has a 300mm square base. I thought that there might be smaller units made to suit European camper vans and the like and was hoping for user comment.

Jonathan

 

[V1701]

Have a look on canalworld forum, there'll be some threads on there. They all have to have a flue 'cos of the BSS...

 

[rotrax]

No BSS down under sport..................................................

Most instant gas hot water heaters or 'Califonts' are unvented. Thousands in use in Aus and NZ in both campers and boats.

I just searched on the NZ equivalent of 'ebay' the Trade Me site.

69 hits with " Califont gas water heater".

Fill yer boots Neeves

 

[Neeves]

Have a look on canalworld forum, there'll be some threads on there. They all have to have a flue 'cos of the BSS...

Thanks.

I had already recognised that this might be the wrong source for information - most people here rely on the engine to heat water - gas boilers are a bit niche (for yachts). I had thought caravans and motor homes might be the right venue but thought to start my research by asking on YBW (as I do know some members have motor homes).

On venting - I know people here have gas monitors/alarms so venting is an issue. For us its a non- issue - we currently vent out and can think of no conceivable reason not to actively vent out in the future.

I have always been concerned, in general, that hobs and ovens on yachts (as far as I know) are not vented out and found it all slightly contradictory - especially as I recall crude heating techniques being discussed putting an inverted earthenware flower pot over a burner to heat the interior of a yacht in winter. It always seemed a recipe to disaster fo me.

Jonathan

 

[DownWest]

One of the problems is that even a small 'instant' water heater is around 6kw and that needs a lot of ventilation. It was a common problem in Portugal, where deaths from CO poisoning were not unusual. Poor flues and lack of fresh air vents, esp in winter. Electricity was not an option out of town and pretty unreliable anyway back then.

 

[rotrax]

One of the problems is that even a small 'instant' water heater is around 6kw and that needs a lot of ventilation. It was a common problem in Portugal, where deaths from CO poisoning were not unusual. Poor flues and lack of fresh air vents, esp in winter. Electricity was not an option out of town and pretty unreliable anyway back then.

The cooker and oven on our boat are non vented. Probably a bloody sight more powerful than a small Califont!

I have never had a vented cooker on any of my boats. Hired a Willow Wren camping boat on the GU Canal once that had a coal fired Rayburn.

What you say is possible, but the use of instant gas hot water heaters, even when showering, is measured in minutes. Our gas oven will be on tonight for an hour and a half!

Of course CO poisoning is a serious issue.

But not a problem for those who understand and use the kit properly.

 

[vyv_cox]

In UK surveyors hate them, for no justifiable reason. We had one on our GK29, condemned when we sold it. No more dangerous than boiling a kettle but so much more convenient.

 

[DownWest]

The cooker and oven on our boat are non vented. Probably a bloody sight more powerful than a small Califont!

I have never had a vented cooker on any of my boats. Hired a Willow Wren camping boat on the GU Canal once that had a coal fired Rayburn.

What you say is possible, but the use of instant gas hot water heaters, even when showering, is measured in minutes. Our gas oven will be on tonight for an hour and a half!

Of course CO poisoning is a serious issue.

But not a problem for those who understand and use the kit properly.

Yes, but a neighbour got dizzy in their small shower room with the heater in it... Realized something was up and got out quick.
The regs got changed and are now very tight.
As you say, if one understands the situation. But the average bod just uses what's fitted, without understanding that simple mistakes can be fatal.

 

[DownWest]

In UK surveyors hate them, for no justifiable reason. We had one on our GK29, condemned when we sold it. No more dangerous than boiling a kettle but so much more convenient.

Yes, but the average cooker top burner is 2kw? or less on a boat, while as I said, the little gas heaters are 6kw and and one for a kitchen and bathroom double or treble that. They use a lot of gas and the necessary % of air for an efficient burn.
I suspect the surveyor was worried about people shutting up on a cold night and using the heater without enough fresh air. Very similar to student digs in University cities where the 'cosy' gas fire offed them due to poor ventilation.

 

[rotrax]

Yes, but the average cooker top burner is 2kw? or less on a boat, while as I said, the little gas heaters are 6kw and and one for a kitchen and bathroom double or treble that. They use a lot of gas and the necessary % of air for an efficient burn.
I suspect the surveyor was worried about people shutting up on a cold night and using the heater without enough fresh air. Very similar to student digs in University cities where the 'cosy' gas fire offed them due to poor ventilation.

You are talking about large domestic ones. The Califont fitted to our Kiwi boat-a Rinnai IIRC- was nowhere near 6KW. The burner was about the same size as the large ring on the stovetop.

It was a great answer to having convenient hot water at the opening of a tap.

And, as I have said, only on for a few minutes and far away from the curtained shower cubicle. The Hartley 32 had a flush deck, good headroom and a large interior volume. When in use I slid the hatch open six inches or so, unless it was pissing down.

We had no problem with CO tonight - over an hour to cook using the main oven on 180 and both rings for the veg. Force 10 unvented cooker on propane.

I also know the correct burn colour for bottled gas flames and make a point of checking regularly.

 

[thinwater]

The cooker and oven on our boat are non vented. Probably a bloody sight more powerful than a small Califont!...

A common misconception.

The stove and oven, at typical use rates, are about 5,000-8,000 BTH/hr with several burners lit.

The Califont is about 120,000 BTU/hr.

The water heater is about 15 times MORE heat than the stove. This is why ventilation is so critical. Check the maths.

(Can you heat 3 gallons of water every minute on the stove? Not hardly. To heat 3 gpm from 60F to 110F requires 75,000 BTU/hr. A typical stove burner is about 8,000 BTU/hr, or more than 9x less.)

 

[thinwater]

A common misconception.

The stove and oven, at typical use rates, are about 5,000-8,000 BTH/hr with several burners lit.

The Califont is about 120,000 BTU/hr.

The water heater is about 15 times MORE heat than the stove. This is why ventilation is so critical. Check the maths.

(Can you heat 3 gallons of water every minute on the stove? Not hardly. To heat 3 gpm from 60F to 110F requires 75,000 BTU/hr. A typical stove burner is about 8,000 BTU/hr, or more than 9x less. Yup, you can shower in a trickle with less. And hope ho one turns on a tap while you are showering ....)

 

[coopec]

I wouldn't use an unflued gas HWS (or stove) without proper ventilation.

YACHTING WORLD - BOAT VENTILATION


18 July 2021 — There have been 46 carbon monoxide deaths on boats in the last decade, according to the U.S. Coast Guard. But experts Inside Edition spoke with say that number may be higher, because they can often be mistaken for drownings....
How to Recognize the Signs of Carbon Monoxide Poisoning on Your Boat

 

[coopec]

Jon
Have you considered one of these?

Duetto 12V/240V HWS

 

[Neeves]

I wouldn't use an unflued gas HWS (or stove) without proper ventilation.

YACHTING WORLD - BOAT VENTILATION


18 July 2021 — There have been 46 carbon monoxide deaths on boats in the last decade, according to the U.S. Coast Guard. But experts Inside Edition spoke with say that number may be higher, because they can often be mistaken for drownings....
How to Recognize the Signs of Carbon Monoxide Poisoning on Your Boat

In winter, depends on how cold is your winter, most yachts are well sealed. Hatches are closed and people are enjoying the comfort of their diesel heater. Without ventilation there would, or could, be an issue as I'm not aware of any attempts on a yacht to offer ventilation except that provided (ie actively opened) by the owner.

We actually have ventilation ('by accident') as I installed ducting from the anchor/chain locker which, when at anchor, is orientated to catch the air flow. This has a computer fan to force feed the air and was installed to cool the fridge and freezer compressors (we have a separate fridge and freezer). The air heated by this simple modification is then ducted to the engine vents in the transom (another computer fan). The 2 fans are wired to come on when the compressor fans supplied with the compressors come on Our gas boiler flu is vented to the cockpit.

I have wondered when we bake bread of ventilation.

We did once use the oven, don't recall what for, and we ate the resultant meal (maybe roast lamb, or lasagne, cleared up, read books, had a drink or 4 and retired to bed. In the morning I discovered I had not turned the oven off.

The problems, or potential problems, are of higher concern for those who overnight in winter in cold latitudes and others who have poor memories (like me).

It would be interesting to see the geographic location of the deaths mentioned by the US Coast Guard. My guess would be - excludes Florida - where the concern is how to keep the vessel cool.

Duetto - was not aware of it. I'll look and see if there are any independent reviews. It seems small, low volume (compared with instant hot water) and may use a lot of amps....

Jon

 

[Whaup367]

I've seen portable camping showers advertised on a campervan forum:

Kampa Dometic Geyser - Camping Hot Water System LPG Gas

No personal experience but the brand is reputable. 5KW gas power seems a bit light for a shower but it's designed to draw from a bucket of water, so a high flow would be problematic.
Obviously intended for outdoor use.

 

[coopec]

Beware “lethal exhausts” unsuitable for boats - Practical Boat Owner

 

[apogee]

I have a Cointra on my cat, has worked well for five years.