Fun with Water Heaters!

[chala]

I suppose you will also install an insulated thermal anti syphon.
I keep the non return valve it will prevent the heater element burning out if there is a leak on the feed line and some one open the hot water tap and drain the tank.
If you also need to heat up the boat the higher the set point the better.

[captain58sailin]

Thanks Christian,
I ordered a set solar powered hot water plans off the net. I would think one could set up a heat exchanger under existing solar panels and get good hot water, then use the onboard hot water tank as a storage unit. We used to heat our water by running a short coil through the wood stove and the hot water heater was never wired in, it only served as storage, 30 minutes after the wood stove was fired up we had unlimited hot water. I should think the solar panels would serve the same purpose.

[Cheechako]

nice job! but why do you need all that again? all my boats just had a hose barb......

[s/v Jedi]

About the temperature... it should be above 70 degrees inside the hot lines when they are infrequently used; it is always done in Europe where thermostat equipped mixing valves are used at the faucet when scalding is considered a risk. It will not be a problem when you use hot water frequently though. When you leave the boat for some time and come back, never flush the lines using a shower head. The mist carries the bacteria and this is how 32 people died during a bathroom-show in Holland.

Cowboy: Geyser is from Dutch but in Holland it is a propane instant water heater. The water heater with electric element is called a boiler in Holland... nice and confusing ;-)

A water heater or geyser or whatever should always be set well ABOVE 120F, at least at 158F. It is the hot water lines from the heater to the faucet that can go lower. Also, when using a heat exchanger, it'll get hotter anyway.

cheers,
Nick.

[ggray]

GordMay said:
"Yes. Asco, IPV, and others make Two-Way Solenoid Valves (/w 12VDC coil), suitable for domestic hot water use."

Thanks Gord. I'll keep these companies in mind.

[scotte]

Originally Posted by Cheechako

nice job! but why do you need all that again? all my boats just had a hose barb......

Yeah, I'm kind of wondering about that myself. I need to replace our hot water heater - the current one doesn't have any of this stuff, and quite frankly I don't see the need...

[GordMay]

Originally Posted by s/v Jedi

About the temperature... it should be above 70 degrees inside the hot lines when they are infrequently used; it is always done in Europe where thermostat equipped mixing valves are used at the faucet when scalding is considered a risk. It will not be a problem when you use hot water frequently though. When you leave the boat for some time and come back, never flush the lines using a shower head. The mist carries the bacteria and this is how 32 people died during a bathroom-show in Holland...

Basic Rules to prevent the proliferation of Legionella

Keep the system clean: Flush the system after initial installation and after any work has been carried out on the system.
Check and clean line strainers as required by site conditions.
Change fine (less than 80 microns) filters as recommended by the manufacturer.
Keep expansion vessels and shock arresters correctly charged.

Water temperatures are critical:
Keep cold water below 20̊C (68̊F) maximum
Keep stored hot water above 60̊C (140̊F) minimum
Keep the return temperature of a secondary return system above 50̊C (122̊F) minimum

In March 1999 one of the largest outbreaks of Legionnaires' disease since the first described outbreak in Philadelphia (1977) occurred in the Netherlands. The outbreak originated at the Westfriesian Flora, an annual flower show combined with a consumer products exhibition, held February 19-February 28, 1999. The flower show was visited by 77,061 persons, and Legionnaires' disease developed in at least 188 (at least 32 died).

The outbreak was associated with a contaminated whirlpool spa. A water sample from one of the whirlpool spas, in the consumer products show, was positive by PCR for Legionella pneumophila; but legionella could not be cultured.

All Legionella bacteria are normal environmental organisms that are part of virtually every fresh-water aquatic habitat (although at low concentrations). They have special abilities to grow inside of free-living amoebae and other protozoa in these environments. Disease occurs when conditions in building water stimulate the growth of Legionella to high numbers*.

Legionella are then transmitted to humans via contaminated aerosols from these aquatic habitats associated with building water. The three most common sources of transmission are domestic hot water systems, cooling towers, and heated whirlpool spas. However, other sources have been observed, such as indoor decorative fountains, grocery store vegetable misters, and even potting soil.

* Legionella thrives in warm environments 25 to 45 ̊C (77 to 113 ̊F).
According to Reliance**,
Temperature affects the survival of Legionella are as follows:
* 70 to 80 ̊C (158 to 176 ̊F): Disinfection range
* At 66 ̊C (151 ̊F): Legionellae die within 2 minutes
* At 60 ̊C (140 ̊F): Legionellae die within 32 minutes
* At 55 ̊C (131 ̊F): Legionellae die within 5 to 6 hours
* Above 50 ̊C (122 ̊F): They can survive but do not multiply
* 35 to 46 ̊C (95 to 115 ̊F): Ideal growth range
* 20 to 50 ̊C (68 to 122 ̊F): Legionellae growth range
* Below 20 ̊C (68 ̊F): Legionellae can survive but are dormant
➥** Reliance World Wide

[Christian Van H]

Originally Posted by scotte

Yeah, I'm kind of wondering about that myself. I need to replace our hot water heater - the current one doesn't have any of this stuff, and quite frankly I don't see the need...

You dont "need" any of this stuff, just as you dont need pressure water. The tempering valve simply mixes cold water with your (much hotter) hot to s-t-r-e-t-c-h your hot water supply... something you think about when you have a bath tub aboard. The one way valve was recommended by the manufacturer, however it may not be necessary, as Jedi pointed out. The rest of the stuff is just to make plumbing the other two possible...

[witzgall]

I installed one of those sensormatoc pumps a few months ago. It works brilliantly.

Chris

[Cheechako]

"Yeah, I'm kind of wondering about that myself. I need to replace our hot water heater - the current one doesn't have any of this stuff, and quite frankly I don't see the need..."
I think it's the legal world trying to keep us from being responsible for our own safety again... frankly I never found it an issue even after motoring for most of a full day. My tap water at home can be pretty hot if I dont mix in some cold also... I guess I'm just a KISS person.... It is a work of art though!

[s/v Jedi]

Gord,

Well, I had the number of 32 people dying right and it -was- a bath/spa thing that caused it... but only your post made me remember it was a show for flowers, not bathrooms like I wrote ;-) I'm still wondering why a bath was at a flower show...

Anyway, it was bad and it's always in my mind when I switch the water heater on. We mix water at the faucet, which saves just as much hot water as when mixing at the heater and the idea that all the bacteria get killed when that 90C hot water runs through the system is what I need ;-)

The thing is that liveaboard cruisers won't have a problem with this but when you use your boat for weekend / holiday sailing it's a different game and well worth keeping this nasty killing bacteria in mind when flushing the lines every weekend.

cheers,
Nick.

[chala]

Quote:
“When you turn off the pump, you don't get hot water from cold faucet. You only get hot water when you open up the hot-water line (or hot faucet). The hot water doesn't run back out the heater's inlet because there's nothing coming into it's hot-output (vacuum).”
Nick.
Your vacuum theory holds true only if no air can enter the system. In most cases of a failure of the system, air will be able to enter the system and the system will drain. Also the omission of a non-return valve will prevent the thermal expansion valve from operating properly. A non-return valve is mandatory which is why I suppose the valve was supplied in the first instance. To save space, often the approved isolating valve incorporates a non-return valve. (pic.1)
A pressurized electrical water heater going wrong and exploding can destroy a house or a boat.
For the above reason a pressurized electrical water heater should have at least the 3 following safety features:
A fail proof thermostat, which should open both Active and Neutral or short circuit the electrical supply. (pic.2)
A fail proof thermal expansion valve. (pic.3)
A fusible plug fitted to the vessel of the water heater.
Many countries require the installer of water heaters to be licensed and installing a pressurized water heater not knowing what to do is an accident waiting to happen.

[chala]

If Legionella is still a concern, here is some more information.

[s/v Jedi]

Originally Posted by chala

Your vacuum theory holds true only if no air can enter the system. In most cases of a failure of the system, air will be able to enter the system and the system will drain.

Exactly, that's what I called "open up the hot-water line". However, this will cause the system to drain at the point of failure. The waterpump will keep the pressure up and that pressure will be the highest pressure in the system (the line is open to the atmosphere during failure).

So, let's look what happens when a hot water line starts leaking: the fresh water pump will try to keep pressure up so all hot water will flow out of the burst. The checkvalve is irrelevant to this mode of failure.

Next is a leak in the cold water line: the fresh water pump will try to keep pressure up so cold water will flow out of the burst. Without a checkvalve, hot water from the heater will only backrun into the cold line until the pressure inside the waterheat is down to the same level as that of the pump. Vacuum in the hot water line prevents it from further discharge. Apart from a small amount of hot water (from the coldest part from the tank), a checkvalve is irrelevant to this mode of failure too.

However, if we start to perform maintenance on the system, we might open up both hot and cold water lines with the pump switched off. When the pump is switched off, we enter a new game. Now, the hot water can flow back into the cold lines. But a closed valve at the hot water output of the heater prevents that as good as a checkvalve. Also, checkvalves tend to fail over time and have no visual sign of proper operation, making this less safe than a hand operated ball valve.

Also the omission of a non-return valve will prevent the thermal expansion valve from operating properly.

Pls. elaborate. My view is that the thermal expansion valve protects the tank against too much pressure and will provide that protection regardless of a checkvalve. The only difference is that without a checkvalve, the whole system is at the same pressure while a checkvalve partitions the system and the tank + hot water lines can have a higher pressure than the cold water lines. The primary function of the expansion valve is to protect the tank and that mode of operation isn't affected by having a checkvalve or not.

Also, the waterpump has a checkvalve so the water can't run back into the tank.

A pressurized electrical water heater going wrong and exploding can destroy a house or a boat.

Pls elaborate. The tank will only explode when it's internal pressure becomes higher than it's designed maximum. Even with a checkvalve (which still works) installed, the hot water lines and faucets are at that same pressure level. Before the tank explodes, the thermal expansion valve opens and reliefs the pressure. No explosion and no destroyed boat.

In short: the checkvalve does not prevent explosion or enable the relief valve to work. The relief valve (thermal expansion valve) works on pressure.

Many countries require the installer of water heaters to be licensed and installing a pressurized water heater not knowing what to do is an accident waiting to happen.

The only major accidents I am aware off are caused by propane water heaters.

cheers,
Nick.

[JiffyLube]

Originally Posted by s/v Jedi

About the temperature... it should be above 70 degrees inside the hot lines when they are infrequently used; it is always done in Europe where thermostat equipped mixing valves are used at the faucet when scalding is considered a risk. It will not be a problem when you use hot water frequently though. When you leave the boat for some time and come back, never flush the lines using a shower head. The mist carries the bacteria and this is how 32 people died during a bathroom-show in Holland.
cheers,
Nick.

If a person does not use the shower for some time, and the shower line is not flushed because of the possible risk of infection, are you saying that the shower can now never be used again? I think that the shower line can be flushed with hot water, with the shower head directed 'into' the head sink in a matter that will not produce mist.