Hot Water Heater

Ignition protection in an electric water heater would be the thermostat. The thermostat would have to be designed to be ignition protected i.e. designed either to not produce a spark or to isolate any spark from potentially explosive vapors.

When thinking of things like ignition protection, I am not concerned with insurance (which would be in force regardless), but with the safety of myself and my family.

Not too long ago, a boat exploded and burned just after being launched at a local boat ramp. Fortunately, the people were able to get off without injury but it could have ended differently if they had been away from land.

RickB said:

Easily done and inexpensive as well:

B3 12A 10 Plate Heat Exchanger 7 5" x 2 9" w Studs Stainless Steel Copper Brazed | eBay

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The unit you refer to is finned, therefore designed to dissipate heat, not collect it and is most likely too small, the same mfg. does have a $250 exchanger but by the time you build a heat trap box around it and add a pump or engineer and build a heat siphon ... well, like I said... you don't.

WesK said:

Ignition protection in an electric water heater would be the thermostat. The thermostat would have to be designed to be ignition protected i.e. designed either to not produce a spark or to isolate any spark from potentially explosive vapors.

When thinking of things like ignition protection, I am not concerned with insurance (which would be in force regardless), but with the safety of myself and my family.

Not too long ago, a boat exploded and burned just after being launched at a local boat ramp. Fortunately, the people were able to get off without injury but it could have ended differently if they had been away from land.

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Ignition Protection



ABYC Definition of Ignition Protection




E11.4.15 Ignition protection - the design and construction of a device such that under design operating conditions:

a. it will not ignite a flammable hydrocarbon mixture surrounding the device when an ignition source causes an internal explosion, or

b. it is incapable of relasing sufficient electrical or thermal energy to ignite a hydrocarbon mixture, or

c. the source of ignition is hermetically sealed


What this means
If gasoline vapour is present in a space all of the electrical equipment in the space must be ignition protected to avoid causing a fire. Unless specifically labelled "Ignition Protected" all electical equipment is assumed to be capable of causing small sparks which can start a fire. Even fuses can cause a fire when they blow unless they are specifically designated as ignition protected fuses. The standard also applies to spaces with CNG or propane in specified concentrations. Ignition protected equipment is specially designed to prevent sparks either because the electrical connections are in a hermetically sealed container or because they have been designed to prevent heat transfer to the atmosphere.

Which is nothing more than a metal screen as in a backfire flame arrestor....the engine still backfires but the flame front is dissipated by the screen...as are the screens on many alternators...

How does a Flame Arrestor Work? - Ask.com

How does a Flame Arrestor Work?


Answer

Flame arrestors work by providing enough surface area to extract energy from the front of flame to extinguish it before it exits flame arrestor.




2 Additional Answers


A flame arrester functions by forcing a flame front through channels too narrow to permit the continuance of the flame. Flame arresters are used to stop the spread of an open fire, to protect explosive mixtures from igniting, and to confine fire within an enclosed, controlled, or regulated location.



A mechanical flame arrestor is filled with metal or ceramic and this absorbs heat from a flashback, quenching it to a temperature below what is needed for ignition.

boatpoker said:

The unit you refer to is finned, therefore designed to dissipate heat, not collect it and is most likely too small, the same mfg. does have a $250 exchanger but by the time you build a heat trap box around it and add a pump or engineer and build a heat siphon ... well, like I said... you don't.

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Would someone care to explain a plate heat exchanger to a surveyor?

FF said:

One concept to avoiding a ruptured tank might be to use a FW pump that has much lower pressure.
And cycle the overpressure valve on the heater tank more often.

Might make the dishwasher or washing machine unhappy but normal living should never notice.

The larger the supply tubing , the easier it is to live with 20 - 30 PSI instead if 55psi.

Be sure to use a rebuildable and adjustable pressure regulator if you run dock side water aboard to the boats FW system.

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I don't think the water pump was the culprit, The pressure might of come from high pressure from the hot water and pressure relieve valve failing, however it worked. The crack in the tank was well oxidized leading me to think the aluminum had weakened due to the welding of the tank. At any rate Seaward didn't sound surprised and suggested the adding a an anode.

boatpoker said:

The unit you refer to is finned, therefore designed to dissipate heat, not collect it and is most likely too small, the same mfg. does have a $250 exchanger but by the time you build a heat trap box around it and add a pump or engineer and build a heat siphon ... well, like I said... you don't.

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That's a plate heat exchanger and is a similar size as the Alfa Laval I have sitting in my shed as a someday boat project. I was going to use it for hydronic heating, but it would work well for hot water too. I like the idea of having a closed circuit on my coolant line as it supplies the turbo jacket.

Northern Spy said:

That's a plate heat exchanger and is a similar size as the Alfa Laval I have sitting in my shed as a someday boat project. I was going to use it for hydronic heating, but it would work well for hot water too. I like the idea of having a closed circuit on my coolant line as it supplies the turbo jacket.

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I bought one similar to what Rick linked...maybe a higher BTU exchange/better quality (I hope) as it was a bit more expensive.

I was nervous about adding a bus heater along with the existing hot water heater so I looped the two of them and now the engine coolant loop is only 2 feet instead of 20+..makes me feel a bit better but I'm not sure that's the application Rick was posting for...

I'd have to think a bit longer on uhow I would use it on a hot water heater without an internal exchanger...sure I can think of a couple ways...just wonder what would work best.

Take a look at these pumps for when you get around to it...mine works pretty well...$50 or so...

Solar Hot Water Pump Run on 12V Battery or Solar Panel Good to 230° F 145PSI | eBay

On most >marine < hot water heaters you can not use a box heater in series with the FW unit.

Many FW heaters attempt to limit the temperature in the water by shutting down the coolant flow.....Much Ungood with an inline heater.

Two parallel circuits is required , an added high volume pump may be required for the box heater as many are 40,000 btu to 120,000btu and need Lots of supply to function .Usually a centrifugal ,as with engine power 10A to move the water is no problem.

FF said:

On most >marine < hot water heaters you can not use a box heater in series with the FW unit.

Many FW heaters attempt to limit the temperature in the water by shutting down the coolant flow.....Much Ungood with an inline heater.

Two parallel circuits is required , an added high volume pump may be required for the box heater as many are 40,000 btu to 120,000btu and need Lots of supply to function .Usually a centrifugal ,as with engine power 10A to move the water is no problem.

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Geez, I am shaking my head ...

"Shutting down coolant flow" ... look at the water heater connections on your engine. I believe 99% of you will see that that water is tapped off in a manner which has zero effect on the engine. How do you think a cab heater works in a vehicle which uses the same engine? Your engine probably has shutoff valves in that loop anyway. Are they part of a self-destruct system? I think not.

The link to the plate heat exchangers shows multiple sizes and ratings.

Installing a plate heater on the engine coolant loop is a no brainer. If you already have connections for a water heating loop, it simply replaces that one. A thermosyphon requires nothing more than a connection to the w/h drain fitting to supply cool water to the hx inlet, and a connection at the hot outlet at the top of the tank for the warm water from the outlet

A temperature limiting or blending valve on the heater outlet ensures there are no issues with boiling water. Your hot water system should have one in any event, it is a safety item.

It doesn't get much more simple and foolproof.

RickB said:

Would someone care to explain a plate heat exchanger to a surveyor?

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The referenced heat exchanger is identical to one on my vessel used for the hydronic heating system. These types of exchangers are and have been used in all sorts of applications for a very long time and conceptually identical to steam radiators used to heat buildings and homes for pushing two centuries,

The heat exchanger is about the size of two packs of cigarettes. It is attached on the engine side "heater" hoses and provides boat heat when cruising with diesel fired boiler off but the hydronic loop pump on..

Interestingly, when at the dock or at anchor and the diesel boiler operating to provide boat boat heat, it will passively heat the shutdown engine quite nicely provided the "heater" valves are open. It could heat a hot water tank the same way, either with the boiler operating or the engine running.

My Torrid hot water tank has the internal engine loop heat exchanger so on that engine I have no need for the plate heat exchanger.

A plate heat exchanger and an old fashioned radiator are completely different and that is how and why plate heat exchangers are so efficient and have replaced shell and tube units in so many applications.

They have all but completely replaced shell and tube coolers on most larger diesels and I notice they are becoming very common on the smaller engines as well.

Notice the big rectangular thing with MTU written on it? That is the end plate of a plate heat exchanger.

The man asked what time it was, he didn't ask how to build a watch.

WesK said:

The man asked what time it was, he didn't ask how to build a watch.

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I personally like the cutaway that shows how the watch functions

HOLLYWOOD

I would say the thread is still on track in that it is furthering possibilities beyond just "replacement units" and explaining/showing how these units/parts can be more efficient of how used within a hot water system.

The nice thing about plate and frame units for industry is there is no size limitation so it can be as big as a bus if needed. The most interesting one I worked with heated/cooled about 1,000 gpm of warm acidic solution so it was very pricey utilizing 904L SS as I recall.

As with the small P&F units Rickb has so kindly posted a picture of here, clean solutions are required or they will plug up. Which means don't let your coolant get too fouled.

sunchaser said:

As with the small P&F units Rickb has so kindly posted a picture of here, clean solutions are required or they will plug up. Which means don't let your coolant get too fouled.

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You'd be surprised how dirty of s fluid can run through them.

It's a fine line to maximize your velocity between plates to increase wall shear stress to reduce fouling and produce high heat transfer coefficients, but keep them low enough to not cause wear due to entrained particles.

I tend to keep a 10% fouling margin and put in strainers if I find the particle size is 50% or more than the plate gap.

Of course the size and hours on a recreational boat, this doesn't matter much.

I do think the fusion and brazed plate technology has gotten to the point where we will see them used in more and more energy saving consumer and domestic applications.

WesK said:

The man asked what time it was, he didn't ask how to build a watch.

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The man said:

"The unit you refer to is finned, therefore designed to dissipate heat, not collect it and is most likely too small... by the time you build a heat trap box around it and add a pump or engineer and build a heat siphon ... well, like I said... you don't."

I simply showed the readership that the man doesn't know what he is talking about and his advice should not be considered by those who believe that "surveyors" necessarily know their bowsprit from their sternpost.

I use a small plate cooler with a thermo regulating valve to transfer heat from my Hurricane heater circulation loop to the potable water system. It works well, it is not an experimental system, and the heat source could just as well be the jacket water of any diesel engine.

DArn it, two more projects to ponder.
-- The exchanger can be used to heat the H.W. tank and the pump to force circultaion of the fresh water so it heats.

-- The pump can be used to force circulation through my diesel stove heat coil and then to heat the fwd. cabin. I'd looked periodically for some thing like this but never thought of a solar source.

T.Y. psneeld and RickB

Poorly worded but I'm lazy tonight

C lectric said:

DArn it, two more projects to ponder.
-- The exchanger can be used to heat the H.W. tank and the pump to force circultaion of the fresh water so it heats.

-- The pump can be used to force circulation through my diesel stove heat coil and then to heat the fwd. cabin. I'd looked periodically for some thing like this but never thought of a solar source.

T.Y. psneeld and RickB

Poorly worded but I'm lazy tonight

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That's OK...much of the time I read these before the second cup of coffee or during happy hour so some posters make sense at all......making a few mistakes is small potatoes....

RickB said:

A plate heat exchanger and an old fashioned radiator are completely different and that is how and why plate heat exchangers are so efficient and have replaced shell and tube units in so many applications.

They have all but completely replaced shell and tube coolers on most larger diesels and I notice they are becoming very common on the smaller engines as well.

Notice the big rectangular thing with MTU written on it? That is the end plate of a plate heat exchanger.

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mtu means more trouble underway,

capt jerry said:

mtu means more trouble underway,

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Good one.

The long term problem with all these setups (excepr the Rheem) is the storage tank has a very finite life.

So however it gets warmed , the HW tank needs replacing on an expensive ,constant basis.

UGH!

Yeah, really expensive ... about the price of 5 or 10 gallons of diesel a year by the time it fails.

FF said:

So however it gets warmed , the HW tank needs replacing on an expensive ,constant basis. UGH!

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The OPs tank is likely 24 years old. For the standard home hot water heater 10 to 15 years is the norm so it appears the OPs boat tank did pretty good.

To me the takeaway here is when buying an older vessel, especially one with an unlined Al tank, be sure you can remove the HW heater without having to tear the boat apart.

Another one "Bites the Rust"

I replaced my prehistoric hot water heater a couple of days ago. I was amazed at how bad of a condition it was in. Fortunately, there was a large spill pan under it which drained into the bilge so there wasn’t any damage to boat. The new one went in pretty easily. We capped off the exchanger lines.

My neighbor suggested I turn it into a thermobaric weapon (fuel/air bomb) and address it to Mr. Putin (oh-oh). KJ

Hi kj
What brand did you replace it with ?
m

It's a Whirlpool from Lowe's. Works great. Put in a new fridge last month. Probably install a new inverter next month.

Don't ya love winter projects? KJ

KJ said:

I replaced my prehistoric hot water heater a couple of days ago. I was amazed at how bad of a condition it was in. Fortunately, there was a large spill pan under it which drained into the bilge so there wasn’t any damage to boat. The new one went in pretty easily. We capped off the exchanger lines.

My neighbor suggested I turn it into a thermobaric weapon (fuel/air bomb) and address it to Mr. Putin (oh-oh). KJ

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I'll see you…and raise you one...as mine, believe it or not, was still working and not leaking, just slow to heat because of grot-filled pipes to and from the cylinder. This affected the new one until I disconnected them and flushed them out - now we get such great hot water, I would never bother with any other method. (Thinking of the other 'hot water on demand' thread.)

The pump can be used to force circulation through my diesel stove heat coil and then to heat the fwd. cabin.

Most ranges only have one or two coils in the fire.

The Antartic has 7 turns in the fire , and does work to heat a modest , insulated cabin .

The Dickinson units are only 16,000 btu at full blast , so the cabin has to be good enough to be heated with 3000 -5000 BTU , check the cold weather cabin heat requirement with a small electric heater.