Posted by daestrom on September 3, 2007, 5:27 pm
> wrote:
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> >> > the rather inconvenient temperature that liquid
>> >> > hydrogen requires, it's propensity to leak through near everything,
>> >> > the way it changes materials, it's cost, flammability or explosive
>> >> > nature.
>>
>> >> As the reference indicated, I'm talking about gasous Hydrogen. They
>> >> sell the cylinders in the Yellow Pages, it can't be rocket science.
>> >> Liquid H2 is rocket science.
>>
>> > House builders don't really like installing mains pressure unvented hot
>> > water storage cylinders for safety reasons - or rather the extra
>> > paperwork
>> > required.
>>
>> Might you be talking about the UK?? In the States, most all hot water
>> heates are piped directly to 'mains pressure'. A combination
>> temperature/pressure relief valve provides more than enough safety in
>> just
>> about all cases. The only hot-water cylinder 'explosions' I've ever
>> heard
>> of in modern times have been propane gas leaks and pilot lights.
>>
>> daestrom
>>
>>
>>
>> - Hide quoted text -
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> Agreed, but just one nit. Building codes in the US require the hot
> water tank to have a pressure capacity at least equal to the mains
> pressure, and be equipped with both an approved temperature/pressurue
> release valve with a pressure setting less than the burst presure
> rating of the tank (which is required by law to be stamped on the
> tank's label).
> Also, they are required to be equipped with a pilot light sensor
> (generally using a thermocouple) which turns off BOTH and main burner
> valve and the pilot light gas feed if the pilot light were to be
> extinguished for any reason. The same is true for gas operated home
> furnaces.
Nevertheless, gas hotwater heaters have 'exploded' causing fires. I think
it's not so much the tank bursting from overpressure but a question of
combustible fumes finding the lit pilot light. Probably a misnomer to blame
the hotwater heater, it was only the ignition source. (the 'common
knowledge' not to store flammables in a basement near the heater is
sometimes not so common).
> Some states is the US also require a gas water heater to be equipped
> with a "vacuum breaker" valve on the water feed line, which allow air
> to enter the tank if a negative pressure were to develop in the water
> supply line. This can happen if a fire developes in the neighborhood,
> and the fire department is heavily pumping from nearby fire hydrants.
> In Europe, things are quite different. There the tankless "instant hot
> water" type systems are much more common. I have no idea what
> regulations apply to them, but in fact believe that in a failure mode,
> they could be quite dangerous.
> Here in the US, most hot water tanks fail gradually, by leaking their
> contents all over the floor. This generally happend withing a year or
> two of the tanks warranty expiration. :-)
Yep, been there. Can be extended if you take the time to check the zinc
anode, but most folks don't even know where to look :-)
<snip>
> p.s., Plus, it always happens on a weekend or a holiday!
Aint that the truth!!
daestrom
Posted by News on September 4, 2007, 5:23 pm
>> > House builders don't really like installing
>> > mains pressure unvented hot
>> > water storage cylinders for safety
>> > reasons - or rather the extra paperwork
>> > required.
>>
>> Might you be talking about the UK??
>> In the States, most all hot water
>> heates are piped directly to 'mains pressure'.
>> A combination temperature/pressure relief
>> valve provides more than enough safety in just
>> about all cases.
In the UK they have to be fitted by certified people G3 under building regs.
They also need an annual service if there is burner incorporated or not.
The UK has the highest standard of unvented cylinder protection of any
country and still wants only certified trained people to touch them.
>> The only hot-water cylinder 'explosions' I've ever heard
>> of in modern times have been propane gas leaks and pilot lights.
I know of one that exploded because the pressure vessel failed and the
pressure relief valve leaked. A smart DIYer stopped the leak by capping the
pipe with a compression cap. Kaboom!!!!
http://waterheaterblast.com
> Some states is the US also require a gas water heater to be equipped
> with a "vacuum breaker" valve on the water feed line, which allow air
> to enter the tank if a negative pressure were to develop in the water
> supply line. This can happen if a fire developes in the neighborhood,
> and the fire department is heavily pumping from nearby fire hydrants.
What is wrong with a check valve?
> In Europe, things are quite different.
> There the tankless "instant hot
> water" type systems are much more
> common.
Combis with most being small wall mounted boxes - brilliant for apartments
saving much space. Some are floor mounted Combines the central heating and
instant hot water. Some of them can belt out the flowrates, especially the
floor mounted units. The cheaper wall mounted units are so cheap they are
virtually throw way items. All parts are replaceable, but the cost sometimes
is more than a new unit complete with a guarantee.
> I have no idea what
> regulations apply to them,
> but in fact believe that in a failure mode,
> they could be quite dangerous.
They are full of high limit devices to cut out the burner and a pressure
relief valve.
Posted by News on September 4, 2007, 5:33 pm
>> Here in the US, most hot water tanks fail gradually, by leaking their
>> contents all over the floor. This generally happend withing a year or
>> two of the tanks warranty expiration. :-)
> Yep, been there. Can be extended if you take the time to check the zinc
> anode, but most folks don't even know where to look :-)
In the UK unvented cylinders "tend" to be stainless steel. Look at this all
in one stainless steel boiler and tank-in-tank design - a tank inside a
thermal store:
http://www.acv-uk.com/heatmaster35.htm
Manual:
http://www.acv-uk.com/pdf/HeatMaster%2035-85TC.pdf
The manual explains the operation very well with nice diagrams too. It
always condenses promoting high efficiency.
Here is a Dutch copper design - still very good.
http://www.atmos.uk.com/product_group.asp?section
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>>
>>
>>
>>
>>
>>
>>
>>
>>
>> >> > the rather inconvenient temperature that liquid
>> >> > hydrogen requires, it's propensity to leak through near everything,
>> >> > the way it changes materials, it's cost, flammability or explosive
>> >> > nature.
>>
>> >> As the reference indicated, I'm talking about gasous Hydrogen. They
>> >> sell the cylinders in the Yellow Pages, it can't be rocket science.
>> >> Liquid H2 is rocket science.
>>
>> > House builders don't really like installing mains pressure unvented hot
>> > water storage cylinders for safety reasons - or rather the extra
>> > paperwork
>> > required.
>>
>> Might you be talking about the UK?? In the States, most all hot water
>> heates are piped directly to 'mains pressure'. A combination
>> temperature/pressure relief valve provides more than enough safety in
>> just
>> about all cases. The only hot-water cylinder 'explosions' I've ever
>> heard
>> of in modern times have been propane gas leaks and pilot lights.
>>
>> daestrom
>>
>>
>>
>> - Hide quoted text -
>>
>> - Show quoted text -- Hide quoted text -
>>
>> - Show quoted text -
> Agreed, but just one nit. Building codes in the US require the hot
> water tank to have a pressure capacity at least equal to the mains
> pressure, and be equipped with both an approved temperature/pressurue
> release valve with a pressure setting less than the burst presure
> rating of the tank (which is required by law to be stamped on the
> tank's label).
> Also, they are required to be equipped with a pilot light sensor
> (generally using a thermocouple) which turns off BOTH and main burner
> valve and the pilot light gas feed if the pilot light were to be
> extinguished for any reason. The same is true for gas operated home
> furnaces.