[Greenbuilding] Fw: Tankless HW and hard water

[Steve Holt]

Hi Aaron:

I'm not a science guru, however I'm a HVAC Tech and I have some practical 
insight into your question. Tankless water heaters perform superbly, 
remembering that you normally get what you pay for.
A coil heater will always fail before a tank type heater in a hard water 
condition. Smaller water passages and higher temperatures around the coil 
cause this to happen. Once the coil becomes partially blocked, the flow is 
reduced further and the problem accelerates. Once the heat exchange is 
burnt, it will normally leak and require replacement. Other problems that 
are associated with a blocked HX, is that heat is reflected back into the 
combustion area, resulting is failing burners, flame safeguards etc.
Deliming and cleaning any coil heater can be a pain, however tankless 
water heater have accessory kits, and sometimes built in fittings to 
facilitate flushing. If you will perform regular maintenance this may work 
for you.
Explore water treatment, and perhaps a high efficiency tank type heater to 
reduce maintenance.


Steve Holt 
416-574-6523



Aaron Lamperti <aaron.lamperti at montshire.org> 
Sent by: greenbuilding-bounces at listserv.repp.org
09/06/2006 10:29 AM

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greenbuilding at listserv.repp.org
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Subject
[Greenbuilding] Tankless HW and hard water






Hi All,

I apologize in advance if this question has received lots of time on 
the list in the past.  I tried to scan the archives and didn't find 
anything.

Does anyone have experience/opinion regarding use of tankless hot 
water heaters with hard water.  A quick scan of internet opinions 
turned up a range of concerns (doesn't it always!).

1.  Shouldn't use tankless because lime will block heat exchanger and 
reduce efficiency
2.  Lime won't form since there isn't a point heat source to boil water
3.  Back flush every (insert time range here) with vinegar to remove 
lime
4.  various filter/softener arrangements

Thoughts?

Thanks!

Aaron Lamperti
Norwich, VT

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