[RE-wrenches] Pt valves as overheat control

[Glenn Burt]

Radiantec makes a heat dump valve that activates at a temp you set via a
controller that may be a safer way to divert over heated water...
 
http://www.radiantec.com/pdf/End_Uses_of_the_Solar_Energy.pdf
 
pp4
 
-Glenn Burt

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From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Roy Butler
Sent: Tuesday, November 11, 2008 11:15 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] Pt valves as overheat control


Hi guys,

I have been using the SS water loop in my Amish wood cookstove
for my domestic hot water for 9 years now. My tank is a 40 gallon 
electric water heater (space saver unit) and is configured for thermo 
siphon operation.

The P/T valve is all I have for protection and I have to be honest, 
I kind of knew this was probably not a great idea right from the start!

But it works....the valve opens up and discharges into a piping system
located under a raised bed planting area in our attached green house.
So we get the benefit of the 'waste' heat. The valve opens, on average,
about 1 or 2 times a week during the coldest part of the winter.

I replace the P/T valve every other heating season because it does
begin to weep a bit. So that may be what's saved my ignorant butt
from being blown to bits.....maybe.

My question....is there a more robust version of that P/T valve
that I should be using? Something that you would use in a boiler perhaps?

I'm hoping to not have to change the system too much....I love the 
long, guilt free showers....more so because the electricity for the
pump comes from my off-grid hybrid system.

I'm so much better at PV and wind systems....hot water scares me!


Roy Butler

NABCEP Certified Solar PV InstallerR

NYSERDA eligible PV & wind installer 

Four Winds Renewable Energy, LLC

8902 Route 46

Arkport, NY 14807

607-324-9747



www.four-winds-energy.com

www.nationalsolarsupply.com



Although no trees were killed in the sending of this message, 

a large number of electrons were terribly inconvenienced.




Todd Cory wrote: 

Sure, but the discussion was about preventing hot water storage tanks from
exploding. Putting BTUs into a tank, whether that  be from a wood stove loop
or 5 kW electric heating element is not the issue. Relying on a P/T valve to
regulate overheating is of course not a good idea, but it will prevent the
tank from exploding.

Todd



Conrad Geyser wrote: 

Todd,



I'm afraid that any PT valves that I've ever known have continued to weep
indefinitely after one or two overheat triggers.  

I would not recommend relying on them for heat control devices.



Conrad 

Cotuit Solar

NABCEP thermal cert.


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