[RE-wrenches] Pt valves as overheat control

[Chris Meier]

	I have been at Trane testing facility to see a live display of
what can happen. That is why I am very concerned about using a T/P as a
controller. The main issue is the conversion of water from liquid to
vapor. Under pressure water will absorb heat but change state. As soon
as the pressure is relieved by the tank splitting or a faucet turning on
all of that  super heated water converts from liquid to vapor in an
instance the rapid expansion is the cause of the explosion.

	So by building a primary control system that can open below the
boiling point by using a zone valve or bi metal temp valve you can stop
the pressures from happening then use the T/P as the safety to that.

	Again most safety device are not designed to be cycled on or off
just fail at the right time. A while ago at Trane they would test 5000
high temperature limit switches to see if they would fail at 180 degrees
+- but out all of the test they never checked the same switch twice. But
control switches are cycled thousands of times.   

Chris Meier

Product Manager

UniRac, Inc.

1411 Broadway Blvd. NE

Albuquerque, NM   87102-1545

Ph:  505-242-6411 

Fx:  505-242-6412

Email:  chrism at unirac.com 

Web:   http://www.unirac.com

 

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-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of jay
peltz
Sent: Wednesday, November 12, 2008 9:35 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] Pt valves as overheat control

Hi Chris,

Here is the mythbusters video.

http://www.youtube.com/watch?v=JmJoyuUJj2Q

jay
peltz power
On Nov 12, 2008, at 8:00 AM, Chris Meier wrote:

> 	Please do not forget any safety device in HVAC or plumbing is
> not designed to cycle open and close as a controller. They are  
> designed
> to fail and in a lot cases they are designed to fail once. After the  
> T/P
> opens it may never really reset which is ok because it will leak but  
> the
> P/T could also loss the calibration which means they can stay closed
> even if they should be open. In many cases this means the house is
> leveled when the explosion happens.
>
>
>
> Chris Meier
>
> Product Manager
>
> UniRac, Inc.
>
> 1411 Broadway Blvd. NE
>
> Albuquerque, NM   87102-1545
>
> Ph:  505-242-6411
>
> Fx:  505-242-6412
>
> Email:  chrism at unirac.com
>
> Web:   http://www.unirac.com
>

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