[RE-wrenches] Pt valves as overheat control

Chris Meier chrism at unirac.com
Wed Nov 12 08:00:05 PST 2008


	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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-----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: Tuesday, November 11, 2008 8:24 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Pt valves as overheat control

Hi Drake,

I don't know if you ever watch Myth Busters, but google them and check  
out the water tank they exploded.

Short version is they took a standard 40 gallon electric tank, put  
into a small building, no PT valve, heated it until it exploded.
It flew something like 200' into the air, just amazing and super scary  
to see.  I'm with Jeff, I'd put a second in just for safety.

jay

peltz power
On Nov 11, 2008, at 4:40 PM, Drake Chamberlin wrote:

>
> At 09:15 AM 11/11/2008, you wrote:
>> 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 not really a hot water guy either, but I'm scheming on putting  
> in solar hot water with a wood stove backup loop.  I was thinking of  
> using a valve from a dishwasher or washing machine.  They are  
> electrically controlled, and designed to take hot water straight  
> from the tank.  Control the electric valve with an aquastat.  If  
> there is no place to thread the aquastat into the tank, it would be  
> more difficult, but still possible with a bit of plumbing.  For sure  
> the T/P valve would be needed for whenever the power went down.
>
>
> Drake Chamberlin
> Athens Electric
> OH License 44810
> CO License 3773
> 740-448-7328
> 740-856-9648
>
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