Differences between pressure-only relief valves?

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Sluggo

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I'm going to be installing a tankless water heater for a small bathroom and will be installing a Watts LFTWH-FT-HCN Service Valve Kit with the heater:

Watts1.JPG

The hot water valve has a port for a pressure relief valve, and although the manufacturer of the tankless water heater says a pressure relief valve is not required, I'm going to put one in anyway. The appropriate Watts valve, which I haven't been able to find locally, is a Watts 3L 150 PSI:

Watts PRV.JPG

I did find a similar Zurn Wilkins pressure relief valve locally -- a P1000A -- that has the same pressure spec:

Wilk.JPG

I assume these two valves are basically about the same function-wise and quality-wise. Am I missing anything here, or can I use either one of these valves in my setup?
 

DonL

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If you look close at the spec some valves Do Not not comply with ASME requirements/Not Listed and are not certified by CSA.

And most likely say Made in China.

Even tho they both may work.
 

Sluggo

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DonL-
Thanks for the response. Here is the tag from the top of the Zurn Wilkins valve and it appears to address the spec issues you raised. It lists CSA, ASME, and ANSI:

ZW.jpg
 
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Sluggo

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It has a 200,000 btu rating. Is that more than the tankless water heater's input?

hj-
Thanks for pointing that out. I checked and the water heater is 18 kw, which I calculate to be about 61,000 Btu/hr. So it looks like I'm well within specs on that.
 

Tom Sawyer

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hj-
Thanks for pointing that out. I checked and the water heater is 18 kw, which I calculate to be about 61,000 Btu/hr. So it looks like I'm well within specs on that.

It would be good to understand the relationship between pressure and temperature. Its a tankless heater. It doesn't need a pressure relief valve so don't install one unless you like wasting time and money.
 

hj

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quote; Its a tankless heater. It doesn't need a pressure relief valve so don't install one unless

EVERY tankless heater i have installed came WITH a pressure relief valves and the inspector insisted that it be installed. Some even want a T&P valve in case the heater goes wild.
 

DonL

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Seems to me that just killing the heating power would be better, than a pop off.

If you have a Over Pressure, and the Valve opens, Because of controller failure, then you get Hot water instead of cold.


That is what I think ? I was wrong before.
 

Sluggo

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As I mentioned in my initial post, the manufacturer says that a pressure relief valve is not needed (the circuitry is supposed to shutdown the unit if the water is being overheated). However, being a belt and suspenders type, I asked if there was a downside to installing a pressure-only valve if the circuitry failed, and was told "no."
 

DonL

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As I mentioned in my initial post, the manufacturer says that a pressure relief valve is not needed (the circuitry is supposed to shutdown the unit if the water is being overheated). However, being a belt and suspenders type, I asked if there was a downside to installing a pressure-only valve if the circuitry failed, and was told "no."


There should be no problem installing one.

Redundancy can be a good thing.


Good Luck.
 
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