T&P Valve for Vitocell 300H (Model EHC-350) - Does it really need to be 100 psi?

Vito333

My 8 yr old Vitocell 300H tank is leaking at the T&P valve (currently a small trickle). It was installed with Watts LF40XL-8 T&P with set pressure 100 psi. This is virtually impossible to source with ETA from Watts USA to Canada estimated at 8 weeks if it even comes.

If I go with 125psi or 150psi, the LF40XL-8 is much easier to buy. Do I really need to stick with 100psi?

Viessman quoted the replacement part as Viessman p/n 7561002 "T&P Valve (Conbr.) ¾ x 8" 100PSI LL" with an 8 week eta as well. Unfortunately, they cannot tell me the Conbraco p/n .

It seems I don't have many options if I need 100psi.

Please advise. Thanks.

hot_rod

Here is what a tech brochure shows

A common water heater is allowed a pressure relief of 1/2 the test pressure. Tanks are tested to 300 psi, so 150 is acceptable 

Im not sure how Viessmann rates their tanks, or any published test pressure.

125 psi valves were common, and maybe easier to find

you might put a recording pressure gauge on it and see what pressure it runs up to Does it have a thermal expansion tank connected

Vito333

Here is the Viessman doc:
https://www.viessmann-us.com/content/dam/public-brands/ca/pdfs/tanks/vitocell-h_300_tdm.pdf/_jcr_content/renditions/original./vitocell-h_300_tdm.pdf

On page 10:
Temperature and pressure relief valve
A temperature and pressure relief valve (T&P relief valve)
is supplied with the tank. The heating contractor must
install the valve on each tank in a method meeting code
requirements. If local codes require a different relief valve,
substitute the manufacturer’s supplied valve. The tank is
approved for 100 psig where a CRN is required. Maximum
operating pressure is 150 psig.
For steam applications, a field supplied 1” T&P valve must
be utilized

T&P Valve set pressure: 150 psig
ASME pressure steam rating: see ratings marked on the T&P valve
CSA discharge capacity: 205 MBH
Relief temperature : 210°F (99°C

------------------------------------------

Not sure how to interpret as a layperson with respect to the suitability of using a T&P above 100 psi because it is stated in terms of psig.

Larry Weingarten

Hi @Vito333 , Are you in Canada? It turns out that the CRN means Canadian Registration Number: https://www.pveng.com/home/canadian-registration-number-crn/introduction-and-faq/# It would not apply to you unless you're in Canada. I'd probably still go with the 125 pound valve.

Yours, Larry

Vito333

Larry Weingarten said:

Hi @Vito333 , Are you in Canada? It turns out that the CRN means Canadian Registration Number: https://www.pveng.com/home/canadian-registration-number-crn/introduction-and-faq/# It would not apply to you unless you're in Canada. I'd probably still go with the 125 pound valve.

Yours, Larry

Yes, I am in Canada. I just checked the paper manual for my Vitocell H 300 and it says:

"The T&P relief valve supplied with the tank is manufactured by Watts Industries (Model 40XL-8) set to 100 psi for Canadian installations and set to 150 psi for US installations (where applicable). The valve is ASME pressure steam rated for 998 MBH and CSA temperature steam rated for 200 MBH. It is tested under ANSI Z21.22 code for Relief Valves and Automatic Gas Shut-off Devices for Hot Water Supply Systems. The relief temperature is set at 210°F / 99°C. "

Not sure why 100 psi for Canada and 150 psi for US. Is this more of a regulatory issue rather than a design constraint? Does this confirm that it is ok for me to use 150 PSI despite being in Canada?

hot_rod

There are different requirements under the CRN
listings
If the tank was manufactured in Europe there may be a handful of other Euro listings 

Sometimes 
it changes in the BAR to psi conversion

Mad Dog_2

If it's not doing any damage, another option is waiting for the right one?? Mad Dog 🐕