Tempering Valve Design Assumptions

BigRob

We'll be upgrading our tempering valve in the near future and I'd like to bounce my design off you guys.

The tempering valve is at the very top of the building.

The building is a 12 unit condo building.
We've got about 115 Hunter's curve fixture units: 12 dishwashers, 12 kitchens, 24 full baths with shower/tubs that are mainly used as showers, 6 half baths, and 12 laundry.
Static pressure at the tempering valve output is 45psi and it's at the very top of the building.

The distance from the valve to the highest fixture is down 15' (negative 15').
The largest horizontal distance from the valve to a fixture is 60'.

Running various manufacturer calculators at 20psi drop, I wind up with recommendations in the 1" outlet class with a Cv of around 9 and gpm of 30 for the various tempering valve manufacturers. For example, the Powers SH1432, the Leonard TM-520B-LF-DT, and Honeywell MX128 are all recommended.

When I decrease the pressure drop to 10psi I'm in the 1-1/4" outlet class.

Does this seem like the right ballpark?

hot_rod

What type of expected flow at peak demand, in gpm?

The challenge for a TMV is the ability to regulate at very low flow,as a single faucet, and also regulate at the highest expected flows. Often times a high low assembly is the best choice. A small 3/4 valve for low demand, a larger valve piped with it for full load conditions. Keep an eye on pressure drop at demand flow rates.

The industry is moving towards DMV Digital Mixing Valves.

They offer tighter temperature regulation, wide flow regulation, less required maintenance, ability to work with automation and offer data logging, anti legionella function, and more.

Recirc is simple,balance valves are eliminated, and positive shutoff on the hot side. Today's fast electronics and actuators make this all possible.

Go to PM Engineering.com and watch the webinar that a Todd McCurdy presented last week for info on one of the brands that are currently available

Just looking st that potential load I'd be cautious about a single TMV solution. A hi/Lo thermostatic or DMV maybe worth a look.

BigRob

Generally, work day mornings would be the highest demand. I am thinking maybe 6 showers on at any one time.. call it 15gpm, but can't be sure. Some of the faucets are 0.5gpm.

I looked but could not find his webinar under the webinar section. I would like to watch it.

I'm 100% in on the ETV/DTV and just wanted to confirm my design assumptions. I'm tired of the thermostatic maintenance costs.

The Heat-Timer product looks ok. I see Powers is in the game. I was just pricing out a home build using the Honeywell T775R2001 to modulate the actuator and activate the safety solenoid. I would prefer a 120V floating actuator and 120V solenoid if I was to home brew it- easier to add a UPS, although a springed "normally cold" actuator might eliminate the scald solenoid. Any ideas?

Is Caleffi in the game in the US yet? I prefer Caleffi stuff. It's well thought out and made.

hot_rod

We have a product in the works, not listed yet. The webinar was on the Powers offering. Well presented info. I'll look for the link

BigRob

Why is Powers using all those pressure sensors? Seems like any condition that would cause runaway heat would be picked up by the output temperature sensor.