The Holby Valve and multiple domestic HW temps

Mad Dog_2

Someone had asked about doing this a few months ago, but I just dug out the picture from my archives. This was around 2013 in a NYC School.  If I remember correctly the 3 temps were
120, 110, 105.  It was a NYC School Construction Authority Sec.  This spec is the last bastion of Old School Plumbing: All underground must be lead and oakum!  I was in my glory.  The SCA plumbing inspectors hold your measurements to 1/4"...YES!  That fussy....Mad Dog 

Big Ed_4

The Hobie mixing valve needs to be heat trapped

Mad Dog_2

Put in many...never a problem...Mad Dog 

Big Ed_4

Check out the paper work from the manufacture .

Mad Dog_2

I've seen the same drawings, Ed.  May have done a heat loop once or twice, until my foreman told us it was a waste of time and materials in most cases. I found him to be right.  I've  Very rarely seen one installed in almost 40 years running in and out of NYC Basements. Unnecessary waste of piping in most cases.  I've seen the same heat trap drawing on some water heaters and indirect over the years too.  Never a problem.  Mad Dog 🐕 

Big Ed_4

The diagram was for a recirculation line , The cheaper 1/2" Hobie recommended a trap on the hot water in supply . The migration of heat would cook the bulb . Did they change ? I went over to Taco years ago . Just what remembered to help out ...

hot_rod

Big Ed_4 said:

Check out the paper work from the manufacture .

Wouldn't a check at the cold inlet accomplish the same thing?

Interesting T&P location, must have a 16" long temperature probe Good spot for a float air vent though.
The probe needs to poke in to the top 1/3 of the tank.

If that valve doesn't have 100% cold shut off it would be prone to temperature creep piped like that, especially with constant circulation. During low or no use you end up with warm water at the cold port of the mix valve and it loses its mind and overshoots to tank temperature.

It's our most common tech support question, "why does my thermostatic valve over-shoot?"

Larry Weingarten

Hi, Maybe it's just a hard water problem that mixing valves get limed up when they see hot water all of the time. I've had lots of valves get stuck open in my area. I wonder about calling out 27" deep for the trap. I've found six inches works pretty well most of the time.

Yours, Larry

Mad Dog_2

I agree Larry.  I rarely see Ghost flow or unwanted hot water migration with the Holby Valves.  I see many that are VERY old (piped in Red Brass)  and still working perfectly.  Mad Dog 🐕 

DanHolohan

Did any of you ever meet Arthur Brown?  He developed the valve. Passed on in 2007, at 99 years. A true New Yorker. 

Mad Dog_2

No...but I've heard of him . Holby was on like 2nd Ave Midtown Manhattan up to a few years ago.  Mad Dog 🐕 

JohnNY

I've always questioned the necessity of a heat trap loop on a system with constant recirculation. In fact, I don't use the trap where I know there will be near constant flow. Throw an aquastat or a timer on the pump and I add the loop.

hot_rod

I think the concern is periods of no demand, as such no cold entering the valve, and the potential for hot to rise up to the valve. Not so much recirc flow?

Their manual describes the cause of creep and droop, but I don't see their piping correcting it without two valves? Looks like a 2020 rewrite?