Tampering valve for older building

samstu

Hi all,

Working on an older building (10 units) and the dhw is supplied by a steam boiler coil. The mixed water temperature fluctuates all over the place, leading me to believe that the old tampering valve needs to be replaced. However, I spoke to a very helpful person at one of the tampering valve manufacturers and they said (as I understood it) that since the building has no hot water return piping and no recirculating pump, at times of no flow (i.e. no usage), the hot coil water (which can reach highs of 212) will heat the whole mixing valve and it will be ruined in a couple months. His suggestion was to possibly install a “fake” return line from the furthest point in basement that has a dhw line and install a pump on that line, with the purpose of creating flow through the mixing valve which will keep cold and tampered water at the mixing valve.

Any thoughts on the above? Many of these older buildings don’t have return lines or pumps on the dhw lines, what is traditionally done to keep water at 120 in these buildings?

Steamhead

What kind of tempering valve is there now?

EBEBRATT-Ed

I tend to agree with what they told you.

With no draw on the DHW the water in the coil will be at the steam temperature which will vary with the steam pressure say 212 deg.

At the same time with no draw the water in the hot water supply pipes will be at basement temperature 60 deg?

It's asking the mixing valve to do a lot of fast reaction.

Using a return line and constant circulation will smooth out the operation.

I would think it would extend the life of the mixing valve. Based on using a seft contained thermostatic valve

samstu

Steamhead said:

What kind of tempering valve is there now?

Watts, I'm not sure on the exact model.

EBEBRATT-Ed said:

I tend to agree with what they told you.

With no draw on the DHW the water in the coil will be at the steam temperature which will vary with the steam pressure say 212 deg.

At the same time with no draw the water in the hot water supply pipes will be at basement temperature 60 deg?

It's asking the mixing valve to do a lot of fast reaction.

Using a return line and constant circulation will smooth out the operation.

I would think it would extend the life of the mixing valve. Based on using a seft contained thermostatic valve

I'm just so curious how all the other buildings in NYC do it without return lines and circulation pumps? How was it done for the past 100 years?

Steamhead

What kind of tempering valves do they use- Holby?

EBEBRATT-Ed

@samstu

I am not saying it won't work without a circ pump and a return line, of course it will, but you talked with the mixing valve mfg. (or rep) and they gave you their advise which I tend to agree with.

So you have a choice, take their advise or not.

They know their equipment better than you or I

mattmia2

What about moving the tempering valve further from the boiler and putting a flow check in the line from the boiler so it would only see boiler temp water on the hot side when there was demand?

hot_rod

If it is a listed valve ASSE 1017 for example it is rated and actually tested with 212F at the listing agency

Solar rated valves are rated a bit higher inlet, but a limited selection.

Putting some piping distance between valve and supply will help

Also look at EMV electronic mix valves. The Caleffi Legiomix is a basic 3 way ball valve with actuator. No worry about wax motor or bimetallic element damage

samstu

> @Steamhead said:
> What kind of tempering valves do they use- Holby?

I’m sorry I don’t understand, who’s they?


> @EBEBRATT-Ed said:
> @samstu
>
> I am not saying it won't work without a circ pump and a return line, of course it will, but you talked with the mixing valve mfg. (or rep) and they gave you their advise which I tend to agree with.
>
> So you have a choice, take their advise or not.
>
> They know their equipment better than you or I

Makes sense, just trying to figure out an alternative to reinventing a setup that supposedly worked all these years in many buildings.




> @mattmia2 said:
> What about moving the tempering valve further from the boiler and putting a flow check in the line from the boiler so it would only see boiler temp water on the hot side when there was demand?

Very interesting, my concern would be though that on demand the tampering valve would suddenly be hit with much higher temp water and wouldn’t be able to adjust fast enough.


> @hot_rod said:
> If it is a listed valve ASSE 1017 for example it is rated and actually tested with 212F at the listing agency
>
> Solar rated valves are rated a bit higher inlet, but a limited selection.
>
> Putting some piping distance between valve and supply will help
>
> Also look at EMV electronic mix valves. The Caleffi Legiomix is a basic 3 way ball valve with actuator. No worry about wax motor or bimetallic element damage

Very interesting information thank you. Anything special about solar rated valves that would cause an issue in a steam/coil system?

Steamhead

samstu said:

> @Steamhead said:

> What kind of tempering valves do they use- Holby?



I’m sorry I don’t understand, who’s they?

The other buildings you mentioned.......... I'm assuming you've seen their equipment?

Intplm.

"Older"or "Newer" building really shouldn't matter.
If the mixing valve cannot maintain temp. It's more than likely the mixing valve.
Go to the nearest HW fixture and run the HW. If it is fluctuating as you describe, go ahead and then try the farthest hot water fixture (if for nothing but peace of mind cause the closet fixture should be enough). If it fluctuates you have your answer.
The mixing valve needs to be replaced.

hot_rod

If the valve was accurate in the past it may just need a rebuild?
It is almost impossible for a large valve like that to be accurate at very low flow rates. id ask tenants if it ever controls accurately
Check the spec it may need 4 gpm or more to regulate accurately. Usually a building like that would have a hi-low, a small and large valve piped parallel. The small valve would handle low, 1/2 gpm flow the larger for flow over 4 gpm
It looks mid applied to me?

https://www.caleffi.com/sites/default/files/file/idronics_11_na-r2.pdf

hot_rod

Better examples of hi-low

https://www.caleffi.com/sites/default/files/coll_attach_file/idronics_22_na.pdf

Be very careful of leaving your name and fingerprints on a valve that could potentially scald someone, that could be a huge liability issue with temperatures you mentioned

samstu

I think I found a solution. Honeywell MX Series is rated up to 221F (bottom of table 1) and the product literature shows a setup without recirculation lines. (Figure 3 in the attached).

Install/Spec sheet:

https://customer.honeywell.com/resources/Techlit/TechLitDocuments/38-00000s/38-00035EFS.pdf

Steamhead said:

What kind of tempering valves do they use- Holby?

-Good point, I should try to get into some other basements and look around Holby literature requires a return line and circulation pump.

Intplm. said:

"Older"or "Newer" building really shouldn't matter.
If the mixing valve cannot maintain temp. It's more than likely the mixing valve.
Go to the nearest HW fixture and run the HW. If it is fluctuating as you describe, go ahead and then try the farthest hot water fixture (if for nothing but peace of mind cause the closet fixture should be enough). If it fluctuates you have your answer.
The mixing valve needs to be replaced.

-True, just seems that a lot of manufacturers are taking for granted that there is a return line, which I guess wasn't so common 100 years ago.

hot_rod said:

If the valve was accurate in the past it may just need a rebuild?

It is almost impossible for a large valve like that to be accurate at very low flow rates. id ask tenants if it ever controls accurately

Check the spec it may need 4 gpm or more to regulate accurately. Usually a building like that would have a hi-low, a small and large valve piped parallel. The small valve would handle low, 1/2 gpm flow the larger for flow over 4 gpm

It looks mid applied to me?



https://www.caleffi.com/sites/default/files/file/idronics_11_na-r2.pdf

-I'm honestly not sure that it performed consistently in the past...The replacement I have in mind requires only 1 GPM minimum flow.

mattmia2

100 years ago if you had running hot water at all, it came from a coil or tank in a cookstove

BigRob

The watts/powers large valves have interchangeable parts. You can turn a hi valve with 4gpm recirc requirement into a hi/lo with 0.5 gpm recirc requirement. Not sure it’s worth it but just a FYI.

hot_rod

If you are looking at the 1" size, it is a 4 Cv valve. With 10 units flowing maybe 30 gpm at peak time, here is what a 30 gpm flow looks like in a 4 Cv valve, 56 psi pressure drop! Excel sheet example.

That is why a hi-low is a better option. Our electronic mix valve EMV.

Accepted engineering practice in no more than a 20 psi drop, 20∆P in a plumbing valve, so about a 13 gpm flow would be suggested max for that valve.

Here its what Caleffi LegioMix looks like with a full port 3 way ball valve design. The 1" size has a 21 Cv max flow of 94 gpm.

samstu

hot_rod said:

If you are looking at the 1" size, it is a 4 Cv valve. With 10 units flowing maybe 30 gpm at peak time, here is what a 30 gpm flow looks like in a 4 Cv valve, 56 psi pressure drop! Excel sheet example.

That is why a hi-low is a better option. Our electronic mix valve EMV.

Accepted engineering practice in no more than a 20 psi drop, 20∆P in a plumbing valve, so about a 13 gpm flow would be suggested max for that valve.

Here its what Caleffi LegioMix looks like with a full port 3 way ball valve design. The 1" size has a 21 Cv max flow of 94 gpm.

Yup, I was considering the 1" in order to get down to 1GPM minimum flow. I counted 30 fixture units and using Curve C I arrived around 13-14 GPM? And I understand that even the modified hunter curve is outdated with the newer lower flow fixtures? I can't get this to run on my system but came across this:

https://www.iapmo.org/water-demand-calculator/

Appreciate all the help by the way, thank you!

samstu

@hot_rod I wish I could get an electronic mixing valve in there but apparently it's not in the budget...

hot_rod

The valve will struggle at a single lav or kitchen flow to be accurate but that may not be a common condition. 14 gpm would be acceptable thru a 4 Cv valve. Here is the pressure drop at 14 gpm thru the valve.

If the need ever arises the LegioMix is actually less $$ than a hi-low station and you get legionella protection option if the building has a recirculation loop.

samstu

@hot_rod thank you, but it seems that the Legiomix also requires a minimum flow (except if there's a recirculation line and pump at least equal to the minimum flow rate) ?

hot_rod

All mixing valves will have a minimum flow, no way around that.

All mix valves will work below that minimum, but temperature accuracy goes south and it cannot meet the listing requirement accuracy

I suspect people just get used to that small temperature variation not knowing it can be eliminated with properly sized parallel valves. That is why hi lows are used.

As long as that temperature variation does not get to high to scald a child or cause a liability issue. Setting a high hot water temperature on the tank increases the scald potential

I just worry when budget $$ overide public safety. I would let the owner know of the concern in writing.

Was a time when folks understood radiators got hot and water could scald, those days have passed us by. Now a days it’s everyone’s fault except the person turning on the faucet.

FortyTwo

I have this exact issue at a few apartment buildings and need to bring the temperatures down after the mixing valves and keep them more consistent. I can't afford the expensive electronic mixing valves but insurance companies are pushing hard on bringing water temperatures down and the current mixing valves aren't doing the trick

I don't fully grasp the fake circulator loop concept - can anyone point me toward any diagrams, examples, or reexplain it so maybe I can understand and implement it?

Would I tee off a tempered water line in the basement, and feed it back into the tempered water line above the mixing valve, with a circulator pump that is activated/deactivated based on a temp sensor on the tempered line within that loop?

And regardless of my understanding that correctly or not, the end result a correctly done fake-loop would equate to more stable mixing valve operation that i can control better?

hot_rod

Do these buildings have recirculation loops on them?

If so a very common issue is called temperature creep, it's caused by mis piping the recirculation loop into the mixing valve.

Some good reading and drawings of proper piping here.

Also large buildings are best served with HiLo mixing stations, a large valve with a smaller valve piped parallel. With or without recirculation it is a stable temperature method for flows down around 1 gpm.

Although some brands of electronic mix valves are less $$ than HiLo stations


https://www.caleffi.com/sites/default/files/file/idronics_11_na-r2.pdf

FortyTwo

I have to take a closer look but I don't think they have recirculation loops, that's why I am curious about the "faux loop", if they do not. Some may have recirculation loops but none are pumped and the feed to the mixing valve is the cold water supply. (Besides one building which does seem to have a recirculating line plumbed alongside the main cold water line feeding the mixing valve)

By doing the hi lo and piping it in parallel, do you essentially mean 2 mixing valves in a row?

Thanks for the reply, diagrams, and info.

hot_rod

First step is determine the maximum flow rate and size the main valve to that. A smaller 3/4 valve pipes in parallel to accurately cover the small load. The best way to pipe them is with a pressure reducing valve. The Prv senses the pressure drop when the smaller valve cannot keep up and allows flow thru the larger.

FortyTwo

Ok that sounds like a pain and a secondary option to the faux loop with circulator I think. Now I just need to figure out what that means - back to square one.

mattmia2

Of course by the time you do that you're approaching the cost of a valve and electronic control.

hot_rod

That faux loop would need to have some sort of a heat dissipator.

The reason the mixing valve creeps is it starts seeing hot water on the cold port.

The reason one schematic I show works, and eliminates "creep" is it has a balance valve. That valve adjusts so the recirc loop has just enough flow to overcome the heat loss in the loop, the balance of the recirculation flow goes back to the tank.

If you have a thermostatic valve on a recirc loop improperly piped the entire loop will eventually reach the temperature in the tank. Depending on flows that could happen in minutes or hours. Often when the system runs overnight with no HW draw, meaning no cold to the mixer, it will creep up.

Mixing valves need to see a hot and cold supply to blend, if they see hot on both ports they lose their mind.

So temperature creep is always blamed on a bad mixer when in fact it is usually the mis-piping that is causing the temperature to rise.

An electronic mixer can eliminate the need for the bypass, but it still needs a minimum flow to be accurate.

The minimum flow is to assure the sensors have enough resolution to make accurate decisions.

One other option depending on what the total rpm requirement is, would be to put two small valves in parallel. Smaller valves have less minimum flow requirement to be stable, two piped parallel doubles the Cv. Depends on what you total gpm requirement is.

Or build your own HiLo with off the shelf parts, this example will work with accuratly or without recirc

You could also control the recirc pump with temperature to help prevent creep.

FortyTwo

Thank you. I'm going to have to look at those closely after I have some sleep and coffee. But I'm thinking about your final thought in that post, "you could also control the circulator pump with temp to help avoid creep". That catches my eye bc of the simplicity. Does that mean I could just wire it to a break on rise aquastat sensor on the faux line that would cut the circulator Everytime it passed a certain temp point? I'm thinking that means it would stop circulation every few minutes when it hit my desired line temp during both no water usage and water usage times.

I have questions on some of the diagrams but I want to sit and read that whole thing and look them over closely.

Thanks once again for your help and input

hot_rod

To me a DHW recirculation loop should get the same attention as a hydronic design, determine the load. That is the correct way to size the pump. Many, probably most larger buildings have oversized, grossly oversized recirculation pumps.

The "load" is the heat loss of the DHW piping, going thru the building, it's really a hydronic hosting loop.

It takes a few steps but you can determine the required flow by gauging an existing pump, and also the temperature drop to determine the load. Size and balance the circulator to that number.

All sorts of "smart" DHW recircs on the market, Taco has 4 or 5 options, as do most other brands. Some are timer, some timer and temperature,some actually use an algorithm to learn the systems needs and adjust accordingly. Some can be retrofit with a crossover valve using the cold as the return.

I have not personally used a smart DHW recirc, I have used time and temperature successfully, depends on how much technology and $$ you want to throw at the job.

I'd sell it to the building owners as an upgrade that saves big $$ and can easily pay for itself on reduce electrical (ECM technology) and hot water fuel costs, in addition to less water down the drain and happy tenants.

FortyTwo

I'm the owner and I'm pretty handy. I'm mainly looking for stable lower and more controllable hot water supply temps to the tenants for as cheap as possible. No existing recirc pumps to measure from. I have one building where I think the recirc pump installation would be pretty easy. If i start there, I'll have a better idea of how to do it on other buildings. I'll take some pics today.

hot_rod

There comes a point where it becomes almost impossible to supply a stable mix temperature over a wide flow range. Current lav faucets can have as low as a .35 gpm flow. So a central mixer would not be able to handle that low, and also a 10 gpm or more, accurately.

The only fix currently is to add POU "point of use" mixing valves at critical faucets, tubs and showers for sure. Most new shower valves have either temperature or pressure, some both anti-scald function, that leaves two handle type faucets, kitchens, etc..

Why this is becoming such an issue is the legionella and other bacterial potential and scare. Buildings may soon be code required, health and plumbing codes, to run in excess of 140 on the DHW to kill bacteria in the piping, for a period every day.

There are also chemical and electronic options for bacteria control.

I suppose it depends on how far you want or need to go to protect tenants and provide liability protection from a scalding incident?

As a manufacture, among many brand options, we try to provide a solution for any application. You decide how much $$ and technology to throw at the concern. We build mix valves from 3/8- 3". .35 gpm to over 2000gpm range

Know also any valve or device that sees constant fresh water will require maintenance, hard water can scale a valve in-operable within months. Pipe them with service in mind

FortyTwo

It's funny.. the city says landlords have to provide a minimum of 120 degrees at the tap but does not cap a maximum, and the insurance company says not over 129. In the end.. the insurance company is King.

FortyTwo

In this situation, where would u think a faux loop could go?

hot_rod

FortyTwo said:

In this situation, where would u think a faux loop could go?

Best go back to whomever told you about a faux loop, that is a new one on me

Is there a building department or code official for your area. They could cite the code they enforce for delivered water temperature.

I suspect state or local code may win over the insurance companies suggestion if ever a lawsuit was brought. I'd ask the insurance company to cite the code section and number for that 129F. Maybe get it in writing. There are a number of different codes used and different versions adopted or amended by AHJs.

One example below

120F seems to be the number the days, Daycare and facilities for elderly often have a lower maximum delivered temperature required by code..

Julius Ballanco is my go to guy for questions like this. He sits on many of the committees that make these temperature decisions and is a forensic engineer that gets called to be an expert witness in scald liability cases
.
https://www.pmengineer.com/articles/93805-julius-ballanco-hot-water-temperature-conundrum

FortyTwo

The faux loop that I'm talking about is from the original poster where he is told it by a tampering valve manufacturer as a workaround. I jumped on this thread after reading that because it could help my situation. So I have no direct knowledge of faux loops otherwise.

The reason I say the insurance company is king is because the code makes no difference in regards to what they want. If they tell a landlord to do something and the landlord cannot do it, they simply will cancel the policy. Often insurance companies go above and beyond the code. In some real estate markets there are very few insurance companies operating so you cannot easily just go with another one if your insurance company asks you to do something that is beyond code, expensive, or difficult. This applies to things across the board: fire safety, electrical, plumbing, etc.

I'm in a good position now but I'm trying to prepare myself and put myself in the best position because they get stricter every year.

hot_rod

Your call, to me it seems odd that insurance companies can superseded plumbing or any health safety code that are adopted by your state or city, especially if they are suggesting exceeding the temperature limit dictated by code?
What is the point of codes if the insurance companies claim they supersede them?

I suppose if they are paying the attorney fees if you should find yourself in a soft tissue lawsuit.

So then it comes down to what you feel is right or safe for your tenants.

Knowing plumbers that have been named in soft tissue lawsuits and what they went through, I'd error on the safe side being a licensed plumber and the one that ends up in court.

This temperature/ legionella controversy and the litigious society we live in is why we and other manufacturers add data loggers into electronic mixing devices. It give you documanted proof of what the system is doing at any point in time.
It alarms if temperatures are above or below the safe range, it can even dial your phone or txt an alert to you your plumber or building chief.
Maybe that's you