Thermostatic Mixing Valve for Jobo -- how senstive to pressure drop?

[Kino]

Finally getting around to mocking up my plumbing for my darkroom. The picture is how I have my Hass Intellifaucet plumbed temporarily; the PEC rings have not been clamped yet. That's the beauty of PEC, the pipe is dirt cheap and you can try all kinds of arrangements without a huge cost. The connectors and tools on the other hand... whew!

Kind of worried that when I turn on a valve in the sink downstream of the mix valve, it might cause temperature fluctuations due to the pressure drop.

Anyone care to chime in? Obviously not finished but far along enough to see where I am heading.

I might be overthinking this a bit...

EDIT: Actually "Water bath to Jobo" should be "water jacket supply for jobo"

 

[AgX]

It is a issue. Though the effect sure depends on design.

I got some data at hand for a german bathroom thermostat:

max. pressure 10 bar
min. pressure 0.5 bar
advised pressure range 1-5 bar
above 5 bar a pressure reducer is advised

At differential pressure of more than 6 bar between cold and warm water the valve itself must be adjusted for proper working

However in practice the situation may be different, as the differential pressure may change. For instance the pressure of the warm water may be buffered by a nitrogen-filled bellows, whereas the pressure of the cold water may rapidly drop at directly flushing a toilet.

 

[Kino]

It will be hugely expensive if I have to install a cold water manifold on the house supply and run a new line to the darkroom. Ugh...

 

[ic-racer]

My Powers unit is sensitive to flow. Which is to say, if you alter the flow on the water panel from minimal to more than that, the temp changes. So, I always set the flow volume first. In fact I keep it at the minimum all the time which is usually more than enough. In the Powers, it is not a good idea to have a valve downstream of it's built-in on-off valve because it can overflow the anti-siphon vacuum breaker valve (not seen; inside the unit). I think this is a universal standard. In fact, I had to re-do my filter placement, because it has to be below the valve.

I put my filter after all the pressure valves, so I don't have to worry about the filter leaking or exploding when I'm not home.

I also put two ball valves between the whole thing and the house supply. So I can re-configure it or remove it easily.

The red ball valve is for the Jobo Cold Water intake. But, not unexpectedly, the cold water is frequently about the same temp as the ambient temp in the basement, so it is not much use. That has its own small pressure relief valve (hard to see) to allow disconnecting it from the Jobo without spraying.

I used to leave this cold water hooked to the Jobo all the time, and use it to fill, but it was too slow. Now I use an extension hose and fill with tempered water, which is quicker to heat anyway.
Here is another trick. I fill all the bottles with the tempered water and use the water in those bottles to dilute the chemistry. The Jobo can be used almost immediately that way.

 

[Kino]

Thanks for the details of your system, Ic-racer.

The problem with manually filling my Jobo is that it is the 2200 ATL with an automatic fill solenoid, which can call for water at unpredictable times and needs an "always on" supply. It is usually, however, a very brief spurt to top off the tempering bath, but it might be enough to tumble the tempering valve at a critical moment.

I do have a Watts 288A atmospheric vacuum breaker behind where the tempered water "T"s to the Left (Jobo) and Right (sink).

Maybe if I move the valve on the tempered line from the Jobo side to the short pipe just coming out of the mix valve, or just place another valve in the short pipe, it will work properly. I don't see any reason why the line cannot "T" at the atmospheric vacuum breaker, as long as it is the highest point in the water system. For safety sake, I could valve off everything to the sink while running the Jobo, but it would be nice to be able to use the sink while the Jobo was running.

I also plan on installing one-way check valves PRIOR to the water filters, so that will probably avoid any problems with the atmospheric vacuum valve.

Of course, you'd never want to leave this system pressurized after a run and if could be purged at the end of the day by closing the yet to be installed valves before the filters and opening the faucets in the sink.

I installed the 5 micron filters prior to everything to keep from cruddying-up the mixing valve itself, as our house doesn't have a whole house filter...yet. I plan on doing that soon to avoid having to change these filters so often.

 

[ic-racer]

Yes, I think you need to relocate your ball valve. In fact my Powers mixing panel is made by Watts and has the same vacuum breaker inside the box. Here are the installation instructions for the vacuum breaker:

 

[Kino]

This might give you a better idea of the location of the panel.

 

[ic-racer]

If there is a solenoid valve on the supply line to that Jobo, you need a separate circuit, bypassing the vacuum breaker. I don't know if that is OK for building code in your area, but I know my refrigerator ice maker and washing machine don't need vacuum breaker since they are hooked up all the time and the line is pressurized.

Nice Jobo BTW!

 

[Kino]

If there is a solenoid valve on the supply line to that Jobo, you need a separate circuit, bypassing the vacuum breaker.

That is the "T" in the blue (cold) line that feeds the cold leg of the water tempering valve. The unit fills the circulating tempering bath and, if you change processes, say from color to b&w, will inject cold water into the circulating bath to bring it rapidly to the lower temperature.

However, the tempered water input is also controlled by a solenoid. The machine controls rinse, injects tempered water into the drums and dumps them automatically. However, Jobo DOES recommend a vacuum breaker for the mixing valve. Confusing...

I don't know if that is OK for building code in your area, but I know my refrigerator ice maker and washing machine don't need vacuum breaker since they are hooked up all the time and the line is pressurized.

Same here.

Hmmmm...

 

[ic-racer]

One thing almost certain, if the vacuum breaker is pressurized it will leak and make a mess! Mine leaked with just the small pressure head from the filter being higher than the breaker in post #4.

Best to check with a plumber or building inspector, but some codes indicate that if the water flowing into the device (as in my case the Jobo solenoid fills above the water level with an air gap) is protected by an air gap, no vacuum breaker is needed. So on your Jobo, the question is if the tempered fill has an air gap from where it enters the tank.

 

[Kino]

Great. Looks like I wasted money on a vacuum breaker I didn't need...

I think the check valves prior to the cold and hot water filters would qualify as adequate protection. I'll study it more, but get the feeling I simply do not need the vacuum breaker.

When the machine shuts down, it opens a drain solenoid for the tempering bath (check that, it is a manual valve you have to turn -- been a while), but in the past I have had to close a valve on the tempered water line input to the Jobo and then briefly start it in one of the programmed modes for it to relieve the pressure on the tempered line.

Looks like I will have to do the same here OR build in a relief valve for shutdown.

 

[ic-racer]

It might be nice to have a general purpose hose from the tempered water, you can put the breaker on that line.

 

[Kino]

True, but my panel is located so high, it would have to be on a 5 foot tall pipe!

 

[Kino]

Found the manual:

3.4 Rinse water temperature
Your new ATL 2200 uses two water supply lines, one cold and the other tempered. The tempered water line should be adjusted to
within ± 0.5°C of the process temperature. To deliver the tempered water JOBO recommends our water mixing panel (#4189). It
has a low-flow mixing valve and a trickle line; both are needed for optimum results. Also, the water panel is designed with a
special valve to allow you to fill the processor with tempered water to speed the warm-up time before the first run of the day.
If processes are run at temperatures below ambient room temperature, the temperature of the supplied water must be lower than
the processing temperature. A water chiller should be used if the supplied water is warmer than that required by the process you
intend to run.

(Looks like I will have to figure out a way to make a trickle line and a quick fill tempered line. Never had one before, but I didn't process much color before either.)

(snip)

4.2 Water connection
Your new AutoLab uses two water connections with European hose thread. Two washers and two brass adapters are included to
convert the threads to standard US threading. The two water connections are located in the rear of the processor above the fan
and power cord. Connect the gray hoses to the solenoids, the hoses to the brass adapters, and the adapters to your cutoff valve.
Make sure you use the washers at every connection.
The tempered water supply connects to the solenoid coded with a red dot. The cold water supply connects to the solenoid with
the blue dot. The tempered water supply should always be set to within ± 0.5°C of the processing temperature. Screw the hoses
on tightly, but do not strip the threads.
Depending on the condition of your tap water, you may want to install a water filtering system to prevent any contamination
caused by particulate matter.

 

[Kino]

OK, new configuration without the atmospheric vacuum breaker.



I just got my check valves that will precede the hot and cold water filters, so there shouldn't be any issues with backflow into the house system.



I went a ahead and fabricated small Hot and Cold water manifolds to try to minimize the flow disturbance. Everything is clamped and I am awaiting word from B&H on my sink.

 

[ic-racer]

Nice.

 

[bdial]

As to your initial question, my Intellifaucet hasn't had any problems from pressure drops. Mechanical mixing valves need a compensation mechanism, but the Intellifaucet is measuring the output temperature and adjusts the input as necessary to maintain the setting.

 

[Kino]

As to your initial question, my Intellifaucet hasn't had any problems from pressure drops. Mechanical mixing valves need a compensation mechanism, but the Intellifaucet is measuring the output temperature and adjusts the input as necessary to maintain the setting.

Good to know.

I guess I have the proverbial belt and suspenders, but that's OK by me.