PLC Environment Controls Anyone? PID?

[mjwalsh]

When we decided to use a PLC for our Dog Wash we did so partially because we wanted to improve the accuracy of our water temperature & make up air. Also, so we could more efficiently save BTUs by reclaiming our 180 degree surface temperature in our dryer exhaust ductwork. The PLC allows us to tweak the controls better to achieve the least amount of BTU waste.

The reason for this post is to ask if anyone is familiar with PID that some PLCs are capable of using? Info says that it tends to be more accurate than the more simple on-off or simply open or closed. In other words it can make proportioning water mixing valves & vents adjust quickly to the "in between" needed position according to the current variables.

It seems to make sense unless everybody has had great experiences with tempering valves etc.

 

[Ghetto Wash]

PID will provide a more accurate tepmerature. 130 degrees for example. Not 129 and not 131. With a simple thermostat like on my boilers, I wouldn't be surprised if the actual water temp varied up to 10 degrees or more.

I'm not sure it adjusts quickly as you suggest, I think it more predicts where it needs to be to keep the temperature constant.

Before carwashes I was in the custom plastic profile extrusion business (like Extrutech) and all the temperature controllers for melting and forming the plastic were PID because of accuracy.

I don't believe that a PID controller would be any more energy efficient than any other control method.

 

[pitzerwm]

What about a $60 Delta shower control, it would control the temp and it keeps them from frying the dog.

 

[MEP001]

I used one recently along with a single Paloma PH28 for a 4-bay wash. I set the Paloma to 160? and tempered it down to around 110?. It was inexpensive and so far has been completely reliable, and it's accurate enough that you can't feel a change in temperature with increased or decreased flow.

What about a $60 Delta shower control, it would control the temp and it keeps them from frying the dog.

A friend of mine recently had a seizure in the shower and managed to knock the valve to full hot before he fell. The apartment's water was 180? and he was burned severely. If they'd had at least a simple tempering valve he wouldn't have been.

 

[pitzerwm]

That is all you can buy now in bath fixtures.

 

[PaulLovesJamie]

I use a PID controller on my smoker, it is incredibly accurate.
For controlling water temp though, I'd use a simple mixing valve. I have a lawler thermostatic mixing valve providing water to my RO unit, it keeps the water temp within 1 or 2 degrees.

 

[mjwalsh]

I had a Watts at one time for the car wash & possibly because I had no recirculaing line & a 50 foot pipe run it could be why it did not seem good enough. I am using 2 Symmons (one as a backup) with a recirculation line for the car wash. They worked great for a few years but it seems like they may need to be overhauled with all the fancy components or a rebuild kit inside. It just seems like the Belimo Porportioning valve is simpler & could be more trouble free except for the initial PLC programming setup part of it.

Anybody else can share their experiences with tempering valves-----especially if they actually log the temperatures vs just occasionally glancing at a gauge?