controlling FV temperature with solenoid valve

[MikeMarcus]

Hi All

I have been working on a FV cooling project for a while now. The plan is to divert the recirc water from a Cornelius Maxi 210 chiller through a coil welded into my conical depending on the output from a PID controller. When the PID sends an "on" signal to the solenoid, it flows the water through the coil and when it doesn't, the water just returns to the reservoir.

Here is a diagram of the system (the solenoid defaults to the 1 position):



And a photo:



Close-up of flow and return:



Close-up of PT100 probe screwed into port in FV:



And the stainless coil welded into the lid of the conical (while I was getting it welded, I got a corny gas-in post put on to the lid so I can keg under pressure):



I spent ages (and too much money) arsing around trying to find the correct connectors for the cheap chinese solenoid I bought from eBay. Then a few hours into testing, it crapped out. Can anyone point me to a source of reliable 3 way solenoid valves suitable for the job?

[stu-le-brew]

I am a little worried that you may not be succsessful using a PID to control a selenoid valve, I use a PID to control an immersion heater element for my HLT. The output from a PID is essentally on for a proportion of the time ie say 33% - thats a third of a second you will have to have a very strong selenoid to switch on/off that many times - so maybe thats why it died.

My PID can also has a relay output which could be used to control the selenoid, this may work for you.

I am no expert on this, but my PID does work for me - I use a SSR (solid state relay) to contol the power to my immersion element

very impressive work by the way - good luck

[MikeMarcus]

I have the cycle length set at 120 seconds so the solenoid doesn't change state more than twice every 2 minutes. It is wired to the relay output as the current necessary to drive the coil is minimal. Switching a solenoid with a PID is pretty standard in industrial applications.

[Fil]

Cracking stuff.. all you need is a nice box for the pid..

whats the thruput thru the solenoid like? i ebayed something similar which had a mircodot of a bore, designed more for gas than liquid? an alternative i have yet to take a punt on cos i cant find one cheap enough is a US style sprinkler solenoid valve, nice big bore and 12 or 24v switch, but killer shipping costs from the states on the ebay options i found. i ask as if too restricting the solenoid valve may stress the pump at worse or just perform poorly cooling.

cracking idea tho..

[MikeMarcus]

The bore is tiny. That is one of the issues that I have. I don't think the pump will suffer as it is designed to push water around a long python. It only get's the system down to about 8°C though. With a better (lager bore) solenoid, I'm guessing that the greater flow will get me down to about 4°C which is where I want.

I'm finding it a bitch to source a decent 3 way solenoid at sub £100 prices so I might go for two solenoids instead - one normally open and one normally closed. Wiring (and plumbing) them in parallel should lead to current opening one branch while closing the other. This will achieve the same effect as a three way solenoid.

I'm thinking of these:

http://www.ebay.co.uk/itm/290714018544
http://www.ebay.co.uk/itm/140723199376

[stu-le-brew]

I have the cycle length set at 120 seconds so the solenoid doesn't change state more than twice every 2 minutes. It is wired to the relay output as the current necessary to drive the coil is minimal. Switching a solenoid with a PID is pretty standard in industrial applications.

You clearly understand what your are doing with PID's, I will just watch this thread with interest
bon chance

[Fil]

this is the sort of thing ive looked at, low dc voltage..
http://www.ebay.co.uk/itm/Orbit-57101-1 ... 3123wt_813

but prohibitive delivery costs...

[Shippo]

I was looking at achieving the same results - i.e. keeping the maxi pump running constantly but only pumping around the FV when necessary. My solution is a little different though. I have a separate reservoir and pump fluid from that using a cheap pump controlled by the PID, via one of the product coils in my maxi, to the FV.

Pump was £6.40 delivered from china from eBay, and the reservoir was one of a pair of plastic tubs from poundland so cost 50p. A few extra quid covered the additional connectors etc. The only problem is if your cooler doesn't have the product coil fitted, but sounds like they are probably a lot cheaper than those solenoids.

I've got as far as proving the pump gets the chilled fluid round the system and gets the pipes (very) cold - next test is to see the effect on a full FV but all looks good so far.

[Shippo]

Edit: duplicate post!

[themadhippy]

why not use a central heating 3 way valve.

[Hogarth]

Sorry if I'm missing something, but would it not be easier to switch the pump on and off?

[gnutz2]

Sorry if I'm missing something, but would it not be easier to switch the pump on and off?

Exactly my thoughts, turn it on/off with a digital thermostat or your PID set as you have it.

Nice setup by the way

[MikeMarcus]

Sorry if I'm missing something, but would it not be easier to switch the pump on and off?

That would be great but 65L of wort fermenting at 21 degrees doesn't need a lot of chilling. The pump would go on so infrequently that I'm worried it would freeze. Am I missing something here?

why not use a central heating 3 way valve.

Can you point me in the right direction?

Edit: you mean like this? http://m.screwfix.com/p/siemens-cmv322- ... alve/45944

How quickly does it switch?

Edit2: seems like there are two types; mid position and diverter. Spring return 3 way diverter seems to be the correct type for this system. Drawbacks are price and the fact that they are only rated down to 5 degrees.

[gnutz2]

Run glycol in it maybe?

[Kev888]

Nice setup!
I'm thinking of something similar, but can't decide between solenoids switching the flow from the python pump or just separate cheap pumps. The separate control is needed in my case (rather than just turning on/off the pump) as I want to control more than one FV independently.

If I do go with solenoids I was thinking of using cheap washing machine/dishwasher inlet valves, such as these, though they're mains without an enclosure and would require some sort of simple logic circuitry to make two behave as a single 3-way one so the cheapness has some hidden costs in effort and money.

Cheers
kev