PID wiring

[Rob-b]

Ok, i've read til I'm blue in the face about PID set ups off the veggie forum etc. and it continues to baffle me. Anyone able to put up a laymans wiki and show what wires go where and to what? the schematics have me equaly bamboozled. I am more of a frabricator than an electrical wiz.

I am currently building a new set up and to date have the reactor up on legs now with the cone formed and welded in, first pump in place, in line heater done, two twin eductors made and ready and have got a heat exchanger ready to go on. Will be starting on the quad core condenser and cone for the top next and finally the squirrel set up. Just this flippin PID side of things.

I have opted to keep things as simple as I can, and will be putting pockets in the still head, squirrel pipe work and processor for monitoring heat, but still think the PID for controlling it. Also bought a float switch set up for the tank heater, which will help with the squirrel.

Would add pictures if I knew how.

[Julian]

Rob,

Have a look at this thread ... http://www.vegetableoildiesel.co.uk/forum/viewthread.php?tid=20452   I've not put it on the wiki as there were criticisms that the control circuit should be low voltage to make things a little safer, which is probably a fair point.  Only using 240v does keep things simple though, just be careful to make sure everything is correctly insulated and earthed.

To my knowledge at least a couple of people have used the diagram without problem .  If I can get someone qualified to check it over,  I'd be happy to put together a "Noddy speak" page for the wiki, but until that time I'm a little reticent to proceed.

In a similar vein, if you're unsure about any aspect, get a qualified electrician to check things for you, what I've offered is for guidance only.

Re your build, if you have a series of photos as work progresses, we can easily put together a build sequence page.  There are several people on here who can now help you do it or do it for you.

[Rob-b]

 Julian

thanks for that, I will scrutinise the thread later.

I got the info for the float switch on the wiki and feel the same sort of info on PIDS will be invaluable. I bought this as a result of the reading.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=270583994811&ssPageName=STRK:MEWAX:IT

My set up will be an in line heater from pump 1, heating the oil with another heater in the tank to help the squirrel, taking oil from just above the heater with pump 2. I want to be able to control both pumps with a PID OR PIDs, what type of PID do I need and is the SSR I already have ok for these as well. Can I control two heaters from one PID?

I think I may have to bite the bullet and get an electrician in for this once I can bottom out what I need to buy.

I am taking photos as I go, do you think folk would rather see the progress as it happens or wait til it is finished?

[Tony]

Wow that is one meaty SSR.

Why do you want to control the pumps with a PID?  Is this purely to shut them off if the overtemp alarm condition is reached?

If you have one place in the processor you measure temp there is no reason why you can't use one PID to switch both immersions.  But once the PID is tuned you'd have to always use both (couldn't just revert to using one sometimes).

[Rob-b]

Sorry Tony

my mistake, I don't want to control the pumps but the heaters of course, with your reasoning I think maybe two PIDs in that case as I don't need to run both heaters at the same time, only when I am demething with the squirrel.

The SSR is overkill maybe but having seen Mark's melt down with the Chinese one think 'buy cheap buy twice' as the saying goes in this case, or even burn the shed down.

[Julian]

Rob-b...

I'm not an expert, but, it's probably not a good idea to run two heaters from one PID/SSR combination.  You will only have one point of control (the thermocouple), so one heated area may get over or under heated.  It would seem far more logical to have a TC/PID/SSR combo to run each area.

That said I'm not sure about increasing the temperature in the squirrel pipe work.  It seems logical, but Jim warned of possible danger if the parameters he specified were exceeded.  Might be worth posting the idea on the VOD forum to get opinions.

We have electricians on the VOD forum and I'm sure collectively there's enough talent and knowledge, there to assist.

Tony ...

Although my current PID doesn't have it, I'd have thought that the auto-tune facility fitted to most modern PIDs would cope with different levels of heating or points of control.

[Rob-b]

I'm trying to convince HC II to build me a control box and photograph its progress showing physical wiring as well as posting schematics, for the wiki to help others. I think his only stumbling block is achieving a good enough front face for the unit, I've still not heard back from him yet but keeping my fingers crossed.

If not I may have another who can design and build my control box and I will photograph it for the wiki, my only concern is that I wouldn't know how to explain it.