Profitec Pro 500 PID overheating

Equipment doesn't work? Troubleshooting? If you're handy, members can help.

#1: Post by jamisons »

Help! First post, after a lot of surfing for my issue.

Lots of posts about the SSR failing and the boiler not getting up to temp. But my machine consistently overheats every time I turn it on. After getting to the boiler set temp (120C), the PID stops calling for heating (the little dot doesn't appear in the PID display) but the element is definitely still heating and the temperature rises until the boiler safety valve activates. Whole Latte Love had me check voltage on the relay, and I found that both DC and AC are seeing the right voltage. The other thing that happens is that the brew group gauge shows pressure of up to 10 bar even though the pump isn't operating. I don't know if this is related, but I don't recall seeing this before.

Is there a case where the relay fails on?! So far, my googling and forum surfing here hasn't turned up anyone else experiencing this problem.

I'm able to "solve" the problem by turning the machine power off, operating the brew group level and draining off a bunch of water from the group, and venting steam through the steam wand to lower the temp. After several cycles of this everything starts to behave. But after cooling off and turning it on the next day, I get to start over. Side note - when I drain the group, the pump doesn't refill it when the power comes on and it make a crazy clicking/popping sound for a couple minutes. I don't recall ever hearing this before.

I'm happy to replace the relay if that's the likely culprit but I'd rather have more certainty that it's actually faulty before I do.


Team HB

#2: Post by JRising »

What does " I found that both DC and AC are seeing the right voltage" mean? Did you measure 11 to 17 VDC across the DC terminals and more than 110VAC across the load side?

Yes, there are many cases where a relay fails "closed". Though if you're reading 110+ VAC across the load side of the relay, then it's not "failed closed", it's not powering the element.

The fact that it resumes working properly makes me believe that the SSR is overheating and failing closed when it's on for any length of time, then when the boiler's heated and the SSR needs to only pulse, it's not on too much and doesn't overheat and fail. You could test it further, but just replacing the relay probably isn't a waste of time.

jamisons (original poster)

#3: Post by jamisons (original poster) »

Confirmed, the relay was bad.

Next issue... I'm an idiot, and when I installed the replacement relay I wired it backward (despite checking several times) and fried the new relay. So I reinstalled my old relay and turned the machine on. The green main power light comes on but the PID display is blank, so I assume that it's fried as well.

I definitely need another new relay and I assume a new PID controller as well, that's easy enough. Is there anything else in the DC circuit between those two pieces that would get damaged by AC power, or is it just those 2 parts? I assume that everything on the AC side of the relay won't have been affected, but I also assume that I can't test the AC side until I get the DC side working again.

I'll be tracing the wiring later today but thought I'd ask here in case there are any folks who already know.


#4: Post by canatto »

well, sometimes siht happens. But, before you go out and buy a new PID replacement, did you have the water tank in the machine and there was good amount of water in it when you power up the machine and the amber light won't turn on?

I think there are 6 wires going into the PID box. Two SSR triggering wires, two power wires, and two temperature probe wires. I can't think of a way that you could fry the PID by messing up the wiring at the SSR.

p.s. here is a page from Clive Coffee describing removing PID from the machine. I guess may be you could pull the PID and do some basic test, such as feeding the power transformer directly from the wall outlet and go from there. ... eplacement

jamisons (original poster)

#5: Post by jamisons (original poster) »

Yeah, funny that... I did have water in the tank the first time I tested it, but apparently I didn't have enough. Reading through some other posts/forums earlier today I was reminded about the tank level sensor so I tried it again.

So I was fortunate; the PID is still functioning and I only need to replace the relay, again.
But thanks for the extra reminder, and thanks for the discussion on the PID.