Greetings,

I have a dual boiler Expobar Brewtus IV-R. I'm noticing that even after a single shot of about 25-30 seconds, the brew temperature on the PID can drop from 96C to 95C. I used to be able to pull multiple shots without such a temperature drop.

The brew boiler is filled up with the steam boiler. The steam boiler should be very hot so if all you are doing is pulling shots, the brew boiler gets filled with the very hot water from the steam boiler. One would think that you could pull several shots then without the brew boiler temperature dropping. In fact, that used to be my experience.

At first I thought this was due to the faulty vacuum relief valve. This would result in the valve leaking and the steam boiler not being as hot as it is supposed to.

I did successfully replace the vacuum relief valve. It no longer leaks or hisses. So, I would think the steam boiler is full of very hot water.

If I try to pull two shots back to back, the brew temperature can easily drop from 96C to 94C or even 93C.

Any thoughts?

Dunno. How old is the machine?

I have the same B-IV-R, no issues. It might drop 1F between a couple of shots, but is pretty stable. It will drop about 2F for <1 minute when I pull a warming flush before my first shot. Overall, a pretty stable machine.

thanks Otto,

My machine is just over a year old. I did notice that the vacuum relief valve was failing and pressure continued to leak. That's about the same time I noticed the temperature drops. I thought that made sense since with the vacuum valve leaking, the temperature in the steam boiler would not be as high. the brew boiler fills from the steam boiler so that too would not get as hot water as it should.

I replaced the vacuum relief valve and expected the issue to go away. However, I'm still finding that the temperature can drop 1 degree C after even only one shot.