Hot Rocket (Temperature Issue)

[CaffèDaddy]

I have had a Rocket Appartamento for 11 months with Eric's group head thermometer installed. Throughout this time, the Appartamento has regularly idled at 207-208 F following a one hour warm up, allowing me to flush a few ounces of water (per Eric's recommended techniques) before pulling shots at around 201-202 F.

Over the past three weeks my Rocket has suddenly started to idle at a much higher temperature - between 210-211 F following warmup. I must now flush 20 ounces of water just to get it back to 207 F. It can take 20 minutes of flushing to get the water to drop to about 201-202 F, an unsustainable amount of time to spend on one shot.

This morning, the temperature reading was again 211 F. After flushing water, boiler pressure jumped to 1.6, as if the boiler was seeking to maintain pressure and temp in the higher range against my efforts to decrease them.

When steaming milk, the thermometer in the pitcher seems to climb more rapidly than before as well.

The machine is still useable and is not accompanied by unusual noises or hisses as others have reported, but the change is noticeable. The Rocket is still under warranty for one month. I contacted the retailer who has said, "it sounds normal, but let's keep an eye on it." I'd also like to avoid the shipping cost to the west coast if possible.

Any thoughts about what it going on with this machine? Thank you in advance for your thoughts on this issue!

Other info: there has been no change in ambient temp (70-72 F) and no change in altitude (900 ft above sea level) during this time. All maintenance is regular (daily backflushes, monthly backflushes with detergent, use of Rocket water softener packet, cleaned the group head once in August and was planning on doing it again over the next week or two, etc.)

[JRising]

This morning, the temperature reading was again 211 F. After flushing water, boiler pressure jumped to 1.6, as if the boiler was seeking to maintain pressure and temp in the higher range against my efforts to decrease them.

I think it's overheating from time to time, the typical deadband that normally keeps the appartamento's boiler pressure falling from 1.3 back to 1.0 or 1.1 is often overheating, allowing the boiler to heat up to 1.6 or so. When idling at a higher temp the heat exchanger water is going to superheat to a higher temperature, that's going to thermosiphon and heat the heat to a higher temp. And although it will be possible to bring it back to brewing range with a cooling flush, that flush will take a lot longer. Just my 2 cents worth, but watch the boiler gauge for a while, see if it's reaching different and strange upper limits sometimes, before the element is switched off and the pressure begins to creep back down to the 1.1.

Do you know how your appartamento's element is wired? The element's load directly switched by the Pressostat (thick wires at pressostat), or load switched by Gicar (thin wires at pressostat)?

[CaffèDaddy (original poster)]

Thank you very much for your reply!

After my post earlier today, the boiler pressure no longer fluctuated. It seemed to be pinned in the 1.1 to 1.3 range. Still, the temperature problem persisted. The issues might be worse after initial one-hour warmup in the morning.

I have a couple of photos of the inside of my machine, which also captures the pressure stat. Are these helpful?

[homeburrero]

After my post earlier today, the boiler pressure no longer fluctuated. It seemed to be pinned in the 1.1 to 1.3 range. Still, the temperature problem persisted.

So it appears your pStat and controller are functioning normally. As long as the boiler has pure water vapor (no air) and your gauge is working, then a relatively constant pressure is a a guarantee of a relatively constant steam boiler temp.

The HX-thermosyphon temp and group temp can go astray though. Typically it goes cooler than expected because of a vapor pocket causing a thermosyphon stall. But I've noticed that if you drain a lot of water from the group with the pump off it can unexpectedly go hotter than usual. On my Rocket Giotto I've experimented with draining water with the lever at midway (pump off and inlet solenoid closed) and have seen my EricS thermometer that normally idles at 203F go as high as 220F! (I've theorized that the mechanism here is that the upper part of the TS loop is vapor, and is rapidly condensing at the top of the group which would transfer a lot more heat than circulating hot water would.)

This might be related to your problem if you are not careful about leaving your lever in the midway position.

P.S.
Your pictures show the upper black wire of your pStat going to the thermal safety switch rather than the controller. This indicates that your pStat is directly controlling the switching of the heavy load of the heater circuit. (Most of us think this is much better than the alternative scheme, where the controller relay does the frequent heavy load switching based on the pStat continuity.)