Steam Boiler Temperature Drop

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BaristaBoy E61

#1: Post by BaristaBoy E61 »

Why does our Steam Boiler temperature drop by more than 10˚F on the PID display while steaming - even before there's a call to refill the boiler?

I understand the rapid drop in pressure but why in temperature?
"You didn't buy an Espresso Machine - You bought a Chemistry Set!"

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#2: Post by Jeff »

When in equilibrium, the steam temperature and pressure are interrelated. "Saturated steam table" is a good search term.

One example is ... metric.htm

Is this in line with what you're seeing?

0.9 bar ~ 246°F
1.0 bar ~ 249°F
1.1 bar ~ 252°F
1.2 bar ~ 254°F
1.3 bar ~ 257°F

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BaristaBoy E61 (original poster)

#3: Post by BaristaBoy E61 (original poster) »

Thanks very much Jeff, that makes perfect sense. I'll check the PID display & Steam Boiler Pressure Gauge next time. It lines up with what I remember.
"You didn't buy an Espresso Machine - You bought a Chemistry Set!"


#4: Post by godlyone »

Ideal gas law... PV=nRT

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#5: Post by EddyQ »

On my KvdW, the PID probe is in vapor above the liquid in the boiler. The reason they measure temperature there is due to a more rapid drop in temperature (as described above). The fast drop due to steaming quickly turns on the heat which has some lag. The end result is apparently more stable boiler temperature.
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