Is there a temperature vs boiler pressure table?

[Kristi]

is there a temperature vs boiler pressure table?

Can someone please point me to it?
Thanks

[HB]

Saturated Steam Tables

[jesawdy]

Here's Eric's table adjusted for altitude



IIRC you have to add the barometric pressure to the gauge pressure to use the steam table link that Dan referenced above.

[Kristi]

Thanks.

Why, on the table, does 250F => 2.05bar and on the graph 250F = 1.05bar?

(I am at sea level)

[gabriel]

does a table exist to show the relation between the boiler temp/pressure to the brew-head temp on HX machines ?

[jesawdy]

Why, on the table, does 250F => 2.05bar and on the graph 250F = 1.05bar?

Eric's graph indicates "gauge pressure". When you use the steam tables, you have to add "atmospheric pressure" (Patm) to "gauge pressure" (Pg) to get "absolute pressure" or P.

Adding 1 bar at sea level is about right.

1 bar = 0.987 atmosphere = 29.53 inches of mercury

To be precise about it, add the atmospheric pressure (as reported by the weather conditions in your area) to your gauge pressure reading to determine absolute pressure, P.

[jesawdy]

does a table exist to show the relation between the boiler temp/pressure to the brew-head temp on HX machines ?

Ah, there's the rub.... this will vary machine to machine.

Depending on what machine you have, someone here may have a good idea of the approximate temp difference, but only with testing could you determine that, and you still have the variable of how much one flushes.

[Kristi]

Eric's graph indicates "gauge pressure". When you use the steam tables, you have to add "atmospheric pressure" to "gauge pressure" to get "absolute pressure" or P.

Adding 1 bar at sea level is about right.

1 bar = 0.987 atmosphere = 29.53 inches of mercury

To be precise about it, add the atmospheric pressure (as reported by the weather conditions in your area) to your gauge pressure reading to determine absolute pressure, P.

THANKS!

So if I am measuring a temp of roughly 250F on the side of the boiler under insulation, and the boiler gauge says 1.5, something is screwy?

[jesawdy]

So if I am measuring a temp of roughly 250F on the side of the boiler under insulation, and the boiler gauge says 1.5, something is screwy?

Maybe, maybe not. How accurate is your temperature reading? Meter? Thermocouple? Calibrated? And finally would the outside boiler temp equal the internal temp? (Of course it should be close)

1 bar (Patm) + 1.5 bar (Pg) = 2.5 bar which corresponds to 261F on the saturated steam tables.

[Kristi]

Maybe, maybe not. How accurate is your temperature reading? Meter? Thermocouple? Calibrated? And finally would the outside boiler temp equal the internal temp? (Of course it should be close)

1 bar (Patm) + 1.5 bar (Pg) = 2.5 bar which corresponds to 261F on the saturated steam tables.

aaaaah

hmmmmm

250F - 1.05Pgauge
261F - 1.48Pgauge

so a difference of .5 boiler Pgauge bar only yields 11F
But it seems more like raising .25Pg gave me a rise of 15F....

Accuracy - K tc on a Fuji Pid being used for temp read only. Fine wire K - bare wires twisted on end.

tc is under scotch double sided tape pad stuff so it acts as a bit of an insulator, with insulation over that. tc is attached to bottom of boiler.

tc checks out at 32.6 and 212.5

What started this was I am questioning the accuracy of the boiler gauge and wanted to """calibrate""" it.

The other prob is that my Mater seems to want to have a .3 or .4 deadband and probably needs replacing, but since it works I'll just leave it (I took it off and checked the microswitch, but all looks good. But it's 4 years old.)

Put it back together and running
1.20bar ON 240F
1.45Bar OFF goes up to 245.5

But I have no idea of the accuracy of the gauge.

[jesawdy]

Accuracy - K tc on a Fuji Pid being used for temp read only. Fine wire K - bare wires twisted on end.
....

The other prob is that my Mater seems to want to have a .3 or .4 deadband
....

But I have no idea of the accuracy of the gauge.

Well, that should be accurate enough.... could be the gauge and/or pstat.

That deadband is not too good, lots of bad Mater pstats threads lately as well.

(P.S. Junior is no more?)

[Kristi]

Well, that should be accurate enough.... could be the gauge and/or pstat.

That deadband is not too good, lots of bad Mater pstats threads lately as well.

(P.S. Junior is no more?)

I took it out (Mater) and put it back and deadband is more like .25 - basically normal for a Mater. Certainly good enough for me unless I get bored at some point and put in a CEME with adj deadband or something else that's inexpensive. But this is just fine.

I was hoping if I read the temp I would know the pressure but I guess not really.

gauge 1.2-1.45bar yields 240-245F range
gauge 1.0 -1.25Bar yields 237.5-241.5 range

I was hoping to figure if the gauge was high or low and by how much. The tables don't seem to match what I read others are getting. Or maybe the gauges are just inaccurate...



Yeah, someone bought the Jr. Too big for me. Too much warmup time for me. Very nice machine, though! Priceless experience playing with it! So I grabbed Cliff's Tea. Also a very nice machine, and much better suited for my purposes!