Vaportstat and PSI

Brad White_203

The size of the boiler has nothing to do with the pressure setting (a 1 million BTU boiler and a 50,000 BTU boiler at 1.5 PSI still create 1.5 PSI), -but the rate of steam production of course differs just a wee bit :)

Not sure how over-sized your boiler is, but the venting rate has to equal the steam production rate or else the pressure will increase by back-pressure before the vents start to close. Again, good venting practice.


Now, for that model number, 1009?

Or do you mean the L408J 1025? Just curious.

Jean-David Beyer

Vaportstat and PSI

Hi.
It seems that most Wallies here suggest a 16oz vaporstat to keep pressure low in the steam boiler.
Dan's book mentioned 2psi for a pressuretrol setting.
if one was to replace a pressuretrol to a 16oz vaporstat, why wouldnt the 4psi vaporstat model be recommended?
i know the pressure is the lower the better, would a 16oz(1psi) cause short cycling?

JohnNY

Steam boilers come with a standard pressuretrol that doesn't go down into the ounces range. A vaporstat is an upgrade to that device.


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Brad White_203

Just putting a 0-16 Oz. Vaporstat

on your otherwise unimproved steam system is likely to create short cycling on pressure. This tends to be due to inadequate venting. Any vaporstat upgrade should be done in concert with a detailed venting assessment, both main vents and radiators.

If you cannot get the air out of the way, the boiler still sees pressure.

The 0-4 PSI vaporstat is a good commercial range, especially where a constant pressure must be maintained (such as for control valves in a 2-pipe system). But for "direct to radiator" systems, 0-16 ounces is appropriate.

Jean-David Beyer

As always, Thanks Brad!

i will try and pick up the honeywell 1009.

venting is a cause of concern for pressure buildup, but if i have a oversize boiler shouldnt i be concerned with that too?

carter_3

per a previous posting by scrook, he noted
"Note that L408J1025 (& L408J1033) MAKE on pressure rise ONLY.
The L408J1009 (0-1 psi) & L408J1017 (0-4 psi) are full SPDT so can BREAK on rise, and/or MAKE on rise."

So since the 1009 and the 1025 both make on pressure rise, why not pick up the 1009 that will break on pressure rise too?

im thinking added feature for same price.... both are 0-1psi.
What u think brad?

Brad White_203

Duh, my bad

I had thought it was a break on rise and you are correct. The one I have on the shelf (I forget the model number) is the kind that can be wired either way for each application. I should be much more careful!

When I searched for "1009" I came up with certain thermostats and covers, so my query.

Brad

carter_3

perfect, thanks brad.
the 1009 it is!!

Thank you so much.

BAB

1025 vs 1009

We improved our 2 pipe heating system so we have better venting. A week ago I asked for advise on this site for the correct vaporstat (0-16 oz/sq in). You suggested the L408J 1025. We followed your suggestion & installed the vaporstat. After troubleshooting & rereading the directions many times we decided the only way we could make it work like the removed presuretrol was to add a relay. In short, using the same wiring arrangement just did not work with the 1025. The day was up so we put the original pressurtrol back & set the cut out at 2 psi. Since our system rarely runs over 6 oz per sq in we would really like the vaporstat to work. In view of the above postings are you now saying we need a 1009, not a 1025? Would like to keep the wiring the same and not add a relay.