Which Vaporstat for stage-firind boilers?

vaporvac

Here is the situation. I have a Trane vaporvacuum system that will soon be using two Slantfin Tr 50s with Riello g400 gas conversion burners, stage-fired. I have the old mercury vaporstat that reads inches of vacuum and ounces of pressure which I will reuse on one of the boilers in addition to the pressuretrols that came with the boilers. A couple of questions:

-Should i use the old pressuretrol as well or are the new ones better?



-Do I need two vaporstats? (I'm thinking yes.)



-Which is the best vaporstat? Is anything available besides the Honeywell. Do either of them read inches of vacuum? The L408J1009 will do 0 to 16 oz, and the L408J1017 will do 0 to 4 lbs. Which would be best for my application?

Anyone know of any resource for the old vaporstats?

Thanks for any feedback here. Colleen

Jamie Hall

Pretty sure...

that you will need two vapourstats -- leastways, I've never heard of one which has two trip points.  And for your system I would get the new one to be the 0 to 16 ounce variety.



And I would keep the pressuretrols, as backups.



Here's where the fun begins: if it were mine to set up, I would put the two vapourstats on a pigtail and a T arrangement, with a vapour vacuum gauge (if you can find one) or a pressure gauge with a maximum of 3 psi -- and hook that up to the header which feeds the system and which is fed by both boilers, rather than mount them on the boilers.  That way they would be reading true system pressure, and both the same pressure, rather than boiler pressure, which could be slightly different.  I would give them both snubbers, as well, to minimize the effect of short pressure fluctuations.  I would also be inclined to wire the assembly with a switch (four pole double throw) so that either vapourstat could control either boiler; that way you could change which boiler was lead and which was lag from time to time.  Which would probably be overkill.



I would have each boiler with its own pressurestat (or pressurestats) mounted in the usual places.



I know of nothing wrong with the Honeywell vapourstats, other than that they need calibrating (for the new mechanical ones) or levelling (the old mercury ones) -- hence the pressure gauge.

vaporvac

Food for Thought!!!

Hmmmmmmmm. Very interesting. Definitely an evening's worth of thinking in your reply, Jamie. Thank you so much! I'm actually currently reading another reply of yours concerning other controls which I'll post on as well after i digest it.

http://www.heatinghelp.com/forum-thread/145847/Lead-lag-set-up-for-two-steam-boilers

I'm liking the relative simplicity of this set-up. My question regarding the pressurtrol was if there was any benefit in keeping the old one or should I just replace with the two new that came with the boilers.

thanks for the quick and thoughtful reply. Colleen

JStar

Vaporstats

Here's the Vaporstat staging we did on the VECO system. Very simple to set up. You should also install a 2-stage thermostat as well as the two Vaporstats.

vaporvac

From a bit further back?`

Holy moly Jstar! that is awesome...looks like it could take me to Mars. Do you have a pic from a bit further back? Could you please take a look at my post on controls, as well. I know you are also experienced with those. Thank you. C

JStar

Vaporstats

No further photos. The Vaporstats are located after the last main take-off, before the equalizer.