pressure-trol set wrong??

ethicalpaul

https://forum.heatinghelp.com/discussion/comment/1690000/#Comment_1690000

reggi

Thermostats are : Off

Zone valves: Closed
Outdoor Reset : ON (50° or below Nov-March)
Boiler : Running 24/7
Pressure: Builds to 4-5 lbs Drops to 2 and repeats

The boiler is getting a signal from the Outside that the conditions are 50° or below so it runs.
The zone valves are CLOSED because the the Thermostats are turned down
The Boiler fills with STEAM to a pressure of 4-5; lbs then Cuts out..
Drops to 1-2 lbs and repeats the cycle

Now even I can see that something is incorrectly wired or failed..

EVEN with a Vaporstat it will run to the limit and cut back in at the bottom.. With more precision and more often..

The Boiler is firing and with the valves Closed the pressure builds no matter how you look at it..

Is this really just so simple that only I could see it...or am I missing something (probable) no offense intended of course

EBEBRATT-Ed

That is a 24 volt power relay. That coil uses a lot of Va

Jamie Hall

If it runs to 4 to 5 psi and then cuts out, either the vapourstat is way out of adjustment (a 0 to 4 psi can't be adjusted for a cutout above 4 psi) or simply isn't in the circuit at all, or is wired in parallel rather than in series in the control loop as it should be.

And with both zone valves closed but the outside control telling it to run, of course it will run up to pressure -- whatever that is -- and shut off. What, exactly, do you expect it to do? The poor thing is doing quite precisely what it's being told.

The problem -- as you may have surmised -- is that the fundamental control scheme is just wrong for the application. That scheme does work moderately well for an application where there are many zones -- not just two -- resulting in there being a very good chance that some zone, somewhere, needs heat at any given moment.

That's not your situation.

I believe I suggested a rework above, but to recap: you should select one zone -- I believe you mentioned a day care -- which needs heat, at least off and on, all day every day. That will become your master zone. When that zone valve opens, it commands the boiler to on. The boiler runs, you get heat. If it happens that the other zone is also calling, it's zone valve will also be open and it will get heat. Now another possibility is to wire the two zone valve end switches in parallel to the boiler. That way when either zone calls the boiler will run and the calling zone will get heat -- and the other will also get heat, if its zone valve is open.

I'd ditch the outdoor control entirely. It has no bearing on whether something in the building needs heat or not, so why is it there at all?

reggi

Yes Dear Watson I believe the case is solved.. We had been distracted and sidetracked with wanting to solve the case that sincerity of the witness blinded the fact that the logic was flawed..( Though I think I picked up on that 15 or so posts ago... maybe more 🕵️‍♀️ ) The rest is out of my league so Good Luck and I think it will be above 50 at the Church Tues or Wednesday so the Reset won't be functional 

nicksxvs

Sorry i was awol, i kind of gave up. thanks for the comments. a end switch sounds like the way to go. And ditching the outside temp switch. i don't know electronics so i'm not able to figure the 24 volt relay. unknown what va means. i attached a picture of how the boiler is wired and i'm in over my head. i could hook up end switches but idk where to connect to the gas control wire? if it had a vaporstat the pressure could be lowered so the burner on time would be less. they are $200.00 plus but should be installed by someone qualified who knows how to get the benefit out of them. the pastor had a tech look at the boiler and recommended a new and improved for a reasonal fee. doesn't anyone want to fix anything anymore. (sarcasm). heating season is about over. small churches are getting hammered these days.old ladies too.

nicholas bonham-carter

What is the desired goal here with this inquiry- more comfort-lower operating cost?
Many posts are here about the inadvisability of using zone valves on steam systems-especially one pipe.
There are also many posts, detailing problems with an outdoor temperature control such as you seem to have.
I would control the boiler with an interior thermostat, which can have several averaging remote sensors in different locations, and disable the zone valves if possible.
Also look at your main venting, so that the air can very quickly escape, as steam rises from a call from the thermostat.—NBC 

SteamingatMohawk

From my reading about outdoor resets, it seems they are not suited for steam, because the temperature cannot be adjusted downward, unless it is operated in a vacuum environment.

The literature says for hot water systems, the boiler output temperature is reduced to better match the demand on warmer days.

My view on these steam systems is to "Keep It Simple".

nicksxvs

to nbc, keep costs down...... there are two zones with two valves each. the building is heated using a x pattern which is not important just for your information. i would get rid of the outside temperature switch in a second and control the boiler by thermostats. as suggested above keep the daycare on one stat and when the sanctury calls for heat to open the second zone. it seems to be simple enough but i don't know how. the pastor called one guy to look at it and he recommended replacement. the pastors trying his best.

JUGHNE

There was a similar situation in our school.
2 zone valves run by 2 tstats. Boiler was on all heating season running up to 7 PSI.

Got pressure down to 2.5 PSI with standard ptrol.

Redid control wiring such that when zone valve opened, boiler would fire.
Typical oversized boiler had no problem building pressure within minutes.

Tstat would energize relay that opened zone valve, that relay would also energize another relay to close TT (start burner).
Same for the other tstat/zone valve.
Relays have to isolate signals from each other.

My zone valves were power open and power shut with no end switches.

I was concerned about "cold start". This was a 1955 steel fire tube boiler and when cold starting it suffered from condensation within the tubes.
So I added a aquastat with probe in the lower water of the boiler to maintain some warmer water inside. It turned out not necessary as once the beast was fired it stayed hot for almost days.

The lower PSI setting did not eliminate short cycling.
Perhaps the smaller zone would call and for that the boiler was 4X btuh needed.
If both called then only 2X oversized.

The 4" HW zone valves had both failed....that would be about $1 grand each.
The gas train had a 2 1/2" non repairable leaking diaphragm main valve which would requiring several more $1 G bills.
Plus oversizing issue.

The solution was to eliminate the zone valves and install 2 new boilers.
One for each zone....simple KISS operation.