Woke up to a cold house this morning

JimmyNJ

Last night before I went to bed I thought I would modify the program the thermostat slightly by having a 2 degree setback from 10pm to 5:30am (going from 70 to 68). This morning we woke up cold with the house at 63 degrees. I went downstairs and saw on the thermostat that it was calling for Heat, went down to the boiler, took out my flat head screwdriver and slightly turned the cut-in screw on the pressuretrol half a turn and the boiler started up. I am stumped why this happened since the pressuretrol settings have been set the same for over a year. I did clean out the pigtail about a month ago as part of regular maintenance so I don't think that's an issue. The only "change" to the system was that I had a radiator added to the system on Monday - but the system worked fine Monday night through yesterday late evening. My wife even commented that she woke up in the middle of the night a few times to the air vent "whistling" so I think the boiler was working during the night until a point. I also noticed once I got the boiler firing this morning that the water in the sight glass almost disappeared. I assume this is due to the oil that may be in the boiler now from the pipework done earlier in the week (I know I will need to give it a good skim). Any ideas on why the boiler would not start firing until I adjusted the cut-in slightly? I know the Honeywell pressuretrols are not the most precise instruments but still feel it was strange that I needed to give it a slight adjustment. I have attached a pictures of the current "cut-in" setting plus pressure observed a few minutes after start-up plus sight glass.

ChrisJ

Has the Pressuretrol ever cut out on pressure before this?

The specific Pressuretrol you have is known for getting stuck like this if it's at the extreme low end of it's range.

Unfortunately they get a little flaky around 0.5 PSI or lower.


If you are running your system at this low of a pressure or lower and using the Pressurtrol to control it I would recommend getting a 0 to 4 PSI Vaporstat as they are more reliable at these pressures.

JimmyNJ

ChrisJ said:

Has the Pressuretrol ever cut out on pressure before this?

The specific Pressuretrol you have is known for getting stuck like this if it's at the extreme low end of it's range.

Unfortunately they get a little flaky around 0.5 PSI or lower.


If you are running your system at this low of a pressure or lower and using the Pressurtrol to control it I would recommend getting a 0 to 4 PSI Vaporstat as they are more reliable at these pressures.

I have had issues in the past where the boiler would not fire until I turned up the "cut-in" setting a bit (but this was after I had bottomed it out in my quest for low-pressure Another time I had to do just what I did now, basically adjust it a hair higher before the boiler would kick on. Just curious that after I found what I thought was a good setting (low pressure but enough so it would kick on when thermostat called for heat) that it would suddenly just stop working.

I've read that the Vaporstat's are the Cadillac's of the pressure control on a steam boiler - are they something a semi-handy person can install themselves? Is my understanding right that they work in conjunction with the pressurtrol?

JimmyNJ

Hatterasguy said:

Boiler room just a tad colder on the night of the failure???

I don't believe so - we had much colder weather here in north NJ on Monday and it worked fine then.

Chris_L

ChrisJ said:

Has the Pressuretrol ever cut out on pressure before this?

Yes, and what is the differential set at?

If the differential is too high, the pressuretrol will never cut back in. Set it as low as possible.

This may have never happened before because the boiler hadn't shut off on pressure before.

JimmyNJ

Chris_L said:

ChrisJ said:

Has the Pressuretrol ever cut out on pressure before this?

Yes, and what is the differential set at?

If the differential is too high, the pressuretrol will never cut back in. Set it as low as possible.

This may have never happened before because the boiler hadn't shut off on pressure before.

-The differential is set at 1 (little white wheel in box) which I think is the recommended setting.

ChrisJ

JimmyNJ said:

ChrisJ said:

Has the Pressuretrol ever cut out on pressure before this?

The specific Pressuretrol you have is known for getting stuck like this if it's at the extreme low end of it's range.

Unfortunately they get a little flaky around 0.5 PSI or lower.


If you are running your system at this low of a pressure or lower and using the Pressurtrol to control it I would recommend getting a 0 to 4 PSI Vaporstat as they are more reliable at these pressures.

I have had issues in the past where the boiler would not fire until I turned up the "cut-in" setting a bit (but this was after I had bottomed it out in my quest for low-pressure Another time I had to do just what I did now, basically adjust it a hair higher before the boiler would kick on. Just curious that after I found what I thought was a good setting (low pressure but enough so it would kick on when thermostat called for heat) that it would suddenly just stop working.

I've read that the Vaporstat's are the Cadillac's of the pressure control on a steam boiler - are they something a semi-handy person can install themselves? Is my understanding right that they work in conjunction with the pressurtrol?

I guess that depends on the person.
If you want to use both, using the Pressuretrol as a backup you would buy the 1/4" brass fittings you need to connect both to your pigtail, or, use separate pigtails which is preferred.

As far as wiring, you would wire them in series so if either control trips the burner shuts down.

Fred

Where is the pigtail mounted on the boiler? Is it connected somewhere below the water line? If so, even though you cleaned it a month ago, the oils in the new piping can mix with any crud in the boiler and make a sludge that can get pushed up into that pigtail or the tapping it is mounted to.

JimmyNJ

Hello Fred - the only pic I had readily available is the one attached here. To me it looks like the pigtail is above the waterline.

Fred

JimmyNJ said:

Hello Fred - the only pic I had readily available is the one attached here. To me it looks like the pigtail is above the waterline.

Yes, it is. It could just be a flute that the microswitch in the Pressuretrol didn't reset to close, maybe because the Cut-In was too low. I've had it happen on rare occassion. I also have a Vaporstat on my system as the primary pressure safety device and the Pressuretrol as a back-up. Watch it for a while now that you up'd the cut-in slightly. That may have been all it needed and the fact that you created a set-back at the Tstat just coincidental.

Abracadabra

No setback before. Boiler never cut out on pressure before, so cut-in is never an issue before.

Customer creates a setback with thermostat. Boiler cut-out on pressure, and never cuts-in.

Ensure that cut-in setting is within the normal operating range of the control or replace the pressuretrol with a vaporstat.

JimmyNJ

Any recommendations for a vaporstat? I saw an old thread that Honeywell Vaporstats became unreliable after the new non-mercury switches came on the market:

http://forum.heatinghelp.com/discussion/128249/why-do-honeywell-vaporstats-suck-so-badly

Has reliability improved? If so, any model recommendations?

Jamie Hall

We complain bitterly about things -- like Vapourstats. And it is true, the new ones with the guvmint mandated microswitches are a good deal less reliable than the old mercury ones. On the whole, however, they are reliable. Perhaps more to the point, either they work properly, properly adjusted, out of the box and keep working, or they don't work at all, so you don't have a problem with a failure down the line somewhere.

There are alternatives -- which are considerably more expensive.

ChrisJ

Jamie Hall said:

We complain bitterly about things -- like Vapourstats. And it is true, the new ones with the guvmint mandated microswitches are a good deal less reliable than the old mercury ones. On the whole, however, they are reliable. Perhaps more to the point, either they work properly, properly adjusted, out of the box and keep working, or they don't work at all, so you don't have a problem with a failure down the line somewhere.

There are alternatives -- which are considerably more expensive.

You know what I think is amazing?

People complain when the "guvmint" makes companies get rid of mercury switches, but people also complain about the mercury in all fluorescent lights. I wonder how many CFLs you could make with a single mercury switch, a few thousand?

People are amazing.

Fred

Most of us use the Honeywell Vaporstat.

JimmyNJ

Fred said:

Most of us use the Honeywell Vaporstat.

Any particular model? Looks like Supply House has 4 different models basically costing the same. Also, if one was to get a vaporstat, would I need a new low pressure gauge? I currently have a 0-5 psi hooked up to the pressuretrol along with the useless 0-30psi one.

ChrisJ

If you're running 1.5 PSI I'd go with L408J1017.

A 5 PSI gauge is fine, but for 1.5 PSI I'd use a 0-3PSI gauge.

JimmyNJ

Thanks for the input Chris - one final question of clarification. In theory, if the cut-in on the pressuretrol is set at 0.5 (or as close as possible to make the boiler actually fire up when thermostat calls for heat) and the "cut-out" is set at 1 -- the boiler would shut down if the back pressure hit 1.5 psi on the gauge right? If this is correct - then I am wondering about the accuracy of my 0-5 gauge as I had a problem with short-cycling last year (another thread) when I installed Vent-Rite #1's. After I increased Main Venting the problem went away - but when it did cut-out on pressure back then, the needle never moved past the 1 psi marker, it was more like 0.7 or so. Maybe I will invest in a 0-3 gauge after all. I'll just have to hide it from my wife who thinks I'm already to crazy about our boiler and steam heat in general

Fred

Most Pressuretrols and even Vaporstats are not accurate to the ounce. The Vaporstat will be closer but both can be calibrated to a reasonable degree of accuracy. The key is to keep the pressure low (below 1.5 PSI max) If you don't want to recalibrate the device, you can watch it if/when it reaches Cut-out and just adjust the scale indicator to get you closer to the 1.5 Cut-Out, even though the scale may say 2 PSI. If it actually cuts out at 1.5, that's the goal. In actuality, the Pressuretrol/Vaporstat should only be engaged in cases where the outside temp is extremely cold or you are recovering from a set back. All other times the thermostat should be the control for the boiler operation.

ChrisJ

Yeah, I'd trust the gauge over a Pressuretrol.

If it was my system and I had an oversized boiler that creates pressure while running I'd probably aim for 1.5 PSI off and 0.25 PSI on with a vaporstat. But you want the pressure to start climbing again before it bottoms out so it depends on how fast the system restarts and comes back to a boil.

It'll take some tweaking. I'd just want to keep it at 1.5 PSI or lower, while keeping the widest operating range possible.

As far as how low can the pressure go without sucking air back in on the off cycle, it depends on the system. Mine actually heats the house fine with only 0.006 PSI.

So your mission, should you choose to accept it, is to see how low you can get your vaporstat's cut-in without any of the radiators sucking air back in before the boiler gets back to producing steam.