0-1psi or 0-4psi vaporstat?

Jeffrs

My pressurtrol seems to cut out at 4.5psi according to my 0-5psi gauge, so its not very accurate. Looking to move to a vaporstat. How can I determine whether I need a 0-1 or 0-4 psi vaporstat? I get steam to the radiators with very little pressure, and it'll run for about 10-15mins before it begins to make pressure. The house is old with little insulation between the plaster walls and outside clapboard siding, so it runs for extended periods of time during those real cold days to keep up, sometimes not shutting at all except for level checks and pressure cut out. When it runs that long is when it comes up to the 4.5psi mark, then cuts out till the cut in and then runs for another 5-10mins before it hits the 4.5psi cutout again. The 0-1psi vaporstat should help keep fuel consumption down but won't a 0-1psi vaporstat cause short cycling on those cold days?
Thanks

BobC

If the vaporstat cut of at 1PI the boiler would cycle on and off more than it does now but 1 PSI steam moves faster than 4 PSI steam so it is a bit more efficient. Is this oil or gas fired?

Are you sure the main venting is adequate, you want the mains ro fill with steam as fast as possible.

Bob

Abracadabra

I always install a L408J1025, even on larger buildings. You really shouldn't need more than 1PSI unless there's something else strange going on with your system.

Fred

There is no reason you want your pressure to get to 4.5PSI. Make sure you have good venting on the Mains and that the pigtail the Pressuretrol is mounted on isn't plugged with gunk.
If you decide to go with a Vaporstat, I would use the 0 -1 PSI Vaporstat.
If you have the gray Pressuretrol with the Cut-In scale on the front aand the white Differential wheel inside, you can recalibrate it. Following are the instructions for doing that:
Calibrate a Pressuretrol
Inside the Pressuretrol, right below the micro switch, there is a pivot arm. At the end of that arm you will see a screw pin that is activated by the diaphragm at the bottom of the Pressuretrol. If you look very carefully at that screw pin, you will see it actually has a tiny (I mean tiny) hex head on it. It takes a .050 hex wrench and you can turn it clockwise (Towards the bottom of the Pressuretrol to decrease the Cut-out pressure or counter clockwise to increase the cut-out pressure (which none of us want to do but who knows, your Pressuretrol may be really screwed up!). Turn the power to the unit off first. You may find the first attempt to turn that screw a little bit stubborn (relatively speaking) because it has some Locktite on it but it does turn. Don't turn too much, a fraction of a turn goes a long way towards getting it adjusted where you want it (maybe 1/32 inch turn to start with). You may need to play with it to get it exactly where you want cut out to be.

ChrisJ

What boiler do you have and is it possible to downfire it at all?

Jeffrs

It is a gas fueled boiler. It is a Weil - McLain boiler, I believe an EG 40 but I'm not positive, I'll check once I'm home. The pigtail is clean, I've checked a few times now. I will try to calibrate the pressuretrol with the above instructions. When I moved in, there was no main vents at all, there is 3 mains, I added a vent at each Main, but it may not be adequate, as I only drilled and tapped the pipes for a 1/4" nipple with it bushed to a 3/4" maid o mist main vent. I'm sure the 4.5psi is too much, I think it's causing my radiator vents to leak at times under pressure. Sorry for the dumb question but how would main venting have an effect of causing the pressure to be so high? On the real cold days the boiler doesn't really shut down other then water level checks, shouldn't the air be vented out of the pipes already from initial heat up since the boiler never gets a chance to let the pipes cool?
Thank you all for the quick responses.

nicholas bonham-carter

When the burner shuts down, the steam quickly condenses, developing a vacuum, and the air rushes back into all the pipes. The next cycle starts it all again, with the air needing to be pushed out again. It's nothing to do with the pipes being warm.
You will need a bigger tapping into the main (1/2, or 3/4 in.) , for at least one big main vent. The restriction of the little tapping you have now is just too much.--NBC

KC_Jones

The venting really is what dictates pressure. The pressuretrol just stops the pressure doesn't dictate it. Get a straw, put your finger over the end and blow into it. You will get pressure, now remove your finger and blow into it, no pressure. The vent on the main is you removing your finger from the straw. Another thing you can do in addition to venting is measure the EDR of all your radiators and compare that to the boiler to see how well matched the boiler is to the system. This will indicate how well you will be able to manage the pressure. If you are over sized you will only be able to do so well with venting.

ChrisJ

That's too bad.

If it was an EG-45 you could have someone come in and convert it to an EG-40, but you can't go the next step lower.

Jeffrs

Ok, but the pressure doesn't build until long after the radiators are hot, isn't the pressure building since the boiler is continually running and making steam with no place for it to go?
The pipes are 2" so I don't think I can tap the pipes any larger, I'll have to cut out sections and add T's for the main vents, any tips or tricks for doing that with old pipes still in place?
I double checked the boiler. It is an EG 45.
Thank you all very much again for the prompt response.

ChrisJ

Yes, if pressure builds after the radiators are hot it's because the boiler is too big. How long does it take to build pressure and how much does it build?

Good news is if you want an EG-45 can easily be converted to an EG-40.

The burner manifold, rear burner support and drafthood need to be changed. That will reduce your boiler's output from 125,000 to 104,000 btus.


I just did it to mine, though I wasn't having pressure problems.

http://forum.heatinghelp.com/discussion/153322/converting-from-eg-45-to-eg-40/p2

I highly recommend you have this done by a professional if it's how you want to proceed. It will be more useful than using a lower pressure limit in my opinion.

Jeffrs

Is it that the boiler is too big? Or that my heat loss is to great requiring the boiler continuously? There is a capped Tee in the main closer to the boiler so I'm thinking the prior owner removed a radiator for whatever the reason.
Thank you again

KC_Jones

Can't really answer that question unless you calculate the EDR of your system and compare that to the boiler size. A majority of the time the boilers seem to be over sized. If it is, as Chris pointed out that boiler can fairly easily be changed to an EG-40 which lowers the gross firing rate 25k BTU's.

ChrisJ

Jeffrs said:

Is it that the boiler is too big? Or that my heat loss is to great requiring the boiler continuously? There is a capped Tee in the main closer to the boiler so I'm thinking the prior owner removed a radiator for whatever the reason.
Thank you again

Not sure, how does the system perform on the coldest days you've seen?

Theoretically, when it's about as cold as your area ever sees, in a perfect world the boiler should run almost continuously to maintain temperature in the house. This is what yields the greatest efficiency. This is also assuming all rooms stay the proper temperature as well.

My boiler can easily run 40 minutes to an hour and barely create any pressure at all but it heats beautifully. My opinion is a pressuretrol or vaporstat should only be a safety limit and never shut the boiler down under normal conditions. The boiler should be the limiting factor during normal use.

Fred

If the boiler runs for extended (long periods of time) it could be that the thermostat is located in an area that is drafty or the room temp is not representative of the rest of the house, it could be that there is a large hole behind the thermostat where the wiring comes through the wall and that cool air from the basement or attic affects the thermostat. It could be that you are using a set-back on the thermostat that the boiler has a difficult time making up.
Normally I'd say it could even be an under-sized boiler but given that you do shut down on pressure, that is not likely the case for you.
A steam boiler doesn't so much care about heat loss as it does filling the radiators until they are full and pressure builds to a point where the Presuretrol shuts the boiler down. That typically should be no more than a pound to a pound and a half. Most of us like to limit that to no more than 12 ounces. Anything over that is a waste of fuel, slows the the flow of steam and holds vents closed longer.

Jeffrs

The coldest of days the boiler just continuously runs, often if it's really cold out, it doesn't even hit the target pressure that the thermostat is set to, especially if it's windy. It's an old house with little insulation and plenty of drafts that I'm trying to correct over time, but regardless of how long it runs, it sounds like that I really shouldn't be building pressure much. As I read this forum more and read the above posts, it all seems to be making more sense to me that as you've been saying the boiler is too large, making more steam then the radiators can condense quick enough, did I get it right?
also can anyone point Mr in the right direction of how to calculate my EDR, I had bought or downloaded a document I think somewhere here that helped me do it before but I can't remember where it is or how to do it.
Thank you again

ChrisJ

There's a common program made by Slant Fin which is free that you can use. It's only available for Android and IOS.

http://www.slantfin.com/index.php/professionals/heatloss


Once you figure out your heatloss and compare it to your radiation you'll have a better idea of what to do. Fact is, the higher the pressure you run, the more heat your radiators put out because they get hotter.

If I recall, 1.5 PSI = 115F. 2 PSI could be as high as 218F.

I always preach about keeping pressure low, but in your case it may not be the best idea.

Let us know if you need any help using the program and keep us updated with your findings.

Fred

There is this radiator EDR sheet from Columbia Gas as well. Here is the website: http://www.columbiaheatingsupply.com/page_images/Sizing Cast Iron Radiator Heating Capacity Guide.pdf
Calculate the total EDR of your radiators and let's see how that comprares to your Boiler output and decide how best to adjust.

vaporvac

Hi @ChrisJ. I'm not following the heat loss suggestion in this case. What am I missing? I always thought only the edr was important in steam systems, unless building from scratch or replacing rads or is the latter what you're thinking, ie. his rads are too small. Inquiring minds want to know!

ChrisJ

vaporvac said:

Hi @ChrisJ. I'm not following the heat loss suggestion in this case. What am I missing? I always thought only the edr was important in steam systems, unless building from scratch or replacing rads or is the later what you're thinking, ie. his rads are too small. Inquiring minds want to know!

the output you get from the radiators can vary some. The bigger the temperature difference between them and the room, the more heat you get from them.

Running at 2 PSI most certainly will give more heat than running like I am, but it's usually not worth it. If they don't have enough radiation to keep the house warm under some conditions maybe it's worth cheating a little.

My opinion though, is heatloss does matter and you shouldn't necessarily match the boiler to the EDR.

Fred

My opinion though, is heatloss does matter and you shouldn't necessarily match the boiler to the EDR.

Stick me with a fork and turn me over; I'm done You're killing me @ChrisJ
If it turns out he doesn't have enough EDR and he has an over-sized boiler, it may make sense for him to add more radiators or exchange some of the ones he has for larger ones. A heat loss may help him make that decision but he may also address the problem by tightening up the envelope in areas where he knows he has air infiltration, poor insulation.

ChrisJ

Fred said:

My opinion though, is heatloss does matter and you shouldn't necessarily match the boiler to the EDR.

Stick me with a fork and turn me over; I'm done You're killing me @ChrisJ
If it turns out he doesn't have enough EDR and he has an over-sized boiler, it may make sense for him to add more radiators or exchange some of the ones he has for larger ones. A heat loss may help him make that decision but he may also address the problem by tightening up the envelope in areas where he knows he has air infiltration, poor insulation.

Yes, and yes.
But many won't consider swapping radiators or adding them as it's a lot of work.

Me, I've considered busting mine apart to shrink them but apparently I like pain. If there's a can of worms around I'll find it and crack it open!

But I'm trying to help the guy out without making a nightmare for him.

Jamie Hall

It is true that one can get a little more heat out of a radiator with steam at a slightly higher pressure.

However. If the combination of radiation, space, interior temperature, exterior temperature, infliltration, etc. etc. is so close that the difference is important...

In the OP's case, it is stated that the boiler does eventually shut off on pressure, and mentions continuous running only under extreme conditions. My reading of his (? her) situation is that the boiler is pretty well matched to the radiation -- and the radiation to the extreme heat loss. In which case, I'd go with the 0 to 1 psi vapourstat.

And if I wanted to be warmer, I'd start looking at infiltration as the first mole to whack.

Jeffrs

Thanks guys, at work for the night, will do my EDR calculations tomorrow and report back my findings.

Jeffrs

So just to be certain, the calculation for EDR is as follows:
Height and number of columns or tubes variable x number of sections variable x 240btu (for steam)
I have 8 radiators in the house, totaling all up, I come up with 69350btu. The EG 45 boiler is 150,000btu.
Guess I'm pretty well oversized if I did my calculations correctly. Now what?
Thank you guys very much

ChrisJ

If you did your math correctly, and you're sure those radiators are that size. I would definitely recommend converting to an EG-40.

Just remember, there are large tube and small tube radiators as well and they differ in output.

Did you get around to doing a heatloss on the house yet?

Fred

That's a lot over-sized. Double check your radiator calculations and if they are correct, you may want to do a couple things. As Chrisj says, it it fairly inexpensive to down-grade the burner to an EG-40. The other thing I would consider is when you do that, I would have a 2 stage gas valve installed. That is a bit more expensive but at the pressures you are seeing, a 2 stage would work well for you. With a 2 stage, you can set the high flame to run until it gets to a certian pressure, say 8 ounces and then it will lower the flame and cruise until it gets to your Cut-out setting, say 12 or 14 ounces. At the lower flame the pressure may never get that high on a normal heat cycle.