New Steam Boiler Short Cycling - Thermostat?

john_ospnj

Hi All,
Thanks in advance for any tips, always great help on here.
So have a brand new Williamson GSA125, the boiler itself seems to be running fine - main/rad vents all working, good and skimmed/cleaned out, flue operating properly...but it is short cycling, sort of. It shuts off early.
If I have it set to 70 degrees, thermostat will call for heat, fires up, steam fills mains/risers and gets to about the valves on all rads, the room with the thermo gets teased with just a little heat, then it shuts off.
At first I was worried there was a pressure issue, maybe some gunk got into the pigtail or something. The pressure gauge never moves from the pin - but it is one of those 1-30psi basics that comes with the boiler and seems like it is common for these not to register the low pressure of steam. So what I did - cranked the thermostat up to 85 and let it all fire for a good long while - no issues at all. Boiler ran like a jet engine, system great, all rads hot all the way across, no pressure, house got good and toasty. I did this a few times of a few days. No issues.
So, that would eliminate all boiler 'operating' issues, right? Cant be pressure/clogs, or wire grounding out somewhere, or flue issue, or anything else, right? Has to be the Thermostat, or am I missing something?
But then...why. It is an old vintage Honeywell poop-brown T82 mercury switch that worked just fine with the old Crown boiler and everyone seems to feel is superior to modern thermos. I can't imagine that it went defective on the day the new boiler was installed.
Now granted, the thermostat isn't in a great location, it's in the living room which gets the warmest, and gets warm first. The thermo anticipator goes .18 to .9, and I've adjusted it to the longest/.9 setting. This seems to help a little with keeping the system from clicking back on 10 mins after shutting down. But does nothing for making it actually run a full cycle and warm the whole home.
Any thoughts?
Thanks,
John

Jamie Hall

Well... the obvious question is what does the temperature scale on the thermostat say when it clicks off? And the second, perhaps a little less obvious is, if this is a mercury T87, is it level? If it is, as you indicate, level is absolutely critical -- even a very small amount off can confuse it badly.

john_ospnj

If I set it at 70 degrees, it seems to click on just under, maybe 69, then click off at 70. Since it is in the living room, which warms first and fastest, steam never gets far in the rest of the system and the other rooms of house are cold.
With the old Crown, if I set at 70, it would seem to click on around 67 or 68 and run past 70 to about 73 and then click off - this would be a good full cycle and get steam to all rads. Warm house.
It's like the thermo is suddenly hypersensitive with the new boiler, no tolerance for temp differential.
And yes, thermo is perfectly level - I actually re-leveled it when I upped the anticipator. Interesting it was a little off-level while it was working great with the old Crown for all those years.

pecmsg

Why did you “up” the anticipator?

john_ospnj

Because at first, the new boiler was really short-cycling - it would click on, start to get steam, click off, then click back on 10-15 mins later. Repeat.
It seems anticipators should be set to the 'longer' end of scape for steam heat (no?) So that's what I did.
Which did seem to help a little with the 'click back on' part of the above statement, seemed to change it from about 10-15 mins to 30-40mins. But all the really means is that the house has even more time to get cold again.

john_ospnj

So while I've been sitting here at the computer, I did another test. With the thermo cover off, I nudged the setting up until the mercury slid and just barely clicked on the boiler. It only ran for about 6 mins. Didn't even come to steam. I didn't see the mercury slide back but it did, and shut off boiler.

pedmec

it sounds like you need to balance out the venting. Your thermostat is doing exactly what is suppose to do

109A_5

Hello @john_ospnj,

For a starting point the heat anticipator should be initially set by measuring the current through the thermostat. The current may be significantly different with the new equipment, hence your problem.

The 'Steam setting' was typically for much older gas valves and systems that draws too much current through the thermostat for proper T87 heat anticipator operation. The result would be that the heat anticipator resistor would burn up. So the Steam setting effectively disabled current from flowing through the anticipator resistor.

Your heating system installer probably did not verify the current before and after the install.

bburd

There is good advice above. What kind of main vents do you have? They vary quite a bit in capacity. If I were you I would also slow the venting of that living room radiator near the thermostat. What kind of vent is on there? Some vents are quite fast even when apparently closed. 

JohnRambo76

john_ospnj said:

Hi All, Thanks in advance for any tips, always great help on here. So have a brand new Williamson GSA125, the boiler itself seems to be running fine - main/rad vents all working, good and skimmed/cleaned out, flue operating properly...but it is short cycling, sort of. It shuts off early. If I have it set to 70 degrees, thermostat will call for heat, fires up, steam fills mains/risers and gets to about the valves on all rads, the room with the thermo gets teased with just a little heat, then it shuts off. At first I was worried there was a pressure issue, maybe some gunk got into the pigtail or something. The pressure gauge never moves from the pin - but it is one of those 1-30psi basics that comes with the boiler and seems like it is common for these not to register the low pressure of steam. So what I did - cranked the thermostat up to 85 and let it all fire for a good long while - no issues at all. Boiler ran like a jet engine, system great, all rads hot all the way across, no pressure, house got good and toasty. I did this a few times of a few days. No issues. So, that would eliminate all boiler 'operating' issues, right? Cant be pressure/clogs, or wire grounding out somewhere, or flue issue, or anything else, right? Has to be the Thermostat, or am I missing something? But then...why. It is an old vintage Honeywell poop-brown T82 mercury switch that worked just fine with the old Crown boiler and everyone seems to feel is superior to modern thermos. I can't imagine that it went defective on the day the new boiler was installed. Now granted, the thermostat isn't in a great location, it's in the living room which gets the warmest, and gets warm first. The thermo anticipator goes .18 to .9, and I've adjusted it to the longest/.9 setting. This seems to help a little with keeping the system from clicking back on 10 mins after shutting down. But does nothing for making it actually run a full cycle and warm the whole home. Any thoughts? Thanks, John

What’s the outside temp where you’re at? I get that issue too but it’s due to me keeping my Tstat at a temp where if the heat was off the house would linger around that temp anyways if not too cold outside. I keep my house at 64 at night and if the heat was off on say a 40 degree night my house would linger around that temp so the Tstat barely needs to work to reach temp, it’ll dip just below temp to have a call for heat. I have a Honeywell non programmable Tstat so I can’t adjust offsets or anything. If the “heat on” is still showing on Tstat and boiler is off there’s an issue, if the boiler is off and at set point  and no “heat on” is showing your Tstat is satisfied.

john_ospnj

Yes, thanks all for the advice.
To answer venting - Gorton #2's on the mains, Gortons or Hoffman1A's on most rads. The 1A in living room is on 'slowest' setting. But there are also 2 risers in this room going upstairs. I've spent a long time balancing the venting, it seems pretty good. And as said in the orig post, if I crank up the thermo - it all runs great, steam reaches all rads about the same time.
So in summary - no probs with pressure/pigtail right, or something grounding out, or other boiler issue? Or that wouldn't allow the good, long steams with the thermo set at high temp.
It has to be something with the thermo...but all advice above seems to think my old mercury Honeywell is doing what it should. So I don't need to go out and buy a new one. It seems to be a voltage/anticipator thing? Maybe I can just play around with the anticipator setting until I get the longer/fuller steams with less cycles per hour that I'm looking for?

pecmsg

You need to measure the amperage on the control circuit to set the anticipator. 

Jamie Hall

john_ospnj said:

Yes, thanks all for the advice.
To answer venting - Gorton #2's on the mains, Gortons or Hoffman1A's on most rads. The 1A in living room is on 'slowest' setting. But there are also 2 risers in this room going upstairs. I've spent a long time balancing the venting, it seems pretty good. And as said in the orig post, if I crank up the thermo - it all runs great, steam reaches all rads about the same time.
So in summary - no probs with pressure/pigtail right, or something grounding out, or other boiler issue? Or that wouldn't allow the good, long steams with the thermo set at high temp.
It has to be something with the thermo...but all advice above seems to think my old mercury Honeywell is doing what it should. So I don't need to go out and buy a new one. It seems to be a voltage/anticipator thing? Maybe I can just play around with the anticipator setting until I get the longer/fuller steams with less cycles per hour that I'm looking for?

The real question is -- is it heating the house to the set temperature? If it is, it's doing what it is supposed to do... if it ain't broke...

john_ospnj

Good thoughts John Rambo - I've wondered if things would be any different in 'true cold'. I'm in north/central NJ and it's only gotten into low 40's most night, maybe starting into the 30's.
But no Br. Jamie, it isn't heating house to temperature. I also keep it around 65 at nights, and in the morning the upstairs bedrooms are all cold, rads are cold, luke warm at the valves. Downstairs is mostly cold, living room the warmest, with the risers going to upstairs are warm, the living room rad warm at the valve. This room might be just barely at 65. Basement is warmest, smells like a firing boiler, the boiler near-piping is all hot, main lines all hot (and yes, all my piping is well insulated). I can clearly tell that the boiler has been coming on often through the night...which can't be good for the new boiler or my wallet, or my sanity with wife asking why it's freezing in the morning if we just spent $ for a new boiler...

JohnRambo76

john_ospnj said:

Good thoughts John Rambo - I've wondered if things would be any different in 'true cold'. I'm in north/central NJ and it's only gotten into low 40's most night, maybe starting into the 30's. But no Br. Jamie, it isn't heating house to temperature. I also keep it around 65 at nights, and in the morning the upstairs bedrooms are all cold, rads are cold, luke warm at the valves. Downstairs is mostly cold, living room the warmest, with the risers going to upstairs are warm, the living room rad warm at the valve. This room might be just barely at 65. Basement is warmest, smells like a firing boiler, the boiler near-piping is all hot, main lines all hot (and yes, all my piping is well insulated). I can clearly tell that the boiler has been coming on often through the night...which can't be good for the new boiler or my wallet, or my sanity with wife asking why it's freezing in the morning if we just spent $ for a new boiler...

Mild cold then, bump it up to 68….once the temps start going into the low 30’s and 20’s then 64 at night would suit a stable heat transfer considering your home is insulated decently. 

bburd

It does sound like the thermostat is not playing well with the new boiler, which probably has a smaller current draw. If it still doesn’t work well at the longest (highest current) setting, you might consider changing to one of the electronic thermostats that are compatible with steam and use a cycle rate setting rather than a heat anticipator to run the boiler long enough to heat all rooms. The Honeywell Vision Pro series has good reviews here, others can advise you on specific models. 

It’s important to note that many electronic thermostats are not compatible with steam heat. They are generally design for forced air or hot water systems.

JohnRambo76

Bburds, wouldn’t you want a Tstat without an hourly cycle rate considering radiators can give off heat for longer than an hour? I know on some of the coldest days my steam system will cycle for 15-20 mins and be off for well over an hour between cycles. My Tstat isn’t as efficient or fancy, but maybe that’s why it’s made specifically for steam? I have a Honeywell TH1100DV1000. 

bburd

Steam compatible electronic thermostats typically have an hourly cycle rate that can be set for once per hour for steam or gravity hot water; three times per hour for fin tube / forced hot water; or six times per hour for forced air. That is not an absolute number but an approximation since the room temperature and its rate of change comes into it as well.

The point is that steam heat needs a longer and less frequent cycle than hot water or hot air. The OP’s heating cycle is too short.

dabrakeman

@john_ospnj Is it possible that your T-stat is located on a wall right above the boiler? If so, is it possible you are getting more heat up through the floor or the wall than might have with the previous boiler (i.e. new uninsulated near boiler piping)?

BobC

Is the time it takes dteam to get from the boiler header to the radiators longer than it used to be? It's possible the new boiler install caused some unintended shifts in the piping and some pipe slopes have been changed.

Bob