Pressuretrol and quick cycling

melo

Can a pressuretrol go bad if a steam boiler quick cycles. Working on stopping it from quick cycling but I need heat so I have to live with it for the time being. 

melo

I’m concerned since we installed a new pressuretrol and it’s a safety feature. I don’t want it to go bad any time soon and cause problems for me or my family. 

EBEBRATT-Ed

Short cycling is hard on the equipment. Get the venting fixed and get all the radiation to heat and then see what happens

ethicalpaul

How quick? As @EBEBRATT-Ed says, how is your main venting?

melo

Like every 1 minute or so.

You can find the whole story here:

https://forum.heatinghelp.com/discussion/181580/crown-boiler-pressure-syphon-increasing-and-other-issues#latest

ethicalpaul

OK well your near boiler piping is quite bad you've probably already been told. It's too bad your plumber/steam guy can't recognize it.

The other thread had a lot of good advice. Basically:
- make sure the main venting is working. I'm not sure I'd trust your plumber to know based on what I've seen so far.
- make sure your radiators are all receiving steam.
- Calculate the EDR (sq ft of radiation) of all your radiators
- Compare that EDR to the net. sq. ft. steam value of your boiler

We all suspect your boiler is oversized and it may have been exacerbated by your radiator replacements. But even your system should be able to do a decent job. Yes maybe with some short cycles, but hopefully longer than a minute.

Do you "set back" your thermostat at night or other times?

Jamie Hall

The answer to your basic question in this thread is -- no. Pressuretrols are designed for tens to hundreds of thousands of cycles.

Perhaps more to the point, but what you didn't ask, is that the pressuretrol isn't your problem. It is simply reacting to what the rest of the system is -- or isn't -- doing. Don't shoot the messenger.

Depending on when in the course of the boiler coming up to steam and steaming, the problem could be an oversized boiler or really poor venting, or a combination -- but without knowing how fast the boiler comes up to the pressure limit in the first place, nor how much of the system and radiators have steam when it starts, I can't go farther.

melo

Jamie Hall said:

The answer to your basic question in this thread is -- no. Pressuretrols are designed for tens to hundreds of thousands of cycles.

Perhaps more to the point, but what you didn't ask, is that the pressuretrol isn't your problem. It is simply reacting to what the rest of the system is -- or isn't -- doing. Don't shoot the messenger.

Depending on when in the course of the boiler coming up to steam and steaming, the problem could be an oversized boiler or really poor venting, or a combination -- but without knowing how fast the boiler comes up to the pressure limit in the first place, nor how much of the system and radiators have steam when it starts, I can't go farther.

It takes the boiler roughly 20-25 minutes for it to turn off and then start short cycling. Within that 20-25 minutes all the radiators that are piped correctly are hot.

1 radiator is a vertical pipe in the bathroom that we will need to have tapped on and vented. The other radiator is not getting heat because the piping is worng.. it's slanted down so the pressure never goes up and it's filled with water from first use.

My question regarding the pressuretrol was more from a safety concern

Thanks again for your help! I really appreciate it

melo

ethicalpaul said:

OK well your near boiler piping is quite bad you've probably already been told. It's too bad your plumber/steam guy can't recognize it.

The other thread had a lot of good advice. Basically:
- make sure the main venting is working. I'm not sure I'd trust your plumber to know based on what I've seen so far.
- make sure your radiators are all receiving steam.
- Calculate the EDR (sq ft of radiation) of all your radiators
- Compare that EDR to the net. sq. ft. steam value of your boiler

We all suspect your boiler is oversized and it may have been exacerbated by your radiator replacements. But even your system should be able to do a decent job. Yes maybe with some short cycles, but hopefully longer than a minute.

Do you "set back" your thermostat at night or other times?

By setback do you mean like lower the temp so the boiler turns off?

Yes, we do that. We usually try to turn on heating at 7:00 PM and then turn it off by 10:00 PM then we turn heat back up on 5:30 AM and turn it off around 9:00 AM.

We're in NYC so it's not super cold yet... Really need to sort this issue out before actual winter snowstorms.

I'm looking to go out and buy used old school radiators and add more and replace smaller ones.

EBEBRATT-Ed

When the plumber comes to fix the radiator that is piped wrong have him install some main vents

Jamie Hall

"It takes the boiler roughly 20-25 minutes for it to turn off and then start short cycling. Within that 20-25 minutes all the radiators that are piped correctly are hot."

Eureka! That is classic for an oversize -- perhaps wildly oversize -- boiler.

Now the next question is... what, as exactly as you can measure, is the timing of the on and off cycling? How many seconds is the boiler on, then how many seconds is it off, and so on. Measure over several cycles to get good reliable measurements.

It may be that there are ways to tame this beast. Depends on how oversize is oversize... which the cycle timing will tell us.

ethicalpaul

By setback do you mean like lower the temp so the boiler turns off?

Yes, we do that. We usually try to turn on heating at 7:00 PM and then turn it off by 10:00 PM then we turn heat back up on 5:30 AM and turn it off around 9:00 AM.

Yes, that's what I mean. Don't do that

Seriously, try only letting the temperature dip a maximum of 3 degrees instead of turning it completely off.

How much of a temperature swing are you seeing?

A recovery of many degrees will amplify your oversized problem.
Steam works better holding steady.

melo

ethicalpaul said:

By setback do you mean like lower the temp so the boiler turns off?

Yes, we do that. We usually try to turn on heating at 7:00 PM and then turn it off by 10:00 PM then we turn heat back up on 5:30 AM and turn it off around 9:00 AM.

Yes, that's what I mean. Don't do that

Seriously, try only letting the temperature dip a maximum of 3 degrees instead of turning it completely off.

How much of a temperature swing are you seeing?

A recovery of many degrees will amplify your oversized problem.
Steam works better holding steady.

Why is that? I'm just stopping the thermostat from asking for heat by changing the desired temperature. I didn't want heat late at night or during the day.

If that's bad then should I just replace the thermostat with a programmable one that can be set for time?

I'm not getting a good reading on temperate just because the thermostat is in the hallway. However, the temp doesn't rise too quickly.

melo

Jamie Hall said:

"It takes the boiler roughly 20-25 minutes for it to turn off and then start short cycling. Within that 20-25 minutes all the radiators that are piped correctly are hot."

Eureka! That is classic for an oversize -- perhaps wildly oversize -- boiler.

Now the next question is... what, as exactly as you can measure, is the timing of the on and off cycling? How many seconds is the boiler on, then how many seconds is it off, and so on. Measure over several cycles to get good reliable measurements.

It may be that there are ways to tame this beast. Depends on how oversize is oversize... which the cycle timing will tell us.

After I added the a new vent downstairs, it's only taken 20-25 mins to heat up all the radiators. I also replaced all the radiator vents with the huffman ones.

Currently, I'd say the boiler stays on like 1 min and stays off like 45 seconds. That number might be a little higher just because the damper has to turn on and off.. which causes some extra seconds. With the damper forced open, it seems like the boiler is cycling a little quicker.

I'll try to get more accurate readings sometime tomorrow when I try to figure out the venting issue and also actually connect my biggest radiator + hopefully replace the smaller new ones with the old school steam radiators (I'm talking to someone to purchase them today).

Jamie Hall

We're making good progress here! Wonderful!

Yes, I would suggest a simple, battery powered programmable thermostat. Don't get fancy. There are a number of kinds available, and even the ones in the Big Box store are OK. Then set it so that it turns the target temperature down by 3 degrees in the evening, and back up in the morning.

The problem with deeper setbacks -- and why they don't save much, if anything -- is that the whole house and everything in it cools off, not just the air, and the boiler has to run longer warming things up again. Burning more fuel...

Adding the big radiator back in may change the cycle timings. I'd be surprised if it didn't, in fact. The present timings suggest that the boiler firing rate is a bit more than half again as high as it should be. This is not ideal, but is tolerable. As I asked, can it be downfired?

melo

What is downfiring? lol

IDK what that is tbh

JUGHNE

Have you calculated the EDR of your presently installed radiators?
It would be good to know that number and compare to the boiler EDR.

Also, the picture that shows the doorway going into the workshop....with the bench vise....there are pipes connected together at the height of the light switch...brown cover on it.

What do these pipes do?? Are they returns hooked together at the height of the switch? [which is most likely above the water line of the boiler] Then does the single pipe drop to your wet return?
If all the above is so then that is an issue for venting problems.

melo

JUGHNE said:

Have you calculated the EDR of your presently installed radiators?
It would be good to know that number and compare to the boiler EDR.

Also, the picture that shows the doorway going into the workshop....with the bench vise....there are pipes connected together at the height of the light switch...brown cover on it.

What do these pipes do?? Are they returns hooked together at the height of the switch? [which is most likely above the water line of the boiler] Then does the single pipe drop to your wet return?
If all the above is so then that is an issue for venting problems.

That pipe is slanted down and probably filled with water. It was meant to go to the bigger radiator in my living room. Unfortunately, due to bad piping, that radiator is not working. Planning to get it fixed this weekend.

I am planning to do the EDR calculation today and also get the bigger old school radiators.

ethicalpaul

Why is that? I'm just stopping the thermostat from asking for heat by changing the desired temperature. I didn't want heat late at night or during the day.

If that's bad then should I just replace the thermostat with a programmable one that can be set for time?

Thermostat or not, if you have to recover from a deep setback, then what will happen is:

- Your radiators will all completely fill with steam
- The pressure will rise
- The pressuretrol will cycle your boiler

And that last step will keep happening for a LONG time, because your radiators can only heat your stuff so fast.

But if you keep the place at a more steady temp, then when a call for heat happens you'll get this:

- Your radiators will start to fill with steam
- The thermostat will be satisfied, hopefully before they completely fill
- hopefully no cycling ever

neilc

sometimes we chase the perfect to extremes, Paul is correct, but what's a little cycling amoungst friends?

Did we ever establish Main Venting ?

melo

ethicalpaul said:

Why is that? I'm just stopping the thermostat from asking for heat by changing the desired temperature. I didn't want heat late at night or during the day.

If that's bad then should I just replace the thermostat with a programmable one that can be set for time?

Thermostat or not, if you have to recover from a deep setback, then what will happen is:

- Your radiators will all completely fill with steam
- The pressure will rise
- The pressuretrol will cycle your boiler

And that last step will keep happening for a LONG time, because your radiators can only heat your stuff so fast.

But if you keep the place at a more steady temp, then when a call for heat happens you'll get this:

- Your radiators will start to fill with steam
- The thermostat will be satisfied, hopefully before they completely fill
- hopefully no cycling ever

OH SHIEETTT I didn't think about that.

The thermostat calls for heat because it's not satisfied. However, if the temp inside the room is like 69 and the thermostat is set to 70 then the boiler will go up until 70 then stop.. wait for the room temp to drop again to 69 and it will shoot up again. In Theory this shop stop the boiler from short cycling too much as the boiler will be off as the thermostat is satisifed.

Correct?

melo

neilc said:

sometimes we chase the perfect to extremes, Paul is correct, but what's a little cycling amoungst friends?

Did we ever establish Main Venting ?

Main venting definitely needs some work. That pipe going to the front (work bench area) will need to be fixed.. It's pitched incorrectly so the steam never makes it up there and it's probably filled with water at the moment.

Jamie Hall

melo said:

ethicalpaul said:

Why is that? I'm just stopping the thermostat from asking for heat by changing the desired temperature. I didn't want heat late at night or during the day.

If that's bad then should I just replace the thermostat with a programmable one that can be set for time?

Thermostat or not, if you have to recover from a deep setback, then what will happen is:

- Your radiators will all completely fill with steam
- The pressure will rise
- The pressuretrol will cycle your boiler

And that last step will keep happening for a LONG time, because your radiators can only heat your stuff so fast.

But if you keep the place at a more steady temp, then when a call for heat happens you'll get this:

- Your radiators will start to fill with steam
- The thermostat will be satisfied, hopefully before they completely fill
- hopefully no cycling ever

OH SHIEETTT I didn't think about that.

The thermostat calls for heat because it's not satisfied. However, if the temp inside the room is like 69 and the thermostat is set to 70 then the boiler will go up until 70 then stop.. wait for the room temp to drop again to 69 and it will shoot up again. In Theory this shop stop the boiler from short cycling too much as the boiler will be off as the thermostat is satisifed.

Correct?

Got it.

PMJ

Setbacks do save money done properly. They also improve comfort as some folks actually like it a bit cooler at night.

The gas bill is determined by the total heat loss to the outside which is determined directly by the average temperature difference inside to outside over a given time frame. That difference is obviously lower with setbacks. The period of warming the insides back up does not cause more heat to be lost the outside than would have been lost if the higher inside temperature had been held all along. In the simplest form all that is required to come out of a setback not banging off a high pressure device is to put a limit on straight run time with a simple timer. Such a control option should have made it into the standard fare long ago. Such a control would eliminate all the fuss over boiler size too.

So I don't get why it has become by default necessary that all boilers run flat out from whenever calls start to when they are satisfied. It isn't hard at all to figure out how long a boiler in a given structure needs to burn per hour to heat on design day. So why ever let one run more than that in any given hour? Just breaking that burn up into two even pieces spaced evenly in each hour would make all pressure problems go away.

ethicalpaul

@melo has bigger fish to fry than novel steam boiler control mechanisms at the moment

But I don't disagree with you @PMJ

PMJ

ethicalpaul said:

@melo has bigger fish to fry than novel steam boiler control mechanisms at the moment

But I don't disagree with you @PMJ

I didn't mean to suggest he do it. I am expressing dismay it has not been done as a standard already - that the industry has absolutely nothing to offer him and many others when the solution is so simple.

Jamie Hall

"So why ever let one run more than that in any given hour? Just breaking that burn up into two even pieces spaced evenly in each hour would make all pressure problems go away."
Which, of course, is what a thermostat does... assuming it's properly set up...

PMJ

Jamie Hall said:

"So why ever let one run more than that in any given hour? Just breaking that burn up into two even pieces spaced evenly in each hour would make all pressure problems go away."
Which, of course, is what a thermostat does... assuming it's properly set up...

I don't know of a thermostat that can do the burn spacing I suggested, but would be happy to learn about one. Or by properly set up did you mean a regular thermostat and "right sized" everything that will never reach pressure even in a significant setback recovery?

Jamie Hall

something like that...

JUGHNE

I think Melo should set the tstat at 68 or so and leave it a few days. Want cooler at night...open some windows....wasn't it recommended by the CDC because of Covid?

This would eliminate the question if setbacks are causing his problems....some of them anyway.

melo

Would short cycling also be caused by bad pressuretrol settings? Because I’m wondering let’s say I put the main to .5 or 1 psi and Differential to 1 psi. Wouldn’t that in theory make the cycling interval longer? If my boiler is oversized for the radiators?

The steam will rise to .5 or 1 psi. Which would take time in theory and then it will start to fall. Once it falls to 0 psi, the boiler will turn on again. 

neilc

you'll want your main around 1.5~2, and the diff at 1,
post a closeup of that Ptrol,
the main is the cutout, and the diff sets the cutin, correct ?
still going to cycle though.

Jamie Hall

If we take the scenario where all the radiators are heating fully, and assume that that is where we are concerned about cycling, then what we are seeing on the cycling is that the heating part -- boiler running -- is replenishing the steam which has condensed, and the cooling part represents the change in pressure as the steam is condensing. Now if we raise the cutout pressure, what happens is that the extra energy represented by the slightly longer run shows up as compression of the steam and thus boiling at a slightly higher temperature (slower) and condensation at a slightly higher temperature (slightly faster). In theory, i this is taken to an extreme, one would reach a temperature and pressure at which the condensation rate matched the boiler output. We do not want to get there in a heating system (very very roughly, a boiler 50 % oversize would reach close to equilibrium with the radiators at 300 degrees and the pressure at 50 psig, for instance). Within the practical range of pressures we are dealing with, the condensation rate will be almost constant, as will the evaporation rate. So changing pressuretrol settings will have little effect on the overall on/off percentage.

neilc

yeah, but if I see his Ptrol correctly in the other thread,
the main is down at 1, and the diff is at 2, and I think he's bouncing off the switch ,
#not sure

melo

This plumber brought in said our pressure previously was high. He changed it to this now.... 

im getting different answers from different people. It’s ridiculous to be honest lol... this guy works as hvac for a city building that’s being built 2 blocks from me and was recommended by neighbor. 

He didn’t think boiler was oversized but rather the pressure was high... idk. 

This is what he currently set it to. We haven’t turned the heater on. 

Jamie Hall

Oof. I hadn't actually looked at the settings. You'll need to bring the main up to about 1.7 or so, then it will work better.

neilc

ok, right, so,
set the main up 1/2 way to the 2, so it's set at 1 1/2 psi, eyeball that,
and the diff, set it down to 1, eyeball it,
you should shut off at 1.5, and turn back on at 0.5.

do you remember where it, the main, was set to prior?

melo

This is what I have set now. Should I just make main 2 psi?

neilc

I would still dial the diff down to 1,
and those Ptrols not being 100% accurate / calibrated, run it as is, (diff at 1), and see where the pressures are, ya might dial the main down a hair, I'm calling that 1.75.
it will still cycle though

neilc

neilc said:

it will still cycle though

have you done your own edr takeoff yet ?
and compared to what the boiler is rated at ?

melo

https://governaleindustries.com/wp-content/uploads/2020/09/Governale-full-line-lit.pdf

I used that to find the EDR as my radiators are most likely from this company. 19" with 2 tubes and 4 columns. 

First Floor: 

Room 1: 32

Room 2: 16

Room 3: 12.8

Room 4: 16

Room 5: 19.2

Second Floor:
No Clue but we did not change anything second floor. Has old school "big boy" radiators". They have a total of 4 radiators upstairs. 

This is the boiler that I have: https://www.johnstonesupply.com/product-view?pID=L99-655