Pressuretrol and quick cycling

melo

We can't count Room 1 because that's a problem child. I need to get the pitch fixed since it's not working at the moment. Based on my research, I have to calculate BTU by multiplying the EDR by 240. 

My boiler has a 138,000 BTU rating. 

Room 2: 16 * 240 = 3,840
Room 3: 12.8 * 240 = 3,072
Room 4: 16 * 240 = 3,840
Room 5: 19.2 * 240 = 4,560 
= 15,312 BTU

IDK if this is how I'm supposed to do it. Not sure about upstairs with the old school radiators though. 

neilc

yeah, even if you have twice as much upstairs in the old rads,

you need to get a measurement on the upstairs also.

melo

What’s the ideal point that I would need to stop the boiler from short cycling? 

neilc

boiler EDR = house rad EDR (including the one needing repiping),
means a smaller, right sized boiler,
or stop chasing perfect,
you might ask about downfiring, but the napkin exercise shows you twice too big, and that is too much to downfire.

dabrakeman

If that is a BSI138 the EDR on it is 354sqft.

EBEBRATT-Ed

Rough calculation because I could only find the input for that boiler but it's good for around 308 EDR.

The 138000 is the input you take off from that 33% piping and pick up and 80% for efficiency roughly. You end up with a boiler thats good for 308 EDR.

You have 86 EDR when you get room #1 fixe plus the second floor....say it's 65 EDR, it's 4 more rads that gives you a totoal of around 150 EDR

So your boiler is 2 x the size it needs to be, no wonder it short cycles with set backs, poor venting and 1 32 EDR radiator that doesn't work

Nothing else to say

melo

EBEBRATT-Ed said:

Rough calculation because I could only find the input for that boiler but it's good for around 308 EDR.

The 138000 is the input you take off from that 33% piping and pick up and 80% for efficiency roughly. You end up with a boiler thats good for 308 EDR.

You have 86 EDR when you get room #1 fixe plus the second floor....say it's 65 EDR, it's 4 more rads that gives you a totoal of around 150 EDR

So your boiler is 2 x the size it needs to be, no wonder it short cycles with set backs, poor venting and 1 32 EDR radiator that doesn't work

Nothing else to say

I'm planning to add another radiator to the front room (biggest room in house) and make some of the other radiators bigger per say).

If I can get the EDR to 200, would that help with the short cycling? What else can be done to stop the boiler from short cycling so much?

Thanks

EBEBRATT-Ed

Anything you do can help. Fix venting, fix non working rads. Adding larger rads may not be the best choice as you could throw the system out of balance

ethicalpaul

Friendly tip: forget btu. measure EDR of radiators and compare that to the net sq ft of the boiler

@EBEBRATT-Ed I would agree with you, but they had replaced the first floor rads with new small ones so they may be undersized for the spaces

PMJ

The boiler plate states how many btu/hr it can put into the space running continuously. If I intentionally limit the run time I effectively make the boiler smaller do I not? For example, if I limit a 200,000 btu/hr boiler to 15 min burns separated by 15 minute waits I now have a 100,000 btu/hr boiler right? In this way you can cut a big boiler down to any size you want. Gee, maybe match things up this way? You can dial up any on/off combination you want - any fractions of cycles per hour, any net burn time per hour ... anything. And if anyone is worried 2 shorter burns per hour is less efficient than one with a couple of bumps off a pressure device forget it. It isn't.

For about $75 I made it impossible for my boiler to run more than 30 minutes in any hour over 25 years ago. My vaporstat hasn't operated once since. It was quite busy the first couple seasons I lived here. What a waste.

melo

What is this device that would let me do that?

melo

Hey, I have a small problem. 

I’m trying to change the pressuretrol so that the gauge goes to 0 before the boiler kicks back on. 

However, even with the settings it seems like the boiler goes to basically half or so psi then turns back on again instantly to go over 2 psi. I’ve attached picture of gauge... blue is where it starts and red is where it stops. I want it to start when gauge is 0 psi. 

Jamie Hall

A pressuretrol isn't designed to work that way. You can set it to do that, though, if you really want to: simply increase the differential setting so that it is equal to the cutout.

Both of those settings, however, have some imprecision or jitter. typically around 0.1 pound. What this means is that if you do set it to do that, sometimes it will cut back in at slightly more than 0.0. Sometimes, however, it won't cut back in at all (it's looking for a slightly negative gauge pressure). and you'll have to trot downstairs and whack it.

Not sure that's quite what you want.

melo

Jamie Hall said:

A pressuretrol isn't designed to work that way. You can set it to do that, though, if you really want to: simply increase the differential setting so that it is equal to the cutout.

Both of those settings, however, have some imprecision or jitter. typically around 0.1 pound. What this means is that if you do set it to do that, sometimes it will cut back in at slightly more than 0.0. Sometimes, however, it won't cut back in at all (it's looking for a slightly negative gauge pressure). and you'll have to trot downstairs and whack it.

Not sure that's quite what you want.

So the current setting that I have.. is that okay? If so, I'll just leave it at that.

PMJ

melo said:

What is this device that would let me do that?

@melo , It is a delay off/delay on timer. Looking over your posts here this is not something you will be doing yourself. Sadly, as cheap and simple as it is, it is not something any contractor will do for you either.

My comment above was more for everyone. This same scenario plays out over and over again. No one challenges that what I have said it is technically correct. I have proved it out in my own system. Yet situations like yours that these pages are filled with end up with systems needlessly running in pounds of pressure, instruction on how to set pressure devices to balance it there, and then ultimately ending with the advice that the only choice to eliminate the pressure and the cycling is to purchase a smaller boiler.

I'm truly sorry more help is not available for you.

melo

4th heating expert/plumber. He just set the pressuretrol up and told me to keep it like that. It’ll stop the short cycling and eventually boiler will stop once thermostat is satisfied. 

I’ve attached picture with his settings. 

So far it’s been good. Even the front room got some heat now. It’s also feels super warm, no complaints from mom. I understand this isn’t ideal and will burn more fuel but I’m so over it at the moment. 

This person also said the boiler needs servicing. Need to clean out the inside with special liquid. He’s also going to swap out my pressure release valve since it was losing a little steam. He said the boiler was surging and needed some cleaning with special liquid. 

So far, he took his time and actually looked around and gave reasonable answers to my question. I don’t agree with the pressure setting but alas what can I do? I noticed previous owners also had pressuretrol psi set very high if I recall correctly. 

neilc

https://heatinghelp.com/store/detail/we-got-steam-heat-a-homeowners-guide-to-peaceful-coexistence