Is this normal? Short cycling?

ChrisF

So I installed a low pressure, 0-3psi gauge, because my boiler gauge was giving me a reading of close to 15psi. I set my cut in at .5 and differential to 1, and it just seems to me like the pressure goes up to fast. Is this short cycling? Please click on the link below to the video and let me know what you guys think. Thank you in advance.

https://youtube.com/watch?v=wdV6tZp0Tps

Jamie Hall

That video is from a cold start? You need a lot more main venting. What do you have for vents on the mains?

ChrisF

@Jamie Hall Not from a cold start. This is what it does a number of times. I had to calibrate the pressuretrol to cut out at 1.5....otherwise, the pressure just kept rising. Now that it cuts out where it should, it doesn't run as log as it used to, for a cycle. For main vents, I have two Big Mouth vents.

Jamie Hall

How big (EDR) is the boiler? How much EDR is in the building? That rapid a pressure rise suggests either venting problems -- though if the Big Mouths are working, doesn't seem likely -- or a really oversize boiler... In any event, it's not what it should be.

ChrisF

@Jamie Hall Thank you. I'm sorry, I don't know what the EDR is. I've been asked that before, so I should probably figure it out. All I know is that it's a 2100 sf, single family home, and the boiler is a 150,000 btu. I can see that the Big Mouth vents are working, but I do get water hammer in two radiators upstairs. I'm actually waiting to get a hold of a steam expert to come take a look at this, but in the meantime, I guess I have to leave it as is. Thank you.

Fred

How long does it run before you start the short cycles? Do you know what the connected EDR is relative to the Sq. Ft. of Steam output on the boiler is? Do you have any radiators shut off? Are you using a thermostat temperature set back ?

Jamie Hall

EDR is the term for "Equivalent Direct Radiation" -- it's basically a measure of the size of the radiators. There is a table for it around here somewhere... The EDR of the boiler, which should match, is on its rating plate (along with the BTUh, which isn't all that helpful).

ChrisF

@Fred Well, from a cold start, the first heat up with the boiler was about 10 minutes....then it followed with the short cycles. The EDR is one thing I will have to find out, since everyone keeps asking. I'll probably get a professional to figure out the EDR for me. No radiators are shut off, since they don't have a shut off valve. I'm not sure what a thermostat temperature set back is...I have a Nest thermostat. Thanks.

Jamie Hall

The Nest isn't helping you one little bit. Adjust its settings so it maintains a constant temperature rather than responding to occupancy. You will save both fuel and wear and tear on the boiler.

ChrisF

@Jamie Hall Thank you. I'll just keep the nest on all the time. I will try to get someone to check what the EDR is. I just googled a chart for it, but the convector radiators that I have, are not listed. If the boiler is not oversized, could it be possible that the flame is too high and it is overfiring?

ImYoungxD

150,000 is oversized. Pressure went from 0 to 1.5 in 1 minute.

My 130,000 boiler takes about 10 minutes to go 0 to 1.5 (Only if I put the thermostat to 80 or above). It's oversized but .75 nozzle helps reduce the BTU.

Calculate your EDR with this http://www.smithfieldsupply.com/company_info/forms/radiatorest.pdf

Are you on oil or gas?

ChicagoCooperator

Do you have convectors or radiators (or some of both)?

ChrisF

@ImYoungxD Thank you. I actually came across that EDR chart before, and it doesn't seem that my radiator is on there. I have gas.
@ChicagoCooperator I have all convectors (a total of 10) in my house. (Picture below)

EBEBRATT-Ed

@ChrisF

You don't have to find the "exact convector" Just find one with the same or relatively close measurements and you will be close enough

ChrisF

@EBEBRATT-Ed

I figured that much too, but my convectors are only about 3-4 inches tall, and I don't see anything that size. My apologies, I might not know exactly if I have to look for the height on the element itself, or the whole enclosure in the wall.

Jamie Hall

It's the element itself that you are looking for -- the enclosure, within reason, isn't much of a factor.

acwagner

@ChrisF

Do you have any valves located on the steam lines coming from the header? If so, check to see if they are fully open.

Also, it's possible you have a sag in your steam line before your big mouth vents, which is sagging so much water is blocking the steam flow to the vents. I had this happen on my system. When the system is running, check to see if the Big Mouth vents get hot to the touch. If they do, then at least steam is getting to them.

ChrisF

@Jamie Hall Thank you. I'll try to find someone who can calculate the EDR. If I try to look up my convector on the chart, I can't seem to find anything even close. Must not be a common convector.

ChrisF

@acwagner Thank you. No valves on the steam lines.
Hmmm...I will have to double check if there's any sagging in the steam lines. I know for sure, that the vents are releasing some hot air, but I haven't actually touched them.

ImYoungxD

Do all your radiators get hot (200f+)?
I suggest leaving your thermostat at a certain degree that you're comfortable at. No setbacks since it will cause short cycling.
Thermostat cycles per hour should be 2 or 3 with convection rads.

ChrisF

@ImYoungxD All the radiators heat up well. I haven't actually taken a thermometer to check is they get to 200º or over, but I suppose I could check. I will also just keep the thermostat set to the temperature we are comfortable at instead of having it drop down when nobody is home. Thanks!

ImYoungxD

1-2 degree setbacks are fine if you have cast iron rads. But since you have convectors, it should stay fixed at one temperature. It should stop or lessen your short cycling.

coelcanth

is it my imagination/optical illusion or does it look like the 0-3psi gauge got pegged and bent the needle ?

BobC

It's a simple math problem -

Measure the length and width of each fin LxW=plate area
Subtract the areas of the pipe holes this gives you the true area
Count the number of fins and double it to account for both sides
True area X number of surfaces = EDR

This is not exact but it's close enough.

Bob

ChicagoCooperator

Wait, I thought convectors required the enclosure for their full edr? I have Trane Concealed Heaters and there is a big difference between the heights of the chase which can dramatically increase the EDR via more air flow (see the link below). I thought it was the same for all convectors (if not quite as extreme). Obviously a different system than the OP's, but same concept, right?

https://heatinghelp.com/assets/documents/219.pdf

BobC

I had forgotten about the height factor but I don't think his cabinets have any significant height but you could ratio the EDR they give for the cabinet height. that PDF didn't give any shots at the fins so I can't tell if their naked EDR numbers aree tru for the OP's convectors.

I would still do the work to determine the mathematical EDR and then try to ballpark any height multiplier to come up with a best guess in lieu of concrete documentation.

Bob