new furnace short cycle

ajcforest · March 2023

Just had new steam gas boiler installed— Utica Heating brand UH1604HSID 112000 Btu in , 91000 out. This is replacement for Utica brand PEG-C same BTUs, approx 26 years old developed crack at top of corner section cast iron jacket. Typical colonial about 1500 square ft in North Jersey built in the 30's. Plumber recommended this to fit in same location. When comparing Utica brand withUtica heating brand, the only difference I saw was UTICA was blue and UTICA heating was gray. Utica brand had Same controls in a slightly different location , physical size same, same BTUs. I was told Utica and Dunkirk merged or one bought the other, and kept the same original cabinet colors.

Problem is the new boiler is short cycling, really short cycling,

Here is what I noticed

thermostat calls for heat, boiler turns on, builds up steam in about 15 minutes, new LWCO (cycle guard 2090) kicks in and turns off boiler for about 90 seconds, then turns back on

( normal operation—stupid but normal). As pressure builds, pressurtrol (resideo brand—supposed to be affiliated with Honewell and has same model PA404A as Honeywell) cut in set a little above .5 , additive differential set to 1.5. Pressure builds to about 4 psi on gauge, presuretroll activates, boiler shuts down, pressure drops to cut in , in about 1 1/2 minutes, boiler turns back on, now starts to cycle on and off around these points and time. In addition, cycle guard will kick in- turn off boiler, and could happen seconds after cut in pressure was reached—more short cycling. Radiators—5 cast iron baseboard with 2 older tall style—get hot, but weather is now getting warmer here in North Jersey, so not sure how this will work next winter. Also, motorized damper opening and closing with cycle.

Also noticed water level in sight glass, drops and hovering around LWCO level and occasionally will triger amber light on cycle guard until water calms down.

Spoke to plumber, he will be coming back to do skimming.

Any body have suggestions, or have some ideas.

Jamie Hall · March 2023

I hate to ask, but how was the boiler sized? A very very very rough guess on my part suggests that that new boiler is at least twice as large as it should be. (about 380 EDR, and I'll bet your baseboard and radiators are 200 or less).

If that is the case, yes it's going to short cycle and no you won't be able to do anything about it.

dko · March 2023

Would probably wait for plumber to do the skimming, which takes time. Surging to the point it causes dips below the lwco sounds awful.

KC_Jones · March 2023

Skimming may calm things down.

I agree with Jaimie, the likelihood it's oversized is good, especially if they just put in the same thing as before.

Could you post some pictures of the installation? There are things in the piping, that if not done correctly, can lead to poor performance.

Pressurtrol is a safety, if it activates under normal operating conditions the boiler is oversized. Do you know if the old one would shut down on pressure ever?

EzzyT · March 2023

As others have said most likely the boiler is oversized along with improper near boiler piping.

EdTheHeaterMan · March 2023

Perhaps you could post this same question again. Maybe you will get better answers 😈

@Erin Holohan Haskell may be able to combine the 2 discussions and delete this one.

ethicalpaul · March 2023

when I bought my house (a little smaller than yours) in north Jersey it had the same boiler.

It too was cycling on pressure.

It had no main vent and needed service.

I was able to get it into a state where it wouldn't cycle on pressure except on recovery from a setback. There is hope

ethicalpaul · March 2023

easy ed, you never made a mistake on the internet before? 😅

EdTheHeaterMan · March 2023

Just playing. I should know better though, this is an new guest asking for help. They dont Know about my sarcasm. An you are right Paul. I thought there was a pressure difference on the equalizer. You helped change my mind

Paul did you want to add this to your post?

https://forum.heatinghelp.com/discussion/157779/how-to-properly-skim-a-new-steam-boiler

ethicalpaul · March 2023

this post has detail describing surging. Have him skim it and don't let him put anything in there if given the option.

He has to skim. Was he gonna set it and forget it?

Erin Holohan Haskell · March 2023

Welcome @ajcforest! I've merged your duplicate posts into one here. Please let me know if you have any questions about using the forum.

ajcforest · March 2023

Here are pictures of new boiler install,not sure if I loaded in right format. Also, plumber came back today, skimmed system, twice, spent about 90 minutes watching system, added chemical clean steam—powder, turns water green. Still appears to be surging. he said give chemical a chance to work. As for sizing, he went by old unit. I had flucuation in old unit but not like this. Coments?

Jamie Hall · March 2023

Sigh… well, I willsay that the layout of the piping is pretty good. It's rather a shame it was all done in copper — it should have been threaded iron — but for this type of boiler and piped with that geometry, It's not a catastrophe.

Water level is critical in that type of boiler. I hope that the chemical added won't cause a problem, though it may. I'd let it be for a week or two and then drain and refill the boiler with clean water.

EzzyT · March 2023

I would start with figuring what is the heating load of the system and if the boiler is close enough to system load then I would Repipe the boiler utilizing both supply tapping. All piping would be done with black pipe and fittings.
Then I would upgrade the main venting along with insulating all piping.

Last but not least upgrade the radiator venting.

nicholas bonham-carter · March 2023

I would first upgrade the main venting, then skim the boiler properly, using the manufacturer's instructions, with no chemicals. While the skimming is taking place over several hours, measure the radiators correctly, and compare that result to the boiler label. The boiler installation instructions should have explicit instructions to follow, especially pipe sizing.

A new smaller capacity boiler may be needed, properly piped as the manufacturer specifies, if the level fluctuations continue.

Next check the main, and radiator venting, as the new boiler may be generating steam even faster than the old one, and overpowering the existing main vents, and forcing the boiler water to back up in the returns, at 4 psi. The LWCO should be set to limit the pressure to below 1.5 psi.

Your copper piping may go a few years before the expansion/contraction of the copper works the joints loose enough to leak.—NBC

mattmia2 · March 2023

Header has no swing joints, that is mandatory.

These things need to be checked against the manual:
Header size, seems too small but that is a small boiler so it might be ok.

Might need to use both side outlets but might be ok.

Too much additive will cause priming, the water will foam so it wil leave the boiler for a new reason after you skim to get rid of the oil to stop surging. Ideally you would skim to get rid of the oil and not put an additive in it.

Jamie Hall · March 2023

Actually, on that one, @mattmia2 , I thinkk there is enough give in the overall riser/header/equalizzer arrangement to not require a swing joint or two. That wouldn't be true if both side outlets had been used.

Not that swing joints and threaded pipe wouldn't have been better. They would. But the problem is short cycling, and rearranging the deck chairs isn't going to help that.

JohnRambo76 · March 2023

I have the same Utica peg112 boiler. Installed myself, the first month I kept skimming without using a chemical cleaner, still would surge. Used about a third of a bottle of surgemaster and let run for a week, it would turn red and start surging again. Repeated the process of adding a third of the bottle of surgemaster on a freshly refilled boiler about three more times before my boiler was free of oils and running like a champ. I did use a bit too much blue monster which added to my frustration but skim slow and properly and you'll get there. In total it took me almost 2 months to skim my boiler by letting the surgemaster do its process of removing oils and crud from the entire system. Drain entire boiler of chemical a couple times, all the way to where the drip leg is by the hartford loop and fill with fresh water and boil immediately.

mattmia2 · March 2023

https://forum.heatinghelp.com/discussion/comment/1744371#Comment_1744371

I 100% agree that this isn't an acute problem but it has the potential to cause the boiler to leak prematurely.

new furnace short cycle

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