Oversized Boiler, now what?

TomH42

With the help of many and especially Rod, we have come to the conclusion that my boiler is 27% over-sized for the radiators currently attached to it. During a renovation 15 years ago two radiators were taken off line.



While there is a chance one radiator may be replaced down the line, for now I am looking for recommendations on what to do with a system that is 27% over-sized.



Two issues have arisen from this set up. First, the pressure builds quite rapidly. I am having the Gorton #2 replaced (Gorton people are real easy to work with, many kudos to them) just in case this vent for the main line is not venting properly.



The second issue is that the cast iron radiator on the second floor never gets hot because the fin and tube radiators on the first floor satisfy the call for heat from the thermostat.



To circumvent this set up I have the thermostat call for lots of heat and after 30 minutes of continuous running (with a few stops for pressure issues) the second floor radiator throws appropriate heat and warms the area for a good portion of the night. I then manually turn the thermostat back down so the upstairs bedroom does not turn into a sauna.



So my question is what do you do with an over-sized boiler? Can I ask a technician to remove two of the eight burners to slow heating element? Should I expedite the addition of another radiator?



As always, the guidance and suggestions found here are appreciated.



Happy New Year to all.



Tom

Hap_Hazzard

Balance

The issue with the upstairs radiator not heating has nothing to do with the boiler being oversize. it just needs a bigger vent. If it already has a Gorton D or equivalent, put smaller vents on the convectors. Once you get things balanced you can better assess if and where you might need more radiation.

JStar

Boiler

Never remove burners. You can create a very unsafe condition, both for you, and the boiler.



27% is not the worst we see. As long as the boiler is installed above and beyond the minimum requirements, and go real heavy on venting, you can smooth out a lot of the oversizing symptoms.



I would vent the radiator closest to the thermostat a little slower.

Paul48

Main Vents

The one thing you will see in the Steam section,is constant reference to main venting. For some reason, folks will try everything else first, and only after that will they add main venting. Figure out what you need for main vents, and then add some more. You will see drastic improvement from the start.

nicholas bonham-carter

Rapid pressure build up

What pressure is showing on the system when steam is filling the radiators?

You will know your main venting is correct when you have a good low-pressure gauge showing 2 ounces as the air is leaving the main line vents. These can be had from gauge store.com 0-3 psi, and they also are easy to deal with.

Maximum main venting will also help to get the steam up to the slow radiator with a slightly faster vent. Changing the thermostat setting frequently wastes fuel. Getting your system balanced will save a lot.--NBC

TomH42

Venting and pressure gauge

will be the priority now. Thanks for the tip on the low pressure gauge. I have one identified through gaugestore.com. I see the vaporstat/low pressure gauge diagram on this site which looks impressive. Given that the current cleaned pigtail/pressuretrol cuts off at 5 psi and kicks back in at 3psi (according to pressure gauge) would it be prudent to invest in a vaporstat and low pressure gauge? If we go with just a low pressure gauge, where does it get installed?



As for venting, here is a photo of the vent on the second floor radiator. The rest of house has Hoffman 40's. Would that help on this radiator as well? If not, what type of vent would be best?



I have also included photo of main vent and return vent (on left). If I were to add another main line vent would that be done by adding a t union on the pipe headed to the Gorton?

JStar

Vents

That rad vent looks older than its useful life. You can upgrade it with a newer one. That's the easiest first step.



If you post the lengths of the seam mains, we can recommend what to do with the main vents.

JohnNY

27% is no big deal.

I evaluate systems all season long with boilers that add up anywhere from 100%-400% oversized.

For 27%, I'd clock the gas meter and take a little liberty with my manifold pressure, vent the system to death and call it done.

JohnNY

Duplicate post

deleted

Charlie from wmass

Vaporstat

over size boilers like vapourstats as they shut off sooner. If the boiler is off on pressure it's size does not matter. 27% is often as close as you can get with out undersizing within a specific line of boilers. That is why I do not install just one brand of boiler.

TomH42

The steam main is

35.5 ft. long (5 of the 6 radiators (all one pipe) feed back into steam main line. The return for the 1 two pipe radiator is also 35 ft long. The main currently has a Gorton #2 that may or may not be working. Gorton is going to swap it out.



As for the radiator vent, should I go with Hoffman 40?



Thanks!

JStar

Venting

The Gorton 2 should be plenty, but more is always better. It's probably not worth going to any more than two of them.



So, one of the radiators is two pipe? Is that the one that doesn't work?

JohnNY

Like

good answer

will smith_4

I'd agree

As far as oversizing goes, you have to find your edr per radiators, plus your piping pickup, and slightly oversize based on that.  If any system has ever been exactly sized tit for tat I'd love to see it!

Like JohnNY says, you could have it dialed in a bit based on manifold-but our manufacturers limit how far down they'll allow the gas manifold pressure to be adjusted.

Vent Vent Vent!

Happy New Year to all!

TomH42

The two pipe radiator

works fine. It is located on the first floor. All first floor radiators (fin and tube) work well. It is the big cast iron radiator on the second floor that does not get heat, in part because system is satisfied for call of heat (thermostat on first floor) before it gets hot on second floor.



It has been mentioned to get a new vent for second floor radiator. The vent seems to work well when steam finds it's way up to radiator. When the boiler runs long enough to generate the steam necessary, the air venting is noticeable.

Charlie from wmass

Gorton D

vent it with that. Can you slow down the venting om the fin tube? as it has almost no volume to it it is very hard to vent a second floor cast iron as fast as a few feet of fin tube on the first floor. You may need to double vent that radiator to give it a fighting chance.

NYCLandlord

similar prob

Not a PRO here, but we have a similar problem.  Maybe I missed something, but would changing a timer work?



In addition to a new gas boiler, we changed our HEAT TIMER to a TEKMAR.  The Tekmar 279 has a setting that would reduce the ON TIME for oversized boilers.  Instead of running ie: 25 minutes and have it cut-off on pressure 3x, we can program it to run at 75% time, in other words, run it for 18 mins.  While not perfect, it reduces the number of times the system cycles on/off on pressure.

We found that on 45 degree days, it takes the system 13-15 minutes to hit 2psi and cuts off, by tweeking the return pipe temp sensor, cycle time, diff temp  startup, we were able have time the boiler to turn off right before it hits the pressure cut-off.



This may or may not work on yours, but worth thinking about.

TomH42

Pressure builds

so fast the pressuretrol takes over and shuts down within 15 minutes.



I did swap out one of the first floor Hoffman 40's with the vent on the radiator on the second floor. Just started last night.



Is a Hoffman 40 faster or slower than a Gorton D which was recommended?



Thanks.

Charlie from wmass

a 40 is smaller

by quite a bit from the Gorton.

TomH42

Thanks Charlie

I will get a Gorton D for upstairs. I am assuming the Hoffman's are not slow enough with fin tube. Is there some other vent to consider?

nicholas bonham-carter

Timer problems

Have you addressed the main problems of a steam system, such as pressure and venting?

The fanciest control (and you have the best) cannot compensate properly for an unbalanced system.--NBC