Boiler settings and optimization

TC83

Hello all,
New member here and want to start off by saying this website is phenomenal. You are all such an asset to anyone willing to just try and understand their system before wrenching away.

Now, onto the entree;
I have a small 100 year old four story 12 unit property, two adjacent buildings with one ~20 year old boiler (read as long steam main runs to risers).
As of a year ago, we have upgraded to the entech boiler control, with space temp sensors and a bunch of sensors for flue temp, dhw(aqua/coil/mix temps), return, pressure and outdoor readings.
As of now the system typically takes approx. 20-30 minutes to build 1PSI, then continues to do so as normal, up to its current settings which cut out at 5-6PSI and then restarts if target temp is not achieved. I'd like to try and optimize my settings and operation but before doing so want to ensure i fully understand what to do and what to expect from its operation. Some background, i have begun insulating the horizontal main runs with fiberglass wrap, they are approx. 40ft long x 2.5" pipe, risers are 2" pipe buried in walls and in some places exposed within apartments. The boiler also provides dhw with two 10gpm tankless coils through a 1.25" watts n170-m3 mixing valve.
I have changed out the two old and leaky hoffman 75 main line vents with Barnes & Jones Big Mouth Vents and the risers at the top most point have a drilled and tapped hole with a #D 1/8" Angle Air Valve (four risers, each with #D vent).

So, my question is the following, What does it seem like i can do to get heat faster or more economically. Is there anything that can be done for dhw - perhaps this mixing valve is not properly sized or is dhw with steam boilers just a picky issue in general. Alternatively, if this is good enough of a setup it would also be ok with me. The boiler room naturally is a small basement space with beautifully narrow halls and access. Also, if posted in the wrong category, i do apologize. I've spent a couple days searching and have been trying to piece together more info.

captainco

it would help if we knew the btus of the boiler and what btus it is firing. Combustion numbers would be helpful.
O2 - should be 4%-6%
Flue T - should be 525 degrees to 600 degrees.

Jamie Hall

Looks like you are blessed with a lovely mercury pressuretrol. Keep it! Make sure it is exactly level. Then, perhaps with your existing gauge but even better if you can find a place -- maybe on the existing gauge's pigtail -- to mount another gauge, 0 to 5 psi, you can refine your pressure settings. The procedure is simple enough. Fire up the boiler from a cool start, and watch the gauge. If you venting is adequate, it should come up to somewhere between 0.5 and 1.5 psi -- lower is better -- fairly quickly, and then the pressure rise should really slow down. If it doesn't your venting isn't adequate and you need more main venting. Attend to that. If it does, after some time the pressure will begin to rise more rapidly again. That tells you that your radiation is pretty well filled. More important, it tells you that that is when you want the burner to stop to save fuel -- set the good mercury pressuretrol to cutout at the pressure where it starts to rise again, plus perhaps half a pound. Set the differential at about half that pressure.

Keep the grey pressuretrol as your backup safety -- 5 psi cutout is fine for that one.

TC83

Captainco,
I have some info, from whats left of the boilers paper tag, ~2700 sqft steam, 650,000 btu/hr and 760,000 btu/hr water.
From the control sensors, the stack temp measured ~5ft from the outlet, is approx 470F. if i recall last service visit, it has a 7.5gph 60deg nozzle installed.
Is there a preferred combustion meter or method that is used to measure O2.

captainco

7.5 gph is 1,050,000 input and about 840,000 output? The flue temperature is low, which indicates underfiring. Any make combustion analyzer can measure O2 accurately. I use Bacharach but others are okay.

mattmia2

It is hard to say without knowing how big and long the risers are, but usually an 1/8" pipe is too small to vent those quickly.

TC83

Captainco - I just ordered an analyzer, will post results as soon as i get it.

Mattmia2 - There are 4, 2" risers, each with a 1/8" tapped hole with a #D air vent. no access to end of pipe (likely buried somewhere in ceiling). the main runs in the basement are: double 3" taps off boiler into a manifold, splitting into two 2.5"pipes that run approx. 40ft horizontal (somewhere around 80ft total run), each main has a new b&j big mouth vent on them. What are the options for riser venting without tearing up a ceiling or cutting a pipe to replumb?

Steamhead

There's no differential scale on that mercury pressuretrol, so it's the secondary unit and I'm sure has a manual reset. The gray one is the primary- set that as low as possible.

Is that burner set up for low-high-low firing?

TC83

Steamhead - The burner is set up for low-hi fire only. I have never seen it operate as low-hi-low. there is a manual switch for low fire only, but we've rarely ever used that.

TC83

@Steamhead @Jaimehall So the secondary mercury pressuretrol should stay as is and the primary is the adjusting unit i should look to drop once i get a gage on it - correct?

Steamhead

TC83 said:

Steamhead - The burner is set up for low-hi fire only. I have never seen it operate as low-hi-low. there is a manual switch for low fire only, but we've rarely ever used that.

That's called "low fire start". It should be a simple matter to upgrade it, but you'll need a knowledgeable pro to do it. The advantage is that the burner won't stop and start nearly as much, therefore not blowing heat up the chimney during the purge periods. You will need another pressure control, preferably a Vaporstat, to do this.

TC83 said:

@Steamhead @Jamie Hall So the secondary mercury pressuretrol should stay as is and the primary is the adjusting unit i should look to drop once i get a gage on it - correct?

Correct.

TC83

Ok, update time gents
@Steamhead @jaimehall @captainco
I've insulated all mains and as much of the risers in the basement and exposed areas as possible. Also installed a low pressure (0-5psi) gage. Drilled a hole ~10" from boiler into exhaust duct. Readings below; boiler began to build ~0.2psi after about 15minutes. I noticed the resistance readout on primary control was pretty steady @115(low fire start)-123(high running)ohms. I set the pressuretrol to 2psi cut in and 1 on the diff wheel - boiler ran to 5psi and shut off. i suspect this may need cleaning or replacement.
As for combustion testing, it read OL for excess air and - - - for CO2. 22.9% O2 and a temp of 540-544F.
I think i'll be adding another 1/8" #D vent to each of the four risers as i dont have many options for larger venting due to space or access.

Any thoughts gents?

Jamie Hall

Set the cutin as low as it can reliably go (probably around 0.6 to 0.7). The differential is OK. If that doesn't seem to bring the pressure at cutout down, the pressuretrol may need replacement or calibration.

STEVEusaPA

Your analyzer is out of calibration or you are using no excess air at all, which is most likely impossible.
What did the smoke test reveal?

captainco

There is only 20.9% O2 in the air and you are reading 22.9%. Bad O2 sensor.

TC83

Ok gents, round two with a replaced analyzer.
Here are the results. Any thoughts. And I do not have a smoke test pump, so I don’t have that info. But at recent service and oil filter change there was very little soot buildup.

STEVEusaPA

First draft, then smoke. It's the only way to initially set combustion air.
Looks like your meter is on Nat Gas, and you're sampling oil.

TC83

@STEVEusaPA i goofed testing the replaces analyzer and this replacement one and didn’t photograph the corrected settings. I was in a rush to verify the defective unit. I will retest in the morning.

TC83

A little delay due to the holidays. Here are the readings from combustion analyzer. Thoughts?

STEVEusaPA

Smoke? Draft? Pump pressure? Nozzle?
Poor combustion, really underfired.

TC83

@STEVEusaPA Thank you for responding.
Can you clarify what you mean, i do not have a smoke test pump so i cannot comment on that just yet, is it worth purchasing for tuning purposes or to confirm the combustion analyzer results?
The Carlin702CRD burner is set up for low fire start and then high fire run for dhw and heat. low fire is 150psi and high fire is 300psi (although the connected gage reads ~290psi). The nozzle is clean and rated at 7.5gph. There is virtually no soot buildup on the firebox viewing glass or nozzle assembly (turbulator/electrodes or nozzle areas).
So what would you recommend as next steps to correct the underfiring?

STEVEusaPA

Were those results from high fire or low fire (probably low fire)? Yes you need a smoke test to determine proper amount of combustion air.
If you bought an analyzer, smoke gun is a small, necessary requirement-knowing how to use it is equally important.
Still don't know the draft.
What angle nozzle?
Usually you adjust settings on high fire, and low fire tends to be what it's going to be.
Head adjustment, draft, combustion air are all even more crucial, critical numbers on large burners.
I'd use the manual, reset all initial settings, steady state high fire, and work from there.
What's the boiler make/model #?

captainco

Based on the flue temperature it appears to have enough fuel but too much air. But air can only be adjusted using a smoke pump tester.

EdTheHeaterMan

Most of us use the Bacharach TruSpot smoke test pump but I find the TPI A788 Smoke Test Pump is a good value with fewer problems. The actual smoke number over #2 may not be as accurate but who cares.. we are looking for a #0 to #1 smoke to find the sweet spot in the burner adjustment. Once you find that, you will want to add air to the flame to drop the CO2 by about 1% or increase the O2 by about 1%. This ensures enough excess air to account for minor differences in the draft and/or dirt build-up on the combustion fan (in the burner) over an operating season between scheduled maintenance.

TC83

@STEVEusaPA The model of boiler is hb smith 19 series 8, burner is carlin 702crd. i'd have to pull the nozzle to check the angle.
The results i posted were the boiler running on high fire for ~10minutes, so it started low and was steady on high fire.
How do i measure the draft? i will also measure where the nozzle tube is located on the burner, i believe there is a scale located near the adjusting screw. Any ideas on where to locate a boiler manual?

EdTheHeaterMan

burner info https://carlincombustion.com/wp-content/uploads/701CRD-801CRD-Instructions-web.pdf

You may have more than one nozzle inside that burner. Adjusting the High fire then the Low fire can be very tricky. When you get one perfect, the other one needs to be checked to see if your adjustment caused a change in the previous firing rate, and then back again. It can get frustrating for the inexperienced. Make sure you take pictures of the linkages and air adjustments and mark with a scribe original settings before you change anything. Air gate opening, nozzle position, pump pressures on low and on high fire. You will be glad you did once you get into it.

EdTheHeaterMan

Depending on the age this might be the boiler manual

http://www.smithboiler.com/litlibrary/19IOM.pdf

or you may find it here

http://www.smithboiler.com/html/19he-heating-boiler.asp

TC83

@EdTheHeaterMan @STEVEusaPA
Thanks for the resources, here is a smoke test i did and shots of exhaust damper and burner. Where would i begin adjusting. Is there is nozzle/baffle location that is preferred within the burner or should the air just be adjusted to get the best burn. Again, the soot level in the sight glass and nozzle assembly is minimal, and it seems like its close to a decent flame. But if this is being under fired i'd like to correct it. It seems to me that the smoke test shows ~#3, and there is not a scale on the nozzle tube for adjustment as i thought there was.
I did not bother taking the nozzle out to confirm which degree angle it is, but there is definitely only nozzle in this burner.

EdTheHeaterMan

In looking at your pictures and reading your description "Only 1 Nozzle" it appears that you may have a 601 CRD burner. Carlin does not offer that model in Low - High or Low-HI-LOW anymore. (if they ever did) So how you are getting 2 firing rates from one nozzle is by pressure change only. 100 PSI for low and 300 PSI for high. I don't have a resource for that info. So I would start at High Fire and get the best combustion I could at 300 PSI. This will be trial and error on your part. Start at 80% of the recommended firing rate for the boiler. See what nozzle provides that firing rate at 300PSI.

use the approximate settings from the 601 or 701 manual to get close then start adjusting the assembly in then out as needed to see if the combustion instruments improve or get worse.

Once you get high fire where you want it... switch to low fire. now only adjust the air gate on low fire until you get 0 smoke and a smooth cold start. sometimes you will get a smoothe start when the chamber is hot but you will get a rough start if the chamber is cold. This will take some time... even hours or 2 to 3 days because you need to let the chamber cool after each test to see if the cold start is smooth.

Once you get the low fire right. Recheck High-fire and see if your low-fire changes made a difference on high-fire.

EdTheHeaterMan

figure 7 and 8 on page 4 of the 701 manual gives a detail of the nozzle assembly adjustment. the markings that you don't have on your burner are every 1/16th inch and when fully closed there is no tertiary air. When the assembly is fully extended there is 1-1/4" of tertiary air. based on your firing rate at high fire select something close, to start with, then adjust as needed

EdTheHeaterMan

Also, verify your pressure at high and low fire