Learning about combustion and gas valve adjustments

Boon

What class or course can I take to get a better understanding of the gas valve in my boiler [Lochinvar KHN085]? Where do you pros go for education like this, and is it always brand-specific training? I've been googling around but I must not be using the right words because I'm not finding what I think is appropriate.

I ask about brand-specific because (1) I want to make sure the training I get is appropriate; (2) I see Lochinvar has a residential boiler school so I assume the other mfgs do, too. I'd go for more general training. Must admit that I would love to attend Loch's boiler school but I'm not comfortable taking a seat from someone who does this for a living. Lochinvar is a cool company, though, so if I call & ask nicely maybe they'll have mercy on me and pull up an extra chair.

Lochinvar, are you lurking?! Throw me a bone, please! I'll bring donuts every morning and buy a round at happy hour each night.

HVACNUT

Where are you located?

If your serious about servicing your own boiler, their should be a local Lochinvar distributor near you that can give you info on training classes.
I don't know if they accept people not in the industry.

Are you experienced with electricity and gas? If Nat gas, can you clock a meter?

At minimum, you'll need a combustion analyzer, manometer, true RMS multimeter, as well as an array of standard and metric tools.

Some manufacturers don't have gas valve adjustments. If readings aren't within specs, your making a call. Some are adjusted via a throttle screw, high and low fire with the boiler at a steady state condition.
But adjustments are NEVER made without the proper equipment and knowledge.

Zman

Boon,
Check out Coffee with Caleffi,
Combustion: Theory and Concepts for Hydronic Systems.

My experience with manufactures classes is that they don't go too deep. They kind of need to teach to the lowest common denominator. Checking the gas pressure, turning on the analyzer and turning the one screw until the analyzer reads the right number....

hot_rod

I have had homeowners attend my trainings, a lot of them in the solar heydays

Tim McElwain

What is your location? I have a training center in Warren RI and can easily accomodate what you are asking for. Give me a call at 401-437-0557 or email at gastc@cox.net

Boon

I had Coffee with Caleffi this morning and that took a lot of mystery out of it, Good call, @Zman. Thanks. I still want a little more though, so @Tim McElwain I'll be in touch this week. There is a direct flight from here to there (PVD). It's probably overkill for a homeowner but I think I'm working my way into the trade, granted not by a traditional path.

@HVACNUT I own all the necessary stuff. I've only used it once when I setup the boiler. As much as I'd love to pay someone else to do this, I bought the equipment so I should make it worth it.

HVACNUT

> @Boon said:
>
> @HVACNUT I own all the necessary stuff. I've only used it once when I setup the boiler. As much as I'd love to pay someone else to do this, I bought the equipment so I should make it worth it.

Nice!

Boon

On more than one occasion I’ve heard that too much turning of the adjustment screw(s) on a modulating gas valve is bad. The internet is surprisingly void of such caution, or I’m using the wrong search terms.

I was first tuned into this idea when on the phone with tech support last year, and just last week I came across a scenario in which a tech ordered a new gas valve because he didn’t know how much the previous valve was adjusted.

Is this urban legend? What makes them susceptible to “too much” adjustment?

Tim McElwain

There are typically two places on Mod/Con gas valves that lend themselves to adjustment. One is the regulator adjustment which most equipment manufacturers do not want touched (in some cases it actually has a sealant over it). Keep in mind these valves usually have 6 to 7 inches water column pressure on the inlet side of the gas valve (10 to 11 on LP) and at the outlet the pressure is a negative pressure created by the engineering of the gas valve (we cover that in detail in our classes). The other adjustment is the offset screw which is controlling an internal mechanism allowing the right air gas mix. This mix when set to manufacturers specifications will give a certain CO2 and O2 mix measurable by using a combustion analyzer. These valves should not be adjusted by people who are not trained professionals. The amount of adjustment is usually very small maybe a 1/4 turn or less makes a big difference in the air gas flow from the valve. There are procedures to be followed if you screw up or you have just converted from one gas to another (natural to LP).

Some newer systems have a preset feature and are not adjustable. They use the rectification principles to control gas/air flow and never need adjustment. They are self adjusting Viessmann and ECR (the Mac) use these features and I am sure there are others.

Boon

Thanks Tim. The folks/scenarios I ran into made it seem like the consequences of too much screw-turning were not combustion related but more on along the lines of valve damaging or that, like, ten foam snakes would pop out of the orifice - like those fake cans of nuts from the 70s.

ced48

The dreaded pressure offset valve. For me, in an LP situation, there was no way to get the boiler to operate smoothly without using this valve to get low fire balanced with high fire. Lochinvar helped me make the adjustment, and yes, their concern is that if the valve gets to far out of adjustment, it can't be tuned back.

I still have a few spots in the firing range that are rough. I have more or less worked around operating in these spots, because after 2 years of trying, I have come to accept that that can't be tuned out, just like a carburetor on an engine, its going to have at least some rough spots.

Boon

>>> if the valve gets to far out of adjustment, it can't be tuned back.

I was missing the “can’t be tuned back” part. Doesn’t make sense to me but I’ll choose to believe it.

Tim McElwain

It can be tuned if you know what you are doing.

ced48

I believe what they at Lochinvar were saying was that getting the valve to far out of adjustment will damage it. I didn't question there knowledge of this, and have since made minor adjustments, maybe 1/16" of a turn. It is very sensitive.

GW

I know the Bosch Greenstar boiler high fire adjustment is super finicky, trying to move the screw to go up or down 1/10 of one percent takes the most tiny movement of the big plastic screw your wrist can muster. If it’s a full percentage point I’ll get bold and go an 1/8 turn

I don’t understand that comment either, “can’t be tuned back”

MikeJ

check out LochinvarU.com

https://www.lochinvaru.us/videofiles/whn/combustion.mp4