A Question for KC Jones?

Mark N

KC, I'm very interested in how your system is working with the Hi-Lo gas valve. At what pressure do you have the vaporstat set to trigger Lo fire? When just maintaining temp do you even generate enough pressure to trigger lo fire?
What is the input at Lo fire?

Thanks

Mark

KC_Jones

I am using a vaporstat to trigger the lo fire. I have it set to trigger at 3 oz right now. We haven't really had that much cold weather to run the system for very long to judge the performance. I also haven't tuned the gas train yet. I have my uncle coming up in a couple weeks to dial it in for me and check the firing rate etc. So far I only had one day cold enough to even hit the lo fire (that sounds weird doesn't it?) and the lo is too low. It hits the lo fire and the pressure drops to nothing in like 1 minute then back to hi for a few minutes then back to lo. I want to get it to trigger lo fire and stay there. Of course I guess what i have is still better than short cycling on pressure huh? I will post once I get it dialed in and how it runs. I enjoy sharing so I will keep everyone posted. In all honesty looking forward I may develop some alternate method for controlling it since I am not making much pressure. I only hit 3 oz once the rads were about 1/4 filled. I am sure it will take some tweaking to get it right.

Mark N

Thanks KC please keep us informed. Maybe instead of a Vaporstat use a temp sensor at the end of the main. Drop to Lo fire once steam is to the end of the mains. Maybe MarkS has some ideas on how to accomplish this.

KC_Jones

Mark I was actually thinking of something exactly like that, but I feel it's too early to start making drastic decisions about control. Want to get at least one winter under my belt get the venting tuned in see what can be done with the low fire as installed then evaluate at the end of the winter.

Mark N

KC, in the meantime I would clock the gas meter with only the boiler running. Clock it at High fire and Lo fire. At least you would know where you're at. I have a small system like you and never go above 1 oz. pressure under normal operating conditions. I use 3 Gorton #1's on each of my mains (not enough headroom for #2"s) and an assortment of #5's and 6's on the rads. Go to the Heating Museum on the main page then Old Steam. Find the articles "It's All In The Venting" and "The Big Problem With One-Pipe Steam". Lots of great info in those articles.

JStar

Mark N said:

Thanks KC please keep us informed. Maybe instead of a Vaporstat use a temp sensor at the end of the main. Drop to Lo fire once steam is to the end of the mains. Maybe MarkS has some ideas on how to accomplish this.

I'm going to implement this control scheme soon for our staged boilers. I plan to install a temperature sensor on each main, in parallell, so that once ALL mains have steam, the GCV will drop into low fire.

Mark N

Joe, I would be interested in how it works out. Staged firing is usually used on much larger boilers than KC's. I wonder how low you can go with the EG-40 without issues? How much can you safely down fire an atmospheric boiler?

JStar

We've put staged GCV's on boilers as small as 88K input with no issues of condensation or inadequate steam production. As long as the stack temp stays near 350F, we're in the clear.

KC_Jones

Mark I can tell you this about down firing on an atmospheric Weil. My old boiler was an EG-45 and I had 2 burners completely removed because it was oversized. I was firing a 150k unit at 100k and had zero issues. Good stack temps and the whole system was fairly happy to run like that. So that was 33% down firing. Made steam just fine and quieted the system down nicely. My goal with this set up is make steam faster then drop to 100k or preferably less (as long as I make steam) and let it simmer. Waiting on colder weather for longer run times. Another thought I had is I actually put a manual override switch to keep it in low fire. My thought is in the shoulder times I could put it on low all the time and possibly save a little gas. Almost like a manual ODR set up. I like to tinker and learn so everything is a bit experimental.

Mark N

KC, I wouldn't have thought you could down fire an atmospheric 33%. I thought maybe more like 10-15%. How bad does the combustion efficiency drop off at a 33% down fire?

KC_Jones

I don't have a combustion tester to really know. When I did it I was primarily concerned with draft so I checked the stack temp and draft to make sure I was okay. I can't remember the stack temp (was 10 years ago) just remember I was in an acceptable range and still had plenty of draft. If you look at these Weil boilers my new 40 is actually the same block as the 45 so they are firing the same block at 125 and 150, so basically they are down firing by 16.5% already. So if you think about it, it would be like down firing my current boiler by 16.5% so it sounds drastic, but not so much when you dig a little deeper. Now one thing I don't know is if any of the pros have ever seen any long term problems with down firing like this? My old boiler was 32 years old when it started leaking, with 10 years of down firing and in all honesty unknown maintenance before I inherited it (not great judging by the sludge in it when I bought it). I didn't think that was bad service life.