Recent Operating Data

PMJ

Attached is some data for my system for the last 34 days. In in collecting this data I have discovered that my boiler is downfired significantly (like 30%) from what the rating is. There is a regulator which must be lowering the gas pressure that much. I have never before actually clocked the meter as I always felt I had plenty of capacity. But now it turns out that I have lots of experience with a downfired boiler to share. The boiler is rated at 462,000 input and 386,000 output. I have found that the input is really more like 327,000.

When looking at the attached data remember that my goal with my control system is to increase the length of call times to even out the heat. I do this by increasing the number of cycles and decreasing burn times. I am operating on the logic that perfectly even heat is when the room temp remains exactly constant because a magical control system provides exactly what is lost continuously. With such a theoretically perfect control system the first call once initiated would never end. Since burner on/off is all I have to work with I do lots of cycles.

The data shows that my system now spends about 80% of the time calling for heat, cycling the boiler in short runs, and sinking into vacuum between each burn.

I bet I've made a mistake somewhere so I'll apologize in advance. I haven't attached a file before so if it doesn't work perhaps someone can coach me through it.

nicholas bonham-carter

What is your peak pressure when firing? One pipe, or two?
My gut feeling is that lengthening the burn cycles would be better for economy. The burner, and steam production always have a lag in the process, and with more burns, you have more total lag. I haven't gone through Al your posted information yet, but will do so.--NBC

PMJ

nicholas bonham-carter said:

What is your peak pressure when firing? One pipe, or two?
My gut feeling is that lengthening the burn cycles would be better for economy. The burner, and steam production always have a lag in the process, and with more burns, you have more total lag. I haven't gone through Al your posted information yet, but will do so.--NBC

Two Pipe. Peak pressure maybe 2oz. Don't use any pressure control. Vaporstat only really a safety stop and never operates.

Steam lag to rads with vacuum amazingly short - the colder it gets, the shorter it is - around 60 seconds at most. The longer the wait between firings the colder the start, and the less vacuum so the longer the lag. Remember, running this way there are no cold starts with the big lags.

While over time I have become convinced the economy is better this way, it is not enough so to make a big deal of it. I do this primarily for comfort. Rads more the same temp all the time.

PMJ

I don't have a good sqft figure. It is 4000 sqft anyway. That would come to about 10.

I have been thinking that because construction(more windows etc.) and locations are so different that installed EDR really is probably a more accurate estimate of the expected heat demand of a given structure than sqft and therefore a better way to compare. After all, the exact same house in different zones would have been built with different installed EDR. I am thinking of it as "divided by the size of the system". I say if I could have only one piece of information to learn about what it would take to heat a place I would ask for installed EDR.

I got a lot of pushback when I suggested this before but I remember you posted some data a while back and you were also right around 40/btu/dd/edr.

Gordy

Knowing your envelope performance is really the only way to do any type of comparison. Knowing your BTU/HDD/SF performance allows you to accuratley compare heating systems performance with others so long as setpoints, and setbacks are apples to apples. Then you can always dig deeper into cycles, and such.

That being said nothing changes envelopes performance other than wind, solar, and other variables. The heating system is replacing btus at the same rate they are lost is the best you can get. How you do that the best the system allows is another issue.

PMJ

MarkS said:

yes, that sounds about right.

i think that using sq ft or EDR as the normalizing factor both have their drawbacks. Sq ft for the reasons you state. EDR because there's no guarantee that the EDR was calculated to match the construction. If EDR was significantly oversized, like in @ChrisJ house, the result is skewed.

In the end, my belief is as long as you do something to normalize the data so others can compare it to their own system, the data is more useful than just raw numbers. I'm perfectly happy providing both sq ft and EDR as the third term, and others can pick the one they like.

I agree completely. It is so easy to calculate so just provide both and everyone can compare/adjust to suit themselves. It would be interesting to see what we learn looking at both.

We might try to define what should be included in sqft by the way. Generally speaking it is living space I think. I heat a large uninsulated garage - do I include that?

dabrakeman

I agree that both EDR and sqft denominators have their merit. I would only suggest that if using the area that you are heating maybe volume is a better metric that floor space. I.e. a New England cape with 7 1/2 ft ceilings is not really the same as equal sqft in a Victorian with 11 ft ceilings. BTU/hdd/cuft would be the best comparative of your overall heating efficiency relative to the size of your house. Understood this is not "efficiency" of the heating system.

In my 4500sqft with 11ft ceilings I'm averaging for the winter months ~9.5 btu/dd/sqft and ~0.89 btu/dd/cuft. dd balance point 65F. Heat to about 68F during day. Home insulation is poor including all original single pane first floor windows.

EDR is 525sqft.

Mark N

You're under radiated compared to most of us. You have 525sqft EDR for a 4500sqft home. Mark S. has 608sqft in a 3000 sqft home. I have 260sqft in a 1350sqft home.

dabrakeman

There lies some of the difficulty because as PMJ was pointing out our homes are not always one area and one heating system. I have 650 of that area heating by a gas stove rather than the steam system (converted garage area). No way to split its contribution from my total gas usage.

Hot water is also added into the gas use equation although looking at summer month consumption gives you an idea of the relative impact (small).

ChrisJ

Mark N said:

You're under radiated compared to most of us. You have 525sqft EDR for a 4500sqft home. Mark S. has 608sqft in a 3000 sqft home. I have 260sqft in a 1350sqft home.

And I have 392 in a 1616sqft home. My ceilings on the first floor are a hair under 8 foot and on the second floor a little under 7 foot.

Not sure why that is, but after living here for 4 years we don't even notice it anymore.

dabrakeman

Home was built in 1890. It may be that EDR was setup with some reliance still on the 5 (now 4) coal burning fireplaces. Of course homes were kept warmer and often windows left open in the winter for "fresh air" as well so no issues with the current radiators heating the home to my temps. All rads will reach 100% on 2 degree or more recoveries but not on maintenance temp even on coldest days.

Fred

I have 700 sq. ft of EDR for 5000 sq.ft house with 10ft ceilings, original single pane windows throughout and insulation in the attic only. Space between plaster walls and brick exterior is minimal, not enough for insulation and the brick/walls need to breath too.

dabrakeman

Sounds like Fred and I have fairly similar EDR/sqft. My steam heated sqft is 3850 (525 EDR).