Tekmar 279 Steam Boiler Control Adjustments

cubicacres

We're experimenting with our Tekmar 279 steam control on our Weil Mclain EG-75 boiler since we thought we'd save about 20% compared to the older boiler we replaced (WMC-EG85) that had 15% higher nat. gas BTU input & no vent damper & spark ignition that the EG-75 has. Add the condensate sensor we installed, warm whether shut-off at 57deg, and Tekmar's heat curve calculations with the indoor & outdoor sensor, and we thought we'd see another 10-30% reduction in fuel use for up to 50% less fuel with happy tennants. So far we're using 20% more fuel than the old boiler that had a simple thermostat with no other controls or warm-weather shut off. The tenents have told us the temp. is in a tighter range than last year, with the upper floor reaching 76 deg instead of 81 deg last year.

The tenants have been satisfied with the heat on the colder weeks, so we feel the boiler can produce enough steam for the 760 sq ft of radiation in the 4,200 sq ft brick 2 story building with little/no insulation in Milwaukee.

We moved the cycle time from auto (auto made a 53 min cycle time the last 2-3 months with our higher fuel bills & weather fluctuating from 40F down to -5F on the cold days) to 40 minutes, but then the weather warmed up, so we haven't had much time to see what difference that made. The boiler % was at 100% since we didn't know how the new smaller boiler size would fit building, then moved it down to 80%, so that's out next variable to try, along with the design temp at 18 deg, which could be adjusted as well.

Has anyone found adjusting certain variables on their Tekmar 279 for single-pipe steam systems to be more useful than others? If so, which variables would you reccomend changing first? (Design temp, boiler %, steam established, lockout differential, etc.) I think the tenants will tell us if they're cold, so we should know next time it gets colder.

nicholas bonham-carter

How is your main venting? How long does it take for the steam arrival temperature to be established? are you using setbacks?
76 degrees is too high, and is it the same for the lower floor?--NBC

nicholas bonham-carter

More thoughts:
What sort of radiator vents are installed?
Is there a cycle-guard LWCO installed, with its off and on operation complicating the settings? The safeguard LWCO will give the same protection, without the periods of testing the water level.
I would get everything working as well as possible, using a Honeywell Visionpro with remote sensor in the coolest apartment. Using a thermostat will be easier than fiddling with all the settings on the Tekmar
Make certain all radiators are getting steam simultaneously. When you have the balance right, then you can recommission the Tekmar for any added benefit it may be able to give.--NBC

Abracadabra

I've used wireless tags to help me set a tekmar instead of letting tenant's subjective complaining to create an alert that building is too cold.

nicholas bonham-carter

Even better to look at the screen on the Honeywell Visionpro, with remote sensor, in the cooler part of the building, and see what the temperature is in the coolest room.
If the wind gets up during a cold spell, and sucks the heat out of the building, I wonder how the Tekmar will adjust the run times to compenstate. At least with the indoor sensor, the sudden heat loss can be felt, and accommodated. Similarly, if during the shoulder season, there should be a sunny day, which will heat up the south side, then how will the Tekmar adjust that?--NBC

ChrisJ

I've found my house's indoor design temp needs to be about 65F. This is about where the building stops losing heat and will maintain 71-72F I guess just from people, appliances and electronics in the house.

New England SteamWorks

cubicacres said:

We're experimenting with our Tekmar 279 steam control on our Weil Mclain EG-75 boiler since we thought we'd save about 20% compared to the older boiler we replaced... we thought we'd see another 10-30% reduction in fuel use for up to 50% less fuel with happy tennants. So far we're using 20% more fuel than the old boiler that had a simple thermostat with no other controls or warm-weather shut off.

Calculating savings is tricky. At the very minimum, one has to take into account actual degree-day temperature information when doing the calculations. Did you record this data prior to the conversion?

2nd, I have always believed that, even when taking degree-day data into account, building heat loss is exponential, rather than linear. But I have yet to find an equation to represent this fact.

Lastly, the sum total of my life experience concludes that usually the only way one can save 50% on anything is when the savings are based on an inflated initial price or consumption figure.

Folks just seem to be in the habit of stating that virtually any change "will save at least 50%!"

SWEI

RI_SteamWorks said:

Calculating savings is tricky. At the very minimum, one has to take into account actual degree-day temperature information when doing the calculations.

Tricky, yes -- but still not exponentially tricky. It gets easier as you acquire a basic grasp on total system thermal efficiency.

I have always believed that, even when taking degree-day data into account, building heat loss is exponential, rather than linear. But I have yet to find an equation to represent this fact.

I'm no math whiz, but if you can state the problem a bit more clearly, I should at least help quantify the ask. I'll say up front that we routinely promise 30-40% and we have yet to eat any hats.

New England SteamWorks

1. No question you can save 50% on some installs. But only from an inflated basis, as I stated. If what one replaces was never installed correctly, or mis-sized, or insulation non-existent, etc, etc -sure. In the OP's example, we don't appear to have replaced something that was in such a state. And that is what I mean.
2. Quantify: Obviously, the colder it gets, the greater the heat loss. But it seems to me that if it gets twice as cold, the heat loss will be more than twice as much to some exponent. The colder it gets, the greater the heat loss to an exponential amount. And, it seems to me, the harder the boiler will have to work, also exponentially. Might be great, might be minor, -but I doubt it's linear.
3. It's the difficulty in making the calculation that allows for the claims. Just look at the replacement window guys!

nicholas bonham-carter

Therefore go with the interior control, monitored from the most temperature/wind vulnerable section on the building?--NBC

Abracadabra

Hatterasguy said:

Interior controls have their own issues in apartment buildings. You're at the mercy of the tenant in one specific apartment with their set of conditions. Yes, you can use two of them, thereby mitigating the issue somewhat.

My preferred control utilizes 7 sensors with hi/lo limits on each that takes the sensor out of the equation if the tenant decides to use windows or their own electric heat. Really haven't had any complaints anywhere I've installed it.

Abracadabra

http://www.rdcontrolsystems.com/steam-200-series.php

New England SteamWorks

Hatterasguy said:

You make the conclusion that you have a non-linear condition, but, in reality, the wind, in conjunction with the infiltration loss (which might be underestimated) is the culprit.

The culprit may well be infiltration. But my conclusion is still valid. It is hard enough (and seldom done) to keep accurate degree-day records to verify savings or improvements, and even when done, without qualifying the exponent, still not accurate.

Being from New England, it reminds me of DeflateGate and the two (contradictory) ball gauges utilized and the failure to take into account The Ideal Gas Law due to a lack of historical gauge readings.

If we learned anything, we learned that if we have no prior record of readings to form a basis for comparison, we have no way to make a claim on current data.

P.S. Still wondering why the NFL has yet to release the gauge data they recorded over the last season...

Abracadabra

Hatterasguy said:

That would be the AH207?

It appears to be a glorified thermostat with seven sensors. You only can control the boiler run time via the differential. Not a good control strategy.

Now, the SF201 has a slew of interesting features and calculates run time in similar manner to the 279. It can only utilize two indoor sensors, however.

The differential on the rf207 is altered based on outside temperature thereby altering the cycle length. I have not tried installing a sf201

Abracadabra

Hatterasguy said:

Abracadabra said:

The differential on the rf207 is altered based on outside temperature thereby altering the cycle length. I have not tried installing a sf201

I understand that.

However, you're attempting to control the cycle length of the boiler with a parameter that has a total range of 2 degrees. This is exactly what we wish to avoid by leaving the 'stats behind and going with an outdoor reset based system.

Check the "cold weather boost" parameter. I don't recall the max for this setting, but I know I've been able to set it at least as high as 5 degrees for really leaky buildings. I don't recall if the manual specifies a max for this parameter, but I can probably check out what I can set it to within a week or so as I'm sure I'll run across one I've installed. The 2 degrees is the max "fixed" differential setting unrelated to the "cold weather boost" . Both get added together to come up with a eventual total diff.

Adding a "wind speed" boost is an interesting idea as I've run across numerous old Chicago buildings with original 100 year old windows with storms that no one ever closes. The amount of air infiltration difference on a windy day is unbelievable.

SWEI

Many of the newer control platforms can read weather data -- both live and forecast. Wind speed and even direction (for larger buildings) can be helpful in anticipating loads.

ChrisJ

The Ecosteam allows me to adjust a curve to give extra boost for extra cold weather, and reduce it in very mild weather but I'm not using that end at least not yet. I really need the boost in extreme cold due to infiltration. I think I end up a few thousand btu/h higher than expected.

It also has an indoor sensor which allows it to add extra heat if necessary at a point which I set and I tell it how much.

ChrisJ

Hatterasguy said:

ChrisJ said:

The Ecosteam allows me to adjust a curve to give extra boost for extra cold weather, and reduce it in very mild weather.

I discussed this with Mark and understand that he added it to Eco-Steam because some of the buildings did fall behind when close to design.

Fundamentally, the unit provides all the "boost" required at cold temperatures. The conduction heatloss is linear. If the building falls below temperature at colder ambients, my suspicion is that the curve is not steep enough or the winds are playing havoc with the curve.

With such a modification, I'd be curious to see if the building overheats slightly under no wind conditions.

The extra boost is needed because of infiltration.
Infiltration is not linear as I've been informed on here by several people.

No, my house doesn't overheat during calm conditions and the extra boost solved the problem. During very windy days, the system will barely maintain temperature at my set point, but it does. This is how I know I have it set as close to the line as I can get it. When the thermostat never stops calling for heat, yet my room temperature stays where I want it.

ChrisJ

Hatterasguy said:

Why can't you simply raise the curve on one end? Why does the curve require a "knee"?

I'm just not accepting that as necessary.

I did raise the curve on one end.
What are you talking about? You mean the "cut" option at higher temperatures? I've never used it. Mine starts increasing the curve below 12F. I forget by how much.

MarkS

Hatterasguy said:

I discussed this with Mark and understand that he added it to Eco-Steam because some of the buildings did fall behind when close to design.

That's correct, Hat. In fact, I added the feature at Chris' request.

The one on my system can communicate with a host computer, so at the start of a heating cycle it receives the current wind chill temperature fetched over the 'net from a local WeatherUndergound station. The lower of the wind chill and OD temps is used in the ODR equation to determine run time. It does appear to compensate for additional infiltration losses. At least, after five years and three iterations of the system I've never had cause to turn the feature off.

ChrisJ

Interesting.
I already said wind has no effect on it in my house, but I guess that's moot eh Hat?

You're starting to remind me of someone else now.

ChrisJ

Steeper curve messed up everything above 12F, really 10F was when I started having issues. System would run fine 90% of the winter but when it got near or below 10F it would start losing temp, even on a completely calm night. The further below that point it got, the more I needed to increase the heatloss setting. I think I ended up with a 72,000 @ 0F setting when we were -8F out when I used 62,000 @ 0F for the rest of the year.

With the boost, issue is gone. I barely touched the Ecosteam this season and that's saying something.

MarkS

Hatterasguy said:

So, with the wind input, would you agree that you do NOT need the knee in the curve?

I agree that *I* don't need the knee, because my system has access to the wind chill data.

Chris' does not, so the knee, while by no means perfect, offers him some corrective measure.

MarkS

ChrisJ said:

I barely touched the Ecosteam this season and that's saying something.

I'll say. What are you doing with all your spare time?

MarkS

Hatterasguy said:

Well, the question that still remains is whether it is wind driven or not. I still believe it has to be the primary driver down at very low temps.

I am 95% convinced of that, and not just at very low temps. Wind chill compensation works equally well in this house when ODT is in the 30's as it does at near or below design temps.

There's something about ChrisJ's house though. As far as I know he's the only one using the "knee" feature. Were I retired and so inclined I'd install a bunch of data loggers at his place until we got to the bottom of it.

BobC

He has balloon framing and if some of those bays are still open the wind will blast through them. Most of mine are blocked off but not all.

Bob

ChrisJ

Hatterasguy said:

MarkS said:

Hatterasguy said:

Well, the question that still remains is whether it is wind driven or not. I still believe it has to be the primary driver down at very low temps.

I am 95% convinced of that, and not just at very low temps. Wind chill compensation works equally well in this house when ODT is in the 30's as it does at near or below design temps.

There's something about ChrisJ's house though. As far as I know he's the only one using the "knee" feature. Were I retired and so inclined I'd install a bunch of data loggers at his place until we got to the bottom of it.

You use the same percentage for wind chill compensation...........strictly dependent on velocity.............independent of outdoor temp?

I think he has wind that he is not aware of...............

Sigh.

I'm going to stop feeding this troll, that much I know.

Infiltration is not linear and that's that. I had a thread about it somewhere and quite a few guys commented on it.

My 150 year old house is drafty. I know when it's windy, and when it's calm. I'm pretty observant, some would even say obsessive at times.

MarkS

Hatterasguy said:

You use the same percentage for wind chill compensation...........strictly dependent on velocity.............independent of outdoor temp?

Let's say my design temperatures are 0 F and 70 F, and it's 30 F outside per the OD temperature sensor. That's a 57% run time for the boiler given a purely linear curve. Now I fetch the wind chill adjusted temperature (WUnderground calls it "feels like" temperature), and it's 25 F. Since it's lower than the sensor value, the ODR equation uses that as the OD temp, and the result is a 64% run time.

ChrisJ

@Hatterasguy
Just remember.

ChrisJ

That's it.
You're off the Christmas list.

ChrisJ

Hatterasguy said:

ChrisJ said:

That's it.
You're off the Christmas list.

That's a new development??????

For this conversation, yes.

Abracadabra

someone needs to add this:

https://www.adafruit.com/products/1733

MarkS

Hatterasguy said:

Is this calculation done only at your own house?

The algorithm needs a bit of refinement, however. If you use the fixed wind chill values, all houses would have the same compensation for wind. However, we know that the wind component is dependent on the infiltration value for the heatloss. Therefore each building needs a different factor for wind.

A very tight house with an ACH of .5 would have a different curve............markedly............than this place with an ACH of 1.5.

Yes, only at my house.

I believe you would have already compensated for the ACH when you set up the ODR control. An 0.5 ACH house would have a lower heat loss than the 1.5 ACH house, a lower boiler design percentage (on a Tekmar, all other factors equal), and the curve would be lower. Offsetting the ODT by the wind chill temp would therefore have a lesser effect on the run time with the 0.5 house versus the 1.5.

Is it exactly right? No. But for my needs it's close enough.

MarkS

Hatterasguy said:

The problem with ACH is that it only accurate at one specific wind speed.

Whatever curve you setup with a specific ACH is only valid at a single point.

Those with "reasonable" ACH might not notice the difference. Those with large ACH certainly will.

OK, I can see that. Let's say you can get the wind speed, either from the 'net or a dedicated anemometer. How do you determine the ACH factor for the building at various wind speeds in order to set up an ACH compensation curve?

ChrisJ

MarkS said:

Hatterasguy said:

The problem with ACH is that it only accurate at one specific wind speed.

Whatever curve you setup with a specific ACH is only valid at a single point.

Those with "reasonable" ACH might not notice the difference. Those with large ACH certainly will.

OK, I can see that. Let's say you can get the wind speed, either from the 'net or a dedicated anemometer. How do you determine the ACH factor for the building at various wind speeds in order to set up an ACH compensation curve?

Make the system automatically program it self, and tweak it self over time using the indoor sensor.

Everytime it falls short, bump the heatloss up a bit. When it overheats, bump it down. You'd need to throw wind into there somehow. If the inside temp drops, but wind is high, increase the "wind" heatloss but leave the standard setting alone etc.

It'd be the perfect product. Installer / DIY only has to set an initial heatloss setting to get it in the ballpark, it does the rest.

ChrisJ

What are "30K winds" ?

MarkS

ChrisJ said:

Make the system automatically program it self, and tweak it self over time using the indoor sensor.

I believe that's what this does: Exquisite Heat