Older Heat Timer Box vs. New Jazzed up EMS Box

Crunch

John S.

Mark,

Just read some of Siegenthaler's stuff, and the magic bottom line number he uses seems to be 130 degrees for condensation.  Not sure where he gets it from, but he apparently also uses a rule of thumb that flue gases are going to be 7 degrees hotter than the return temp.  If that is a good rule of thumb, then flue temp would be 132 if return temp is 125.

 

He also is very careful to always phrase the potential problem as "sustained" flue gas condensation.  Not sure if a few minutes every hour that dries out immediately thereafter would be "sustained".

 

It would be interesting to see what his thoughts are on a dry shut off at 140+ degrees.



Crunch

Zman

moving target's

Sustained means through the cycle not just at start up. You are doing this. The exact point of condensation will vary. The factors include, barametric pressure,temperature,CO2 content of flue gasses. You cannot put an exact number on it. An oversized or insulated flue will compound the problem.

Crunch

Yup

Understood and thanks.  I think John S. was using 130 degrees as a generic reference.

 

What do you think about a dry shut off at 140+ (tridicator actually edges up to about 145 degrees) after 9 minutes of firing?

 

Crunch

Zman

Return temp

I would want to know what the return temps look like. If 1/2 you cycle is at 120 and the other 1/2 is at 130 I would be concerned. If the boiler return temp jumps up to 135 after a minute and stays there for 8 minutes I would feel pretty good. My concern is that you are very close to a line and you are not sure where the line is. Tell me about the flue?

Carl

Mark Eatherton

The problem with 130...

In an "ideal" world, where everything was perfect, 130 degrees F would be a safe factor, BUT, and note that it is a BIG but, we have hysterysis (slop) that can be as much as 10 degrees F off of actual temperatures, hence the recommendation of 140.



Can the boiler be operated at a temperature of less than this? Absolutely! At the expense of the cast iron boilers. I've seen cast iron boilers with NO protection being operated as snowmelt boilers. And there was no trail of rust running from the boilers combustion chamber. And it had been doing so for about 20 years before it completely failed. But that was an installation at 10,000 feet above sea level, where the humidity is extremely low.



You asked for information. We offered it up. It is your option as to wether you take corrective actions. Or not.



And I have also seen modulating condensing boilers that were in fact condensing at 180 degree F discharge temperatures... Theoretically, there should be NO condensate at that point in the cycle.



Peace, Out.



ME

Jean-David Beyer

modulating condensing boilers that were in fact condensing at 180 degree F discharge temperatures

When my mod-con is running my indirect, and only the indirect (say during the non-heating season), the target supply temperature is 175F. Now it takes about 7 minutes to get the temperature that hot. And the indirect is usually satisfied in less than 10 minutes total. This happens two or three times a day. (I do not use much hot water.)



So I was quite surprised to notice that the condensate pump runs at all. But it does.



My old boiler was a 1950s GE with a replacement Beckett oil burner in it. That boiler was not cast iron, but steel. Probably sheet steel. I had lowered the aquastat on it to run between 130F and 140F. So very likely, it condensed most of the time. It ate flue pipes, but they were cheap and easy to replace. I never thought about that, and knew nothing about condensing. And that thing cycled almost 20 times per hour during the heating season. It was about 60 years old when I replaced it. It was not leaking, so those boilers were really tough.



I think it would be a mistake to say that boilers in general could survive the kind of treatment that I, in my ignorance, gave that old GE. I was very lucky.

Crunch

Return temp

Carl,

 

Haven't parsed it that finely, but I'm guessing Smith might come back with something similar.

 

Don't have a thermometer on the return line and would have to use an IR gun.  Haven't timed the rate of rise on the supply line, but we're starting off at 125, and I'm guessing it is pretty even, maybe at 132 after 4+ minutes at the tridicator, which might mean it is higher at the flue, if the John S. comment holds.

 

What do you want to know about the flue?

 

Crunch

Crunch

Condensing GE

Jean-David,

 

Interesting insight on the GE.

 

I keep hearing that Smith is heavy iron and can take a lot of abuse, so I hope we're okay too.  I don't know the details, but the baffles were replaced a year or two after installation.  God only knows what that was all about.

 

Crunch

gennady

Condensing issues

132F is an empirical temperature of exhaust gases , can vary very widely, but condensation happens at much higher temperature of heat exchanger surface.

Crunch

Other feedback

Carl,

 

Just got some feedback from elsewhere from someone who would know and he leans towards thinking the dry shut off concept would work.  Easy enough to verify by taking the flue connector off right after shut off to see if the flue is dry.

 

He also suggests getting "official" feedback from Smith, which I'm still waiting for.

 

Crunch

 

Zman

Flue

Crunch,

I think it important to also consider flue condensation, especially when running lower temps. I believe that Mark's example of a boiler condensing at 180 was likely condensing down the flue rather then the heat exchanger. I have seen plenty of boilers that run at 180 with flues totally destroyed.

A few things that will cause this are;

Oversized  flues

Short cycling boilers

Flues that make long runs through unheated spaces

Low boiler temps



Many commercial boiler installs with have stainless flues with condensate drains to avoid these issues.



A boiler can have an exhaust temp of 150 and easily condense at 130 before the gas leaves the flue. I like Gennady's technique of watching the plume.



Carl

Crunch

Flue

Yes, I hear you Carl, and I think the flue is where we'll focus, not now, but when we get into the heating season, and before then when we have the burner tuned, when we do a stack test, and when we clean the boiler.

 

I just took a look at the flue, and from the outside, it looks to be in suprisingly good shape.  There's a spot that was patched many years ago where the pipes didn't quite line up correctly, but the rest of it looks good.  Not sure how I'm going to disconnect it after the thing fires as JS suggested, but maybe I'll be able to figure out something.  If I have a chance, I may take some pictures and post them.

 

With his permission, the comment from JS was, with my additional clarification in brackets:

 "I tend to agree with the first group [those advising me that the dry shut off approach should work], that allowing the boiler to shut off at 140F and perhaps "coast" up to 145 F should dry up and residual condensate.

You could verify this by taking the flue connector apart shortly after burner shut off to see if there is any moisture. the flue connector, and not the inside of the boiler is the more probable location for condensation, since it will be somewhat cooler than the inside of the boiler.

The exact dewpoint is not just a function of temperature, but also of gas/air ratio.

You might also want to contact Smith and get their "official" opinion on this."

 

Crunch 

Zman

Nice Work

I think you've "got it"

Nice work with John.

Carl

Crunch

Thanks

Thanks, Carl.  If I get some pictures posted, please let me know what you think.  It may be a while since I don't have a cell phone and my wife always has to show me how to use the digital camera!

 

Any thoughts on my original question as to the value of a jazzed up EMS box in a 6 story multifamily building with a perfectly functional HT Platinum HWR box from 2008, and with hot and cold apartment lines in the building?  My HT specialist is going to be here next week.

 

Crunch

SWEI

to EMS or not?

What else besides space heat would the proposed EMS have control of?

Crunch

Not much

That's really about it.  We heat 27 apartments in the building currently with ODR and 1 outdoor thermometer controlling the HT box.  Coincidentally, that 1 thermometer happens to be mounted on the outside wall of one of the coldest apartments in the building.

 

To qualify for the substantial subsidy from Con Ed, we'd have to add something like 7 indoor thermometers tied into this new box, amongst other things, and nobody has yet been able to explain to me what good that is going to do us, particularly what good it is going to do us relative to that cold apartment on the 1st floor.  The way our board is looking at is that the boiler is going to continue to fire just like it always has if we want to keep the resident in the cold apt reasonably comfortable, but we will have spent quite a bit of money to essentially go nowhere.  

 

I'm looking for insights.

 

Crunch

SWEI

sounds like you;re on the right track

Unless you install a whole bunch of motorized valves, the EMS will not be able to do much anyway.  While it would be nice to have the logging and alarming capabilities, they're hardly going to justify the cost involved.



Adding a few TRVs and fixing any venting issues might make sense.



Not sure if the Heat-Timer is doing ODR?

Crunch

that seems to be the direction we're heading in

Yes, HT box is now doing ODR and it works.

 



TRVs, sealing up the leaks, stopping the air currents, getting the cold apt warm, getting the cold apt line warm, and insulating the hot water heater piping are probably what we'll end up focusing on this year.  EMS and insulating the roof can wait.

 

Crunch

Crunch

Smith

Mark,

 

Confirmed with Smith today that they received my inquiry and that it has been forwarded on to the engineering dept.  I will post when I receive their response.

 

Crunch

Crunch

credit

Carl,

 

As I said previously, I honestly didn't know a boiler from a broiler last September.  Never, ever been around one, and I should give credit for the dry shut off concept to the person who educated me about it:  tk03 at www.comfort-calc.net, based somewhere in PA.

 

The guy's brilliant and he has shared more insight and time with us than I care to count. He almost literally picked this slopped up mess off the floor when the PRV kept going off every time the burner fired, and has patiently guided a newbie like me along without making me feel stupid. We've gone through an expansion tank, a pressure reducing valve, a backflow preventer, a pump, an aquastat, etc., etc., etc.

 

More to go for sure, but we've made a huge amount of progress with tk03's help.  Actually hard for me to believe that it has been less than a year.

    

In any event, tk03 deserves all the credit.  He's a gifted human being, with a great website with tons of useful info on it.  Highly recommended.

 

Crunch

Zman

Good to hear

Crunch,

It is good to here you have found someone who can advise you.

Best of luck in your journey.

The best troubleshooters I know do not start out knowing the answer, then spending endless hours trying to prove they are correct. They look at the problem from an "open" mindset, the problem and solution then presents itself.

Carl

Crunch

That's for sure

Carl,

 

Couldn't agree with you more!

 

My Dad was a veterinarian, and he used to say he had to use all six senses to figure out what was wrong because the animals couldn't tell him.  Kinda like watching God at work and it would get real quiet.

 

Not quite the same, but boilers can't talk either.

 

If you have a chance, stop over at tk03's website and forums.  We'll be picking up on some other stuff probably next week. 

Crunch

Crunch

Heard from Smith

Mark,

Just heard back from Smith's engineering dept and they basically agree with the dry shut off concept.  As long as the water temp in the boiler is 140+ degrees at burner shut off, any condensation that might have formed should have evaporated and would not be an issue.  Sort of as JS suggested, Smith said if we see any condensation remaining after shut-off, increase the temp setting incrementally until it stops.

  

Thanks for your help on this.

  

Crunch

Mark Eatherton

Thanks for the update.

ME