Not So Sucky Mod Con Efficiency (Post Service) ME

Mark Eatherton

Attached please find a PDF of the pre and post cleaning data. I will post the photographs, with comments on another thread under this heading.

ME

[Deleted User]

Cold Cajones... :-)

All,

I finally got the right conditions to do the deed last night. Suprisingly, the appearance of the fire side of the heat exchanger was not as bad as some I have witnessed. In fact, other than seeing the REAL thermal efficiency numbers, I would not have had any concern for what I saw. And for that, the only splanation I can give is that I operate in a low temp condensing mode most of the time. I have seen some boilers with tubercles, stalagtites, stalagmites etc. Wonder that THEIR numbers were prior to service...

All told, if I had not been dinking around with documentation and evaluation, I would probably have invested 1 hours worth of time in the effort.

The bottom line is my clocked thermal efficiency went from 63% to 94% on low fire, and from 85% to 94% on high fire.

Unfortunately, the temperature probe on my analyzer puked (SOMEBODY dropped it...) so I have flue gas sample pre and post, but no flue gas temperature readings, hence no theoretical combustion efficiency numbers. Sorry. Plenty of other opportunities to see what difference it makes in the field.

Besides, I think that those numbers would be skewed because I have 2 (countem TWO) flue gas waste heat recovery devices on my "system". The one that came on the boiler, and the 15' long concentric B vent installed from original mod/con (this is my 2nd one).

Unfortunately, I got called out to a water emergency last night, right as I was getting the boiler re-assembled, so other than the basic math, I've not had a chance to assemble the photographs (LOVE my new camera) nor the math.

So, for the time being, just understand that ignoring required maintenance WILL negate any savings potentials that your customers would have seen, and unless they are watching their utility consumption like a hawk, the change is so suttle that they probably would not notice it.

Now, get out there, have a Merry Christmas with your families, and start an automatic call back service/system to remind the consumers of the need to service the Ferrari in their basement. I will eventually get back with photos and documentation, and I DO have a butt load of it...

ME

Unknown

Mod Con Boiler Eff

Hi Mark. Hope you are well.

Your post regarding boiler eff has been really interesting. Man, there are a lot of real good heating guys out there eh!

I have two of my typical "stupid questions" (sorry if I missed this somewhere along the way). What is the "usual" delta T across the boiler and what is a "normal" return water temp?

AND, most importantly, Merry Christmas and have a great 2009 to all the Wallies out there!

[Deleted User]

Merry Christmas to you and yourn Steve...

And the only correct answer is, It DEPENDS :-)

But you KNEW that already...

I typically see between 7 and 15 degree delta, rarely more than that unless doing a cold start up.

Return temps depends upon the method of distribution, and the required supply temp. It's all over the board to be quite honest. Sorry I can be more specific.

Thanks to you and WILO for the Eco pump donation at school. It piqued the students interest.

ME

Mark Eatherton

Pre cleaning photographs

The HXer wasn't as bad as some I've seen on the field. No major stalagtites or stalagmites and veryfew, if any mouse turds or coffee grounds. This could be a side effect of the operating temperatures that my system sees. I never exceed 160 degrees F except when going for DHW, then only 170 and for brief periods of time.

Shown are left, right, top, and bottom.

ME

Mark Eatherton

During cleaning photographs

I used a plastic toilet brush with a "Stiffy", normally used for cleaning under the rim... I started out using a 50% diluted mixture of CLR. It didn't cut the mustard, nor the corrosion. After two tries, I went to full strength, and ended up doing it twice. Prior to wetting any surfaces, per the manufacturer, I scrubbed loose the clinkers and vacuumed them out, as well as one can given the nature of the HXer.. I trapped what I got out in coffee filters connected to the hose. Photos to follow near the end.

Interestingly, the "green" stains were only on the north side of the heat exchanger. HX Moss?

ME

Mark Eatherton

After cleaning photographs...

I found that although the toilet brush with the stiffy did a reasonable job of getting between the heat exchanger cracks, it did not do a good job of scrubbing the actual exposed heat exchanger surfaces. I resorted t a nylon/sponge scrubby, which did a good job. I think there is a need for someone to come out with a brush to attach to a drill to do a better, more thorough job of scrubbing the crud off these heat exchangers.

Photos of left, right, top and bottom and the two cleaning devices used in the process..



ME

Mark Eatherton

The Credit Card method...

Worked fairly well, although I think it could be improved upon with a real "tool".

Is this an inappropriate use of this particular credit card? Before you start harping, it IS a canceled/expired card...

ME

Mark Eatherton

Filter stains.

I "borrowed" some filters from my wife's coffee maker to filter out stuff coming from the trap and condensate line. Unmarked stain was from the drain terminus, first flushing. Others are marked. All samples are currently drying and will be checked for attraction to a magnet to see what happens. More info later...

ME

Mark Eatherton

Dirty air.

Of particular interest, I draw my combustion air in from the roof of my house, so ground pollution is relatively low. With that said, there is a fairly significant build up of dirt on the inlet to the blower/gas valve venturi.

I think there is a definate need for air filtration. Even the BlowCore people understood this principal, many years ago...

ME

Mark Eatherton

The burner

looked fairly good, considering how many hours it had been running on low burn. I didn't attempt to clean the chain mail cover. There were no rattles coming from inside, so nothing that I could see that needed to be done, other than blowing it off.

That's it, got questions or comments?

ME

Mark Eatherton

Final comments...

This is not the first heat exchanger that I have serviced, nor will it be the last. I believe HR had some good ideas about cleaning kits and tools for the efficient models, and I would strongly recommend that someone (Millrose Co, or HR) develop these tools for use and distribution.

Also, this is NOT a clean, easy dry process. I got water EVERYWHERE. It took an 1/2 hour just to clean up my mess. Unfortunately, the remote readout for this particular boiler sits below the lowest point of the heat exchanger, so it got wetted in the process. I attempted to dry it out with a hair dryer, and when I finally powered it up, it read NC, meaning Not Connected. The following morning, it was OK (WHEWWww)

I also se a need for a small rotating water spraying head that would do a better job of spraying the water directly where it NEEDS to be, as opposed to where it END UP going, which unfortunately, in those close quarters, is every where.

There was a substantial amount of slime (bacterial) in the trap and drain line going to the receiver/neutralizer. I had previously treated my trap with copper sulphate, and it was in need of additional treatment, hence the need for annual treatment. This is something that I think all manufacturers needs to address, because if left unchecked, it will cause the condensate to hang out in the combustion chamber where I think it can cause additional problems.

Lastly, the Viessmann manual calls for treatment of the cleaned heat exchanger with a passivation material. As I remember, this paste was only available from a local welding shop. Why is Viessmann the only company to call for this? SHould we consider it for non V heaters?

Thanks for your patience.

ME

TimS

OK may I ....

The heat exchanger pics look normal to me no concerns just typical 2yrs of use.

Dirty air pics are a little odd I would have removed and washed the burner dry out well before firing. TIP you hold open end of burner right up next to your eye in good lighting or out doors you will see how well light infiltrates a clean burner compared to a dirty burner.

I dont know the make and model of your boiler it may or may not matter .I think I'm close on my questions correct me if I'm off.

Why does your flow rate change?
Flow rate seems a liitle low?
The combustion is odd has it been set up properly ? normally there is a relationship with excess air/ co / co2 / o2 / yours is not making sense to me is there a problem with the analyzer? I dont think these values are within the speced range.

The fan speed RPM seems too high for 50,000 btu input and not low enough in low fire do you have a programming issue or is it normal for your model?

I hope this helps, then some , I'm ready to learn.

Plumdog_2

A cleaning wand

The Trinity people have a cleaning kit that consists of a wand that (I believe) connects to a pressure washer, the shaft slides thru a gasketed cover that you bolt on in place of the burner door, and has a rotating head with what looks like wire fingers. I haven't tried it because it is too pricey, but I may make my own. Could be it would fit other makes with similar heat exchangers.

Doug_7

Reduction in Boiler Heat Losses

Mark - thanks for posting the boiler performance numbers and pictures before and after cleaning.

I was intrigued by the very large reduction in heat losses after cleaning the boiler.

On low-fire, before cleaning the boiler was losing 9,816 Btu / hour at 63% efficiency and after cleaning the boiler it was only losing 857 Btu / hour at 94% efficiency.

A reduction of 8,959 Btu / hour in boiler heat losses and turning this loss into useful heat is huge. Do you know where all this lost heat was going before you cleaned the boiler ?

I always try to balance the equation: Heat In = Heat Out + Heat Losses. It is very useful to measure or calculate the heat loss part of the equation.

I rely on the fact that the heat Input always goes somewhere. The trick is to know where and how much.

Doug

Steamhead (in transit)

Nice job, ME

unfortunately, too many people think gas equipment doesn't need any maintenance. I think you've given us a glimpse of things to come........

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Simply Rad_2

Inspiration

ME
after reading your post I decided to service my home boiler.
It was installed 14 months ago, natural gas, vent through the roof. We have a mix of radiant and panel rads. VERY simple yet elegant system. We are able to use the onboard pump for the system. Constant circ using the remote comfortrol for the main zone with TRVs on the other zones. The panels are very comfortable, just ask my wife cause she is the coldest person around and she loves the system and that is all that matters. I also chose the combi unit, which provides around 2gpm. We have 1 1/2 baths and olny the two of us. Works great!

I have done dozens of mod con services and I have never seen so much green.....especially on the burner.
I did perform a combustion test and the CO2 was low 6.8% so I played with her and got the levels up to 9.5% I do love fingering(adjusting the air intake) the Vitodens and giving her that love!

Does anyone have thoughts on the green or is my boiler just that efficient that it even burns "Green" if so Viessmann should be all over the marketing of this GREEN product!

I am going to call Waterloo tomorrow and show em some pics.

I am off to Panama for 10 days of fun in the sun in the islands! Big change from skiing yesterday when the temp ways a balmy 4F

Happy holidays

Jeffrey

Simply Rad_2

I forgot the pics!

Simply Rad_2

I forgot the pics


Here are some pics. Kind of ironic ME that you are using a used petroleum credit card to clean the boiler! My HX was actually very clean inside other the the mysterious green on the burner. I also lower my pump speed for low fire to 10% output or around .28 amps or 55 watts. Our heat loss(25,000 btus) allows us to operate in low fire for heating 95%of the time. I wish these mod cons could modulate down lower cause our boiler does short cycle alot. I will be addressing this next.

Jeffrey

Derheatmeister

Jeffrey !!

Hey Jeffrey call Me or the Bo man..Richard

Simply Rad_2

Heatmeister

Simply Rad_2

Heatmeister I will call you tonite!

Mark Eatherton

Green indeed...

Just guessing here. I'm guessing that your boiler is located in or near the laundry room, and I am also guessing that your wife (or you) uses a lot of Clorox bleach on your clothes.

When you are using the clothes washer, you are generating a need for DHW, and the boiler fires. The vent, serving the plumbing system discharges someplace near the combustion air intake vent for the Vitodens. I fear your boiler is ingesting chlorides...

Am I close? I guess the guys at the factory can probably tell you more.

ME

Mark Eatherton

Yes you may...

And hopefully we will ALL learn something from the exercise.

Your comment regarding visual appearance echo mine. Nothing to cause me a whole lot of concern, but MAN, does it make a difference on the thermal performance side. Remember, I can see my flow rates on the hydronic side as well as the flow on the gas side, so I can gage EXACTLY what is going on with my system as it pertains to the thermal performance side, not the theoretical combustion efficiency side. When I get a new jack for the thermal probe, I will compare theoretical combustion values with actual thermal performance values, and we will see if they match.

I intentionally did no adjustments on installation, and quite honestly, I don't remember what the combustion gas numbers were when we first fired it, but obviously, nothing was so far out of whack as to cause me concern....

And to be quite honest, the only post cleaning number that really causes me any concern is the air free CO, which looks higher than it should be, but remember, I had JUST cleaned the heat exchanger, and had knocked loose a bunch of crap, and I ind of think it is to be expected. I will re run the numbers again later this week and see what they look like.

As for high and low RPMs, I was flowing with the tide, as opposed to manipulating the tide. It was what it was. The high RPM number comes from doing DHW in my reverse indirect. THis is a HTP product as made by Gianonni. It is called the Absolut Condens, and can be seen at http://www.giannoni.fr/Prod-ABSOLUT-CONDENS.html It was designed to go as high as 80,000 btuH for DHW production during short bursts, but at this altitude, it struggles to get there, but for my applications, it works perfectly fine. If I had real natural gas here, it would probably work just fine, but our gas is derated by pumping air into the gas mix by the local utility.

As for variation in flow rate, my heat loss calcs dictated a 2.5 GPM flow rate at a 30 degree delta T, hence the 2.6 GPM flow rate. When it kicks in for DHW, another separate pump kicks in and the flow goes to 3.6 GPM .

We just had the analyzer re-furbed and certified this fall, so I doubt it is too far out of whack.

My comfort system is a one pipe system with venturi tees serving panel rad's, radiant floor (with al plates), radiant ceilings, cast iron radiators, a towel rack and a radiant cast iron tub with TRV's through out.

ME

Mark Eatherton

Doug....

I have to expect that it was going up the flue, because it wasn't going in to the water. One can only imagine what the thermal efficiency would have been had I not had tow heat recovery methods on the flue gas exhaust system...

ME

Unknown

Mark the folks from Mestek

have an air inlet filter on their new Ray for that very reason.

Unknown

You can\"t use

standard combustion charts when testing a lot of this high end equipment (I have found that out the hard way). The excess air will vary and at times be out of sync with normal chart rates. We actually need a lot of combustion research to be done on these units in order to get some realistic charts for measuring accuracy.The rate of modulation and varying combustion air blower speeds make it difficult.

I tend to try and trust what the manufacturers give for anticipated readings on their units. I wish they would give us all their test results under varying conditions as it would really help when trying to diagnose behavior.

Mark is going to see different variables at his altitude and with the air/gas mix he has. A normal optimum 10% gas 90% air mix will give the hottest flame with all other things being equal. I would imagine Marks numbers are different. The BTU content is also affected so things will be difficult to compare when looking at under 1,000 feet measurements.

All his other measurements should be fine as far as flow rates and temepratures along with thermal efficincy measurements.

Unknown

The insulating problems with dirty coils

means that the heat transfer will be affected and a failure to transfer BTU will result in losses through the jacket and out the flue with increased flue gas temperatures. This is why I have concerns when CPVC (200 degrees) and PVC (140 degrees) are used. This can also affect the condensing rate of the equipment.

Unknown

The cause of the \"green\" is from

chlorinated hydrocarbons, you may have some chemicals around somewhere that you are not aware of. Do you have a swimming pool? If so the outdoor air being pulled in will turn the burner green as the air has chlorine in it even if the pool is closed but still has water in it.

I have seen this a number of times in my career.

Even the next door neighbors pool can cause it.

scott markle_2

Vito short cycle

I just did a direct connect Vito with panel rads and some extruded plates.

I used oventrop bypass vales on the radiators 11 of them home run piped with 3/8 pex. The plates only serve a small area of the house and are served by the 3/8 return lines from several radiators.

Works very well, no mixing, no P/S no indoor t-stat. TRV's on all the rads except for one large salvage CI left wild.

I struggled with the vito short issue in my own house, which has a heat loss even lower than yours. My solution was to set the burner potentiometer to it's lowest setting and run the system at a target temp. of 114 controlled by an ODR based variable interval timer (Tekmar steam control) wired to the external demand for heat contact. This works surprisingly well. Indoor temps are a bit less consistent than with the original control but this doesn't bother me, my reset is intentionally a bit deficient to give my wife a reason to light a fire in the wood stove.

The boiler is never able to reach the 114 target on low fire and usually settles in at around 105. The shortest cycle I get is a 2 min burn every 35 min. At design I'm probably running around 20 min every 35 min cycle.

It was hard to let go of the elegant comfortrol interface, but I could find no other solution. The main issue as I understand it is that the NA vito lights on high fire, when target temperatures below around 92 are called for short cycle is almost inevitable in smaller systems that have flow rates in keeping with there thermal requirements.

ME I use diluted a citric acid product (steller solutions 77 plus) as the cleaner it does some passivating while cleaning, but to get that fully passivated look you need something stronger, not sure I want to get all toxic to add a few more years on the HX life though. I believe that 3m makes a scotch bright like abrasive disc that would fit in the grooves and to do the credit card trick, A teck support guy at Viessman gave me a part number that I misplaced. The type of abrasive on that brand of sponge is in my opinion inferior to 3M green scotch bright.

I Need to put some white split loom over the exposed pex on floor fed rads.

troy_8

efficiency monitoring

Mark: I have a customer that tracks her cu. foot of gas usage versus degree days. When the boiler starts using more gas she calls for service. I told her she was dreaming. She makes it about 14-15 months between cleanings. She affirmed that the usage numbers correct themselves after cleaning. I really questioned this fact but you have confirmed it. I admit- we don't do a preclean combustion or efficiency check. Now- to get customers to accept this need to be cleaned.

Mark Eatherton

Tim...

This is an area that requires a lot of research, not just in the modcon arena, but also the conventional and mid efficiency markets. I have personally tested some copper gas appliances (Italian job) and found that there was absolutely no co-relation between combustion efficiency and thermal efficiency.

In todays world, there are too many untrained technicians walking around with instrumentation that gives them a "number", and they have no idea what is required to get to that particular number, or how many different combinations can be used to get to the same (Stoichiometric) number. I'm fairly certain that Jim Davis will chime in here :-) I have instructed my field technicians to turn that function off whenever possible, and if not possible, to ignore whatever pops up.

One of these days, when I have LOTS of time on my hands, I want to do some thermal performance testing and combustion testing, just to show people how little those numbers (combustion efficiency) really mean as it pertains to thermal efficiency. I hate to be the one who has to point out that the emperor has no clothes, but someone has to do it. Maybe I should call Myth Busters and have them do a segment eh... Boy, would THAT put people to sleep :-)

The IMPORTANT things, are,

1. What happens to the oxygen content (burner efficiency in oxidizing fuel and oxygen and converting to useable heat)

2. How much excess air is in the process (carrying off paid for light and heat)

3. How much CO is present in the fuel stream (unburnt, paid for fuel and potential future fowling).

The biggest problem is that most field techs STARE at the "combustion efficiency" number, and DON'T pay attention to the important details.

If you ae one of those tech's that are reading this, the best advice I can give is to get yourself in to a qualified class (Jim Davis, Tim McElwain or Rudy Leatherman come to mind) so that you will KNOW what it is that you are looking at, and what adjustments you can safely make to change those numbers and bring them in to compliance.

It's more of a a science than an art.. and the need for education was never greater.

ME

Mark Eatherton

Smart woman...

She has YOU for a contractor, doesn't she ?;-)

Most consumers are a lot more attentive than we give them credit for, and some are more boisterous than others.

ME