Water Tube HX's

Tinman

Since we got a bigger shop, I've had more room to play around with different boilers. And if my wife is working on the weekend, that's what I do. I don't golf or fish or hunt. I go to the shop, turn the radio up loud so I don't have to think, and I tear things apart.

This weekend it was a Munchkin. I'm going to put it back together with new gaskets, a clean HX, flame sensor, electrode, and use it for training purposes. Customer had problems with it starting after the 2nd or 3rd year and called us about 9 years after it was installed. The piping was a terrible attempt at P/S. There were leaks everywhere so it was exposed to fresh water all the time. Terrible install and never serviced. The owners were adamant about going to something newer and better because of all their frustrations over the years, so that's what we did.

But as I was doing it, I couldn't help but think that the water tubes have been getting a bad rap because so many haven't done their jobs in terms of the installation and follow up service. I have yet to see a textbook installation of one of these guys. Hot Rod has always been saying if you pipe them right and provide the right flow, they're good. I was a bit reluctant to believe that but I do now. In the beginning, I stayed away from them like the plague, choosing to offer the Buderus GB142's instead. So, I missed many of the nightmares that others went through.

I guess my point is that history may be kind to the Giannoni? If contractors follow the same path with the Fire Tube HX's, we're going to be looking at too many failures again. Probably not as many because these HX's appear to be more forgiving.

SWEI

The Giannoni HX has a perfectly acceptable track record in Europe. The combination of bad piping, hard water, and lack of maintenance is just more than it can handle.

We've got a couple o the Lochinvar CDN040's out there direct-pumped and they seem to be doing OK so far, though the service requirements are still higher than for a downdraft fire-tube.

hot_rod

The Sermeta style, formerly Giannoni, is still a viable option, with proper care and routine maintenance their are examples running 20 years now.

I have not touched my mother in laws Laars Mascot in at least 4 years. When I do open it I do not find the mouse turd deposits, like many do. Which is why I stopped yearly service of it. I haven't replaced a single part and it does cycle a lot as it has a DHW plate HX. It probably fires dozens of times a day for DHW, and very short cycles.

At their website Sermeta mentions a .8 KW ( 2700 BTU/hr) minimum turndown? Although the smallest size I see is a 18 KW.

They also mention 30-1 turndown I suspect that is with three 10-1 ganged together.

I see plenty of failed fire tube style as I travel to wholesalers across the US. True, many are related to fluid, some are weld, or assembly attachment issues.


http://www.sermeta.com/en/

I asked John Barba this week at his seminar about mod cons and ∆T pumping. He suggested a buffer or hydrosep on all mod cons. Use the manufacturers suggest pump on the boiler side, ∆T only on the distribution was his recommend.

With that requirement, the water tube only costs you some additional pumping power over the fire tube. With an ECM on the boiler side, that consumption isn't a deal breaker.

Solid_Fuel_Man

Seems like those water tube HX could actually be more reliable as there are much fewer welds and thermal expansion is delt with better than a tube sheet with several feet of laser welded fire tubes. Just more restrictive water side and not self cleaning like firetube. Just speaking hypothetically as I have not delta with FT yet.

Taylor

hot_rod

From what I have been told, the weld area presents the most potential for crevise corrosion. If you have fill water with high chloride levels, which is becoming more common, all those welds could present more leak potential.

The tank collects sediment like a DHW tank. Clean, TDS free water is just as critical in fire tube style hx.

Here is the mechanism for the failure.

SWEI

To be fair, when operated in systems which do not consume makeup water, the downdraft HX design seems to keep (wash, really) itself clean for many years.

hot_rod

Agreed that the inside of the fire tubes may wash clean, with proper combustion adjustment, of course.

With the water tube the inside scours clean with proper flow. The outside stays clean with proper combustion and intake air.

I think it is about 6's. Arguments either way, both based on fluid and air quality and proper flow.

Fire tube brings some fluid capacity to the game, and possibly lower flow rate requirements, those may be the top.

In about 15 years we will see how the fire tube last as more manufacturers enter the market. TT switched manufacturers for a reason?

Henry

As with flate plate heat exchangers, a certain flow rate (velocity) must be maintained as not to allow suspended particles to adhere to the tubes of the heat exchanger. We have replaced a number of heat exchangers from boilers installed by other companies. They use 35 or even 40F as a boiler Delta T so that they can use a $300 cheaper pump.

hot_rod

Henry said:

As with flate plate heat exchangers, a certain flow rate (velocity) must be maintained as not to allow suspended particles to adhere to the tubes of the heat exchanger. We have replaced a number of heat exchangers from boilers installed by other companies. They use 35 or even 40F as a boiler Delta T so that they can use a $300 cheaper pump.

The flow rate also assures turbulent flow for best best exchange. I suspect this is why the fire tube designs are asking for a minimum flow rate. They may operate with low or 0 flow like a cast iron boiler, but to get efficiencies up they show min flow rate.

Perhaps this is why the small HTP fire tube asks for a min 5 gpm?

In a perfect heating fluid there would be no suspended particles We have started promoting DI water for boiler fills. This handles dissolved minerals, and also the killer chlorides.

Some of the boiler treatment chemicals will keep solids in suspension, but it is still best to never introduce them.

Rich_49

Hot Rod Said;

" I asked John Barba this week at his seminar about mod cons and ∆T pumping. He suggested a buffer or hydrosep on all mod cons. Use the manufacturers suggest pump on the boiler side, ∆T only on the distribution was his recommend."

I have to question the accuracy of this statement . I know John and what and how he instructs very well and have a hard time picturing these statements coming out of his mouth . I'll leave it there .

Hot Rod also said ;

Perhaps this is why the small HTP fire tube asks for a min 5 gpm?

I attached the manual to verify . For the EFT the minimum flow rate for the small HTP is 3.5 gpm . Page 16 .

hot_rod

Rich said:

Hot Rod Said;

" I asked John Barba this week at his seminar about mod cons and ∆T pumping. He suggested a buffer or hydrosep on all mod cons. Use the manufacturers suggest pump on the boiler side, ∆T only on the distribution was his recommend."

I have to question the accuracy of this statement . I know John and what and how he instructs very well and have a hard time picturing these statements coming out of his mouth . I'll leave it there .

Hot Rod also said ;

Perhaps this is why the small HTP fire tube asks for a min 5 gpm?

I attached the manual to verify . For the EFT the minimum flow rate for the small HTP is 3.5 gpm . Page 16 .

The were about 130 people at the seminar, I asked the question at the end Q&A session. I don't recall seeing you there?
So assume what you want.

I appreciate the way John presented the choices between ∆T and ∆ P selection, I felt it came across much better than the Providence training a few years back at the BB unveiling.

Rich_49

John would advocate for a separator since getting anyone to do P/S properly with closely spaced tees is almost impossible . This I can see him saying . I can also see him advocating for buffers on some mod cons that require such a device . However , the language you put your statement forth in would suggest that John said , all mod cons require buffers and hydro seps .

Everyone knows John works for a company that does plenty of OEM work and as such will not recommend anything other than Mfgr. recommendation when to comes to their equipment . Now , if you had asked John about newer boilers like the HTP UFT or the Lochinvar KHN that do not require P/S using a Delta T circ you may have gotten a very different response indeed , along with all the "It depends " that must accompany any discussion about such things .
Take into account that a discussion in a setting such as you were in as opposed to a private discussion group setting where a different knowledge level exists may go a completely different direction altogether .
You're right , I was not in attendance . I assumed nothing Bob .

Tinman

Bumping this thread because, this past week, we started servicing fire tubes we installed 12-14 months ago. All the boilers were sized correctly, piped correctly, vented correctly, and a combustion analysis was performed at the time of installation.

Every cleaning was well worth the effort because we vacuumed, wiped, or flushed a fair amount of debris and discoloration from each. The chips in the neutralizer kits were already degrading so we restocked all of those too. We followed the manufacturer's instructions to a T. The second one we did took only half the time as I figured out better ways to attack it and better tools to use.

I guess I'm sharing this so we don't drop the ball and believe that these are in some miraculous way, self cleaning. They aren't. My .02. Go get'm.

Tinman

One more thing - both systems were cleaned with Rhomar product and both systems have Rhomar conditioner in them.

hot_rod

Stephen, do you test the fluid quality with the Rhomar test kits?

If so is the fluid staying stable, or do you need to boost occasionally.

Do you blend the Rhomar with site water?

I saw this condensate makeup in a boiler manual recently, Viessmann perhaps? i wonder what the purpose of the information?

Certainly the ph would be something an installer would need to know and address.






The question I have, could any of those ingredients, or combination of them cause PVC to breakdown or leach chlorides. And what how would elevated temperatures, like a boiler in DHW mode, change the reaction to PVC vents?

As far as combustion side cleaning, really what you get with fire tube is more space for deposits to store
The creation of those deposits still seems related to intake air quality, fuel gas makeup or blends, re-circulation of the venting gasses, and burner adjustments.

Solid_Fuel_Man

When we are talking PVC and leaching chemicals, wouldn't those simply go out with the flue gasses? Wouldn't just the intake piping have an effect on combustion, and it shouldn't be subject to much over ambient Temps. Trying to follow this a bit. I see a fee installations with polypropylene venting and PVC intake. Would polypropylene be best for both?

hot_rod

The condensate running out the drain in the bottom of the boiler is the "waters of combustion" Some of that comes down the venting pipe, runs across the HX before it is conditioned and drained away. So some of that condensate has come in contact with the venting product.

The failures in some of the PP venting resulted from low spots in improperly supported connections. The condensate waters (low ph) would lie on the gaskets and cause them to fail. So the venting also needs to slope back to the boiler to assure all the condensate can drain from the venting.

The lower the operating temperature of the boiler and return, the more condensate you will get peeing out.

Tinman

Hot Rod - Yes, we check the Ph of the system water as well as the condensate. The system water in our area seems about as close to 7 as possible. We haven't had to do anything with that. What surprises me is the number of contractors not using neutralizing kits on the condensate; even with them the water is slightly acidic.

hot_rod

Start checking TDS of the fill water also. Rhomar tells me they are getting samples sent to them from public water supplies in the 100- 200 ppm range. That is too high for hydronics, the boiler manufacturers are giving us more guidance on the fluid quality, check the I&O manual on fluid quality.

Here is a recent one from Peerless. Also a few other brands, some are vague, some breakdown the various concerns. Some are in metric units

Fill water can be treated by filtering, or conditioned by adding the Rhomar type products. It depends on the quality as far as the best fix, chemicals can only do so much, at some point the water needs to be deionized for best results.
You will use less hydronic conditioners if you fill with low TDS water.

NY_Rob

^ and how many homeowners that have condensate neutralizers are going to remember to check/clean out and replenish their condensate neutralizers on a semi-annual basis?

I observed about a 20% reduction of the marble/lime chips in my neutralizer after about 7 months use on my 80K BTU mod-con... and the first four months it was only used for the 30 gal DHW indirect tank heating. I imagine after 12months or so of normal use it would be pretty messy inside and pretty low on chips.

Canucker

@hot rod Do you happen to know if anyone has done an HPLC or NMR analysis of the condensate? It might be interesting to see what is actually in it and see if any of the chemicals found match up with the chemicals used in the pipe manufacturing process.

JUGHNE

So is it thought that PVC wash back by condensate water produces the "coffee grounds" (which can be picked up with a magnet BTY)? I ventured this theory forward in the past but heard no response.

If the drain back across the HEX is a concern then a simple collector trap at the flue gas discharge would catch most of the liquid.

I read a lot about neutralizers for boilers......do we see them on condensing FAFs? I do install them as there are a lot of cast iron drains on change outs.

njtommy

@JUGHNE I've wondered the same thing with force hot dust 90 plus units and how come you don't need an acid neutralizer for them as well?

hot_rod

Canucker said:

@hot rod Do you happen to know if anyone has done an HPLC or NMR analysis of the condensate? It might be interesting to see what is actually in it and see if any of the chemicals found match up with the chemicals used in the pipe manufacturing process.

I think Richard "heatmeister' Graves out in the mountains of Colorado had done some lab analysis of condensate fluids.

As I recall he samples the system fluid and condensate from boilers he works on. You see some of the samples in his shop are glycol, some are burned or degraded glycol, the coffee colored ones. The ones with sludge in the bottom are probably magnetite from old non barrier tube systems. I asked him to stick a magnet on those jars to confirm that is the expansion tanks and pump p bodies lying in the bottom of those jars

Early on there were many aluminum block boiler failures. It was determined glycol that wasn't ph adjusted "AL glycol" could go after the aluminum. Aluminum block boilers have a very tight ph acceptability range. I had one aluminum boiler manufaturer tell me this summer that they are still trying to find the perfect IC internal coating to protect the aluminum.

Pin hole problems continued even after the AL fluids were used. Richard wondered if the aluminum degrade was caused by the condensate outside the HX block not the fluid inside.

He has the rest of the story.

Also, here is some research done on PVC leaching. The chemical names and terms are a bit above my pay grade.

https://nepis.epa.gov/Exe/ZyNET.exe/20016SY7.txt?ZyActionD=ZyDocument&Client=EPA&Index=1981 Thru 1985&Docs=&Query=&Time=&EndTime=&SearchMethod=1&TocRestrict=n&Toc=&TocEntry=&QField=&QFieldYear=&QFieldMonth=&QFieldDay=&UseQField=&IntQFieldOp=0&ExtQFieldOp=0&XmlQuery=&File=D:\ZYFILES\INDEX DATA\81THRU85\TXT\00000013\20016SY7.txt&User=ANONYMOUS&Password=anonymous&SortMethod=h|-&MaximumDocuments=1&FuzzyDegree=0&ImageQuality=r75g8/r75g8/x150y150g16/i425&Display=hpfr&DefSeekPage=x&SearchBack=ZyActionL&Back=ZyActionS&BackDesc=Results page&MaximumPages=1&ZyEntry=1

Tinman

@njtommy - the condensate from 90% eff. furnaces is acidic too. Neutralizers have been offered early on for those too.

Tinman

Bumping it again. Cleaned another one this afternoon. This one was converted to LP when we installed it in Dec. of '15.

Clean as a whistle. Even the condensate trap had clear water in it. First off, I'm shocked. Any ideas as to why this one is so clean?

njtommy

@Stephen Minnich Does air quality have anything thing to do with how Dirty the chambers are?

hot_rod

njtommy said:

@Stephen Minnich Does air quality have anything thing to do with how Dirty the chambers are?

No doubt.
Dusty parking lots, dirt roads, pollen from nearby trees. Fireflies get sucked in sometimes, lots of suction at those inlets.

I have seen some mod cons with intake air filters. The Polaris tanks shipped with a large truck looking air filter.

They are what they breath.

Tinman

Good points. It's very possible. The two NG units we cleaned earlier in the week were in the City of Chicago. The one today was out in the middle of nowhere in southern Wisconsin.

Solid_Fuel_Man

Shows that maybe LP isn't as dirty as we may think. May have more to do with outside factors (literally). Considering that most NG units will be urban, and LP country.

Mark Eatherton

I had a Munchkin that sat right next to a large bunch of corn fields. In fact it was surrounded by corn. On the first annual inspection, the heat exchanger was so badly blocked from cooked corn pollen, that we had to replace the boiler. NY Plumber has begun including an air filter on modcon boilers, and said he has seen a significant difference in the combustion chamber.

I also had one in downtown Denver that was 1/2 block away from the longest commercial street in the US (Colfax Ave), and an annual cleaning was not enough. Had a black (think automobile pollution., carbon type of accumulation in the chamber that was hard as cut nails.

I also had one on a million dollar horse barn. Boiler was on the second floor of this barn, and its intake air was a good 25 feet above the outside grade, but it kept plugging up with dust and horse dander. Installed a simple filter on it, and it too made a huge difference.

I really think that all modcon boilers should have an air cleaner on them.

ME

Mark Eatherton

Mark Eatherton

Credit to Tim Reini, Total Home Comfort for coming up with this simple design. Called it the Reini Confiney.

Magnahelic showed when it needed service.

ME

Solid_Fuel_Man

That's creative! Seems that the filter paper would add significant restriction to the intake. Maybe a truck type filter would serve well.

The magnaheilic is a nice touch to monitor it though! I also notice the blue painters tape with notes when to change the paper.

JUGHNE

Is that an external condensate drain that is field added for the discharge? Keeping excessive water out of the HXC?

A throw away lawn mower has an air filter doesn't it?

Mark Eatherton

Jughne, that was a vertical vent condensate drain from the manufacturer (Buderus).

SFM, we tested the fire side post filter install and it was fine. Left the company, so really don't have any more history on it. The gunk that came out of the condensate trap pre filter smelled exactly like horses (dander). That is what brought the dirt problem to our attention. The condensate didn't drain and the igniter drowned... When fan ran for pre purge, it gurgled...

ME