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CPVC

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1. Show me a copper fin tube boiler whose water ways are 100% non ferrous... Don't waste too much time, there MIGHT be one (Raypak bronze potable water boiler).

2. Who's in charge of checking the fluids and making sure that they are kept in good shape to avoid the inevitable corrosion? It won't be the homeowner. Trust me,on this, I saw PLENTY of this non maintenance as an expert witness.

It's a bad idea, and it was done to satisfy the needs of a few tubing manufacturers who wanted to get their non barrier tube out in front of the heating contractor.

I've run the numbers, and it is NOT that much less expensive to go that route, and all of these suposed good deals are coming back to haunt the minicipalities who approved them.

There is no right way to do things wrong...

ME

Comments

  • CPVC instead of copper

    anyone played with this?

    Maybe it's a dumb idea, but the stuff has the same ratings as PEX, less expansion (though enough to have to accomodate in high temp applications), and would appear to be easier to work with and much, much cheaper than copper.

    Downside is expansion.. 0.4" per 10' on a 100 degree rise (high temp), enough to accomodate.. also, not an o2 barrier.

    Any other downsides? I mean other than, no one does it. glycol?

    I've been asked about it twice in the last two weeks, and I just assumed it was a bad idea, but after doing some reading I'm not absolutely sure it is...
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928
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    Have never used it in a heating system but must admit that I have occasionally used it for domestic.

    Other downsides:

    1) It gets brittle with age. Doesn't burst, but quite prone to inpact damage and hard to get a nice clean cut when making changes/repairs.

    2) Male adapters are notoriously weak.
  • Ross_7
    Ross_7 Member Posts: 577
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    No oxygen barrier

    I do belive that there is no oxygen barrier in cpvc so i.e.
    can only be used in open systems. Maybe I'm wrong.
    Ross
  • [Deleted User]
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    BINGO!!

    And if I have my way about, the use of non barrier pipe and tubing in closed loop systems will be illegal in the very near future...

    ME


  • Why?

    If you have a non ferrous heat source and non ferrous pumps, the only downside is possibly a reduction in glycol inhibitor lifespan.

    I'm with you on not doing freshwater systems for cross contamination issues, but oxygen diffusion is an issue that can be handled two ways... keep it out, or don't use ferrous components. Right?

    Heck, the way copper it going it won't be long before it might make sense to heat exchange to replace copper and still protect the boiler....
  • mtfallsmikey
    mtfallsmikey Member Posts: 765
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    A little known fact

    Most CPVC male adapters are NOT rated for hot water usage


  • interesting, thanks


  • actually, another possibility would be if this were, in fact, cost effective, to get CPVC made with an o2 barrier....
  • Glenn Sossin_2
    Glenn Sossin_2 Member Posts: 592
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    Time to cure joints

    You have to wait for the joints to cure. I don't know specifics, but I believe its close to 8 hours to get to 60% of the joint rating. Up to a day or more to get to 95%. Most people want to turn on the water right away. I remember using it for hot and cold piping once and turned the water on after 1 hour - the joint developed a leak.
  • Drew_2
    Drew_2 Member Posts: 158
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    CPVC

    One more to add to your list.
    Propylene glycol will cause CPVC to fail.


  • Use a heat exchanger mark. problem solved. Use a water heater. There are many ways to do open systems (to oxygen, not freshwater systems) safely such that corrosion is a non-issue. There are thousands of such systems out there having been in operation for decades... not on boilers, of course.

    It looks like CPVC is a bad idea, for a lot of reasons, but I'm not with you that oxygen diffusion is a deal breaker. It may offset the economics of a non barrier system (and, back in the day, I ran those numbers many many times indeed) to need a heat exchanger, and frankly I don't LIKE non-barrier systems and don't typically design them these days, but illegal? That's a bit far to go.
  • [Deleted User]
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    Field experience...

    dictates otherwise my friend. I have a friend who makes a living changing out the exact system you are talking about. Not by choice, but rather by trade. What should work theoreticaly in the field doesn't. What is considered a "non ferrous" heat source (CFT boilers) in reality does have its tube sheets rolled into mild steelheaders in most cases, and cast iron headers in other cases, and as I said, one fully bronzed header in another case.

    The problem with writing code is that you can not specifically exclude certain products that are approved for the application (boilers for example) but you can outlaw the use of non barrier tube because there is an alternative readily available.

    I don't have a dog in this race. We NEVER use anything but barrier tube. It's the continuous calls from the customers in the field with leaking boilers on systems that are less than 10 years old that depresses me. Oh by the way, did I mention litigation? Trust me, it's already happening. If you want to (can afford) to be a part of that, then so be it...

    As for the use of water heaters as heat sources, it can be done, but it is occuring at an efficiency hit of around 30%. If your customers knew that it was going to cost 1/3 more to heat their home with a water heater than with a true hydronic heating appliance, do you think it would sway their decision?

    And yes, I have installed a few water heaters as cheap heat sources, but I made sure the consumer was aware of the efficiency hit prior to pulling the trigger.

    And finally, why would someone want to design and install a system using non oxygen barrier tubing and more expensive stainless steel/brass/bronze components? Is it because it is a superior design with much higher efficiencies? Or does it come down to cost... And if you were to look at it from the life cycle cost point, which system do you think will shine?

    I'm just tired of seeing systems fail way to early in life Rob. Time for change. The change won't be that significant for most people on this forumn...

    ME


  • We only use barrier tube these days as well, because I believe in future flexibility.

    But if you are designing low-pump-count systems, it's one non ferrous pump and a heat exchanger.

    Is it better? No. But if copper, for instance, keeps going up and becomes a true "precious metal", then we'll need replacement material. If a replacement material is not an O2 barrier, it still might be worth getting the heat exchanger and non-ferrous pump.

    Or, maybe not. but the option should be there. Perhaps your focus should be on people rating boilers as non-ferrous, that fail when exposed to oxygen?? Because oxygen itself doesn't make the system any less efficient.

    I also think your 30% number is a bit wildly overstated mark...
  • [Deleted User]
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    30 % is UNDERSTATED

    Rob, I used to live with one of these (water heater heat source) in my own home. And it was not your typical on-off bang bang water heater. I modified it such that it was on full outdoor reset, and when I replaced it with a mod con, I reduced my energy consumption by 30%. Had the water heater been used in its conventional one temperature setting, the savings would have been even greater.

    30 % is not an overstatement. Where do you get your numbers from?

    ME


  • mark, I've mentioned before that I don't think it's fair to rate water heaters based on your experience with one that you rigged up to act nothing like a regular water heater acts. That is anecdotally interesting, but it is not scientifically defensible at all because neither you, nor I can forsee all the effects that might have on the units operation. also, there is a very wide variety of water heaters out there, and so making blanket statements about them all isn't fair either.

    I used to work for a company that did "open direct" type systems, close water heater systems, the whole nine yards. We would occasionally check out fuel costs, which, as you know, are nearly impossible to nail down in the field since we are not monitoring DHW usage, but honestly the fuel usage was not insane. Other discussions have shown that the energy factors of water heaters, measured for DHW, are UNDERSTATED for water heaters in a heating application because the standby loss assumption is much smaller in a continuous draw heating system situation.

    Now, I only use water heaters on very small loads because efficiency is a big deal. But so many people are superinsulating houses now, that there are significant number of very small loads out there, so this is not just an esoteric discussion either.

    Currently, I assume 75% eff on a water heater, based on the previous years of experience, though I have seen some systems that performed poorly and some that performed better than that... since I don't do a lot of these anymore, I can't say exactly why the variance, but I suspect it has to do with sensor position in the tank in different models of water heaters, or something to do with the return water flow characteristics on individual systems, given the behaviour I've seen from the poorly acting ones (constant cycling and overheating/stratification of the tank). On properly acting tanks, I didn't see any major eyebrow raisers.

    on a low temp system I assume 95% on a mod con, based on documentation and faith and feedback from you guys, primarily. That's a high differential and that's big, but it's not 30%, and it is not ALWAYS enough to justify the trade up (though usually it is, for sure). and if I'm blunt, on a low load situation unless you add a buffer tank I wouldn't be sure the mod/con is 95% in cycling mode. But it'll be more efficient for DHW as well so I consider that assumption a decent one overall.

  • [Deleted User]
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    Rob...

    I don't want to appear to be coming off as confrontational, but your 75% number doesn't hold water either. Per the ACEEE, gas fired tank style water heaters have an EF (Efficiency Factor) of between .63 qnd .67 %.

    I suspect the reason that the manufacturers DON'T have an equivilent rating system like AFUE for their appliances is because they would rate so low, but that's just my take on things.

    All things being equal (or almost) the difference between .95 AFUE and a .67 EF is around 30% no?

    Here's a link to the ACEEE web site discussing EF as it pertains to water heaters.

    http://www.aceee.org/consumerguide/waterheating.htm

    ME


  • Mark, if you have the same standby loss, but one heat source produces ten times as much heat a day as a second, identical heat source... which one will register a lower efficiency?

    You can't just call EF the same as AFUE. Note that they only figure a 0.92 to 0.95 EF for electric water heaters. Would you call an electric boiler only 0.92 to 0.95% efficient? EF takes into account standby loss.

    According to what you yourself just posted: "The energy efficiency of a storage water heater is indicated by its energy factor (EF), an overall efficiency based on the use of 64 gallons of hot water per day."

    Call it a 60 degree rise, if you like. 64 x8.3x60 = 32,256 BTUs a DAY. that's barely more than 1kBTU/hr in heating load.

    If your average water heater loses 1/2 degree an hour, 12 degrees a day, 30 gallon tank (for fun) that's 12x30x8.4= 3024 BTUs a day in standby loss.

    That would drop your EF ten percent. You lost ten percent of your total heat for the day.

    Now jack your output up to even 5kBTUs/hr... 120 kbtus/day. You're only losing 2.5% on your EF.

    The heat source didn't change at all here. The amount of standby loss didn't change at all... just what percentage of the total load that standby loss represents changed.

    What you need is a cumbustion efficiency number, not an AFUE, assuming you are heating in the heating season and standby losses are not "lost".

    no worries anyway mark, I like to debate, especially with people I respect, and I respect you more than most by a long shot. But that doesn't mean you're perfect either ;)
  • [Deleted User]
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    We are all human...

    and subect to issues. It just really tires me to see people making the same mistakes over and over and over again, and then the lawyers get involved, and a lot of money gets spent, for nothing.

    In these days of enviromentally correct decisions, we would all be wise to step back and take a second look at what and how we do things.

    No one knows every thing there is to know about everything... ME included.

    Proceed with caution.

    ME
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