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Q on cost benefit of installing ODR for a cast iron boiler

MaMa Member Posts: 18
Hopefully this is one of those basic questions that many of you can

answer in your sleep, if I am careful enough to provide sufficient info!

We purchased our home in WI over the summer that has for a heating

system 1950s baseboard  being fed by a boiler system replaced in 2005. 

The boiler is just for hydronic heat; we have a separate, direct fired

water heater system. I have created and attached to this post a diagram

of my system, should it help.  Briefly, it is a Buderus G124X/32 boiler

supplying 3 zones, one for each finished level of the split level house

(about 2500 sq ft).   I don't think the insulation in the walls have

ever been in improved,

and there is not attic (flat roof) & a LOT of windows, but on the

other hand almost all those windows are Andersons installed five years

ago (after the boiler was installed).  So it may be oversized?

It got a bit chilly Friday evening so we fired it for the first time

(since inspection).  It worked fine from a functional POV, but the

creaking and clanking from the pipes in the wall throughout the night

was a BIG issue with the wife and kids that night (and me as well, to be

honest).  So I went on a crash course to learn more about how this

thing works this weekend, and what I have figured out so far is below:

first my conclusions, then my

questions leading from them:

1) the noise is not from air in the pipes, given there is a Taco air scoop installed,

2) I believe the noise is caused by expansion and contraction due to

temperature change, because when I briefly cranked up all the zones to

90 degreesin order to get all zones to run continuously, after an

initial few minutes the noises mostly subsided, and did not return until

after I turned the thermostats back down (this also is further evidence

against air in the system being the issue).  Is this a valid

conclusion?  I figure that the temperature in the pipes and baseboard

probably had a fairly big swing because it was not that cold out, so the

system would go a long time between runs, and all the pipes would cool

almost down to room temperature, then get jacked up quickly to 180

degrees when the boiler kicked in.

3) reading here and elsewhere (e.g. Tekmar "essays"), the established

way to minimize these large temperature swings (and thus the noise) is

to install and outdoor reset control, with an outdoor sensor on the

north face of house, which will make the boiler heat to a lower

temperature when it is milder outside & there is no need for such

high temperature water to circulate.  For a while it sounded like the

Intellicon HW+ might get me what I want without ODR, but seeing so much

skepticism about it, something like the Tekmar 256 costs the same (parts

not labor) and is a more reliable/capable/believable option.

4) reading further, I have learned that one complication for my

situation is that the Buderus G124X is a cast iron boiler, and there is

apparently a minimum water temperature it needs to supply in order to

avoid damage from condensing.  However, the Buderus operation manual I

have says nothing about it, and I am finding contradictory information

on these forums, some have said 104 degrees, some 120, some 130, and

some 140,

5) I have also read that further improvements may be obtained by adding a

mixing valve, and/or indoor sensors, plus of course a control that can

handle them.


OK, so my questions, assuming all those conclusions are correct:

A) what is the minimum temperature the Buderus G124X should be run at

(what would the "MIN BOIL" of the ODR control need to be set to?  I see

that Buderus puts silicon or something in the cast iron of my boiler,

does that open the door to lower temps?

B) based upon the answer to (A), is that number so high that the

benefits of installing an ODR would be too minimal for my cast iron


C) Should I be looking at more than just simple ODR only?  How much

additional cost benefit might i get from other alterations, such as

mixing, indoor sensors, etc?  Factoring into this question is that I've

installed Aprilaire 560 humidifiers (also with sensors) in two previous

homes, so I think I can take on something like the Tekmar 256 myself

(seems like a very comparable install), and I work in IT as an analyst

so I'm comfortable with the idea of trial & error and tweaking.  But

I've never done DIY plumbing work.  So there would probably be a larger

than typical difference in cost for me between ODR alone (which I would

do DIY) and something involving messing with the plumbing itself (which

I would probably contract out).

D) Does the fact I have three separate zones factor into any of the

above answers?  Additionally, it seems to me, just based upon logical

deduction, that those three zones with three completely independent

thermostats might cause the boiler to cycle more than it needs to,

because maybe each zone calls for heat at a different time, and

furthermore maybe one of the things that causes the pipes to heat so

rapidly is that many times only one zone is receiving all the boiler's

output.  So is there some other control aspect I should be considering

to address that?

Thanks for any guidance you can give!



  • Ironman
    Ironman Member Posts: 7,224
    Look at Using...

    The Buderus 2107 Logamatic control. It's made specifically for that boiler and will maintain a 104* min. water temp. Get a Buderus Pro. to install it and you should see a 30% minimum reduction in fuel consumption as well as a much quieter system. :)
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • MaMa
    MaMa Member Posts: 18
    edited September 2011
    Thank you for the reply, ironman

    I'd seen the Logamatic 2107 mentioned and looked into it.  Is there any particular reason I should strongly prefer that unit over the tekmar (for example)?  Yes I know it is the one sold by buderus, but it is also many times more expensive than a tekmar 256, based upon google shopping search, and I found a few comments across the net along the lines of this one by JackR:

    Great control but..............

    way more than you need. Don't get be wrong, the 2107 is a great control but if your just looking for an outdoor reset to use in conjunction with baseboard a standard off the shelf Tekmar, Honeywell or any other outdoor reset will achieve what you want it to do for much less. The control has many functions but is very limited in what it can do for your system. I'm certainly not bad mouthing the control just trying to be realistic.


    Based upon his other posts he sounds like a professional in the field, referring to various installs he's done.  Maybe more reassuring is the endorsement of the use of a Tekmar control by Joe@buderus:

    Outdoor Reset

    ......The use of an outdoor reset control either by Buderus or Tekmar will help decrease your fuel consumption and provide a more comfortable heat. Tekmar Controls are acceptable on Buderus equipment if not using our Logamatic R2107.  If there are any questions please contact us at 1-800-283-3787.


    Remember, I do not need the DHW controls of the 2107 because I have a separate direct water heater.  Is there any other feature relevant to my installation that I would get with the 2107 and not a Tekmar 256, besides freeze protection?  And if that was important couldn't I just get say a Tekmar 260 and still save over 50%?
  • Slimpickins
    Slimpickins Member Posts: 335
    pumping issue

    Yes,like Ironman said, the 2107 Logamatic control is a great addition and will give you ODR and many other energy saving features. Your piping diagram shows that you're not "pumping away" and there is a great book about it available under the resources tab above It's late and I'm too tired to explain it but you will experience noise and early pump failure the way it is piped now.
  • MaMa
    MaMa Member Posts: 18
    Thanks for the reply, slimpickens

    Are you referring to the fact that the pumps are on the return side? I didn't know if it was a big deal, and didn't connect it to the issue of greater noise.  Given that one of the three pumps looks quite old, I'm guessing that is the way it was originally installed in 1956.

    I will try to find this resource you mention.  But this sounds like a much larger scale alteration, to move the pumps to the supply side.  If I understood you correctly.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,840
    Multiple issues at hand...

    Conservation is always a good idea, but in your case, it "sounds" as if you are having other "issues" with your new home/heating system.

    My definition of comfort is 'Not being aware of your surroundings. You are neither hot, nor cold, and you DON'T hear any noises associated with the delivery of comfort." Your is more of a noisy comfort issue than it is a conservation issue, and that can be addressed with controls to a degree, but I suspect you will throw some money at the "problem" and the noise will get better, but it will still be an issue. This is quite common in our industry. Unless you are living in a medium sized McMansion, you could probably get by with one pump serving all three zones. The individual pumps serving the zones are grossly oversized, and every time there is a call for heat, the water is WHIPPING around the system much faster than it need be. So, even though you will be putting and ODR on your boiler, every time the boiler starts, the pipes will go from tepid, to whatever temperature is dictated by the ODR, and the pumps will still be moving too much water around the system, and the pipes will still expand and contract.

    You have numerous options, none of which are inexpensive, but definitely worth while.

    There are non electric thermostatic controls available to be placed directly on the baseboard convectors that you have in your home. Remember, these are piped in series, so place them with that in mind. Their control function is proportional. If the zone needs just a little flow, then that is all it gets. If it needs a lot of flow, then the valve opens up more to satisfy the need.

    This will then allow you to move the pump to the right location (purchase and read "Pumping Away" from the book sale section herein the SHOP button to the upper left) and put it into a continuous circulation mode. Replace the 3 pumps with one variable speed, constant pressure pump (google WILO Eco or Grundfos Alpha) which will also work in a proportional mode. If all 3 non electric thermostatic valves are open, then the pump is at its maximum speed and production. If all three valves are barely open, the pump is at its minimum capacity. The application of a control is a good idea, and the Buderus boiler is capable of the lower water temperature (104). I don't think brand is as important as function (boiler protection is critical).

    As has been pointed out, there are no less than a hundred different ways of achieving this same goal, but I always like to employ the KISS principle,and what I've laid out for you should achieve this. It will require some near boiler piping changes, but it will definitely satisfy all of your wishes, wants and needs.


    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • MaMa
    MaMa Member Posts: 18
    Thanks Mark

    Mark I  think you comprehend my concerns correctly.  I have not had a lot of free time to follow up on your comments during the week, but I do at least have a general idea of what your "pumping away" reference is now (watching a couple videos at the "little red schoolhouse" was very helpful). 

    I'm still not sure that the location of the pumps is the major issue, based upon my observations.  As I mentioned, when I turned all the thermostats up to 90 so the boiler pumps would all run a long time at temperature, the noise issues all but disappeared after a few minutes.  If the pump location was behind it (causing air to come out of suspension), wouldn't the noise be continuous and unvarying for as long as the pump was running and valves open? Instead I get most of the noise at startup and (I think) after shut down of "bang bang" operation.

    Your comments on the mixing have me really thinking though, as well as reading more of the "essays" at tekmar.  I think you are probably right (if I understand you), the closer I am to continuous circulation, the closer I will be to silence, and mixing is probably going to have to be part of the mix.  Still, I am tempted to just try ODR alone, because I can do it quick, and frankly I don't have much cash reserves after buying the house!

    I am going to read and think more if I have time this weekend.  Thanks again.
  • Ironman
    Ironman Member Posts: 7,224

    The Tekmar is fine control and also could provide boiler protection. The Buderus 2107 operates slightly different when providing O.D. reset. The Tekmar seeks to achieve a certain boiler temp upon a call for heat based on outdoor temp. The 2107 maintains a constant boiler temp based on outdoor temp whether the thermostat calls or not. The 2107 can achieve what Mark suggested without the need of a mixing valve if properly setup. It's ideal for constant circulation.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • MaMa
    MaMa Member Posts: 18
    edited October 2011
    Update: went with 2107 (to start with); two more questions

    Had opportunity to pick up the Logamatic 2107 at a significant discount.  Since IronMan & slimplickens both recommended that, and indeed I was first looking at using that myself but was only deterred by the cost, once the financial issue was mitigated, I decided to just go ahead with that, and then reevaluate how things are working, and if I need to look further into more major surgery as Mark E suggests to switch to a single pump, "pumping away" et al, I will still benefit from already having the Logamatic.

    So here I sit with the Logamatic 2107, planning the installation on my G124X and I have two questions. 

    First question: currently the G142x's 120V power supply is wired through a switchbox, which the previous homeowner (and now I) used to turn the system on & off at the start and end of the heating season respectively.  I am thinking I want to keep the wiring to turn the Logamatic on and off by that same switch?  Or is there reason I'd want  to keep it powered even after the heating season has ended and I've shut off the boiler, in order to not have to re-input the settings each year? (I'm not sure what kind of settings memory the Logamatic has, volatile or non-volatile)  Reminder: I don't have DWH provided by the boiler, I have a separate direct water heater, so nothing for the Logamatic to manage 6 months of the year.

    Second question: Currently the pumps for each of my three zones has its own power switch, creating the ability to turn the circulation pump etc for each zone on independently of each other, and more to the point, independently of the boiler itself. In other words I have four switches in the furnace area, one controlling the boiler and the other three each controlling one zone pump & valve.   Each zone is also controlled by a wall thermostat, and each thermostat appears to be running into the wiring boxes for each of the three zones.  There is nothing connected to the Circulator C1 and C2 terminals on the L8148E aquastat.  I don't know if this is typical or not.

    First, a query I may not really NEED the answer to, except that it might help me understand the answer to my real question: What is the point of not running this through the same switch as the boiler?  To have a second way of turning individual zones off in addition to using the thermostat?  And, am I correct that there is no reason I would ever want any of those three switches to be left on when the boiler switch is off, and in fact it may be a bad thing if they are left on & somehow the thermostat makes a call for heat when the boiler is off?

    Now back to my actual question:, now that I am going to add the Logamatic into the mix, do I have an issue here with how the pumps/aquastat are currently wired, can I leave it set up this way after installing the Logamatic?.  It seems like I shoudl be able to, even if ti is not optimal (?), because all the Logamatic is altering from my current setup is more efficiently managing the temperature control, and altering nothing at all about when & how the pump is started, no?  It already works, so it will keep working?
This discussion has been closed.