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  1. #1
    Join Date
    Aug 2012
    Posts
    43

    Buderus - constant circulation?

    Just got my new Buderus G115 installed last week, with logamaitc, outdoor reset, and room sensor. We have a single zone and DHW.

    I am curious whether the single zone circulator pump is supposed to be running constantly, even when there is no call for heat. Yesterday it was about 65-70 outside, room sensor was set to about 68, actual room temp was about 72, and the water seemed to be circulating constantly even though there was no call for heat in the house. I eventually figured out to drop the outdoor temp cutoff to 62, so summer mode kicked in, but it seemed odd that the ciruclator would be constantly running when the room temp was higher than the set temp. When the DHW production kicks on and the single zone circulator is going, doesn't that circulate hot water around my house?

    Also, on the logamtic the room temp was showing 79, even though it was actually about 72 in the room accoridng to a regular thermometer. Any idea why it would have such a high difference?

  2. #2
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    I thin we'd have to see the piping diagram. But I don't see why the circulator pump would run, unless the Indirect tank is on the same circulation loop as well and thre are simple solinoids for the radiant loops.

  3. #3
    Join Date
    Aug 2012
    Posts
    43
    Don't have a diagram but basically there is a single pipe from the boiler that splits in two, one for the heat and one for DHW, and each has its own Taco circulator. (obviously there are more pipes, but that is the gist of it).

  4. #4
    Join Date
    Aug 2001
    Location
    Pavilion, NY
    Posts
    2,139
    If your dhw circulator is running , your loop circ should not. There are several ways this can be piped but if done correctly you should have (3) pumps. 1 for dhw,,,,1 for primary loop,,,,,1 for secondary loop. If wired correctly the boiler will turn off the primary loop circulator and turn on the dhw circulator. There are several other possibilities of piping but this is typically how it is done. I would call back the installing contractor.
    ...

  5. #5
    Join Date
    Aug 2012
    Posts
    43
    kangaroogod,

    I only have one heating zone. So, wouldn't I just have DHW and a primary loop? what would the secondary loop be for?

    It does appear that the primary pump shuts down when the DHW kicks on, but then the primary pump kicks back on when the DHW is finished. Is that just how this system is designed? In other words, other than for DHW priority, is it designed to circulate water 24/7 so long as summer mode doesn't kick in? The room sensor temperature does not appear to impact whether the ciruclator is running?

    If that is the case, I am starting to think that the solution is just to set my summer mode to 60 or 62. That way, nothing circulates unless I really need some heat. When I do need heat, the constant circulation does seem to keep things a nice even temperature. It is only when it is 65-70 out, and it is still criculating 80 degree water that I have felt there was an issue.

    BTW, is my electric bill going to jump because the Taco criculator is constantly running?

  6. #6
    Join Date
    Nov 2011
    Location
    Long Island, NY
    Posts
    280
    If your WWSD "summer mode" is set correctly the heat only circulator should not run. When the outdoor temperature is above the warm weather shut down it should disable the heat only circulator. If that's not the case it is either not wired correctly or your missing a flow check. How about some photo's?

    The room sensor will tell you when your in WWSD. By the way constant circulation for heat is "the bomb" it doesn't get any more comfortable unless it's radiant.

  7. #7
    Join Date
    Aug 2012
    Posts
    43
    The WWSD is set correctly but the outside temp was below the WWSD temp so it kept going, even though the room temp was way above where the room temp was set.

    If I read the manual correctly, however, it looks I may need to check to make sure it is in "RMSETBACK" mode. The manual says in that mode the circulators shut down when actual room temp exceed the "nighttime" setting, which mine doesn't seem to be doing. (For mine, the "nighttime" setting applies to most of the day).

    I wil post a pic when I get a chance tonight so you guys can critique the job. So far I am happy with it. I definitely like the constant ciruclation when it is colder out. Keeps the house much more even.

  8. #8
    Join Date
    Nov 2011
    Location
    Long Island, NY
    Posts
    280
    The circulator will not shut off unless above WWSD. What it will do is draw the boiler down to room temperature. The room sensor should be able to adjust the ODR curve to make that happen.

    I think your on the right track, I think it may be a programming issue. The Logamatic has DHW priority built in and will stop the heat only circulator on a call for domestic hot water.

    What happens after a call for DHW is it sort of purges the boiler heat into the heating zone.

  9. #9
    Join Date
    Aug 2012
    Posts
    43
    Yeah, I think that is exactly what happens -- it is getting rid of excess heat into the house, which is fine when it is cold out, but not so great when warmer. It may be mostly a matter of getting the WWSD set just so.

    But I will try to check that RMSETBACK setting too.

  10. #10
    Join Date
    Aug 2001
    Location
    Pavilion, NY
    Posts
    2,139
    Primary/secondary piping is used for several reasons but in your situation the main objective it to guarantee an adequate flow rate through the boiler. A properly sized primary loop will ensure you get enough gpm through. If you simply tie a loop into the supply and return then the flow rate may adequate enough and the boiler will not modulate properly and my times will go off on over temp. I believe that when in wwsd the boiler will disregard a call for space heat and only allow a call for domestic water. It does not seem correct that the space heating loop is running without a call for heat period. I think the pump in not wired correctly.
    ...

  11. #11
    Join Date
    Nov 2011
    Location
    Long Island, NY
    Posts
    280
    RMSETBACK just enables the room sensor, this could explain overheating issues with a room sensor if it is programmed to SETBACK.

  12. #12
    Join Date
    Aug 2012
    Posts
    43
    if i did this right, these should be pics of my new installation.

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  13. #13
    Join Date
    Aug 2001
    Location
    Pavilion, NY
    Posts
    2,139
    Well,, my thoughts are that the install looks good. Propress fittings look nice. The tiger loop ultra for your oil line is a great bonus. The issues I see is that it appears as though you have radiators in the home thus you have a very high mass volume of water. When the water heater calls the boiler races to limit ( typically 180 degrees ) and then shuts off. If the space heating has been off for quite some time, the cold water will rush to the hot boiler and could cause thermal shock to the casting. The plus is that the buderus is a very very forgiving casting. The second concern is that the high mass of water will keep the return temp to the boiler very cold for quite some time and the boiler can become too efficient and condense. Both of these situations can be resolved with primary secondary piping. Wwsd is a feature that can lower your utility bills for 1 reason only. If for example it is set to 68 degrees it will not allow anyone to turn the boiler on if above that temp thus saving money but in almost every situation people find this to be a nuisance. Let's say you go on vacation for a few days during fairly mild weather and you turn the heat off. When you return home on that 68 degree day and the house is 60 degrees and you turn the heat up to take the chill out of the house you are out of luck. In all honesty I usually set them to max or disable for this reason. Iam not sure what is going on with your setup but I still don't think your system pump should be running unless you have a call for heat.
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