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Secondary Boiler Temp

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Doug613
Doug613 Member Posts: 9
in THE MAIN WALL
Hey Guys,
Been awhile, So I have this primary/secondary mod/con boiler setup. The system has run great for ten years with periodic cleaning and maintenance. The secondary loop use to have temps corresponding with the boiler temp but I have noticed the temps are really low now compared to the boiler. I am thinking that the secondary circulator is not working and the primary is doing the whole job. The secondary is running but I got a feeling that the impeller is shot. I don't want to bleed down system if I don't have to but have not ran into this particular problem before so thought I would see if you guys had any ideas. The boiler itself seems not to be modulating, it just runs up 130 - 140 on out door reset and then goes down again, but the temps on the secondary are maybe a hundred degrees or so

Any help would be great

Doug C.

Comments

  • delta T
    delta T Member Posts: 884
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    What kind of heat emitters? Can you post a picture of the primary/secondary piping? If the secondary loop was not circulating the boiler would be cycling very quickly as it is only heating up the water in the boiler and primary loop, also, you would not have any heat in the house. We need some more info to help you, pictures are a great start.
  • hot_rod
    hot_rod Member Posts: 22,161
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    Pictures or a good drawing would be the best info you could provide
    Primary secondary has been used to describe all sorts of piping arrangements
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Doug613
    Doug613 Member Posts: 9
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    The setup is a radiant system. Been in about 10 years with relatively no problems except for a circulator and couple of zone valves. The boiler itself is a NTI Ti-150 combi, I am not using the DHW at present. The first thing I would like to point out on both the digital and combi temp pressure are about the same. But when the boiler cycles it runs right up to 155 degrees and then down to about 120 and rinse and repeat, this all takes about am 1.5 min. so is definitely not modulating. Sometimes when it is cycling the I get an error code ASO but it doesn't stop the burner blower and is only on for about 2 sec. This ASO I think indicates the air flow switch or the blower is faulty. The outdoor sensor is working. I hope I have give you what you need here in the pics

    Thanks again Doug C.
  • hot_rod
    hot_rod Member Posts: 22,161
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    Looks like the flow is, supply out of the boiler, through the Spriovent?
    Is the Grundfos secondary pump pumping away from the primary loop?

    Should be that pump pumps away from the first secondary tee, through the zones and returns into the upper secondary tee.

    Hard to decipher the actual flow direction in pictures sometimes
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Doug613
    Doug613 Member Posts: 9
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    Yes Hot Rod,
    Flow is out of the boiler and then carries on through the 2 1inch tees and then around the primary to the taco pump and in the boiler again. The Grundfos (UP26-64F) is pumping away from the tee on the primary and on to the zones and back again. The house its in is an old 2 story Victorian, about 22 hundred square feet. I built that system and over the years have added to it but always on the secondary side. I have got to know the little idiosyncrasies it has. I am a retired plumber out in the Canadian north and access to parts is a real pain but doable! lol

    Thanks for your interest
  • hot_rod
    hot_rod Member Posts: 22,161
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    Is the green Taco pump pushing into the boiler? If so then it seems the Grundfos should be pumping away from the lower tee?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Doug613
    Doug613 Member Posts: 9
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    Taco is pushing into the boiler and the Grundfos is pushing toward the zone valve feeds.
  • hot_rod
    hot_rod Member Posts: 22,161
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    From the picture it looks like this is the flow path? If so the Grundfos pump appears to be in the wrong location
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Doug613
    Doug613 Member Posts: 9
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    I can't see all of your top diagram but that looks to be it. The second circ is pulling from the primary loop towards the zone valve feeds and the second tee is the return.
  • hot_rod
    hot_rod Member Posts: 22,161
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    Here is a better drawing. I think what you have is the upper drawing? Check flow directions by arrow on the pump bottoms to confirm.

    The correct piping for Primary Secondary is for the flow into the secondary to come off the primary (boiler) loop on the first tee, return into the second, downstream tee.

    It will work with those crossed, like I think you have it now, but you are mixing temperature between the tees and will not necessarily see the highest temperature to the distribution loop.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Doug613
    Doug613 Member Posts: 9
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    Hey Bob,
    thanks for catching that! I can't believe I didn't catch that after all these years.......I guess worked and didn't look further. I will disconnect the 1" return and connect it above the 1" feed tee to get the proper flow going. I have the room above so was thinking that would work. Comments?
    I have fixed the asc code Seems it was the air switch all along. Now I just get that tee in the right spot and should be half way there.

    Thanks Doug C

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