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Upgraded boiler.

Radman174
Radman174 Member Posts: 3
Hello everyone I've gotten an incredible amount of information and guidance from this page and need some advice. 

Me and my girlfriend own a boarding kennel in Western NY on Lake Ontario. We have radiant heating in the kennel area where the dogs are boarded and it isn't staying warm enough while running 24/7. I currently have a traditional cast iron hamburg boiler manufactured in 1999 and an output of 65k btu running on LP. Obviously this thing drinks propane like crazy.

The kennel room is 50' by 20' and has dog doors for each of the 20 kennels that open to an outdoor slab. The ceiling has uninsulated sky lights. We bought the place last year so I have no idea how deep, far apart the pex lines are as well as if any insulation was used. Currently the temp outside is 25° and the room won't get above 50°. The temp going out is around 130° but coming back is only around 60°  I understand the return temp is detrimental to the boilers operation and has likely ran like this from day 1.

It has one external circulator pump (007 taco) on the return to the boiler. And also the expansion tank is shot as its leaking water from the air fill side. 

I got a quote from an hvac guy for a new mod-con type boiler. He gave me two options between a Laars wallhung manifold T 200k btu. And a weil mclain evergreen 200k btu boiler. Is the weil mclain worth the extra cash? Also I don't know if he is oversizing here as the old one was only 65k btu.

Comments

  • Hot_water_fan
    Hot_water_fan Member Posts: 266
    edited January 13
    I don't think the boiler is the problem, so probably time to talk to someone else. Is there a manifold anywhere you can see?
    kcoppSuperTech
  • Paul Pollets
    Paul Pollets Member Posts: 3,451
    I have a feeling there should be a 4, 6 or 8 port radiant distribution manifold hidden somewhere. If there's not, it's likely there's not enough tubing in the slab to heat the space.
    kcoppSuperTech
  • Radman174
    Radman174 Member Posts: 3
    Sorry I forgot to add the picture of the manifold. Here it is!
  • Jamie Hall
    Jamie Hall Member Posts: 17,766
    That very large delta T (130 down to 60) tells me right away that you don't have enough circulation through the floor. Now... that may not be entirely too low a flow rate, which a bigger and more ambitious pump would correct. There is another, most important question: is the boiler big enough (clearly your two heating guys don't think so, and they may be right -- or they may not). To get at that aspect, you need to look at two things: first, what is the actual heat loss of the building? You need that information anyway, to size the boiler, and your consultants should be able to provide that. While the building is a bit out of the usual, a calculator such as this one: https://www.slantfin.com/slantfin-heat-loss-calculator/ with reasonable assumptions should be able to get you close. The other is can, in fact, that heat loss be provided through the radiant slab, or are you going to need additional heat to keep the pups comfortable? A radiant slab may be able to give you as much as 30 BTUh per square foot without being unduly toasty underfoot, which in your building would be only 30,000 BTUh. Does your existing boiler actually run continuously? A very rough back of the envelope calculation suggests that somewhere in the vicinity of 100,000 BTUh may be all you really do need.

    So... what would I do? First, I would increase the flow rate through the floor. I'd try to get it up to 7 to 8 gpm; You might try switching to a Taco 008 instead as a first try.

    Then I would get somebody -- it could be yourselves -- to run a heat loss calculation on something better than the napkin I just used to get a better idea of how much heat you really need -- and from that whether you can achieve that with just the floor, or whether you may need to add additional radiation.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • hot_rod
    hot_rod Member Posts: 15,392
    4 loops if what looks like 1/2 Pex will determine how much heat you can move into the slab

    A 1000 square foot space? With 4 loops of 300’ you would have 12” or a bit tighter spacing, an IR camera  would show them

    Ideally dog kennels have a small section on the room that does not have tube, so the dogs can get off the warm floor occasionally to regulate their body temperature. Or a platform for them to get up into.

    A unit heater may be a good supplement to circulate some air?

    What temperature are you trying to maintain?
    What is the floor surface temperature average?

    A building like that with high infiltration can be a sizable heating load 

    A larger circ is an easy try, Since you have a 3 Cv mix valve, getting higher flow rate will take a larger circulator


    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Tom_133
    Tom_133 Member Posts: 796
    The location of that circulator in the last pic isn't right. It appears to be on the return pumping from right to left? If thats the case its part of the problem. It should be after the mixing valve on the supply pumping toward the loops
    Tom
    Montpelier Vt
    kcopp
  • kcopp
    kcopp Member Posts: 3,890
    I agree with @Tom_133 Circulator need to be pulling out of the mix valve. Try that 1st...
  • Radman174
    Radman174 Member Posts: 3
    Okay so first I'm going to remove the taco 007 pump on the return line and install a taco 008 after the mixing valve going out to the floor. While I'm at it I'll replace the bad expansion tank as well.

    As for the heat loss using the slantfin calculator there's a few things I'm unsure about. I'm constantly coming in around 90k btuh. The calculator has a field for the amount of radiation tubing but how do I convert my pex tube run to baseboard so I can use in the calculation?

     Right now we only have a few dogs due to Covid cancelations so most of the runs are empty at the moment. I can insulate the dog doors that aren't being used and cover the ceiling sky lights as well that should help a bit. Only the first few kennels going out are warm, and the back of the kennel close to the dog door is much warmer then the front of the kennel. I can grab a temp gun later when I get home and get the average floor temp. We give almost all the dogs place cots for them to lay on unless they are shreaders. The goal is to get the room to maintain 60° which it can barely do now if it's 40° outside. At 0° the room is around 45°.

     To answer Jamie's question when I said the boiler runs 24/7. I meant it will runs for about 15 minutes until the coil hits 180° and stops. Then it will stay off for about 15 minutes until the temperature hits 140° and it will fire up again. Seems like alot of short cycling to me but I don't know. 

    I have a ~25k btu space heater from my old house that I can wire up to give the room a boost. I can ask my boss if I can borrow our flute thermal imaging gun to identify the pex runs but I doubt he'll let me take the thing over the weekend. 

    Another note, I've read that I should install boiler protection with a thermostatic valve to keep the boiler return over the dew point of the flute gas. Is this something that's critical right away or can I try to get this boiler to warm the room before I go spending money on the temp control valve.

    Thank you guys! And I hope I answered all your questions. Let me know if you want the room dimensions for the heat loss.
  • Hot_water_fan
    Hot_water_fan Member Posts: 266
    edited January 14
    To answer Jamie's question when I said the boiler runs 24/7. I meant it will runs for about 15 minutes until the coil hits 180° and stops. Then it will stay off for about 15 minutes until the temperature hits 140° and it will fire up again. Seems like alot of short cycling to me but I don't know.


    @Jamie Hall knows his stuff - right now, there's no indication that this is a boiler size problem. Do you know how much LP you've used?

    There's a high chance that space heater can handle the building with the boiler.
  • EternalNoob
    EternalNoob Member Posts: 23
    @Tom_133, @kcopp,

    I've heard that said before but i've never been clear on why. It seems to me to be completely symmetrical in terms of pressure and flow for the pump to pull downstream of the radiant rather than push upstream of it. Also, when pulling from the return you're using cooler water which is healthier for the pump, "pump the cold" philosophy. Not trying to sound argumentative, I'm just genuinely curious to understand why it's better. I also know that I've seen systems with pump pulls from return that work just fine. "works" not the same as "best", but...

    The only thing i can think of is if the MV's cold take-off downstream of the pump is at significantly higher pressure, this might cause a pressure imbalance between cold and hot inlets to the MV and not mix properly? If that were the case then testing the output temp of the mixing valve is a good idea, actually a good idea regardless, perhaps worth doing before re-plumbing to the "better" pump orientation.
  • kcopp
    kcopp Member Posts: 3,890

    @Tom_133, @kcopp,

    I've heard that said before but i've never been clear on why. It seems to me to be completely symmetrical in terms of pressure and flow for the pump to pull downstream of the radiant rather than push upstream of it. Also, when pulling from the return you're using cooler water which is healthier for the pump, "pump the cold" philosophy. Not trying to sound argumentative, I'm just genuinely curious to understand why it's better. I also know that I've seen systems with pump pulls from return that work just fine. "works" not the same as "best", but...

    The only thing i can think of is if the MV's cold take-off downstream of the pump is at significantly higher pressure, this might cause a pressure imbalance between cold and hot inlets to the MV and not mix properly? If that were the case then testing the output temp of the mixing valve is a good idea, actually a good idea regardless, perhaps worth doing before re-plumbing to the "better" pump orientation.

    .....

    Its just the way the mix valve works. Its Not a better/ worse thing. The Mix valve works on pressure. Its designed to have water pulled out of it. If it senses that water in being jammed back into it, by design it will throttle the flow down to nill.