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A boiler too large

Matto
Matto Member Posts: 3
Hello,



I have a 2400 sqft insulated slab on grade, single zone (rehau 8 loop manifold w/ flow control 1" in out 1/2" pex loop) Averaging the heat loss calcs. I get about 75k btu max load. And, because I'm an idiot... An OMNI 250k btu waste oil boiler (I believe it is a Crown triple pass boiler with omni's gun). In my defense there is also a 3600 sqft garage and a 1500 sqft lofted space the will also (eventually) be plumbed for radiant. Regardless 250k input 84.3% eff 7% derate for altitude (1800ft) = 196,000 btu.



So this is what I was thinking: I got a screaming deal on a 220 gallon vertical tank that I would insulate and use as the storage tank. Yes, it is for pressure vessel use, 125psi rating with the cloverleaf (ASME U). Dead simple plumbing 11/2" straight from boiler to tank and back (I have an ESBE valve to protect the boiler) Hot in the top, return from bottom. Another top and bottom leg to feed the zone, Which will eventually become zones as time and money allows. Set the boiler temp on at 85 off at 200 = 253k btu storage.



So I guess my question(s) is/are.

1) Am I hunting ducks with a rake? Does this seem like it would work all right?

2) I was hoping to use a single type of pump for the primary and the zone. Maybe Grudfos 26/99? Just so I could keep a spare on hand and cover my bases.

3) Amtrol SX-60v x-tank for now and add another when I add on in the future?



I am by no means a pro. But I have read Mr Holohans books. The boiler has never been fired, and all of this stuff is too expensive and potentially dangerous to commit to without advice.

Thanx guys! I hope I gave enough info to make this easy to answer!

Matto

Comments

  • hot_rod
    hot_rod Member Posts: 15,028
    waste oil

    can be a very messy fuel to deal with. The boiler will need frequent cleaning, the ash byproducts contain cadmium and other potentially hazardous materials. Glycol, paint, all kinds of fluids get thrown into waste oil tanks.



    Double walled tanks for the oil storage are often required better check with your local codes to see if it is even "permit-able" in your area.



    Here is some info on installations in MA,

    www.mass.gov/dep/recycle/laws/spacehtr.pdf



    And Ohio www.epa.ohio.gov/portals/32/pdf/Used_Oil_Burner_Guidance.pdf





    The EPA has been watching them carefully, along with wood burning equipment. Add that to the grossly overside issues you face...



    Is the juice really worth the squeeze??



    hr
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Matto
    Matto Member Posts: 3
    Technically it's a multifuel boiler

    For me, its worth the effort, I have a centrifuge to deal with the moisture and other issues, and I can still burn #1 #2 kero, bio, fill in the blank. So at worst I am no worse off than everyone else who has to buy fuel, and at best I'll be toasty warm for free! Options.



    But this is off topic from the questions I asked. Not what is the thing producing too much heat, but how can that too much heat be dealt with. I was actually hoping at some point to maybe utilize some evacuated tube solar into the aforementioned storage tank (hoping to garner some green street cred LOL) but first things first. Any insights?
  • hot_rod
    hot_rod Member Posts: 15,028
    edited June 2010
    use it or lose it

    is the short answer.



    Either use the energy at the rate the boiler produces it, or store it until it is needed.



    With storage you will lose energy related to the insulation on the tank, piping, boiler.



    Loss back through the boiler and up the flue pipe if proper piping and check valve location is not used.



    The ambient air temperature around the tank is a factor in the amount of loss.



    The biggest factor may be the amount of $$ you want to spend to limit the loss.



    No amount of insulation will stop the transfer 100%. The recent large solar tanks I was involved in , 1500 gallon tanks, had 3" of spray insulation, with a hard coating applied. Piping had 1"



    The pump and expansion tanks need to be sized with the job in mind. The pump curves supplied by the manufacturers are used to select a pump based on the GPM you need to move and the head loss through your boiler, pipes, fittings, everything in the piping path.



    The expansion tank is sized based on total volume, temperature difference and pressure relief valve settings. Again manufacturers can help you size once you have all the system data. Or use sizing charts available online.



    hr
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Matto
    Matto Member Posts: 3
    Thanks!

    Well it seems like a lot of people have looked at my post, and no one gave me a Hindenburgesque warning of doom, so I will proceed. My thanks to Hot Rod for chiming in a couple of times. Hopefully I won't have to be posting on the heater from hell threads!

    Great resource!

    Matto
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