1. Welcome Hearth.com Guests and Visitors - Please enjoy our forums!
    Hearth.com GOLD Sponsors who help bring the site content to you:
    Hearthstone Soapstone and Cast-Iron stoves( Wood, Gas or Pellet Stoves and Inserts)

Add storage tank to boiler loop?

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by feet1st, Dec 2, 2007.

Thread Status:
Not open for further replies.
  1. feet1st

    feet1st New Member

    Joined:
    Dec 2, 2007
    Messages:
    2
    Loc:
    Minnesota
    I've seen some similar threads, but they all are rather different situations. Or, perhaps you are all so accustomed to the terms and acronyms that I didn't recognize a similar situation.

    I really have some very basic questions about my radiator heat system. I have an LP boiler and 2 heat zones with continuous loops (i.e. no bypass or valving and thermostat in each room). My home is poorly insulated, and about 3700 sq ft with lots of windows. I live in Minnesota, so -40 is something you can count on at some point each year. My house was built in 1971 and just has insulation in the 2x4 rafters. I'll work on that. But that's not my question.

    I notice that the boiler seems to run in very short cycles. Generally less then 5 min., sometimes less then 1 min. It seems to me that this is probably due to the water temp returning to the boiler hot enough that it would boil, so the flame is cut. It also seems to me that this is probably inefficient and placing needless wear on components.

    I am considering two things:
    1) adding a heat storage tank to the loop.
    2) adding an off-peak electric water heater to the loop.
    ...perhaps both.

    I understand I must keep domestic hot water seperate from my boiler. I just intend to use the water heater as a readily available way to use electric. During off-peak, I can use electric for half price (about 4 cents per kWh). By my estimates, that is significantly less then the cost of LP... but only for 10 hours a day.

    First off... am I correct that running the furnace for longer cycles would generally be a good idea for efficiency and wear? ...and that adding a heat storage tank to the loop would be a simple way to do that?

    My main objectives are:
    to reduce the banging and clunking noises as the boiler starts up.
    to reduce the expansion and contraction sounds in the radiators.
    to keep a nice even cozy temperature
    to be more efficiently using the heat in the boiler

    I want to keep the system simple. While computer controls and lots of new plumbing and circulating pumps and etc. would be nice... the system is working, and I think all of that is overkill.

    I'm concerned about the operating temps. I've read on these boards that my radiators probably need 180 degree water to operate efficiently. And I certainly will need all the heat output I can get, at least for that coldest 2 weeks of the year. That doesn't leave me much room to draw down the temp in the storage tank.

    I'm thinking that I'd be better off basically trying to keep the water in the radiators at the temp needed to replace the heatloss and keep a more consistent temp throughout the system. And the storage tank would certainly make a more consistent temp. It is just a question of whether it might take too long to warm up the house, and thus lose that "even cozy temp.". If that's not feasible, then I'd be content to just have the furnace run for longer cycles.

    My best guess is that I've only got about 10 gallons of water in my radiator pipes, and so it would seem a 100gl storage tank would really increase the mass in the system. And then adding an electric water heater to the loop would add further mass. Would a 2 stage thermostat be the way to keep it simple and yet allow dual fuels? First trip going to the electric heater (may or not be allowed to run at the time) and the circulating pump. The second goes to the LP boiler. Basically assuming that while the electric is active, the thermostat will demand heat and basically charge the system (by tripping the circulating pump).

    I was originally thinking it would be great to allow the house to get 1 or 2 degrees cooler then normal just before the off-peak electric is about to kick in... but it sounds like you don't really have a good way to determine when that will be in advance. And then to super heat the water with the cheaper electric and circulate that after the electric is cycled off again. ...but then I was also hoping 100gl might heat the house for more then an hour, and reading other posts, that sounds unlikely.

    I'm picturing placing the storge tank before the boiler. And if I add an electric water heater, I would add it before the storage tank. Seems like that way if the house continued to get colder and the second temp kicks in, then the LP COULD fire, even when the electric is active. That would keep the house warm. But such an event should be pretty rare... right?

    nofossil has posted about scaveging all the heat out of the boiler when it kicks off. It seems to me as though most of that heat remains in my house though, at least when the furnace kicks off due to high temp, because the circulating pump is still active until the desired room temp is reached. Am I right there? Or is it going up the chimney? And perhaps cooling the circulating water as it does so? To me knowledge, my chimney does not have any damper in it. Would that be another good investment?

    Any advice, experience, tips, appreciated.

    Helpful Sponsor Ads!





  2. feet1st

    feet1st New Member

    Joined:
    Dec 2, 2007
    Messages:
    2
    Loc:
    Minnesota
    Oh, and was also wondering if anyone has an idea how many degrees warmer the water gets as it passes through the boiler. Obviously it depends on flow rate, and BTU of boiler, but I'm just wanting to get a very rough idea. Does the water flow through the loop 3 times before it reaches max temp? Or I guess another way to put it is, what would the max allowed temp of water flowing back to the boiler be for the burner to keep running? 180?
Thread Status:
Not open for further replies.

Share This Page