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Steam Boiler with DHW - How can I improve this system?

We have a steam boiler that also provides our DHW.

I'm looking for ways to save energy and thus money. It has been suggested that we add a water heater, electrical or hybrid depend on how much we want to invest. (They also talked about a wall mounted propane unit, but we currently don' t have propane, but we could get it.) They said it could be setup so the boiler would preheat the water in the winter when its running, before going to the water heater (basically free heat, they said).

What do you guys think, is this the way to go?

The issues that brought this up:
Sometimes, not always, but sometimes we don't have any hot water for about 10-15 mins. I have figured out that if I raise the thermostat to force it to call for heat before i fill the tub for example, then we don't have an issue. The boiler is located on the other side of the house from the fixtures, but the response time is typically good and is nothing to complain about. It's just every now and then we don't have hot water for a long period of time. I have also maybe 5 times in a year run out of hot water in the middle of a shower.
The other thing is, the cost, during the summer months, (little less than 4 months) our oil bill was over $450 dollars to just heat the hot water. That's about what the electrical water heater advertises the cost to be for the whole year. Hybrid even less.

If I have a stand alone water heater, I could turn the boiler completely off during the summer months, correct? or is this bad for the boiler?? I should also mention that we have a 2nd source of heat with a wood boiler, so we generally don't turn the steam boiler up until the colder winter months. A lot of times I will just run the steam once a day first thing in the morning, to get us back up to 70, the wood then maintains that temp all day, dies out sometime when we are sleeping, temp in the house drops to 60 and we start the process over again. I work from home so I'm able to feed the fire all day. Days that I'm feeling lazy I will use the steam all day.

Any better suggestions?


  • Jamie Hall
    Jamie Hall Member Posts: 22,100
    Hard to make a specific recommendation, as it really comes down to dollars and cents and convenience and comfort, and that's a balancing act you are going to have to make.

    Hybrid water heaters aren't cheap to buy. They do work well, however. Hybrids, however, are less expensive to run than straight electrics. Both hybrids and electrics have the disadvantage that their recovery is somewhat slow, so one has to figure in that recovery time in relation to how you use water, and select a size (often a bigger tank than one might think) which will give you the hot water you want when you want it.

    From the standpoint of overall energy use and efficiency, hybrids are at least in the same ballpark as stand alone oil or propane fired heaters. They are somewhat better than your current tankless coil setup, since one doesn't have to run the boiler in the summer (as you noted). Straight electric heaters are much less efficient, from the standpoint of energy use.

    Wall mounted on demand heaters, such as the propane unit you mention, do work well, provided they are really sized properly for the water temperature you want at the demand rates you have. In my humble opinion they have no real advantage over either a stand alone oil or gas tank type heater, or a hybrid, but that's my opinion and others, quite legitimately, differ.

    Not running the boiler in the summertime won't hurt it, but I can't recommend draining it. Just let it be, and be sure to have it cleaned and adjusted in the fall -- but you should be doing that anyway. That will save some oil, but remember that it will still take energy to heat your water anyway!

    I have to admit that I seriously question whether you are saving much, if anything, by letting the house drop at night so much, and then running the steam pretty hard to bring it back up in the morning. There is something of a consensus that very large setbacks actually use more energy than they save, but the debate is quite inconclusive.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Eric_32
    Eric_32 Member Posts: 267
    edited January 2016
    It sounds like you may have a tankless coil in your oil fired boiler. If so you could also switch to an indirect fired water heater as an option.

    Basically a storage tank for potable water that uses the boiler water to heat it. They are super efficient, most made of stainless steel and have a limited lifetime warranty against leaks (limited to the original owner) Then you could disable the low limit control that keeps the boiler hot 24-7 to maintain temp for HW. In the summer time, and when your burning wood in the winter, the boiler many times will reach room temp before firing for either HW or heat. Doing this, you will save on oil and have more hot water than you are able to get now thru the tankless coil in the boiler. That would still be there but disabled and no longer used.
  • Steve_in_NH
    Steve_in_NH Member Posts: 70
    I just looked up nhsaves and they have a $500 rebate for 50 gal heat pump water heater and $600 for a 80 gal.

    Does this change your opinion of which would be better? or is indirect still likely better??

    To throw in another wrinkle the wood furnace that I have has the add on option to add a hot water preheat coil. It cost over $200 for the part though. It's a Daka wood furnace. It's located right under the kitchen and I could install the water heater right next to it.
  • Eric_32
    Eric_32 Member Posts: 267
    I like the heat pump water heaters. There's definitely a place for them.. your situation is one possibility.
    There's a minimum size room they have to be in to pull enough heat out of.. you'd have to check make sure yours is enough.. they do have a shorter life span than the indirect.

    I like the idea of wood coil also ;) but I can honestly say I am not a fan of the existing tankless coil your using now for HW. lol

  • SteamingPile
    SteamingPile Member Posts: 14
    i'm in Mass.. and I've got the same dilemma.... an old AS boiler that's way oversized (not that that necessarily impacts the HW) and the boiler currently provides 100% of our hot water. Wife takes 15 minute shower... I hop in and get 30 seconds of hot water. It doesn't seem to be able to keep up.

    I'm probably going to go the hybrid electric route.
  • Steve_in_NH
    Steve_in_NH Member Posts: 70

    Can't believe they charge $300 for a piece of pipe and some fittings! I have found it other places cheaper but not by much.
  • JeffM
    JeffM Member Posts: 181
    I have a similar system to yours (also in NH) - a Weil Mclain steam boiler with internal coil providing domestic hot water. I have never had the hot water run out on me or be unavailable, so I wonder if you have an aquastat which perhaps is "sticky" and doesn't always keep the boiler at the proper temp to provide your hot water. Just changing that is fairly simple and could solve your intermittent issues.
    Long term to save energy (and $) I'd go with an indirect tank. Personally, I have looked at all of these options and done nothing, as the payback on adding a tank is too far out (I don't plan to be in my current home beyond 10 yrs). I'm in Manchester and we have natural gas, so I did switch the boiler from oil to gas a couple of years ago which cut my running costs in half so your payback using oil would be much sooner.
  • Steve_in_NH
    Steve_in_NH Member Posts: 70
    UPDATE: I had a plumber come over and look at the system to get recommendation / cost to add water heater.

    He is recommended that I go with an Electrical Hybrid unit.

    The reason against indirect was that he would have to tap into the wet return piping and it would be more labor involved and he was leaning towards the electrical option anyway.

    So the question I have for the experts on here is about how he proposes to the plum up the electrical/hybird heater.

    He first was talking about putting it next to the boiler and installing a circulating pump between the boiler and water heater.

    After some discussion, we talked about that it would be best to install the water heater closer to the kitchen/bathroom which are on the other side of the house from the boiler. Basically abandoning the boiler hot water system.

    But then he had the idea that we could just leave the existing system alone, install the water heater on the other side of the house, tap into hot water line that was coming from the boiler (before it branches off to the kitchen), have that hot water line enter the new water heater on the cold side. Which would then exit the water heater, reconnect to the hot water line going to the kitchen/bathrooms.
    So in the winter the boiler would preheat the water to the water heater and the summer it would just bypass through the boiler that we have manually turn off for the summer.

    This would be a really basic install (he said he could probably do it in a couple of hours), no pumps involved either.

    Does this make sense? Is this ok?

  • Steve_in_NH
    Steve_in_NH Member Posts: 70
    Basically I would like to know if it is ok to feed 120 degree water directly into a water heater.
  • kcopp
    kcopp Member Posts: 4,303
    edited January 2016
    Save your money and just install a regular electric water heater.
    Hybrid heat pump WH are fairly loud and will make your basement cold.
    The newer water heaters have 2+" of foam around them and hold the heat in better.
    If you lived down south then a hybrid makes sence....here in NH not a great option.