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Oil Boiler and Inconsistent Domestic Water Temperature

Slick0001 Member Posts: 3
I'm hoping someone can offer my some advice. A few years ago I bought a home in the Washington DC area with an oil boiler (V8 Burnham) with 4 zones for baseboard heaters, as well as the domestic water. I'm having a problem with consistent hot water in two bathrooms by the bedrooms that are on the other side of the house from the boiler. For example when I take a shower in the morning, I have to keep adjusting the water from hot to cold to keep it from being scalding or too cold. Also, it takes forever to heat sometimes, especially if I'm running the washing machine or dishwasher. The bathroom nearer to the boiler's not an issue, neither is the sink in the kitchen. Also, this really is only an issue in winter - summer time is fine. I was thinking about adding a mixing valve to prevent scalding, but I think that may make the time lag and consistency issue worse.

Any advice for what I should do for to fix this? I was thinking about installing an electric tankless water heater near the problem bedrooms, but the size I would need (5 GPM) would require 150 amps by itself - seems like overkill. I don't have natural gas, only oil and a 100 gal propane tank, and with the installation and venting costs, I don't think gas tankless is a smart option.

Another option is to install a regular 80 gallon electric tank for the domestic water. I live in a rambler with no basement, so it would have to go next to the boiler, or if I could find a small enough heater to fit in the crawlspace, that may work too.

Another option I was looking at is to have an indirect water heater or hot water tank installed on the boiler. But after looking at the cost of it, and low efficiency in the summer, it may not be the best option.

Does anyone have experience with this and could provide some advice, or let me know if you have another option I'm not thinking about?


  • newagedawn
    newagedawn Member Posts: 586
    try turning your heat loops off when using the hot water, in winter the heat loops will take over the domestic demand, an indirect or other option will help this
    "The bitter taste of a poor install lasts far longer than the JOY of the lowest price"
  • bob eck
    bob eck Member Posts: 930
    Any oil boiler with a domestic coil has limited domestic hot water output.
    Do you have hard water? Get you water tested. If you have hard water the coil will build up with lime limiting heat transfer and not good GPM production of hot water. If you have hard water install a water softener.
    When you need hot water for showering and the boiler is running it’s heating zones the hot water in the boiler is going to your baseboard thus reducing you domestic hot water GPM.
    I would look at installing a Burnham Alliance 35 or 50 gallon indirect water heater. The contractor and use controls to give the indirect water heater priority so if the baseboard zones are calling for heat and you jump into the shower the baseboard zones will shut off giving all BTU in the boiler to producing domestic hot water. Install a Burnham Alliance 35 or 50 gallon size. I would store the water in tank 140-160 degrees and use a mixing valve to send 120 degree water to the showers. If it takes a long time for hot water to get to the bathrooms look at installing a Taco or Grundfos domestic hot water recirculation system so you have hot water at your faucets as soon as you turn the faucet on. There are systems where you do not need a return line run back to the indirect water heater.
    I was told when using a oil boiler and an indirect water heater you can lower your yearly oil gallons used by 100-200 gallons. Over the upcoming years the savings of oil will help pay for the indirect water heater plus you will not run out of hot water.
    I would also look at replacing you shower valves to anti scald faucets this way you protect yourself and other family members from getting scalded and burned with excessive hot water.
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,127
    I second the indirect. I have one in my home (60gallon). When the boiler isn't needed for heating, it only runs maybe 3 times a day for about 10 minutes. That's less than a 1/2 gallon a day-15 gallons a month, even at $3/gal, that's like $45. You'll spend more than that with an electric water heater.
    The only time it runs more is filling up a ridiculously oversized tub (that my wife 'had to have' when we remodeled).
    I'd also consider pressure/temperature balancing at the shower fixture(s), and mixing valve for your domestic coming out of the boiler.
    Seems like you have cold water laying in the lines, then you get the blast of hot from the boiler (at least it's hot).
    Is the boiler keeping up after you adjust temperature?
    The hot water pipes running to the bathroom in question, long run? Un-insulated? Going through some cold space?
    Insulation would help, and maybe some re-circulation.
    EBEBRATT-Ed Member Posts: 13,424
    I would look into installing an indirect as well. You will be much happier.

    You should have your service technician check what you have first. Tankless heaters are somewhat problematic, but it could be as simple as replacing the mixing valve on the tankless.....which I assume you have one....pictures??
  • Slick0001
    Slick0001 Member Posts: 3
    Looks like a lot of votes for the indirect. I talked to a technician today and he actually suggested that I get an electric instead. He said I could pipe the hot water from the boiler into the electric to help with some efficiency, but given the price of oil, he said electric would be more efficient/cheaper. He also said that my boiler was designed for a house of 2, with only 3 coils (I think, or maybe he said 3 gals?), which is another reason why he suggested electric instead.

    The pipes all run in the crawlspace, which is very well insulated with about 2" of insulation all around. I will check if the long runs to the other side of the house are insulated though - I assumed they were, but maybe not.

    And you're right, once I get the water somewhat stabilized, it's fine, unless my wife turns on the washing machine or something, then it gets cold and can take some time to heat back up (I usually turn off for a few seconds and it's good). I do not have a mixing valve, which I agree I need to install if I stay with the boiler domestic water. I'm a little confused with the indirect though - why would I need a mixing valve for it if I can sent the temp to what I want?

    See pics below

  • Grallert
    Grallert Member Posts: 563
    Abandon that tankless coil and install an indirect. It will drop your fuel bill a lot I see averages of 30% and some folks have said near 50%. Doesn't take long to recover the cost of adding that forth zone. you can then lower the low limit all the way. Aside for making lousy hot water that coil is always asking your boiler to come on to the standby loss of the boiler. That's why you hear it coming on often all summer even when no hot water is being used. an indirect will nearly eliminate that, an electric wont change a thing. Yes you'll have hot water but at an even greater cost in utilities.
    bob eck
  • Dave H_2
    Dave H_2 Member Posts: 526
    Go with an indirect and add a mixing valve. The mixing valve will not only add capacity to the tank (store in the tank 145, mix down to 120) it wont have a full draw off the tank and therefor extend the capacity when multiple fixtures are used. It will also add consistency to the temperature output.

    Also put it on priority which means when the indirect tank needs heat from the boiler, it temporarily turns off the heating zones so that the tank takes everything the boiler can do. You won't notice the heat being off for a few minutes anyway.

    As for waiting for hot water at those far away fixtures, look to install a recirculation system, it is easy to retrofit and automatically schedules itself to run when you use hot water.

    Dave H.
    Dave H
  • Jamie Hall
    Jamie Hall Member Posts: 21,093
    Indirect. And I find it very hard indeed to believe that your electricity in the DC area is cheap enough to be comparable to oil and the indirect.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    EBEBRATT-Ed Member Posts: 13,424
    A mixing valve and a flow restrictor would make the tankless heater work better.

    The electric water heater is a good choice. You can use the tankless heater to preheat the electric tank and the electric will only come on during high demand. Once the tankless heats the electric storage tank you will probably find the electric heater is hardly ever used due to the increased hot water storage capacity that you now have. An electric tank is probably cheaper than an indirect
  • Slick0001
    Slick0001 Member Posts: 3
    You all are giving me a lot to think about. I will need to talk to an installer in the area who works on these boilers. I'm liking the sound of the recirculation system, indirect, and mixing valve, but the up front costs looks like quite an investment. The challenge will be to find someone in the area who is both trustworthy and knows boilers - I generally know one or the other, but not both.
  • bob eck
    bob eck Member Posts: 930
    Check this site for professional contractors in your area. You can also call some plumbing and heating wholesalers in your area and ask for a list of contractors that install boilers and indirect water heaters.
    Sure installing an electric water heater is the lower cost but like many on here said and so did I installing an indirect water heater can lower your oil used by 100 to 200 gallons year after year. If oil is $3 per gallon you can save anywhere from $300 to $600 per year. Let’s spilt this and say you are saving $450 per year. You will save year after year. If the cost of oil goes up your payback will be faster.
    Installing an electric water heater and still running through your domestic coil first and then into the electric water heater you will not lower your gallons used per year. Plus your electric will go up.
    Did you have your water tested? If you have hard water there will be lime hardness on the inside of your domestic coil in the boiler and that lime acts as an insulator and it takes more BTU (heat) to produce your domestic hot water causing you to use more oil than you should. Installing an indirect water heater your oil gallon savings could be even higher.
    Many indirect water heaters come with or you can purchase as an extra a life time warranty.
    Water heater will have an 6 year or 10 year warranty.
    Some times doing the right thing and spending more than what you thought is the way to go.
    If the indirect water heater is installed, piped in the correct way and if the contractor gives the indirect priority over the heating zones stores the water at 140-160 degrees and uses an mixing valve you should never run out of hot water.