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Heating Domestic Hot Water With A Steam Boiler

I live in a historic 1836 home that is heated by a steam system. I currently have my hot water heated by an Indirect hot water system heated by my furnace. I use my furnace as a back up for heat and use a wood stove. The problem is that I need hot water for showers, dishes, an so on. I feel like I am wasting a ton of money keeping my boiler ready 24/7 for heat in order to have hot water when needed. I am searching for a system that would allow me to have hot water, but basically shut my furnace down. I am looking into oil, gas, and electric models. I do worry about my furnace in my moist basement with no use. Maybe I need to turn my aquastat down? Maybe shut my emergency switch off until I need hot water? Any thoughts would be appreciated.

Re: Heating Domestic Hot Water With A Steam Boiler

Is this an oil-fired steam boiler, or a gas-fired one???---you have a boiler there, not a furnace.

Your first step should be to monitor how much gas or oil you're using and actually check past fuel bills for past years before you decide you're "wasting fuel".

Most indirects have their own thermostat range that you can manually set downwards to save fuel to say, 120 or 130 degrees rather than a higher number, which will burn slightly more fuel.

If you can post photos of your aquastat, or provide the model number, you can compare it to the photos in the article below to see if you can turn down the "low limit" knob when you remove the metal cover.

There are many different aquastats used in steam and hot water boilers---if you have an aquastat that looks like the ones at the site below, with a Hi limit and a Lo limit, the Lo limit ALWAYS HAS TO BE SET AT LEAST 20 DEGREES BELOW THE HI LIMIT.

But you will STILL be burning fuel in the warmer months to keep the indirect primed with hot water, which usually ranges from 120 degrees to 140 degrees---indirects, because they are so heavily insulated, are considered very efficient in their use of fuel---I would estimate that you would do considerably worse if you switched to some other way of providing domestic hot water aside from what you have now.


Re: Heating Domestic Hot Water With A Steam Boiler

Thanks for your information. I have a Burnham Model KV75 boiler installed in 1996 and an indirect Burnham Model # PAL41. I used to use 1800 gallons in a heating season. With the increase of oil prices, we installed a wood stove into our fireplace and insulated with cellulose. I used 1000 gallons and 5 cords of wood last season and I am on track to use 800 gallons and 4 cords this year. As I become more energy efficient, I realize the amount of oil I am using, basically for hot water only, domestic. My boiler comes on 3-4 times an hour each and every hour of every day. My aquastat is a Honeywell and is currently set at 180 on the lower and 200 on the higher. I am told this is pretty high. Can I adjust these numbers to like 140 and 160 without hurting my hot water temp at the faucett? I have the water tank set at 120 on the bottom of that tank. It appears that my boiler will always be ready to heat, as it should. But by hardly ever using it to heat with, maybe I could shut my emergency switch off and turn on like 1 hour before I will need hot water? My wife and I currently use about 35-40 gallons a day. Again, I appreciate your thoughts. We are looking into switching to a forced water system and getting rid of the steam, however, this seems pretty expensive. After all, we are trying to save money by heating with wood. Thanks again

Re: Heating Domestic Hot Water With A Steam Boiler

I heat with oil. I just looked at my aquastat and it is a Honeywell Model L4006A2007. Looks like a single function unit? I am reading about the aquastat that I have to be sure we do the correct adjustments. Thanks again for any info.

Re: Heating Domestic Hot Water With A Steam Boiler

Yes, that sounds like a lot of oil to be using during a heating season.

I'm not familiar with the controls or wiring of this particular aquastat---if, as you say, it has a hi and lo control, make a note of the present settings and adjust to 140 lo and 160 hi & see if that improves oil efficiency---this would make only hot water, & not steam, but you may not need as much heat as spring approaches.

If the aquastat is instead a single set unit, try making a note of its current setting & reduce down to 140 degrees for a trial run.

You could also call Burnham & ask for the technical help dept. & see if they can make any suggestions on the aquastat and burner nozzle settings-- or call the burner mfgr (Beckett, Carlin, Riello) for their suggestion.

Also ask Burnham if they allow a "downrating" of the oil burner nozzle from what you have now, down to a next size smaller---this can have a dramatic effect on oil usage for a nozzle that costs only $2 at a heating supply house.

Often the nozzle size burns oil at the rate of 1 gal per hour, or even 1 1/2 gal per hour, if you can reduce it to 3/4 gallon per hour, the burn cycles will be longer, but the system will still heat what you need for less oil used.

What is the total square footage of the heated space you have there---do you have a tight building with double pane windows or storms and insulation (R19) in the exterior walls, and R40 in the attic????---- what is your general location??? do you have a lot of zero or sub-zero weather????


Re: Heating Domestic Hot Water With A Steam Boiler

Thanks once again for the info. The aquastat is a single set unit and is set at 200, I will check the differential knob today. I looked on line and found the Honeywell model on line with directions for setting. I also e-mailed Burnham last night with some questions, but will call. The nozzle is a great idea, according to the plate on the boiler, it burns 1.65 GPH. Not sure of nozzle setting, but it is probably high with the size of our home and amount of oil previously used. I will check with Burnham. Our home is 2800 sf of heated space. We just had cellulose pumped into the attic after a complete airseal of the attic. Floor boards removed and 15" installed for an R-60. Our walls were dense packed to capacity of like 4", I believe like R19? Our windows are old wooden and fully restored. There is an exterior storm in place. We are in the process of installing Poly Flex around the windows to air seal. We also use heavy curtains and shades after dark. I live in Massachusetts, so it does get really cold, especially in January, many sub zero days and nights. I have a Plumber coming today to look at our project. The Oil Company came yesterday and tried to talk me into changing to water and dumping the steam boiler. Good idea, however, I really do not use the system for heat. I do want it for a back up to wood. After all, there are times when we have to be away in cold weather for an extended time frame. I am also exploring turning the aquastat down from the current 200 degrees and possibly turning the emergency switch off to completely eliminate the 3-4 times an hour heating the boiler belly. Turn the switch back on in the morning to bring the boiler up to temp and shut off until we have a need for hot water, planning ahead. When we were heating with steam, it was "free" water. Now it is very costly. 700 gallons at $2.75 a gallon really adds up. I believe we should be around 300-400 gallons a year, maybe less. Thanks once again for your help, I appreciate it.

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