I'm new to this, Advise needed on oil-fired tankless coil DHW

[mjstev01]

Hi All, I'm new to this forum and currently obsessed with making my home as energy efficiant as possible. My first (and most likely my last) home bought July of last year. One winter on oil was enough. I recently purchased a pellet stove (Harman Accentra) for the 1305 sq. ft. I've opened up a new doorway b/w the kitchen and living room so the air can circulate properly. I've also just recently properly vented and insulated the attic.

This past heating season, I burned 864 gallons of fuel oil in my oil-fired Burnham tankless coil boiler. The aquastat was and still is set with a min 165, max 180 temp. The differential is set on 20. When running the hot water and watching the guage at the same time, it seems the boiler fires on at roughly 180, then clicks off around 200-205, but increases in temp to roughly 210 before beginning it's slow decent.

Since pellets will now be my primary source of heat in the winter, I am looking for advise on what I can do to make my DHW use more efficiant year round. I have not been able to track this thoroughly, but I am sure the boiler is clicking on numerous times per day, in an effort to maintain the HW temp. I have read numerous posts on this site, but get confused jumping from indirect tank posts, to solar HW posts, to large storage tanks etc...

No access to NG, solar prob a bit too expensive for me at this point. Maybe not? Not really sure. Not out of the picture in the coming years. Electric or enhancements to oil are my options at this point.

1) What does the differential of 10-15-20 on a Honeywell aquastat do?
2) Will lowering the min/max/diff settings help consume less oil? Are there any bad effects to the boiler doing this?
3) Could I turn the boiler off completely while at work and sleeping? (roughly 16 hours per day)? Bad to do this?

And most important, suggestions on how I can make my oil-fired boiler click on less often! Additions, like a indirect tank etc...

Currently just my wife and I demanding HW in the morning for showers and dishes at night.

Really appreciate this site for it's info. Thanks in advance. -Mike

 

[MrEd]

An indirect tank may work for you, something line a SSU-60 or whatever size is appropriate for your household, in that case the oil boiler will run for longer and store enough hot water so that it doesn't need to kick on so often. ANother option is to go with an on-demand propane or electric water heater. I've heard good things about them. Benefit is that if you can heat your house with your pellet stove, you won't need to burn oil at all. The new on-demand heaters are supposed to be very cost effective, small, and relatively inexpensive - with oil at 4.50 a gallon, it doesn't take much savings to pay for itself. If you don't plan on using the oil burner for heat in the winter, or not much, then you are probably heating hot water in the most expensive way possible.

 

[steam man]

I am not sure what boiler you have but it sounds like it will have a relatively large water mass with a tankless coil. I also think an indirect tank would allow you to let your oil boiler set up for cold start not have it always hot for on demand DHW. This may be a relatively expensive problem to fix. If you could get outdoor reset control on your heating system it would lower the set point depending on heating load based on outdoor temperature. This could get pricey depending on what controls you use. Last is my set up-I use an Intellidyne economizer to learn how much heat load is anticipated and fires the boiler accordingly. Basically it scavenges heat out of the boiler before it lets the burner fire. If it thinks you need heat quicker based on the output temperature drop, it will fire the boiler. It also will fire if the boiler is below 140. The boiler has to be setup to allow it to fire to 180. They claim an oil savings of up to 20% by reducing boiler cycling. This is basically the cheapest way out if you can wire it up yourself. It isn't all that hard. I got it on the cheapout of EBAY. It does sound like your setpoint could be turned down so it maxes at 180. Where the boiler senses temperature is probably not optimal. I burned about the same amount of oil you did in a 12 month period in a much larger house. I did burn 5 cords or so of wood. This year I am going heavy on solar so my oil needs will go down so I don't think squeezing anymore efficiency out of my oil boiler is the direction I want to go.

 

[kshultz]

Hi Mike,

My old house had one of those. I do remember mine turning on a lot more often than my current indirect fired DHW. One thing you may want to make sure is that the coil is not leaking and need to be replaced. One thing that I started doing is trying to make sure all the hot water is being used at nearly the same time of day. Something you may want to do when you get up & shower, run the dishes to. Hit the boiler shut off on your way out the door! I'm aweful, at times I have mine off for a real long time w/out the family even knowing. Oil is just damn too expensive. With the prices of oil where it is, it requires a lifestyle change, or a habit change of doing showers, laundry, dishes in the same part of the day so the oil can be shut off for the rest of the day or next 16-20 hours. Sounds extreme, but I paid $480 for 125 gal. of oil early spring. That is a lot of money. - Kevin

 

[mtaccone]

Just to share my usage experiences as I am obcessed with hot water cost these days, I burn 19 gals a month in a 30 gallon tank type water heater and we have an average of 3 LONG showers a day a load of laundry, and dishes also a dishwasher load once a week. We had electric and it cost me $150+/ month. My parents who have a much smaller water load use an indirect fired 30 gallon tank and there boiler hardly ever runs during a day. Just a personal comparison here.

 

[mjstev01]

How many people out there with tankless oil-fired DHW actually turn off the boiler while at work or sleeping? Does anybody use a timer to control when the boiler is on/off? For example, the timer is set for 5 AM for showers in the AM, then turns itself off for the work day, then on for dinner dishes, off for the night etc...?

Is there any bad effects on the bioler (life span) doing this?

 

[phil san]

Hey, I've got the same boiler and controls. Installed 6 yrs ago by a local S.Shore major dealer. Problem I had with oil heat and
DHW coil was the burner was on all summer long. Now in those days it always ran about 45 gallons a month for oil ( figure the cost now). I use to shut off the boiler all the time, when at work in the summer months but it still cost extra for water on demand.
What I did ( and after recent research see a lot of people are doing ), is install an Electric Water Tank heater. I went overboard and even piped it with a circulator so I could run the water in winter through the furnace after calls for heat stopped and store the
water. Then I leave the burner on straight call for heat only with low temp at like 135 degrees.

Basically, family of 4 - costing me about $40 a month for DHW. Best thing I ever did.

ps

This year pellet insert and wood stove. NO oil.