Any thoughts on cutting back boiler cycling for domestic hot water?

[RKS130]

Thanks to the new pellet stove we have not turned on the oil burner for heat, but it is still cycling for dhw, which we have always heated with the boiler. Anyone know if there are controls available to stop it cycling so much, especially overnight when there is no demand for hot water at all?

Would a simple timer, turning the whole system off, say between midnight and 5am, be the easiest solution or are there more elegant ways to go that also decrease the cycling frequency during the day?

Any information would be greatly appreciated.

 

[maple1]

Does it heat DHW with a coil in the boiler? It is cycling to replace heat lost - I don't think there are many choices, aside from lowering your heat loss somehow (more insulation on your boiler?), or turning your boiler down thereby reducing the temp of your DHW.

If you turn it off over night, it will have to run a while in the morning to get back up to temp, so you won't be that farther ahead as far as oil consumption goes - and any time a boiler gets cold, there is way more chance of leaks appearing. If DWH is all you need oil for, I'd get rid of the oil & put in an electric or heat pump hot water tank. If you still want the oil for backup heat, I don't think anything aside from a new cold start boiler & indirect hot water tank will bring much improvement - unless you can insulate your boiler more or live with DHW that is not as hot as now. If you want to shut off the burner for a period, you should be able to wire in a timer to do that (I wired in a simple on/off light switch to mine) - if that's what you want to try.

 

[North of 60]

Time for an electric hot water tank.

 

[homebrewz]

There is a bit of discussion on the topic in this thread:
https://www.hearth.com/econtent/index.php/forums/viewthread/70267/

Hate that sound of the boiler kicking on and making DHW when we don't need it!

 

[RKS130]

Thanks Maple and Homebrew. I was wondering if being off at night would cause an early failure of the boiler and that thread from Homebrew gave me lots to think about. Our DHW is generated by a coil through the boiler which, until this year, was producing steam for our radiators. I loved the heat but hate the cost - hence the pellet stove.

I think I will go a season or two with DHW from the oil burner and see what the real usage is. I do know that between May 26 and Oct 24 I apparently used 131 gallons ($526), as that was the 'top off' volume.

My wife, who is always thinking great thoughts, likes the idea of the boiler cycling on the theory that it will keep the basement warmer and prevent pipe freeze, given that we are now heating the whole house with the stove. Moreover, it helps a bit to not have quite so cold a floor on the first floor of the house. We shall see.

 

[maple1]

I also have a coil in my boiler, that I need to keep hot all summer. It is very aggravating listening to it cycle & burning oil just for that, especially when it is 80° outside. My boiler does leak when it gets cold, I know that - so right now I'm stuck with it. This time next year I'm hoping to have a whole new setup - I figure it's burning about 150 gallons of oil for the non-heating months just for DHW.

 

[RKS130]

My usage is right in line with Maple's. As noted above, 131 gallons between May 26 and Oct 24, when no heat was ever on. Guess I am stuck with it for now, but I may look into a timer to close it down for a few hours per night. The boiler is about 20 years old and has never leaked. I find it hard to believe that being off for 3 or 4 hours a day will harm it.

 

[jharkin]

Since you are on oil I assume piped NG is not an option. If it was I would say put in a tankless HWH.

Another option would be to add an indirect, it only fires the boiler when the tank cools off. We hav ea Superstor Ultra indirect hooked up to our 83% efficient NG steam boiler. In the summer we use about 25~30 therms of gas a month. That would equate to about 18-20 gal of oil. This is a family of 4.

With the price of oil today even the electric option may be worthwhile depending on your rates...

 

[RKS130]

Actually we have NG in the house, which we added when the kids were born and using the electric dryer semed like a waste and Con Ed was still putting the line in for free, but never changed over the boiler to NG. One of those things I probably should have done but never did. As of now we use NG for dryer and cooking. So, assuming we look back at the end of the winter and have not needed the boiler for heat at all, next summer may see us getting an NG fired tankless heater.

 

[mayhem]

I run my boiler in the morning, take my shower and let it refill the hot water tank and warm up the corners of the house that the stove doesn't reach as well, when its done cycling I hit the living room kill switch. tank keeps enough hot water in it for a shower or two and a load in the dishwasher.

Some days I wake up in a foggy stupor and I forget to turn the thing on and let it run for a few minutes before my shower. On those days I wake up REAL fast. But I got my oil usage down to about 400 gallons last year...without shutting it down the boiler would cycle 3x a day just to keep the hot water hot and nobody's using it.

 

[maple1]

NG is a definite thing to consider - didn't know that was in the picture. If you don't want/need the oil unit for backup heat, I think getting rid of everything oil should be a possibility.

I did some rough figuring a while ago, and even though oil is expensive, it is still quite a bit ahead of electricity as far as unit costs go. I based my 'Canadian' figures on electricity at $0.15/kwh, and oil at $1.00/litre - came up with $44/MBtu electric, $26/MBtu oil.

 

[RKS130]

Mayhem's approach is an intersting one. Showers are clumped in the mornings and late night here so a short burst of oil followed by shutdown might work - and might address wife's coincenrs about frozen pipes in the basement. I know there has been discussion of damage to the boiler from shutting down all the time, but if we did not draw DHW off the boiler coil the thing would be off most of the day on a set back thermostat anyway.

Maple's thoughts are also well taken. I would never even consider electric, but NG seems OK, once we have the capital to change DHW over. Having just bought the stove and its accessories (vac/pellets/etc) that may have to wait a bit.

Thanks guys.

 

[Don2222]

Mayhem's approach is an intersting one. Showers are clumped in the mornings and late night here so a short burst of oil followed by shutdown might work - and might address wife's coincenrs about frozen pipes in the basement. I know there has been discussion of damage to the boiler from shutting down all the time, but if we did not draw DHW off the boiler coil the thing would be off most of the day on a set back thermostat anyway.

Maple's thoughts are also well taken. I would never even consider electric, but NG seems OK, once we have the capital to change DHW over. Having just bought the stove and its accessories (vac/pellets/etc) that may have to wait a bit.

Thanks guys.

I had the same situation before uncle Villy broke down. (Uncle Villy was our old Valiant Cast Iron Boiler with the Tankless coil) Then we got a new Buderus Cold Start, Triple Pass Boiler with the outdoor Reset. We call him Big Boo! Because big boo has the ThermoElastic Cast iron it does shut down when not heating the hot water. We can get a programmable aquastat for the SuperStor indirect hot water tank we call him MaxiSuper because he has a lifetime guarantee but we are down to only using 200 gallons a year now with Asti. Asti is our Avalon Astoria wood pellet stove we use for all our heating. Asti uses 3 tons per year of wood pellets. However during the power failure we had to use Auntie Glow for a few hours. She is our Heat N Glo SL550-TRS-D ipi LP Gas fireplace and Stinky who is our Kerosene heater in the garage!!
Cactus Quartz sits by us when we have colds and muscle aches!

See pics of our heater family below!
click to enlarge

 

[RKS130]

Hey Don - you sure are one for names! What do you call your wife?

 

[mayhem]

Maam.

 

[RKS130]

I know a wise man when I hear one!

 

[mayhem]

Been married 16 years. More than long enough to know my place and not step out of it...costs me a lot of money if I do.

Just don't call her "yes dear". Thats code for "f**k you"...and they all know it.

 

[RKS130]

Amen Brudda . . . been married since 1993 and have learned those lessons well.

 

[firefighterjake]

Been married 16 years. More than long enough to know my place and not step out of it...costs me a lot of money if I do.

Just don't call her "yes dear". Thats code for "f**k you"...and they all know it.

Oh yeah . . . they hate that . . . hate that a lot.

 

[stejus]

OP - Same situation as you with no need for furnace to heat the house. If you have an oil burner with an internal water coil, you must have an aquastat connected to the water coil. It may be a Honeywell or something else. There is a HIGH, LOW and DIFF dial. Set the low to 130 with a diff of 10. When I opened mine, my LOW was set to 180 which meant my domestic hot water was being kept between 170 and 180. Doesn't cycle as much or as long now that it is at 130. Still plenty of domestic hot water with it set like this.

 

[EatenByLimestone]

This summer I switched from an oil boiler and 1978 vintage 40 gallon electric water heater to an indirect tank fired by a conversion burner. (My boiler wasn't old so I didn't want to get rid of the whole thing.) I set it up with a primary loop and secondaries loops for the indirect tank, one for the first floor, and Ts for the 2nd floor which I'm currently finishing off. I just insulated my new pipes and found quite a difference on how hot the water stays in the primary loop. The secondary loops have a lot more surface area and half the insulation, so they loose heat faster, but still stay warm much longer. I dropped around 300kwh per month heating my water with the boiler. I was using around 20 therms of gas/mo heating the water, but expect it to be cut down a bit from the insulation. I'll know how much it worked next spring when heating season ends.