# Putting a Timer on my furnace to save oil?



## sopoburner (Mar 5, 2010)

I have a oil burning furnace that supplies forced hot water for heating the house and hot water for sinks and showers.

Since I burn wood to heat my house, now I only really need my furnace for hot showers and other small things. Nothing drives me more crazy than to here my furnace start up in the middle of the day just for the sake of keeping the water hot. 

So I am thinking about installing a timer on my furnace so it only turns on for 1 hour in the morning, so we can take showers and 1 hour in the evening for dishes and general use. 
My question is:
 Do you think it is more efficient for a furnace to keep always keep the hot water at a stable temperature 24 hrs a day or would it more efficient to just have the furnace heat up water for those 2 hours of use a day? 

I believe it takes my furnace about 10 minutes to heat up the water after its been off for 8 hours. (last year I would flip the emergecy shut off switch to keep my furnace from turning on during the day)

I welcome any input.


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## DBoon (Mar 6, 2010)

It might be most efficient to just install an electric hot water heater, provided that you are not using that much hot water, and provided that you don't have to add another 220V breaker or upgrade your service to do this.  If your utility has day/night metering, you can make your hot water overnight when the rates are less, and use it during the day.  A 50 gallon tank is fine for my wife and I except maybe during holidays when a lot of dishes are getting washed.  

FYI, my electric rate overnight is about 10 cents/kWh and this is cost competitive for me.  Oil at $2.50 or more per gallon and typical boiler efficiencies for just making hot water makes water cheaper to heat electrically, in general.   I pay only $20/month for electric hot water heat this way - that would work out to about 8 gallons of month of oil at $2.50/gallon.  I would guess that you are using more than 8 gallons/month of oil.


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## btuser (Mar 6, 2010)

I too, am battling the hot water gremlin.  I found myself asking the same questions I've rattled around.

I'm guessing you've got a tankless coil.  Your boiler likes to keep itself warm, not just for the sake of hot water on-demand, but for the sake of flue gasses.  I found this out after adding an indirect to a steel boiler.  I converted to a cold-start with indirect, and immediately I started getting leaks from flanges that had cooled down.  Not too bad with a steel boiler, but DO NOT DO THIS WITH A CAST IRON BOILER!!  You will get terrible leaks.


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## WES999 (Mar 6, 2010)

I had the same issue. I was spending about $80/mo in oil to heat DHW.
I picked up a electric water heater form CL for $50.
Now I am spending about $20/mo for DHW. 
It is actually less than that since I have installed a heat exchanger on my wood stove to preheat the water before it enters the electric heater.
Oil is probably the most indecent way to heat DHW.
I think my last oil delivery was last June, I still have about 3/8 of a tank left.  

More here:
https://www.hearth.com/econtent/index.php/forums/viewthread/39434/P0/

https://www.hearth.com/econtent/index.php/forums/viewthread/49253/  (See post #6)


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## btuser (Mar 6, 2010)

I've got 4 women in my house.  If there's no hot water  THERE'S NO HOT WATER!!

I'm burning about 200 gallons/day.  Too much for an electric.  I'd like to pre-heat with solar, but when I run the numbers I'd only get about 20k btu/day which is less than 20% of what I need.


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## DBoon (Mar 6, 2010)

Hi btuser, it's going to be tough to get four women in the house to use less hot water, especially if you already have that front loading washer...


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## btuser (Mar 6, 2010)

It's a conumdrum no doubt.  Its a subject I have very little control over.  I can keep the house as 60F and deal with the sniping, but I'm nowhere near prepared for the wrath of a woman who needs a shower.  I'd sooner sleep in the shed.


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## vvvv (Mar 7, 2010)

sopoburner said:
			
		

> I have a oil burning furnace that supplies forced hot water for heating the house and hot water for sinks and showers.
> 
> Since I burn wood to heat my house, now I only really need my furnace for hot showers and other small things. Nothing drives me more crazy than to here my furnace start up in the middle of the day just for the sake of keeping the water hot.
> 
> ...


If you ran the furnace/boiler at will before & it didn't leak you can do whatever. The standby heatloss from a furnace/boiler results from a hot furnace/boiler getting its heat sucked out by the chimney. Ideally, if you can cool the boiler from water usage & it sits cold until next usage its highly efficient & this is the general nature of a "cold start boiler"  I think.


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## DaveM195352 (Mar 9, 2010)

Maine here also.
You didn't mention if you have an in-direct DHW tank that sits off from the furnace.  Sounds like you do.  And since you already have been using the furnace switch with sucess, I think your safe with adding a timer.

Same here with being sick of hearing furance come on middle of day, no one here, or in the middle of the night just to keep my indirect water tank up to temp.  What I did was to add a timer instead of using the furance switch.  Works great.  only two of us here and have a very well insulated indirect tank - so I heat water at 5am - for morning showers and plenty for dishes and etc in the evening.  Only issue I have is a 60 gallon jet tub that the wife uses every 3-4 days  - and for that, we just override the furance, let her have the tub, re-heat the tank, and then turn it back to the timer.

after two years with this set up - I feel we have saved over 100 gallons of oil . $250-$300 savings.


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## DaveM195352 (Mar 9, 2010)

just remembered  - there was chat about this topic back in 2008 here in this forum.

try this link  - should bring up that thread about adding timer and etc.

https://www.hearth.com/econtent/index.php/forums/viewthread/21456/

let us know how you make out.


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## sopoburner (Mar 11, 2010)

I would really like to thank everybody for their awesome input.!!

I will repost with an update once I have it installed.


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## btuser (Mar 11, 2010)

I don't know if you have the capacity, but I'm thinking of my Tekmar 260 to an alarm output on my security panel, so when the system is armed the tekmar goes into unoccupied mode, which shuts off the hot water.


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