Thermostat needs replacing?

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Ctreefer

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Hi, writing this from the office just now so I don't have my specific equipment info, but will add that later tonight when I am home.

I have an indirect water tank adjacent to my 1992 Well Mclain boiler (oil fired). I believe the tank is about the same age. We bought the house in 2009.

I'm probably really an idiot waiting so long to realize there has likely been an issue the whole time we've been there, but here is my experience with my heater:

I have the manual dial thermostat at the base of the water heater dialed at between the 5 and 6 mark on the dial which is significantly above the 120F mark which if i recall is around 4. When we first bought the house, I was surprised it was set so high so I turned it down to 4 and then the next time i used the hot water, it was barely warm (maybe 80 degrees if i had to guess). I played around with the settings and in the end realized that the minute i turn it just below the 5-6 mark, that the water temperature in the tank drops down like 40 degrees. I'm assuming this is a thermostat issue?

I've forgotten about it until this past week when I went and looked at my oil tank level (getting ready for a really expensive oil price this winter) and my 330 gallon tank was just below 1/2 and the majority of this consumption has been just heating the water tank as we had it filled in May which is right at the end of our heating season here in southern CT. I'd say this means we've been using on average about 40 gallons per month. It's a household of 4 when the kids aren't off at school and my daughter does take pretty long showers but the rest of us take about 5-10 minute showers on energy saver heads daily. No bathtubs and no other significant uses of hot water than the normal. If it is 40 gallons per month at the current $4.50 per gallon price, we're paying $180 per month just to heat water!!!!

Does this seem excessive for oil consumption for heating a hot water tank? Should I just upgrade the tank along with the thermostat? Tank seems fine and i've been told by my service guy its a good tank and well insulated. I've also had a water heater blanket over the thing since we moved in along with all the hot water supply lines. The tank itself is powder blue and kind of like a giant Tylenol capsule with rounded top and bottom if that helps in describing before i get more information later.

thanks in advance for any input.
 

John Gayewski

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Something other than the "thermostat" is wrong here. I'm assuming you have an aquastat that runs a circulator? Have you descaled? Whatever type of heat exchanger you have is probably scaled up and causing bad heat transfer which makes your run times many times longer than they should be and your probably running way hotter than it should be while gaining no heat in the actual water. If the amount of money your talking about is right, your probably running the boiler a very long time and most of the heat is just being wasted.
 

Ctreefer

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Something other than the "thermostat" is wrong here. I'm assuming you have an aquastat that runs a circulator? Have you descaled? Whatever type of heat exchanger you have is probably scaled up and causing bad heat transfer which makes your run times many times longer than they should be and your probably running way hotter than it should be while gaining no heat in the actual water. If the amount of money your talking about is right, your probably running the boiler a very long time and most of the heat is just being wasted.
Yes, there's an aquastat running the circulator. I do have the settings on the lower side (135lo/150hi) during non winter season to keep the boiler from unnecessarily heating the boiler so hot during off season to save some $$. I have never descaled the tank since we've been there. I had wondered if this was necessary or not. We have city water and water parameters in our area are not very conducive to lime build up. I had finally decided perhaps wrongly that since coil temperatures inside the tank are pretty low in comparison to an electric element that any scale build up would be minimal.

Also, I don't think scale would cause the issue i'm seeing which is that if i just barely move the dial on the heater thermostat (like from 5 down to 4.5), the water temp of the heater goes from very hot (don't know the actual value but definitely above 120F) down to something more like 80F if I had to guess again. This seems to me more like there is a dead zone on the instrument. Not sure if a thermostat is like a potentiometer, but, if it is, this seems exactly like what is going on. But again, no expert here. This being said, if there is scale, it would impact my heat transfer and hence oil consumption.

Either way, i'm guessing my bad on not flushing the tank as a regular maintenance thing.
 

John Gayewski

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I would start with a heavy descaling operation and see if anything changes
 

Fitter30

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30 year old boiler with hw coil that never has seen service for 13 years that u know of and probably more. Doubt a coil is available. Better off going with a stand alone water heater either electric or heat pump. Descale a coil that old the cleaner would eat a hole in it. Check with ur utility companies and ur tax man for rebates.
 

Ctreefer

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30 year old boiler with hw coil that never has seen service for 13 years that u know of and probably more. Doubt a coil is available. Better off going with a stand alone water heater either electric or heat pump. Descale a coil that old the cleaner would eat a hole in it. Check with ur utility companies and ur tax man for rebates.
Yes, I was thinking the same. Although not necessarily the heat pump option. Electricity in CT is close to highest in the nation and provider is asking for a 5% hike and that’s just for distribution. Generation rates at year end right now are looking like 16 cents kwhr. That would add up to over 32 cents kwhr!!! One thing we’ve learned over the years is the rates only go up and don’t come down at least on the distribution side. If I got a new indirect fired water heater similar to the current, I’m thinking it will be cheaper monthly, plus, if we shut off the boiler for the summer, it will likely spring all sorts of leaks due to contraction of fittings based upon having previously shutting it down for baseboard work.
 
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