Aquastat(?) on Forced Hot Water Weil-McClain(about 25 years old)

[GregoryR]

Hello,

I am very glad I found these forums, and really hope somebody can help. I recently compiled some data from my heating bills. The single oil furnace does the domestic hot water, and the hot water for the baseboard heat. All laundry is done in cold. The home is about 1300 sq ft with about 1000 of it heated in the winter. We have one bathroom and two of us total living here full time. Between last October and this April, we used 2 gallons of oil per day(~345 gallons). We use a programmable thermostat to set the heat at 68 when we are awake and home, and 64 during the night.

I thought 345 gallons was pretty good for a winter. However, in the summer, non heating months, we used ~300 gallons. Only 45 less than the winter?! Granted, there are three people living and showering here in the summer, shouldn't it be less than that?

I took some pictures of the furnace, and an "Enertol" unit. I could not find any documentation on the Enertrol at all online. I did open the Honeywell temp. control(gray) box and set it to 160 Hi/140 Lo, and there was another small dial, VAR, I believe set at 5. (It was at 180/160, 5)

The Enertrol box has a left, right switch and and temp sum. I've attached photos. If anybody can help with this, that would be wonderful. Without touching the hot water, it takes 3:47 to maintain the water temp(i.e., no hot water is used, when the furnace triggers on, it takes this time to heat back up). I also noticed the water in the line for the baseboard heat(under floor)(but not at the baseboard) stays piping hot even during the summer.

Thanks!


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[Tom Sawyer]

The Enertrol is an old style analog modulating control that determines boiler temperature by sensing outside temperature. The dial is set at 220 which pretty much overrides the control however for domestic hot water the control has no function anyway. If you want to save money you need to get rid of the tankless coil in the boiler and either go with a gas water heater or an indirect but the boiler looks to be so old that I don't think I would put that kind of money into it. If you really want to save money, tear the old mess out and go with something more efficient and an indirect like a Buderus BE or Logano series or a System 2000

[GregoryR]

The Enertrol is an old style analog modulating control that determines boiler temperature by sensing outside temperature. The dial is set at 220 which pretty much overrides the control however for domestic hot water the control has no function anyway. If you want to save money you need to get rid of the tankless coil in the boiler and either go with a gas water heater or an indirect but the boiler looks to be so old that I don't think I would put that kind of money into it. If you really want to save money, tear the old mess out and go with something more efficient and an indirect like a Buderus BE or Logano series or a System 2000

Cool to know a little something about that. So is the water actually heating to 220 and being unused in the summer? The water in the line for the baseboard heat is very hot, hotter than we ever get for dom. hot water.

I think there is some dom. hot water storage in the boiler itself(or maybe that isn't how it works), as if you turn on the shower, you will get hot water for a little bit, before the boiler turns on. Any suggestions on the VAR/DIFF switch in the Honeywell box? Or the left right switch on the Enertrol? I am tempted to set this to 165.

Thanks again!


EDIT:Yes, the black pipe coming out of the top of the unit must be >200 degrees. Just the outside is MUCH hotter than anything we get from the faucet. This is the one that goes through the expansion tank and to the baseboard.

[jadnashua]

You domestic hot water is made by running a coil through a small vat of hot water in the boiler. Cold in, hot out through the coil. So, to keep the system able to produce that hot water, the whole boiler stays pretty warm all year, all the time. If you drop the temp down too much, the water through the coil can't pick up enough heat. As a result, the boiler is running all year, all the time (well, it cycles - more in the winter, though, but you understand what I mean).

As stated, the choices are: leave it alone; disable the coil and add in an indirect; disable the coil and add a stand-alone self-powered WH (gas, oil, or electric).

A new boiler would probably suggest an indirect, although that could be added to the existing unit and much of it could be retained when updating the boiler at a later time.

[GregoryR]

You domestic hot water is made by running a coil through a small vat of hot water in the boiler. Cold in, hot out through the coil. So, to keep the system able to produce that hot water, the whole boiler stays pretty warm all year, all the time. If you drop the temp down too much, the water through the coil can't pick up enough heat. As a result, the boiler is running all year, all the time (well, it cycles - more in the winter, though, but you understand what I mean).

As stated, the choices are: leave it alone; disable the coil and add in an indirect; disable the coil and add a stand-alone self-powered WH (gas, oil, or electric).

A new boiler would probably suggest an indirect, although that could be added to the existing unit and much of it could be retained when updating the boiler at a later time.

So the coil would be taken out, and the output attached to a separate tank to store hot water? Would this cause the boiler to turn on less often at all in the summer?

Also, any ideas on the VAR/DIFF setting on the Honeywell box?

Thanks!

[jadnashua]

You don't need to take the coil out, just cap off the inlet and outlet. Then, unless you are installing an indirect (which acts like a zone in your heating system), you could turn the boiler off entirely for the summer. With the indirect, you could probably adjust it so it didn't run until the indirect called for heat, and then it wouldn't be constantly hot all the time. If you go with a separate, stand-alone tank (oil, gas, or electric), you could also shut the boiler down for the summer.

To make hot water with the coil, the aquastat needs to keep the small tank fairly hot. If the min/max are too close together, and the load is low, it will short-cycle and this is very inefficient. The only good thing is that in the summer, the incoming cold water isn't as frigid as it is in the winter, so you may be able to get by by dropping the min (turn-on) temp. Since that imersion tank isn't all that big (generally), regardless, it doesn't take too long for it to recover.

Someone more in tune with the specifics can probably give you more details on how best to set the thing. But, if you want to save some money, you'd probably want to disable the tankless coil and get another means of heating the domestic hot water supply.

[GregoryR]

Thanks to everybody who replied. As a result, I am keeping the setting on 160/140, and have turned the max temp on the Enertrol from 220 to 185, and the water in the shower is still hot.

Still wondering about the DIFF switch inside the Honeywell box currently set to 5. Also, Any ideas on this knob I have?


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[Tom Sawyer]

Normally the aquastat is set a 180-200 for the high and 140-160 for the low.

The high controls the Maximum temperature that the boiler will achieve with the thermostat calling

The low is an internal thermostat that maintains the boiler at set temperature so that there will be domestic hot water available.

The differential is the difference between set temperature and any override and it's there to keep the burner from cycling. So with the differential set at 5 the burner will cycle between 155 and 165. Normally it is set to 10

That dial is a by-pass timer that kicks the Enertrol out of the control loop so that you can have hot water. The Enertrol is wired in series with the high limit. someone probably set the Enertrol at 220 so they would not have to mess with the timer.

You are currently making hot water in probably the most expensive way possible as you are maintaining the boiler at temperature year around and during the off cycle a lot of that heat in boiler is going up the chimney until the boiler cools and then the burner runs again whether you need hot water or not. Very inneficient. A 40 gallon electric water heater would be cheaper to operate.

[GregoryR]

Normally the aquastat is set a 180-200 for the high and 140-160 for the low.

The high controls the Maximum temperature that the boiler will achieve with the thermostat calling

The low is an internal thermostat that maintains the boiler at set temperature so that there will be domestic hot water available.

The differential is the difference between set temperature and any override and it's there to keep the burner from cycling. So with the differential set at 5 the burner will cycle between 155 and 165. Normally it is set to 10

That dial is a by-pass timer that kicks the Enertrol out of the control loop so that you can have hot water. The Enertrol is wired in series with the high limit. someone probably set the Enertrol at 220 so they would not have to mess with the timer.

You are currently making hot water in probably the most expensive way possible as you are maintaining the boiler at temperature year around and during the off cycle a lot of that heat in boiler is going up the chimney until the boiler cools and then the burner runs again whether you need hot water or not. Very inneficient. A 40 gallon electric water heater would be cheaper to operate.

So true. I might actually be able to pay for a HWH itself for less than the cost of 100 gallons of #2. I think I should call my current oil company and get an estimate for a few on demand propane systems, and call another for the cost of installing an electric HWH.

Thanks so much for bearing with me!

[tk03]

Just a few notes here. First off it looks like the slide switch is standard not mode. That means no ODR function. The setting of 220 changes the curve when modulating the boiler water temperature which is not happening in the standard mode. The 220 setting while in standard does nothing as you would than be operating off the boiler aquastat due to lower setting. These usually came with a timer if installed on a boiler with a DHW coil. You have a manual timer which tells me the Enertrol ordered was for a boiler without a coil and than ooops, and added the manual timer to compensate.
My guess is this is in standard due to not working anymore.
The boiler aquastat settings need to be set so the boiler supplies enough hot water. The differential should be set at 20f. This maintaining side of this control has a built in differential of 10f. The water boiler temp drops 10f and starts the burner, and runs until the boiler water temp raises 20f (diff) and shuts down the boiler providing there is no call for heat. Basically it works like this, low water temp - 10 + diff setting. When there is a demand for heat the diff setting is no longer active, just used for maintaining water temperature.
To reiterate the coil is the most expensive way to heat hot water but if you eliminate by cutting off the pipes do not cap it. You will build pressure and possible create an unsafe condition.

[GregoryR]

Sooo. They came to my home to get details for the estimate and said there was no place to put the tank. We live in house(eg no landlord) and there is plenty of room in a back yard. I was a tad suspicious.


They're doing a quote for an indirect instead, but the installer was not sure how much it would cost or how much money/oil I'd save. Any ideas? We use about 300gals in the summer to heat water for 3 people(clothes done in cold).

[Tom Sawyer]

well it looks like you have a Weil McLain P66 series boiler which means that it is a good 20 years old, however, if the burner is properly serviced and adjusted that old girl does pretty well as far as efficiency is concerned. If the boiler is in good condition then an indirect would indeed be a very good way to go but, it's going to cost you a bit over 2 grand what with the tank, piping, valves, circulator and controls so you have to make a decision as to whether the boiler is worth that investment. On the other hand though, if the boiler does crap out in the near future the indirect would be useable on the new boiler. Where in Maine are you? Oh and a differential setting of 20 is way more range than you need, 10 should do it.

[chapchap70]

Question: How do you figure you are using 300 gallons of oil in the summer? If you have a small old Weil McLain boiler (I could not tell the size from the pictures), I do not think it would be firing at a rate higher than 0.85 gallons per hour. I doubt your boiler fires for much more than an hour per day in the summer even with a tankless coil. Are you estimating usage by when you have gotten deliveries?

If you have a triple acting aquastat (Honeywell 8124 or equivalent) with a hi limit setting, a low limit setting, and a differential setting, my understanding is that the hi setting is the hi limit safety control; NOT the operating control. I have our hi limit set at 190, the low limit at 150 and the differential at 20 degrees to keep the on and off times longer. The minimum differential setting on the 8124 is 10 degrees.

The low limit and differential operate the boiler. Many if not most heating people do not understand how this works. If the low limit is set at 150 degrees and the differential is at 20 degrees, the control should turn the burner on at 140 degrees and turn it off at 160. If the differential is set at 10 degrees, the burner would fire at 140 and shut off at 150. The burner should always turn on 10 degrees lower than the limit setting no matter what the differential is set at. The gauge and control are not exactly the same for various reasons. For example, even though my low limit setting is set for 150 degrees, my burner fires when the gauge reads about 135 degrees and shuts off when it reaches 155 degrees on the gauge. Depending on the load, the boiler temperature may continue to rise after the burner shuts off because the iron and firebox continue to exchange residual heat.

This should be sufficient to take showers in the summer but the boiler water might not be hot enough to heat a house on cold days in the winter with ~150 degree water. We have a tankless coil also. I am not familiar with the Enertrol but it seems similar to the Beckett Heat Manager. I do not think the Enertrol is being sold anymore.

About the electric water heater; I don't know what your electric rates are in Maine but at ~25 cents per KWH on Long Island, we still don't even consider it because of price. I don't think you get the same recovery rate with electric as you do with a tankless coil in a oil fired boiler. I would not put an electric water heater outside if that is what you were thinking.

By the way, ~650 gallons of oil per years seems good for Maine with your boiler. My guess is your usage breaks down to around 500 winter and 150 summer.

[Tom Sawyer]

actually on a call for heat the boiler will very often run to the high limit setting.

The coil in a Weil Mclain P366 or 466 is only rated at 2.5 gpm continuous draw and if there is any scaleing ( and after 20 years or so you can bet there is ) that figure changes considerably.

I have never run into any technicians that didn't understand how the differential works.

[GregoryR]

well it looks like you have a Weil McLain P66 series boiler which means that it is a good 20 years old, however, if the burner is properly serviced and adjusted that old girl does pretty well as far as efficiency is concerned. If the boiler is in good condition then an indirect would indeed be a very good way to go but, it's going to cost you a bit over 2 grand what with the tank, piping, valves, circulator and controls so you have to make a decision as to whether the boiler is worth that investment. On the other hand though, if the boiler does crap out in the near future the indirect would be useable on the new boiler. Where in Maine are you? Oh and a differential setting of 20 is way more range than you need, 10 should do it.

Sounds like it wouldn't be quite worth it(2k), and thanks for the advice. We are in central Oxford County.

Question: How do you figure you are using 300 gallons of oil in the summer? If you have a small old Weil McLain boiler (I could not tell the size from the pictures), I do not think it would be firing at a rate higher than 0.85 gallons per hour. I doubt your boiler fires for much more than an hour per day in the summer even with a tankless coil. Are you estimating usage by when you have gotten deliveries?

If you have a triple acting aquastat (Honeywell 8124 or equivalent) with a hi limit setting, a low limit setting, and a differential setting, my understanding is that the hi setting is the hi limit safety control; NOT the operating control. I have our hi limit set at 190, the low limit at 150 and the differential at 20 degrees to keep the on and off times longer. The minimum differential setting on the 8124 is 10 degrees.

The low limit and differential operate the boiler. Many if not most heating people do not understand how this works. If the low limit is set at 150 degrees and the differential is at 20 degrees, the control should turn the burner on at 140 degrees and turn it off at 160. If the differential is set at 10 degrees, the burner would fire at 140 and shut off at 150. The burner should always turn on 10 degrees lower than the limit setting no matter what the differential is set at. The gauge and control are not exactly the same for various reasons. For example, even though my low limit setting is set for 150 degrees, my burner fires when the gauge reads about 135 degrees and shuts off when it reaches 155 degrees on the gauge. Depending on the load, the boiler temperature may continue to rise after the burner shuts off because the iron and firebox continue to exchange residual heat.

This should be sufficient to take showers in the summer but the boiler water might not be hot enough to heat a house on cold days in the winter with ~150 degree water. We have a tankless coil also. I am not familiar with the Enertrol but it seems similar to the Beckett Heat Manager. I do not think the Enertrol is being sold anymore.

About the electric water heater; I don't know what your electric rates are in Maine but at ~25 cents per KWH on Long Island, we still don't even consider it because of price. I don't think you get the same recovery rate with electric as you do with a tankless coil in a oil fired boiler. I would not put an electric water heater outside if that is what you were thinking.

By the way, ~650 gallons of oil per years seems good for Maine with your boiler. My guess is your usage breaks down to around 500 winter and 150 summer.

I made a spreadsheet based on orders for oil. We only order when the gauge has been on empty for about 5-7 days. I've attached it for you. Current differential is at 15. Electricity is 18 cents/kwh delivered here. The tank they were referring to was a propane tank they claimed could not be installed anywhere.

actually on a call for heat the boiler will very often run to the high limit setting.

The coil in a Weil Mclain P366 or 466 is only rated at 2.5 gpm continuous draw and if there is any scaleing ( and after 20 years or so you can bet there is ) that figure changes considerably.

I have never run into any technicians that didn't understand how the differential works.

We have about 35ppm of dissolved solids in our water, but I am sure it has built up as you say. We generally have plenty of HW and would only need to consider something for saving oil or money.

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