cast iron boiler summer settings

mclewis

HI there. I'm seeking advice on summer settings for my cast iron oil boiler furnace. It's a Warden King Sunnyday Seven, 117,000 BTUs/hour, with a burner capacity of 1.50 US gallons/hour, a maximum working pressure of 30 psi, efficienty 75%. It's heating cast iron radiators and DHW.) During summer months, when space heating is turned off, the furnace cycles often regardless of whether there's a call for how water and we are burning 160 litres of oil/month just for DHW standby. I am considering installing an electric hot water tank which could save me 65% of DHW costs during summer, and who knows how much during the winter. I also am looking at installing mini-split heat pumps to further reduce my oil burning for space heating. (We burn 6500 litres annually!) But my oil service technicians warned me that I should never turn off my furnace, because the condensation would cause issues with the furnace such as rust, corrosion, seizing of moving parts. I'm wondering if there's any truth to this?

Here are my questions for oil boiler experts.

1. Can I turn off my furnace when it is not needed to save on the cycling of the boiler during standby without causing damage to the boiler?
2. If not, is there a way I can greatly reduce the cycling, and still protect the boiler? I have a Honeywell aquastat installed (hi, low, and diff controls). Can that help to reduce unnecessary cycling?
3. When it comes to installing an electric hot water heater, I plan to ask the plumber to install a shut off valve so that I can easily switch back to the boiler for DHW during colder months when the boiler will be used anyway. Is this a straight forward job? Is there anything further the plumber will need to do to ensure the boiler no longer receives DHW calls, and no longer cycles to maintain minimum temps for DHW standby?
4. If there is no easy way to greatly reduce the cycling required to maintain temps required for the boiler health, does it make any sense for me to bother installing a secondary electric water heater?

I'm really looking forward to hearing from the oil experts here and want to thank you in advance for your help!

Grallert

I would want to see exactly how your water is heated. I'm not familiar with that boiler. Do you have an indirect water heater or is there a coil in the boiler? How often is the boiler cycling?

mclewis

There's a coil in the boiler and it's cycling several times a day. I have not timed the cycles, and I can do that if it helps, but as I said, I do know that the boiler burned 160 litres/month this past summer to maintain standby DHW temperature. This happened even when there were no calls for DHW. (I did not adjust the aquastat temps and the hi was 180, the lo was 160, the diff was 20.)

leonz

You could also lower the triple aquastat temperatures to 160 degrees Fahrenheit high limit; 140 degrees Fahrenheit low limit which are the same temperatures used for coal stoker boilers with domestic hot water coils.

If possible wrapping the domestic hot water piping with insulation would also be more efficient.

Grallert

If you were to add an indirect water heater to your system ( see Heat Transfer Products SSU 45) for example. You would greatly reduce your summer season fuel consumption Simply by lowering the low limit setting on your aquastat to its lowest setting. This will stop the majority of the cycling, greatly reduce the standby loss from your boiler and store the hot water you're making. The standby loss of your boiler could be up around 30 to 40 degrees an hour where as the indirect might be around 1 degree an hour. And keeping the low limit aquastat set to around 100 or what ever the lowest setting is the boiler will not condense. It'll take a few years for the cost to balance but it's worth it and you'll be happier and more comfortable.

EdTheHeaterMan

I'm only guessing but are you located in the southern hemisphere?

I need to turn my thinking cap around the other way, if that is the case.

Based on the age of the boiler and the way you are heating water there are several things you can do. Thew lowest cost option would be to determine what is the aquastat that is the low limit on your boiler.

On newer models that have a triple aquastat relay like the the Honeywell L8124 it is easy to find. It says LOW on the dial. First find the DIFF and turn that to the lowest setting. Now turn that LOW dial to 140°. See if that boiler temperature produces enough hot water. If you find that water is not hot enough for taking a shower, then turn the setting to 145° to see if that is good enough. keep turning up the dial until your boiler can produce the needed hot water. The idea here is that the lower the boiler temperature is the less stand-by loss up the chimney there will be.

In most of the north east USA and Canada the cost of heating water with electricity is usually more expensive. (but not always) I

If your boiler is very old you may find that there are two or three individual aquastats that will perform that function that may look like this

The two aquastat wiring diagram will have the high limit, that is usually located near the top of the boiler to shut off the burner when the water temperature goes above that setting. That is always the higher temperature setting aquastat. there is no need to adjust that. The other aquastat will be the combination LOW limit/revers. This one has 3 wires connected to it. This is the one you want to set to 140°.

Some older models (pre 1960) may have three aquastats. the high limit, the low limit and a reverse aquastat to allow priority for the DHW. To determine which one is the reverse aquastat, you can look at the mercury bulb inside it to see if the wires are on the opposite side of the High and Low limit.

What ever wiring design you have, all you need to do is to lower the LOW temperature to 140°

The high limit does not come into play for DHW. Only for space heating

If you have the separate aquastat relay and you open it up and find that there is a differential adjustment, set that to 10°

Hope this info helps

Mr. Ed

EdTheHeaterMan

https://forum.heatinghelp.com/discussion/comment/1868900#Comment_1868900

This is a good idea in most cases, but your boiler is operating at 75% efficiency. I would not recommend that job due to the expense involved to repipe the system purchase the tank and all that goes along with it. If I were to install any indirect to replace a tankless coil DHW, I would do more than turn the low limit to the lowest setting. I would disconnect it completely. Why operate the boiler at all in the summer unless there is a call for DHW. If you do not use any DHW at all, Your boiler may stay off for 16 to 20 hours on standby depending on the tank you choose.

As it is now you have standby loss enough to operate the burner every 3 to 4 hours or so. Not the most efficient use of fuel in my opinion.

ethicalpaul

Yes by all means install a water heater and let your boiler rest all summer. The advice you were given was by someone who makes money selling oil.

EdTheHeaterMan

https://forum.heatinghelp.com/discussion/comment/1868904#Comment_1868904

If @mclewis does that electric water heater install, their fuel oil use would most definitely drop. He may save $300 to $400 per summer. I wonder what the electrical bill increases to heating water all 12 months of the year. If it comes to about $300 to 400 per year, OR MORE, what would you then recommend? I know that you do not believe that using a central heating boiler to make hot water in the summer, but have you actually done the math on such a change.

• Price of new water heater installed
• Price of energy to heat that water
• less the Price of fuel saved

I have a customer that did just what you are suggesting in 2012. The plumber did not even lower the aquastat LOW setting so the customer needed to turn off the switch to the boiler in the summer. After 3 years of electric water heater use they were astonished at the high electric bill and how little the oil bill reduced. I then used the abandoned tankless coil to improvise the electric water into an indirect water heater and set the boiler up as a cold start system.

The oil usage never went back to the high summer usage from several years ago and the electric bill went back to what it was before the water heater was installed.  My Pleasantville NJ customer would disagree with your opinion.  

And since you like to experiment and prove your theories I might challenge you to purchase an indirect or  BPHX, a circulator and connect it as a hydronic loop off of your steamer.  I'm sure that you already have your gas usage documented. It would be interesting to see how much more (or less) gas you actually use.  I can see a new video that proves your point or that you learn something from. 

ethicalpaul

I don't promote this idea due to some fantastic savings, but rather for the simplicity and separation.

However, if you do want fantastic savings, then install a "hybrid" heat-pump water heater which often comes with substantial incentives from state government and/or utility

PS: the homeowner in your story was actually astonished by the cost to heat water with electricity? It should have been about $500 per year especially back then.

EBEBRATT-Ed

Liters not gallons so over the summer you burned 160 liters which is 42 gallons/month.

Are you sure that is right?

42 gallons/ month= 42 x 140000 btu/month.=5,880,000 btu/month /30 days=196,000 btu/day/24 hours=8,166/hour.

That seems high to me..

8166 btu/hour assume 50% efficiency so 4033 btu/hour x 24 hours=97992 btu/day. Figure a 70degree rise in water temp so 97992/70=1400 pounds of water/8.33=168 gallons of water/day

EdTheHeaterMan

ethicalpaul said "PS: the homeowner in your story was actually astonished by the cost to heat water with electricity? It should have been about $500 per year, especially back then."

It was actually over $1200 per year, You see that homeowner has a different situation than you have. There was a newborn and 2 toddlers in the household, unlike your situation. They were not using disposable diapers so there was a lot of laundry hot water used. The oil savings over the summer was about $440.00. (basically 110 gallons for those three years. When I made the impromptu indirect, the fuel oil usage increased to about 375.00 that summer, and the electric went back to the original lower bill prior to the stand alone water heater. (it cost 275 to save 1200. The price of the work was paid for itself in 2 years with savings). But all they needed was a SS circulator since the HX was already in the oil fired boiler

However in your case where you have the HPWH and no diapers to launder, you are absolutely correct.  I just don’t see how you can make a blanket statement: Indirects are not good water heaters and that everyone should use a HPWH.  I have installed hundreds of indirect water heaters and have one in my own home (where my son lives now) and the fuel oil bills are very affordable and use about 100 gallons or less over the summer as I recall when I was monitoring that stuff.  Today's oil is about $313.00 per gallon in Cape May County NJ

I can’t wait until the HPWH needs service out of warranty and you end up with $$$$ service bills or end up paying for Resistance electric for your DHW. While my stainless steel tank with the lifetime warrants lasts 20 to 30 years.  I feel that you might look at other potions.  Unless you have solar panels on your roof.  That is a different story.  Your electricity will cost a lot less in that case.  So, cancel the experiment 

ethicalpaul

I wasn’t quoting my hot water costs, but rather the average cost for the average home.

Mine are much lower because as you mentioned I have a HPWH. But I wasn’t even pushing that solution here.

And sorry to disappoint but my HPWH has been in perfect service for 6 years already and has paid for itself.

EdTheHeaterMan

@ethicalpaul said: "And sorry to disappoint but my HPWH has been in perfect service for 6 years already and has paid for itself." I am not disappointed in the least, and I am no wishing you ill will with your HPWH, I just know that they are expensive and that they are using the same tank as the electric and gas water heaters that have 6 and 10 year warranties. With your attention to detail and the maintenance you are obviously going to make the HPWH last longer than the average consumer. I just don't see it being there in the year 2049. But my (now my sons) water heater has been in service since 1999. I would not be surprised if it lasts another 20 years.

Just from experience. I hope you can post the results of any service costs you have had as the HPWH moves thru its expected life in your basement. I like you videos Paul. I would love to see that indirect experiment If you find the time next summer.

Grallert

Lots of options here. Electric or HPEWH and shut the boiler off good options and ones I sometimes recommend do to cost of installation. An indirect off an old inefficient boiler maintaining a very low water temp to prevent condensation saved some folks a lot of money. full disclosure I worked for an oil company at the time and hoped to return to these folks In the at some point in the future to plug and play replace the aged boiler. in the interim I often heard how happy they were with the water heater.

mclewis

Thank you so much everyone for your input! I want to answer some questions that came up and also, to ask a few.

My location is Newfoundland. Coastal climate with lots of wind and precipitation due to the Labrador current. Median temperature in summer in 20 °C and in winter is 0 to -5°C. (68°F in summer and 32°F- to 23°F in winter.)

Yes, we definitely burned 160 litres/month this past summer - July 1 - September 30 - just for DHW standby. There were only 2 people using the house for much of that time. The space heating was turned off and aquastat settings were as follows: hi:180, lo: 160, diff: 20.

The biggest issue I'm trying to solve is to reduce costs (for heating and DHW).

When the oil boiler is providing space heating, DHW heating is piggy-backing on space heating which would reduce (or eliminate) unnecessary cycling to maintain DHW standby temps, so it's hard to say how much oil is burned for DHW in colder months but I've estimated 1500 litres annually for DHW. (At a cost of roughly $2000 CAD).

I'm not hearing anyone say there is a risk to simply turning off my boiler during months it is not needed. Yes?

I'd like to confirm that before making a decision either way. (If I upgrade space heating with mini split heat pumps, I might be able to keep the boiler off for most of the year.)

Under the current oil-fueled DHW setup, I'm spending somewhere between $160 and $220/month CAD for DHW. I expect an electric water heater to cost roughly $60/month CAD to operate. (? Does this sound fair? Electricity rates are .14 cents/kW.) If anyone can provide an idea of what an indirect water tank setup might cost to operate, that would be really helpful.

mclewis

IMG_7935.JPG

Hello there Ed, and and thank you so much for your thorough response! To answer your question, I'm not in the southern hemisphere! I'm in north eastern Canada - Newfoundland to be precise. Thank you so much for those pictures of aquastats. The visuals really help. I've attached a photo of mine which is the Honeywell L8124.

When I had the oil company service guys here recently, I asked them to check those settings. They were the ones who had set them at hi:180, low: 160, diff: 20 and they assured me those were the 'correct' settings for optimum performance. (Unfortunately, I've rarely found them to be helpful when it comes to troubleshooting ways to reduce oil consumption) I've taken your instructions and adjusted the low to 140 and the diff to 10. So far, I am finding the DHW temps just fine, but it's too soon to know whether (and how much) we will save on oil consumption under this regime. I'd be curious to hear from you how much you anticipate this will reduce the oil consumption for DHW?

The last question I have is regarding the "Beckett Heat Manager" that is pictured here. This control had been turned off (by the service guys). I turned it back on, but I have no idea what it is for, or whether it is doing what it should. Wondering if you have any insights to offer? Thank you in advance!

IMG_7936.JPG

pecmsg

https://forum.heatinghelp.com/discussion/comment/1869174#Comment_1869174

An Introduction To The Beckett HeatManager™ | Beckett Corporation

Intplm.

I like the idea of the hybrid water heater.

Has anyone besides me experienced a sectional boiler leaking after it's been shut down for the season, only to leak when it was turned back on?

@mclewis A new hybrid water heater with less boiler temp cycling might be your best option.

EdTheHeaterMan

https://forum.heatinghelp.com/discussion/comment/1869177#Comment_1869177

"Has anyone besides me experienced a sectional boiler leaking after it's been shut down for the season"

in most cases the boiler will not leak when shut down for the summer, however I have experienced very old boilers where the tankless coil gasket was not checked for several years after the initial installation, in those cases where the coil gasket is leaking anyway, the leak does become more aggressive when the boiler is cold and less aggressive when the boiler is hot. If your boiler is in that condition, the correct course of action is to remove the coil and replace the coil gasket. After 500 hours of operation retoque the coil flange bolts and again after 1000 hours of operation. That will be all you need to do for the next 20 years.  This will allow you to reduce your fuel oil usage.

The alternative is to keep the boiler at a minimum temperature all summer, which will cost you $$$ every year until you replace the boiler which may cost much more that the one time gasket replacement job.

@mclewis. Yoiu should be able to shut off your boiler in the summer. Any advice that the oil company provides that will allow you to burn more oil would be suspect in my opinion

Intplm.

@EdTheHeaterMan I agree with your comment above, but have had sections on boiler leaks ( as well as tankless coil gaskets, as you mention above.) I feel it should be a consideration on this subject, especially if the boiler is older. How old is older? Maybe look at my birth certificate?

EdTheHeaterMan

@Intplm. said: "How old is older? Maybe look at my birth certificate?"

My birth certificate has an expiration date on it. So I guess I know when I'm going to die!

Intplm.

AWW come on man… Mine is so yellow and cracked that the print looks like hieroglyphics.