Energy Rater Suggests Re-wiring Boiler to be Automatic?

16 years ago

I just had an energy rating done on my home yesterday. We have an opportunity to make energy improvements during the next month and a half and let Alaska Housing Finance Corp (a state company who we have our loan through) review the improvements so we can get a permanent reduction in our mortgage interest rate.

The rater told me that instead of having my boiler 'hot' all the time, I could wire it so that it would only flame up when one of the zone valves opened. Now, my preference is to just extinguish the pilot and shut it down manually in May, then re-light it in October. If it only flamed up when a zone valve opened, wouldn't it expend MORE energy just trying to heat itself up again, making it more difficult to keep a consistent temperature in the house?

The summer has been cool this year, so there are times when the heat will run even in July. (Rainy days when it can't quite hit 60Â°F outside.)

I'm not convinced that re-wiring the boiler to only fire when one of the two zones are open is the most efficient idea.

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Comments (11)

baymee
16 years ago
There are energy raters on this forum who can answer your question better than I can.

A zone valve is nothing more than a switch. The thermostat tells it to open and it will then cause the water circulator to run. If the boiler temperature is above the aquastat's low limit setting, the burner won't come on until it is; usually fairly soon.

If your weather causes the zone valve to operate, it's going to operate intermittently until the weather warms up again. When you say the boiler is "hot", I assume it's hot enough to heat your house and I also assume that the energy rater wants to let the boiler cool all the way down until there is another call for heat.

It takes an oil boiler about 7 minutes to heat up enough from a 70 degree water temperature to a level high enough for home heating and it takes several cycles a day to maintain 160 degrees. You will probably use more fuel maintaining 160 degrees in the warmer months, but in the winter, I wouldn't bother letting it cycle from 100 to 160 all the time. I'd let it at 160/180. I don't think there is much of a savings, but more importantly, a boiler will endure less stress by keeping it at a nearly constant temperature.

As far a shutting it off during the warmer months, that's OK, but watch out for water leaks at the pipe joints and gaskets. Replacing leaking water constantly with fresh water will also ruin a boiler.

As far as the energy savings, I'll defer to a rater.
User
Original Author
16 years ago
I see what you mean about the complete 'stone-cold' to peak heat being a stress on the system. I experienced the shutdown leaks in the rental home that I used to live in, so I was expecting leaks. (And I haven't shut this unit down this year because the garage fan, which circulates water 24/7, leaked at the bottom connection when the water got down to about 100Â°F.)

The system was flushed in December, a few months before we bought the house. To this day, it still has some air trapped. Not much, but I can hear it in the garage. I figure the air must have come from the fresh water that was taken in. Is there any additive that is ever used to keep the tank and plumbing / gaskets healthy, somewhat like radiator fluid for an automotive engine?

My boiler is 25 years old now. I hear so many conflicting stories about whether it's really worth getting a new one installed. From what I can see, a boiler is a boiler. 25 years old or not. Aside from the reliability, is a 25 year old hot water boiler *really* going to save any energy compared to the old one? The ones that I see in plumbing shops look exactly the same as this unit. I'm not interested in some super mega-efficient system because of the cost and the questionable reliability. (My aunt and her neighbor have experienced the CompleteHeat system. Let's just say that there may be one system left in this city.)
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Andy, I understand your frustration. Hydronic heat specialists are getting more difficult to find, I understand. Just be glad that you don't have steam. If you ever decide to replace the boiler, your engineering background might help. There a several variables and lots of calculations that need to be done to be sure you end up in a working envelope -- water temperature, heat loss from the structure, heat transfer via the radiators, circulation rate, temperature drop in the individual loops,... You could have a new hobby. The boiler heads in those two fora will be able to help you out a lot, I think. Someone there, maybe several people, will know that boiler well. Just tell them you are tired of the excess heat and give them your boiler and indirect hot water tank details. Be sure to ask them about scheduling the boiler on and off when it is only needed for water heating. Look at that this way, if you have your boiler off 16 hours a day while working and sleeping during the week, and 8 hours on Saturday and Sunday, you've solved nearly 60% of your problem. The flue can go in two ways and depends on what kind of boiler you have. There is subtlety that I am skipping. Condensing boilers have low temperature flue gas, and use plastic pipe going horizontally out of the side wall of the house. They are usually using outdoor air for combustion eliminating another heat loss point. Condensing the steam means heat recovery from that steam that used to leave boilers up the chimney. Now it runs down the drain after giving up its heat. All old fashioned residential boilers used to be non condensing. They will have a metal flue pipe that goes up to the roof line in some kind of double wall, insulated metal, or a metal joined to a masonry chimney. The problem is a mismatch between boiler and flue. Obviously a high temperature boiler will melt/burn plastic pipe. I've never heard of that happening. Exhausting wet (and acidic) flue gas in a masonry, or inadequately corrosion resistant chimney will cause a much slower failure and that happens even though it should not. Particularly bad are very old, unlined masonry chimneys no tile liner. The acid gets to the mortar and eats it up leaving gaps. Sometimes, with a change to a more efficient condensing boiler, a plastic flue can be installed within an old-fashioned chimney and go up through the roof if going out sideways is not convenient or not eye-pleasing.
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baymee
16 years ago
The efficiency of a boiler system can be affected by many things. Keeping the flue passages clean is a major plus, to obtain maximum heat to water transfer.

There is a boiler water conditioner which will help keep the water from turning slimy, but the best way to handle a boiler is to fill the system and never mess with it again. It's best to keep the boiler warm, even if it's a very minimal temperature, however, if you can turn it off and it doesn't leak for the summer, then go ahead.

Fix your leaks and while you're at it, install another air vent to better purge the system of air.

A boiler is a box that holds water. Taken care of, it can last a lifetime and more. Unless there is some major reason why you need to upgrade, I would not replace a boiler to increase a few percentage points in efficiency.
mr_havac
16 years ago
Actually you have to look inside the boiler where most people never see to see the difference in newer boilers. One of the major changes is the flue passages are alot closer together. This puts more surface in contact with the flame a lot faster. That also enables the new boiler to be alot smaller which means they hold alot less water but heat the water that passes through it faster. Thats why a new boiler can handle a cold start easier then an older boiler. Most older boilers are bigger and store a good amount of hot water readily available so when a zone calls the boiler run right away. If you are into the habit of getting your old boiler cleaned only every few years forget a new oil fired boiler. They need cleaning "every" year. The sections being closer together tend to clog and soot up a lot quicker. Even a thin layer of soot severely deminishes heat transfer to the water and oil consumption goes up considerably. This is just my opinion but if your old boiler is running in the low 80's or even the high seventies for seasonal efficiency some serious thinking should be done before replacing in with a new boiler. Those efficiencies they rate boilers at are done under controlled lab conditions. I don't know anybody myself who has a boiler installed in perfect conditions like that.
baymee
16 years ago
I think he has a gas boiler.

One bit of inside information I can tell you is that a boiler that was once below the energy star rating can be made to achieve an energy star rating by making a few adjustments in the burner and no other changes to the boiler.

The downside: The life of the boiler will be shortened by the hotter flame.
markjames
16 years ago
When we install a new boiler, the benefits other than increased efficiency, reliability and comfort are proper sizing, piping, pumping, controls, burner setup. Many older boilers are inefficient, oversized and the piping, pumping and controls are poorly designed. With oil fired boilers, sometimes we can upgrade the burner alone, then transfer thenewer burner to a newer boiler in the future, or give the customer a credit for the old burner.

Almost anyone can do a halfway decent job of installing a gas fired forced air furnace, but when it come to oil fired burners and hydronics, the amount of true professionals and knowledge in the market is limited.

Here are few other links where you can get information from seasoned professionals concerning hydronic heating as well as gas and oil heating knowledge.

Heating Help: The Wall is one of the best resources on the net for all things hydronic. Besides Wetheads, some pretty good Oil & Gas technicians post there as well. http://www.heatinghelp.com/wall_forum.cfm

Oil Tech Talk: Plenty of Oil, Gas and Hydronics knowledge in their forum as well. http://www.oiltechtalk.com/discuss/viewforum.php?f=1

The Boiler Room: HeatPro and company offer professional answers and solutions here. http://www.boilerroom.com/wwwboard/homeforum3.html
User
Original Author
16 years ago
These comments are assuring me that the boiler is not "old" due to its age. I had completely forgotten about the passages above the flame that add surface area for heat transfer. The label on the boiler says that it was last drained, filled, purged and inspected last year. The items noted as missing were added (such as a secondary over-temp shutoff control) during our buying process. However, the label does not mention that the combustion area was cleaned. In fact, I haven't really looked at it, myself. It does cycle on quite often, though. Most likely because the circulation pump runs 24 / 7 and the pipes aren't insulated.

Considering that the boiler was the same as what was installed in the other 50 or more homes in this neighborhood when it was constructed, is it safe to even "assume" that a properly sized unit was chosen back then?

I think the first things I'll be doing are A) Insulate the exposed pipes in the garage (where the boiler lives), B) Gain control of the leaky overhead fan and C) Have the combustion chamber inspected / cleaned. I already have my "just in case" item hanging on the wall next to the boiler, which is a spare thermocouple. Learned the hard way about those in a previous home.

Thanks to all of you for your information!
brickeyee
16 years ago
"last drained, filled, purged and inspected last year."

Repeated draining and refilling will beat the boiler up faster than anything else.
Evey time new water is added it introduces another load of oxygen that is only removed by corrosion of the boiler and pipes.
Once the oxygen is removed this way corrosion stops, until you add new water with more oxygen.
Sealed hydronic systems should only be drained if absolutely necessary to make a repair.
Newer units have smaller flue passages and greatly increase4 the length and number of metal pins molded into the jacket sticking into the hot flue gases.
The efficiency improvement is significant.
90% units are not hard to get.
baymee
16 years ago
when it come to oil fired burners and hydronics, the amount of true professionals and knowledge in the market is limited. (Markjames). Yikes, maybe I should demand more money.

An oil-fired hydronic system is pretty straight forward. I encounter many more problems, almost daily, from homeowners with coal fired hydronic systems.
markjames
16 years ago
baymee- We have wood boilers and pellet boilers, but I haven't seen a coal fired boiler since I was a kid.

As far as oil service is concerned, we get dozens of calls per year from customers after service techs told them the don't service Riello burners, let alone carry repair kits, complete burners, tubes, gauges, spare parts etc. This is strange since there are so many Riello burners in the area.

Concerning boiler installations, piping and control strategies, many installers are just cut & run artists. If it doesn't leak, some people are happy.

Not that we're complaining. Poorly designed systems burn more fuel, need more service, don't last as long and many of our new customers are homeowners frustrated with their current fuel suppliers, service people, installers etc.

As far as overall service is concerned, the following video isn't too far from the truth in some areas. I've met quite a few gas installers that don't even own combustion testing equipment.

Here is a link that might be useful: Furnace HVAC Contractors Kill People from Carbon Monoxide CO
baymee
16 years ago
Interesting video. Probably a little embellishment at points.

Energy Rater Suggests Re-wiring Boiler to be Automatic?

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