Will I harm boiler by cycling it daily?


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Old 07-17-09, 12:04 PM
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Will I harm boiler by cycling it daily?

I have a thirteen year old Weil-McLain 115,000 btu/hr oil-fired boiler that is used to heat water to provide infloor radiant heating to a medium sized house. At the advice of my HVAC contractor two years ago I eliminated two 80 gallon electric water heaters that provided domestic hot water and installed a 79 gallon indirect water heater in tandem with the above boiler.

I've since learned that when you don't need the boiler for floor heat, operating the boiler just to make domestic water is expensive. After last heating season was over, for the three months mid-April to mid-July, I used 160 gallons of heating oil to run the boiler just for domestic hot water. Two people at home, don't use a great deal of hot water.

I imagine this older boiler is not very efficient and being large enough to heat a whole house, it's overkill for just the hot water heater's needs. At $2 a gallon, I'm spending a little over $100 a month for hot water heating for two people. You'd think if the indirect water heater is a good one, well insulated, the boiler would not need to run much to keep the water hot if you weren't using any hot water. But our boiler seemed to be running quite a bit 24 hours a day.

The indirect water heater thermostat is set at 129 degrees. We only need hot water in the morning for showers, after that warm water is sufficient. For the last five days I have installed a timer in line with the boiler electric power. I've been powering the oil fired boiler on for just three hours daily, 6am to 9am. Since doing this my experience with using hot water has been perfectly fine. Will this hurt the oil fired boiler & associated plumbing to let it cycle from hot to cold and turn it on and off again everyday-- or is this just another boiler cycle which is a boiler cycle and it doesn't matter?

By the way, when 9am and the timer cut off time comes, electricity to the boiler is suddenly disconnected, as though there was a power outage... does this regular sudden interruption suddenly leave any boiler part dangerously hot without circulation/movement? I am asking if there is a more preferred way to cycle the boiler to off other than pulling the plug. (I have not had to mess with thermostat wiring because the boiler has a switched pigtail power feed for power outage generator use, and so it was easy to plug that into a 120 volt timer to try this cycling idea.)

It may not save much heating oil to heat furiously for 3 hours to bring the temperature up then do nothing for 21 hours, but if this pattern won't harm the boiler I may continue to try it for a couple months of the warm weather and see what the change in consumption is. Thanks for any input.
 
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Old 07-17-09, 06:57 PM
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You have been using $100/month in oil for summer water heating, right? What do you estimate you were paying for the electrical energy when you were heating water that way? What annual savings did your HVAC contractor estimate for going to oil (summer and winter)?

What you describe is a drawback for using your heating boiler for domestic water heating, particularly in the summer. Using a big heating boiler just for hot water isn't all that efficient.

Some boilers are set up for a cold start, like you are now doing. It might be a little easier on the boiler and flue to keep the boiler hot 24/7. But at what cost? I doubt, though, you are harming your boiler much by shutting it down daily.

How much time was the boiler firing when you were keeping it hot all day during the summer? There will be some jacket loss and some loss up the flue, but otherwise, I don't think there would be other losses.

But, I'm spoiled - I use natural gas, with a separate heating boiler and hot-water heater. (Natural gas users here seldom, if ever, use their heating boiler for domestic water heating.) My gas bill for last month (31 days) was $23, which, besides water heating, included cooking, clothes drying, and my outdoor BBQ grill. Most of my bill was for the fixed "monthly customer charge," which is due no matter how little gas I use.

You speak of your "older" 13-year-old Weil-McLain boiler as perhaps not being all that efficient. By boiler standards, yours is virtually new! Boiler salesmen would love to replace your boiler every 13 years. Mine is going on 60 years old. I use about $1000 per year in fuel (natural gas) for heating. If I spent, say, $10,000 to replace my boiler and related piping, etc., and the new boiler heated my house while consuming ZERO fuel, I would be looking at at a 10-year payback period.
Doug
 

Last edited by gilmorrie; 07-17-09 at 07:20 PM.
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Old 07-17-09, 07:16 PM
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What brand indirect, and how is it piped to the boiler?

There are many reasons your setup might be underperforming. Boiler efficiency, poor piping, leaking, poor insulation, faulty control are just a couple.

First thing that leaps out to me is that the indirect is huge compared to the boiler size and your domestic water use. An 80 gallon indirect is typically fired by a boiler nearly twice the size of yours. Your setup is a small boiler spending a lot of time heating a lot of extra water. Like trying to boil a big pot of pasta water using a birthday candle. That extra water will also have a long time to cool off because your demand isn't high. A 30-40 gallon indirect would probably be (have been) a much better match for the boiler's output. But something else must be up.

Say you're using 50 gal/month to heat domestic water. At 75% efficiency, that's 174,000 BTU/day. That no way, no how, should be the case. More details about the system, please. How is the radiant flooring piped off the boiler? What kind of water temperatures does the floor use? What temperature is the boiler aquastat set at? And anything else you can think of....
 

Last edited by xiphias; 07-17-09 at 07:33 PM.
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Old 07-17-09, 09:03 PM
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Pictures would also be good. Check temperature of pipes. maybe heat is also going elsewhere. I agree the tank size is extreme which is as bad as over sizing the boiler but there is more to this then meets the eye.
 
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Old 07-18-09, 08:18 PM
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Thank you everyone for responding. I would like to amend the consumption numbers slightly. I have a six hundred gallon above ground tank and the gauge indicates 3/8 of a tank, or 225 gallons, were consumed in the 3 month period. I also use this same tank to fill two diesel tractors and may have slightly underestimated the tractor consumption. So whatever it's worth I'd like to revise this discussion by saying approximately 117 gallons of fuel were consumed by the boiler alone for domestic hot water production for the three month period mid-April to mid-July.

The indirect water heater is a Buderus LT-300 79 gallon water heater. At the time of the purchase I was told this would save energy, getting hot water from the boiler that was running anyway, versus two 80 gallon electric water heaters. A formal projection and savings calculation was not done.

I have to say part of the purchase decision was the floorspace gained by removing two 80 gallon electric water heaters from two closets. These behemoths were removed and the Buderus indirect was installed in an unheated attic directly above the boiler. So I feel like I got two new rooms in this exchange, but of course what I'm noticing now is the fuel expense in the summer season.

Before I put the boiler on the timer, I would say the boiler was running a lot. The utility room was boiling hot around the clock. It seemed the boiler was running even when we hadn't used hot water in a long time.

The photos below show the boiler. You can barely see in the second photo two pipes on the rear wall going straight up thru the ceiling. That's the supply and return to the Buderus Indirect WH directly above that ceiling in the attic.

The master bathroom is about 45 feet away from this boiler room and a recirculating loop was created. I was wondering if heat was dissipating in that loop but I doubt even that could explain this.

This boiler has been finicky during my four years of ownership. I have maintenance service done every September, but even so, during the winter it will smoke heavily and have to be cleaned out again. The last major repair a year ago was the whole interior had to be cleaned and the liner replaced-- this repair was $700.

We know this setup is inefficient in the summer but I would like to determine the added fuel cost of using the indirect during the winter when the boiler is running anyway.

Or maybe as you are alluding, there is a control problem which is causing the boiler to fire a lot more than is needed anyway. I've never heated with fuel before so I have nothing to compare with, but my annual fuel consumption here is high.

I find the radiant heated floors more comfortable than the heat pump in the winter but the fact is I could eliminate this boiler and still have heat in the entire house except for the master bedroom/bath and the domestic hot water-- which I would have to heat in some other way.

I can get up in the attic to take photos of the indirect hot water heater if that would be helpful. Thanks again for the help. -Gadgetnut





 
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Old 07-19-09, 04:44 AM
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I agree with xiphias that the hw tank is way too big. 40 would be fine.
You have a good idea to shut down the boiler when not needed BUT that boiler was not designed to be operated that way. You could create problems by trying to make it work not as intended.
Some boilers use that concept and use significantly less energy than a boiler like yours. For example see the Energy Kinetics website for an explanation of that concept. I don't sell them now so this is not a sales pitch. I have set up similar system's with other low mass, quick heating boilers, such as Laars Max 75. I disagree with gilmorrie in the case of this system which makes domestic hot water more efficiently than a seperate hot water maker. About 10 gal/mo for hot water only for a family of 4.
I agree that the age of the system is not as important as the design. But there are more choice of efficient designs out now. 30 yrs ago they were not concerned with fuel costs. Now there are so many, with the modulating boilers, condensing boilers and the cold start I mentioned already. My 25 yr old System 2000 and my 10 yr old Laars are way more efficient than a brand new heavy boiler that sits hot and cannot be run low temp or shut off.
xiphias makes another good point about the radiant floor. The old fashioned way was to have the boiler sitting hot and mixing down cooler water to the slab. The boiler sat hot just waiting to add a very little to the floor and/or to domestic hot water.

Now we modulate the boiler temp or shut it down.
I went crazy with the symbols there
 
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Old 07-19-09, 05:33 AM
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Sounds like you've got several variables working against you:

recirc line
oversized indirect relative to boiler output
oversized indirect relative to household demand
poor estimates of actual fuel use

At least the Buderus indirect is a quality piece of equipment.

Still need to know aquastat settings and how this boiler handles the radiant floor heating. It might have something to do with it. All that foil tape and brown corrosion staining on the exhaust makes me think this boiler is/was condensing, which means that the heat exchanger might be shot, or clogged.
 
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Old 07-19-09, 08:04 AM
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The indirect is in an unheated attic? What temperature will that attic be during the winter?

The recirc line: are the feed and return lines insulated the entire run? If not then all you are doing is cooling your indirect. Does the recirc pump run constantly or is it on a timer AND aquastat?
 
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Old 07-20-09, 06:07 AM
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Originally Posted by gadgetnut View Post
So whatever it's worth I'd like to revise this discussion by saying approximately 117 gallons of fuel were consumed by the boiler alone for domestic hot water production for the three month period mid-April to mid-July.
whew i'm glad you revised that...with my old 225K boiler i only used 42 gallons all last summer so 160 seemed a tad high

also i wouldnt trust the gauge i had on my tanks at all. I prefer to figure gallons between billings
 
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Old 07-20-09, 06:23 AM
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Originally Posted by xiphias View Post
All that foil tape and brown corrosion staining on the exhaust makes me think this boiler is/was condensing, which means that the heat exchanger might be shot, or clogged.
You said it! That don't look good at all...

What temperature is the radiant floor heating running at?

How is the water temperature being 'mixed down' from the hotter boiler water?

You really can't, and shouldn't, try to use a standard high temperature boiler for radiant floor heating just by turning the temperature on the aquastat down. There needs to be some controls/piping that allow the boiler to run HOT, and the floor to run cooler.
 
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Old 07-20-09, 07:56 AM
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I totally agree with Trooper. See the following link.
Bypass_Piping_Explaination
There are boilers designed for that type of application and cast iron needs protected against cold water and low temperatures.
 
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Old 07-21-09, 03:54 PM
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Hello, everyone. Sorry for the delay, I had been away from the computer. My oil consumption with this boiler has seemed to be high in both summer and winter, but to be clear, for the period in this discussion, the radiant zones have been turned off--no hot water going thru the floors. I hadn't felt any heat from the floors and I actually closed the supply/return valves at the floor heat manifold, which is about 40 feet away from the boiler. So the 117 gallons of fuel oil usage in three months April to July were for when the boiler's only "official" job was to make hot water. But that's the problem.

The thermostat on the boiler says the water is usually about 160° when the boiler is running. The thermostat on the indirect water heater says 129°. I'm not sure about the floor heat temperature setting but I would say that the floor (porcelain tile throughout) sometimes feels uncomfortably warm to the bare foot during the winter.

My servicing HVAC contractor is not the installer. This may have been a homeowner-designed/installed system. My HVAC contractor certainly characterizes the system (the plumbing particularly) as puzzling or unconventional. Regarding my high energy costs my HVAC contractor asked me to locate photos taken during the house construction. The house is slab on grade and he wondered whether the slab was insulated underneath. The system does not have an electrically controlled mixing valve like I have seen in the past. It seems to perform the mix of the boiler hot water with the return water by means of a variable speed pump.

My HVAC contractor proposed changing out all the plumbing towards a more straightforward plumbing arrangement with mixing valve but I backed out, not knowing how committed I should be to redoing this, and if the investment (one to two days' labor and parts) in system change could actually pay off in energy savings.

Old Grouchy, you asked about the temperature of the unheated attic where the indirect WH is installed-- I would suppose 35 degrees to possibly freezing at the coldest period for four weeks or so. You also asked if the recirc loop is insulated the entire way thru this unheated attic-- I don't know, but I hope so. I will find out and report back.

Yes, xiphias, the exhaust of the boiler is filthy with brown corrosion staining etc. How can I determine if the boiler is condensing and how do I determine if the heat exchanger is clogged or ruined? How is this repaired or replaced? Expensive?

Bilbo mentioned that I am forcing the boiler to behave against its design by shutting it off suddenly everyday for 21 hours during the non-winter seasons. I've just started doing this for the last week. The 79 gallons of hot water has been lasting 21 hours-- no problem. Perhaps I only need to run the boiler for one hour. But can anyone else respond regarding am I going to harm the boiler by running it this way out of season?

As I said, this boiler currently provides radiant infloor heating to my entire house and domestic hot water. My heat pump (completely separate, redundant installation) supplies (noisier, less comfortable) winter heat to 80% of my house. Only the master bedroom + bath does not get any HVAC from the heat pump and the master suite has relied on infloor heat from the boiler. Fact is, I turn the bedroom heat completely off (I like it cold!) and only use the heat in the bathroom floor, which is nice. But my point is: I could abandon this boiler completely if I could figure out how to heat my bathroom and make hot water.

One nice thing about the current radiant system is that during the winter when the power goes out, and it does go out in winter where I live, I can plug the boiler into my generator and easily keep the house warm, whereas if I relied on heat pump only, I wouldn't have any heat during the power outage season because my generator doesn't have that kind of capacity.

I love the radiant heat but I've had a lot of problems and I don't want to waste more money on bandaids for a messed up system. Thank you all again for the help as I try to sort this out!
 

Last edited by gadgetnut; 07-21-09 at 04:03 PM. Reason: Copy and paste error
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Old 07-22-09, 07:25 AM
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To restate the obvious: this week I have discovered that 79 gallons of water in the indirect water heater stays hot for nearly 24 hours with the boiler turned off 21 hours of the day. So why was the boiler running so many hours a day to maintain this? Maybe my boiler is currently set up to keep 160° water ready constantly "in case" a demand requires it.
 
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Old 07-22-09, 03:57 PM
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Does your aquastat have ONE dial or THREE ?
 
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Old 07-23-09, 01:22 AM
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Originally Posted by gadgetnut View Post
To restate the obvious: this week I have discovered that 79 gallons of water in the indirect water heater stays hot for nearly 24 hours with the boiler turned off 21 hours of the day. So why was the boiler running so many hours a day to maintain this? Maybe my boiler is currently set up to keep 160° water ready constantly "in case" a demand requires it.
Now you are starting to sound like the System 2000 folks!!!Beer 4U2
 
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Old 07-23-09, 07:46 AM
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The me the water stays hot is not so cut and dry. It depends on piping from the boiler and domestic. It also depends on ambient air temperature around the tank and the tank insulation. Is the domestic water trapped and insulated leaving the tank? I found this to really stop the thermal cycling of the domestic hot water. Piped straight from the tank vertical to the ceiling the hot line was warm up to the highpoint and even some horizontal. Piped as the drawing shows there is no hot water movement away from the tank until there is a demand for DHW.
http://www.comfort-calc.net/Indirect_Piping.html
 
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Old 07-23-09, 08:03 AM
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Originally Posted by NJ Trooper View Post
Does your aquastat have ONE dial or THREE ?
The control is a Tekmar 353 mixing control with a variable speed injection pump. Not sure but I don't think the outdoor air sensor is being utilized.
 
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Old 07-23-09, 12:21 PM
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Originally Posted by Bilbo View Post
Now you are starting to sound like the System 2000 folks!!!Beer 4U2
Yeah, okay, I may have been a bit hysterical when I posted that, but 1.3 gallons of fuel a day, everyday, for 30 gallons of hot water? While I'm busy contemplating my savings for when I get this straightened out, anyone want to sell me some nice, grade A quality swamp land too?
 
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Old 07-23-09, 03:39 PM
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Originally Posted by gadgetnut View Post
The control is a Tekmar 353 mixing control with a variable speed injection pump. Not sure but I don't think the outdoor air sensor is being utilized.
Doesn't answer my question...

I'm asking about the AQUASTAT on the BOILER, the gray box, about 4x6" on the upper right hand corner of the boiler... how many setting dials in that box?
 
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Old 07-23-09, 08:50 PM
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Thank you, this is good news for other visitors

pret personnel en ligne - Pret personnel en ligne et de comparer les meilleurs taux afin de... La demande de prêt personnel en ligne
 
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Old 07-24-09, 08:04 AM
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Originally Posted by NJ Trooper View Post

I'm asking about the AQUASTAT on the BOILER, the gray box, about 4x6" on the upper right hand corner of the boiler... how many setting dials in that box?
 
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Old 07-24-09, 03:24 PM
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Maybe my boiler is currently set up to keep 160° water ready constantly "in case" a demand requires it.
The previous pic shows that NOT to be the case. Your aquastat has a single HIGH LIMIT which only serves to shut the burner off when the boiler reaches the temperature of that dial setting. There is nothing there to indicate that the boiler itself is set up as a 'warm start' system. Whether another control somewhere is doing so is another question...

rbeck asked this:
Is the domestic water trapped and insulated leaving the tank?
I'm gonna expand on that a bit... what he is asking about is how the domestic water heater is plumbed in. If the piping extends straight up to the ceiling, the heated water in the tank can rise up that pipe via 'gravity flow'. Heated water is more buoyant than cool water, so that hot water will flow UP that piping, and be cooled, and fall back into the tank. In effect, a gravity heating system.

Proper water heater installation calls for a 'heat trap' as shown in the graphic at the website he posted. Here's the diagram: having the piping going down and back up again stops that gravity flow, and the heated water stays in the tank.

 
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Old 07-24-09, 03:39 PM
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But to get back to the original question, "Will I harm boiler by cycling it daily?", the answer for a cold start boiler is "no." Run it for a while to do its job, then shut it off.

But remember there are probably some larger issues here that need to be addressed.
 
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Old 07-24-09, 03:43 PM
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Thanks, NJT. I understand the high limit switch serves to shut off the boiler but in this kind of installation, what typically serves to tell the boiler to start? Does the boiler turn on when its circulating loop of water, whether that loop is being sent thru the indirect water heater or the floors, cools off to a certain point?

Thank you for clarifying the domestic hot water heater trap. I will climb up in the attic and determine if my installation has one. I doubt that it does in that mine is a horizontal tank on the floor of a short attic.

On the other hand, the fact that I am getting lots of very hot water 21 hours after the boiler has been turned off by a timer suggests the heat loss can't be too much too fast.

If the boiler is condensing or the heat exchanger is shot, would this explain long run times?

Also still looking for input as to whether I am likely causing more damage to run the boiler for a timer-limited short duration each day during the non-winter months.

Trying to figure out what other control may be telling the boiler to run so much-- might explain a higher than expected oil usage rate during the winter months as well.
 
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Old 07-24-09, 03:45 PM
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Thanks for the input, xiphias, we replied simultaneously... I was hoping I wasn't doing more harm. Instead of setting the timer for 3 hours daily, perhaps I'll shorten that up and see how it goes.
 
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Old 07-25-09, 04:58 AM
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Originally Posted by NJ Trooper View Post

Proper water heater installation calls for a 'heat trap' as shown in the graphic at the website he posted. Here's the diagram: having the piping going down and back up again stops that gravity flow, and the heated water stays in the tank.
]
since it's being discussed here, let me ask:

my pipe goes up a foot, horizontally a foot, then up another foot then horizontally about 6 ft then down to my crawlspace

http://i371.photobucket.com/albums/o...s/IMG_2101.jpg

from the descriptions here people mostly talk about their pipes directly coming out of the tank and up through their floors.

so i was wondering , does the fact that i only have a short vertical negate most of the 'gravity cooling' being discussed here?
 
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Old 07-25-09, 11:08 AM
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what typically serves to tell the boiler to start?
The boiler will start whenever there is a 'contact closure' on the T T terminals in the aquastat. Depending on the system, this closure could come from a single thermostat, an endswitch of a zone valve, or, in your case from another controller (I believe you said there was a tekmar unit there somewhere?). Without being there to analyze the wiring, controls, etc, it's just not possible to give you a definite answer to your question. If you could draw and post an accurate, understandable schematic of the wiring, we _might_ be able to come to a conclusion...

I forgot you said that the indirect was located in the attic... if it is ABOVE all the other hot water plumbing, it's probably acting as it's own 'heat trap'... hot water wants to rise, and if it's already at the highest point in the system, it can't rise any further!

Also, I didn't read back the thread, but if I recall, you said that you have a HW recirc system in place? And also IIRC, I believe it was Bilbo who asked if the HW plumbing was ALL insulated? If not, that's probably a big factor... circulating the HW from the indirect into uninsulated pipes... there's your heat loss right there... maybe.

Lucky asked:
does the fact that i only have a short vertical
I didn't look at the pic, but if the pipe goes back DOWN at least a foot or two, below the top of the indirect, then you shouldn't have a problem, that's going to create a heat trap for you, but what I would do is insulate AT LEAST that portion of the pipe from the indirect to where it enters the crawl.
 
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Old 07-27-09, 08:04 PM
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There are several things that come to mind.
1) system piping, is there a check valve anywhere in the system to prevent migration.
2) is the indirect aquastat screwed up. I have install many different indirect tanks, and had bad stats right out of the box. If the differential is mess up the boiler will fire a lot.
3) is the boiler staying hot when there is not call.

Sounds like you need a tech to spend an hour or two and document the system pipework and electrical connections. An indirect should be way more efficient than a directly fired DHW tank. Heat has to go somewhere, it gets made by the boiler and goes into the indirect.
Find out the flow of the circulator and take some temperature measurements to determine output of the boiler. Compare that with the input to find the efficiency of the boiler. Or at the very least time how long it takes the boiler to raise that 80 gallons say 20 degrees. Since you know the amount of water and delta T and time you can easily determine your output.
There has yet to be a hydronic system that could not be made into a comfortable heating system with spending a fortune that I have seen.
 
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Old 07-28-09, 07:10 AM
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Originally Posted by NJ Trooper View Post

Lucky asked:


I didn't look at the pic, but if the pipe goes back DOWN at least a foot or two, below the top of the indirect, then you shouldn't have a problem, that's going to create a heat trap for you, but what I would do is insulate AT LEAST that portion of the pipe from the indirect to where it enters the crawl.
i'm starting a new thread so as not to clutter up this one
 
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Old 07-28-09, 04:23 PM
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There has yet to be a hydronic system that could not be made into a comfortable heating system with spending a fortune that I have seen.
TO, did you mean to type "withOUT spending a fortune" ?
 
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Old 07-28-09, 05:02 PM
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yep

Originally Posted by NJ Trooper View Post
TO, did you mean to type "withOUT spending a fortune" ?
Yep sure did.
Thanks, sometimes I don't proof read to good :-)
 
  #32  
Old 07-29-09, 07:18 PM
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he he ... ne meither! but not to worry, got yer back.
 
  #33  
Old 08-11-09, 01:36 AM
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This is one of the most important sets that I have in my entire directory proprietaire simulation rachat credit immobilier consommation - demander un rachat de crédit, faites une simulation rachat de credit en ligne.proprietaire simulation rachat credit immobilier consommation
 
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Old 10-20-09, 03:46 PM
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Hello. Following up. I've been limiting the run hours of the boiler for a few months now. I've been very pleased with the hot water. I was going to be away from home for five days so I turned the boiler off. When I came back I saw a small amount of water on the floor and I see a small drip is coming out of the fitting at the bottom of the boiler. Photos below.

The floor is already stained from a long time ago-- and this apparently has happened before. But is my current pattern of heat up/ cool down harming this kind of connection?

This fitting looks so rusted, is it a good idea to try to tighten this nut? Or does it need to be taken apart? Any input would be appreciated. Thanks!


 
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Old 10-20-09, 04:24 PM
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The fitting is a galvanized NPS union. A male copper adapter is threaded from the right, and from the left is the pipe from the boiler. The turquoise deposit indicates that water has been leaking for some time. The leak seems to be where the copper fitting threads into the union. The turquoise color indicates copper corrosion, not steel.

First, what is that big black thing in the background? It appears that it might prevent getting wrenches around the fitting? Check it out.

This is going to take two pipe wrenches. Drain the boiler and then loosen the two parts of the galvanized union from each other. Then tighten the right-hand portion of the union to the copper fitting. YOU MUST NOT ALLOW ANY TORQUE ON THE COPPER FITTING BY ITSELF - IT WILL BREAK. You must use two wrenches torqued in different directions - so that torque is applied only to the connection being loosened. If you don't understand what I'm talking about, or can't beg, borrow, or steal a pair of wrenches, call a plumber.

If tightening the copper adapter doesn't stop the leak, then you'll have to unthread the right-hand union from the copper adapter. (The right-hand wrench must be on the flats of the copper fitting, not on the copper pipe itself.) Then apply teflon tape and pipe dope to the male copper threads, and reconnect, again using two wrenches at all times.

I see nothing wrong with the galvanized union itself. They should last a very long time, maybe forever. You may have trouble getting the union apart, but it does have to come apart. You'll need two pipe wrenches - at least 14"-18" minimum. Use the same size for each of the two wrenches, or you run the risk of torquing the copper pipe.
 
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Old 10-20-09, 06:37 PM
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Thanks for the input Mike. The black thing in the photo is the swing open door to the boiler chamber, see my larger photo on page 1 of this thread. I hope it is not in the way of getting a wrench on there but that door can be moved by opening it if I need to.

I appreciate the very specific directions on tightening this as I haven't tackled something like this before. I've heard of using pipe dope or Teflon tape, but not both. I should use both, how? Pipe dope the threads, then put tape over that? Also, normal Teflon tape / normal pipe dope is okay for this extremely hot temperature?
 
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Old 10-20-09, 06:44 PM
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Looks like a dielectric union.
Keeps dissimilar metals from corroding due to galvanic action.

There can be some plastic sealing washers or rubber in there, if those have eroded you will never seal it.

Have a new one near you before you do anything.
If the plastic or rubber is bad, as soon as you move anything you will be done.
 
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Old 10-20-09, 06:53 PM
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Okay... if I want to purchase another union like this, would you take measurements and photos and bring to a plumbing supply house? Or where do I buy another union like this?

This by the way appears to be the low point drain for the boiler. I can turn off the nearest valves to isolate this section but I'll still be draining quite a bit of water out of this same fitting... any suggestions for reducing the mess? This room does have a floor drain about two feet away but I hate to flood the whole floor.
 
 

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