How Low Does Your Boiler Temp Drop When a Zone Is Calling?

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wilder11354
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Post Sun. Feb. 12, 2012 9:45 am

curious as to what temp your maintaining in Garage? if garage is not used for working on something daily, or other use.. wouldn't a lower temp, steady feed keep the temp in boiler from drastically droping? continous flow, but at a reduced flow rate? just a thought.


chevymatt
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Post Sun. Feb. 12, 2012 12:06 pm

wilder11354 wrote:curious as to what temp your maintaining in Garage? if garage is not used for working on something daily, or other use.. wouldn't a lower temp, steady feed keep the temp in boiler from drastically droping? continous flow, but at a reduced flow rate? just a thought.
The temp in the garage is set at 48*. there is an apartment above the garage without much insulation after it flooded from a wrongly installed circ pump.

How would I slow down the flow rate? Would it burn up the pump?

Phil May
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Post Sun. Feb. 12, 2012 12:15 pm

What temp are you trying to maintain in garage. I try to keep the garage 50-55 degrees and the mixed water going to floor is 80-85 degrees. It still gives a shock to the system when it comes on because all the return water is 55 degrees. The only way to minimise this is to have constant circulation in primary loop. You will still see a drop but it has not caused me any problems. It is just one of the problems with slab heat. Why are you running a water heater in series with your boiler. Unless your boiler wont do the job I would shut it off or bypass it. A bypass loop will help by getting all the water up to temp when there is no call for circulation.

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steamup
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Post Sun. Feb. 12, 2012 1:04 pm

Radiant floor zones, especially those imbedded in concrete need to be hydronically isolated from a standard boiler system. IE-primary secondary with proper mixing control.

Slabs are especially difficult. I had an aquaintance that wanted radiant heat in his garage. It was a well insulated building and only needed 30,000 buth to heat it, so he fired it with a gas fired domestic water heater. In theory it would work. However, he did not want to heat it all of the time. So when he went to turn up the thermostat, the heater would fire for 24 to 30 hours constantly until the mass of the concrete was up to temp. I did some calcuations and this was correct given the mass of the concrete in the garage.

You need a piping arrangement and controls to insure that the slab will not get overheated. Otherwise expansion and cracking problems could occur.
Steamup

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lsayre
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Post Sun. Feb. 12, 2012 1:12 pm

I can see where a radiant slab would send a good load of cold water back to the boiler. My garage has finned tube baseboard heat, so although the garage zone sends a slug of cold water it does not cause nearly the problem that is being described here.
Last edited by lsayre on Mon. Feb. 13, 2012 9:45 am, edited 1 time in total.
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KLook
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Post Sun. Feb. 12, 2012 2:25 pm

I solved ALL my slab problems, (mine was improperly piped), by installing an Injection system. tecmar control. I constantly circulate the water in the slab and only add heat when it needs it. The outside sensor dictates the water temp that is allowed to go into it and I just play with the heat curve to fine tune it. I highly recommend this system, but he controls are pricey. Maybe find used ones on ebay?

Kevin

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Short Bus
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Post Sun. Feb. 12, 2012 2:59 pm

One solution may be to use a heat anticipating thermastat, I have them in my house, they are simple, once you understand the reasoning. I probalby would not have bought them had I known, but I'm glad I have them. This is a relativly inexpensive solution that may be worth trying.
Heat anticipating thermistats turn on when the temperture is below the disired temperature, and they anticipate that the room is warming and shut off. The reason for this is once hot water starts flowing into a slab, radiators or baseboard the heat is in the room and the thermistat anticipates that the room will warm, and understands it may take some time for the heat to get out of the heating system and to the thermistat. I have a four cubic yard slab in my 16X16 main room and the thermistat clicks on maybe three times an hour or more when it's cold. This constant switching never lets the slab get completely cold.
When these thermistats call for heat a tiny heater turns on inside the thermistat, causing it to shut off premature, turning the tiny heater off, and now the thermistat experiances room temperature and turns back on. Mine turns on for as little as 10 minutes and I know the slab isn't making heat that fast, then it will be off for maybe twenty minutes, and on again, and so on, I have an outdoor thermometer in that room and when I set it to record the high and low for the day somtimes they are both 70 F.

Attached are some pictuers of my thermistat, I added a light to indicate on or off. When the thremistat switch is open the light comes on, and when it closes the light goes out, don't worry about that. In the last picture you will see the heat anticipater dial is set at almost maximum anticipation. This thermistat will stay on for hours if I come back form vacation and turn the temperature back to normal.
Attachments
Thermistat 004.JPG
Thermistat 005.JPG
Thermistat 006.JPG
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CoalHeat
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Post Sun. Feb. 12, 2012 3:54 pm

I moved this discussion to the "Controls" heading since it pertains more to controls and plumbing then to a specific brand of boiler.
Heating a circa 1832 farmhouse with a Harman Magnafire Mark I & a 1959 EFM 350 (heating DHW).
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chevymatt
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Post Sun. Feb. 12, 2012 8:14 pm

Thanks Kevin and shortbus for the info. I'll def check into both

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KLook
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Post Sun. Feb. 12, 2012 9:54 pm

This might work?? Need the experts to judge the worthyness. ;)
**Broken Link(s) Removed**Kevin

I should point out that this control wants to regulate the boiler, it is made for oil or gas, I think mine does also but as it is coal I just don't use this feature. The coal has to "Idle" after all. Mine just regulates the injection pump for the slab. If no thermostat is installed, it defaults to 68*. I have had to decrease the heat curve to get temps lower then 68. I think my thermostat is defective below the default point. It will go higher. No matter, I am maintaining 64* easily with a very defective pipe install.

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KLook
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Post Sun. Feb. 12, 2012 10:20 pm

Here are 2 for $100! May need a sensor.
**Broken Link(s) Removed**Kevin

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KLook
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Post Sun. Feb. 12, 2012 10:29 pm


**Broken Link(s) Removed**This goes with the 253, he is selling it separately, :x

Kevin

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McGiever
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Post Sun. Feb. 12, 2012 10:53 pm

365 is injection, varies pump speed...but reqs. specific piping arrangement...manuals available online.
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Rob R.
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Post Mon. Feb. 13, 2012 7:14 am

The whiz-bang Tekmar controls would be an elegant solution, but a strap-on aquastat on the primary loop would be a very simple and inexpensive way to protect the boiler from excessively low temperatures for the rest of the winter. You could wire it to shut down the primary circulator, or just the garage circulator. Just an idea...

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LsFarm
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Post Mon. Feb. 13, 2012 3:41 pm

I have my supply/return to my shop slab as a primary loop, I have a mixing valve that can be turned down to 85" in the secondary loop, which is the floor system.. there is a Taco 007 pump running 24/7 circulating mixed water to the slab, so it stays at roughly 55* depending on how cold it is and how much heat the shop is losing to outdoors..
the primary loop runs constantly, and is therefore also at a steady delta-T.. so there is no shock of 40 gallons of 80* water hitting the boiler, when the slab wants heat.. the slab is sipping heat all the time..

This constant small load on the system also acts like a timer on the boiler,, about every 30 minutes the boiler runs and brings the water up to 160*..

Yes I do have a few pumps running 24/7, but they are .78amp, so about a 100 watt expense..
Probably better than your 'tankless' DHW heater trying to help out the AHS260,,

And YES that tankless is NOT plumbed right,, it should never be in series or in any way be able to 'help' bring up the boiler water temp, only bring up the water temp going to the taps in the sinks and showers/tubs/laundry.

Greg L
Burning Pea/Buckwheat through an antique stoker [semi retired SSboiler],
Running an Axeman-Anderson 260M boiler burning Pea, About 150-250#per day
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