Hot Water Boiler High/Low temp settings

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Old 09-26-12, 07:51 AM
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Hot Water Boiler High/Low temp settings

I thought I would start a quick thread about boiler temperature adjustments.
As noted in a previous thread, I bought my house with a poorly maintained, hot water boiler.
With a bit of pipe work repairs, programmable t-stats installed, and new bleed screws installed through most of the house, I fired it up last night.

Previously, the boiler had been set to a high temp of 220'F (way too hot).
I had turned the high temp down to the 180'F markings last winter with no luck getting the temp any lower then ~210'F.

Last night after firing up the boiler, checking for leaks, etc, I started playing with the high and low temp settings trying to get it down. I managed to get the high temp down to about 190'F but am not sure how low I should set the low start up temp to.

Because the temp markings on the control pots are not accurate at all, I'm adjusting, wait, adjusting wait.
If I get the high temp to 170-180'F, how low should I set the low start up temp?
I'm hoping I can get the high temp closer to the 170'F end.
 
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Old 09-26-12, 04:23 PM
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Mike, tell us again what controls are installed on the boiler... make and model of boiler, etc...

Some of us are old and forget things easy!
 
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Old 09-26-12, 05:13 PM
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NJ Troupler;
The Controller is a Honeywell Triple Aquastat Type L8124L https://customer.honeywell.com/resou...0s/95-6571.pdf
Was going to get a photo of the internals, but my phone is dead.

The oil burner unit is a Riello 40 Series
Boiler is a Kerr Comet 145 Oil Fired hot water boiler.

I currently have the High and Low temp settings in the aquastat set at ~150'F on each. This kicks the boiler out at about 180'F. Haven't been able to catch when it comes on though. Run time is ~5 minutes when it does turn on to bring it up to temp.
Current water pressure is ~20PSI on the boiler gauge and ~13PSI on the second gauge I just installed on the pipe after the expansion tank, before the tee splitting to the two zones.
 
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Old 09-26-12, 07:08 PM
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The last page of the PDF I linked above (just got to browse through it now), says a minimum of 20'F between the high and low.
Not sure yet what my low is actually set at as the dials are not producing what the markings on them say it is.
Will try to catch the boiler when it fires up again and see what temp it's at.
 
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Old 09-26-12, 08:30 PM
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I currently have the High and Low temp settings in the aquastat set at ~150'F on each. This kicks the boiler out at about 180'F
Good lord man!!!!!. I am sure trooper will be on to set you straight.... If not stand by....

Bad solder joint??????

 
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Old 09-27-12, 06:20 AM
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Good lord man!!!!!. I am sure trooper will be on to set you straight.... If not stand by....

Bad solder joint??????
I suspect the controller is the original from when the boiler was converted over to oil from electric (1970's?), so some of the components have probably gone dry (worn out).
As long as I keep a close eye on things, I should be able to adjust things regardless what the markings on the dials say.

Edit:
Reading through the manual for the aquastat, I'm seeing that there is a submersable bulb that goes into the boiler to obtain the temp of the water. Not sure why I didn't clue in that this thing needs to read temp somehow....
Thinking about it, I would suspect that this temp prob would probably be the higher point of failure then the electronics themselves.

Hopefully I can get a hold of the local boiler guy soon. Need to resolve a new leak (very small one) and do not want to shut down the system too many times. If I can get him in while I'm home, I'll shut down the system, let him do his cleaning while I'll fix the leak and replace the gauge (see other thread).
 

Last edited by Northern Mike; 09-27-12 at 07:19 AM.
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Old 09-27-12, 07:46 AM
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I forgot, does the boiler make hot water also? Coil?
 
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Old 09-27-12, 07:50 AM
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I forgot, does the boiler make hot water also? Coil?
It had, but was shutoff and replaced with an electric hotwater tank by the previous owner.
They had never done anything with their water treatment gear (softener, etc) and the coil kept getting plugged up.
It's still installed, but both the input and exit valves are shut off.
 
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Old 09-27-12, 07:56 AM
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From what I remember reading here is the coil should be left open. Meaning open the in/out valves. Pipes are cut I would assume.

Also since no hot water, then the low should be turned all the way down. I know there is a way to disable the low but cant state here. This would make it a cold start boiler and save you fuel.
 
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Old 09-27-12, 08:12 AM
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Also since no hot water, then the low should be turned all the way down. I know there is a way to disable the low but cant state here. This would make it a cold start boiler and save you fuel.
I was thinking about that on the drive to work this morning (no wife this on the commute, nice quiet time).
From my understanding of that manual for the aquastat (posted earlier in this thread), it looks like I could move my circulation pumps (2 of them, one per zone) and my t-stats to the aquastat and allow the aquastat to control the circulation pumps instead of the relay boxes (which I haven't opened to confirm what is actually in them).
This could potentially remove the relay boxes from the equation (less items to go wrong), and open up the opportunity for this cold start boiler.

Without looking at a thermal graph, I know that heating water at the low end of the spectrum would be much more easier than trying to raise the temp at the higher end.

With a Cold Start boiler, would the boiler shut off when the demand for hot water is gone? If so, this would be by far the most efficient way to run a hot water boiler.
 
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Old 09-27-12, 09:10 AM
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Actually thinking about it, what you want to do is get rid of that aquastat and just put a high limit one in. No call for heat and the boiler will not kick on to maintain temp.

You do not want to modify the current aquastat due to safety concerns from what I remember.

With that said I set my hi this year to 160f. I have a locked in 15 degree swing that I cannot change. So boiler kicks back on at 145f or so on a continual call for heat. I plan on setting the t stat @ 70 f and just leaving it there 24/7.

If the room temp drops and cant maintain 70F I will just crank the aquastat up 10 degrees to 170.

But like I said I am 30ft over radiated according to my heat loss. About 16k btu. Plus I have a 85K boiler and I only need a 30K according to my heatloss calc.
 
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Old 09-27-12, 12:19 PM
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Let me figure out what relay boxes I have before I get too excited.
Figuring out what aquastat to get and from where is going to take some effort once I can wrap my head around what I have and how I can make it work as a cold start.

With my current setup, I have to set my low temp to something proper or the boiler will never fire (t-stats are controlling the circulation pumps through the relay boxes).
 
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Old 10-01-12, 12:10 PM
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lawrosa,
Althought replacing my current aquastat would be ideal, do you think I could use my existing aquastat and set the low as low as she'll go (without modifying the aquastat)?

At a fast glance, the schematic on page 7 of the PDF linked above looks like I should be able to do this.
 
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Old 10-01-12, 12:44 PM
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I dont see the PDF, and I believe 100 f is the lowest you can set it.

So the boiler will kick on to warm up at 90f with no call for heat, and off at 100f.

Set the differential to the lowest setting 10. This way the circ will start running at 100F on a call for heat.
 
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Old 10-01-12, 12:48 PM
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It was in post 3.
Here is the link again for my aquastat
https://customer.honeywell.com/resou...0s/95-6571.pdf
 
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