Help!! My tenants are sweating


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Old 12-04-09, 06:14 PM
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Question Help!! My tenants are sweating

I own a 4-plex and my Crane 100 series HW boiler feeds the units. The boiler is on the bottom floor of the split level, same level as the bottom 2 suites & 8 feet high run to the floor of the top two suites. Each unit is about 1100 sq. ft so it is a good horizontal run. With outside temps hitting lows of -20C, what would be a good range to keep the aquastat? I had it at 165-180 F and my plumber did a mistake by adjusting the lo cut off at 200f and the hi at 180f when I asked him to do a check of the boiler & controls(He is a good plumber, he goofed). I reset it to 170-190F because of the blizzard we are currently having as I write this. Can I get away with 155-175F or could I be causing problems I am not aware of? Zone valves not closing? They are sweating bigtime or put it back to 165-180F and go have a beer. Please help so I can set it and forget it and everyone is happy.
 
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Old 12-04-09, 06:43 PM
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Does each apartment have its own thermostat? And is on its own zone? Why aren't the zone valves closing?

Trying to control room temperature by just adjusting the boiler temperature is a losing battle I fear. Is this a new problem?
 
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Old 12-04-09, 07:45 PM
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My plumber phoned after feeding cows and he said the boiler & all parts were looking good. He did not touch the aquastat but he did say that 170-190F is a good range to be at. He tested all 4 zone valves and they worked fine but he recommended changing the thermostats in each room, they cannot be totally accurate as they could very well be as old as the 4 plex.
 
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Old 12-04-09, 07:53 PM
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The thermostats are what regulate the temperature in the room, not the temperature of the water. New digital thermostats will be more accurate and be less frustrating to set comfortably.

To figure out what temperature water you need you should have a heat loss done on the building. You can save quite a bit of money if you don't need to heat the water up to 180F.
 
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Old 12-05-09, 02:03 AM
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Have a beer in any case! Beer 4U2

I sure wouldn't set the high limit any higher than needed to heat the building, but not low enough that there might be condensation issues.

I have to echo Mike's question... aren't the zone valves closing? Or, is it zoned with separate pumps? Are there flow check valves on each zone? are they set properly? If you've got a flow check that is open for gravity flow, it could explain the overheating.

How could they be sweating if everything is in order?
 
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Old 12-07-09, 07:33 AM
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Each suite has their own zone valve controlling heat. My plumbler manually checked each zone valve and he told me that he did not see any problems with the valves. The only thing that he though could be a concern is the condition of the thermostats in the suites. Some could be old and their calibration could be off, he recommended taking a temperature reading of the suites, comparing them to the setting of the thermostat and replace them. The temperature at the moment is -30C with daytime highs of -21C, I don't think that I am going to get any complaints with the temperature being so tropical as they are now.
 
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Old 12-07-09, 07:52 AM
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Condensation, yes a plumber friend told me about this in passing and I mean fast. How low do you set your low cutoff temperature or conditions before you experience it?
 
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Old 12-07-09, 03:02 PM
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Use this as an opertunity to set the top (or close) of the theoritical heating curve.
Lower it down until the the tenants start closing windows.
Then you will have it about right.
 
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Old 12-07-09, 03:58 PM
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It seems unlikely that all the apartments' thermostats have gone haywire at once.

What's called for here is systematic troubleshooting with a voltmeter.

Is the thermostat calling for heat - if not, continue.

Is the corresponding zone valve got 24V on it?

etc., etc. It's all a matter of logic, not jumping to conclusions or trial and error.

Somebody has figure it out - not just a plumber with his hands on his hips, saying everything looks OK to him.
 
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Old 12-07-09, 04:53 PM
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Originally Posted by skeenabilly View Post
Condensation, yes a plumber friend told me about this in passing and I mean fast. How low do you set your low cutoff temperature or conditions before you experience it?
Think of "Dew Point". Just as when warm humid air meets a cooler object, and the water in the air condenses onto that object, so does the water vapor in the flue gases. It's just that the 'dew point' is much higher... generally agreed to be around 135F for gas fired, and around 120F for oil fired.

So, if you've got fireside surfaces inside the boiler that are cooler than these temperatures, the water vapor in those flue gases will condense on those surfaces. The water itself wouldn't be a problem, it's the ACIDS that form from the other compounds that do the dirty work.
 
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Old 12-07-09, 07:52 PM
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Thanks again!!

Thanks everyone for your comments, funny all I wanted was to see if my LWCO could be tested(it worked fine). Yes, I'll get my friend who is a master electrician to do some digging around and get a conclusion to this thermostat thing and thanks Trooper for the answer what temperaure condensation will begin to form. Technically I could set my aquastat at the 155-175F, eh? or with these cold Canadian winters, don't chance it?

Skeena
 
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Old 12-08-09, 02:41 PM
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Set the high limit to the lowest temp that will properly heat the place, within the limits of the condensation issue. I don't think you'll get by with 150, but 160 maybe... most systems are designed around 180 water, but you could theoretically get by with less, and save a few bucks on fuel. Remember it's the RETURN water that you have to watch the temp of... when that return water comes back cool enough to keep the fireside surfaces below the dewpoint, that's when the problems start.
 
 

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