How long is too long a loop with baseboard? And getting house 70+ when zero

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Old 12-20-16, 02:47 PM
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How long is too long a loop with baseboard? And getting house 70+ when zero

It went down to zero last night. Even with a Viridian delta t circulator on my Peerless 178,000 btu oil burner, I could not get the first floor of my 2001-built colonial past 70 early this am. I had left the thermostat holding on 74 but it was 69 on the first floor. I shut off the basement zone and still after an hour I did not see even one degree rise. I upped the aquastat so now instead of 180 degrees, it is at 195 degrees just to experiment. At 7 am this morning, I finally saw the first floor go up a few degrees.

Conclusions: it is not the pump as that is new and pumping away higher or lower based on how many zones are open (there are five including indirect hot water) at once. It appears to be the first floor loop which I calculate start to finish @ 150 feet from feed to return for that zone. It goes along the outside back wall then cuts in and goes into a connecting 10x15 structure that leads from the kitchen to the garage, then travels back the other side of the house along the front wall. In that 150 feet of travel, half of it is baseboard or about 75-80 feet of baseboard. So I have to think that loop is just too long for 3/4 pipe. Thoughts on that? The second floor is not much shorter if at all and has about 65 feet of baseboard. The master bedroom has about 40 ft of baseboard including the master bathroom.

So it appears that around zero or lower, the house is going to be comfortable but stay at 70. It does not matter much as we have a wood stove but I am curious what you all say about why I can't get the first floor past 70 when it is zero or colder out. I did say I can a few degrees with the water set at 195 but that seems high. Suggestions, thoughts, etc. are appreciated. The boiler is on one side of the house, maintained, and is 17 years old. I now the efficiency is 85% or about 155,000 btu. I guess it is doing fine. The basement zone is 30 feet of baseboard and because it is on the same level as the boiler, it gets hot fast and stays hot fast. Since I could not budge the first floor this morning even with the basement zone off, I have to think besides topping out the capacity of the boiler at zero outside, the loops are too long and water is cooling off half way and coming back to the boiler. Pump capacity means little but water temp of the boiler does. But nobody is going to up to 200 or above on the aquastat, right? That is just too hot or am I wrong when it comes to such very cold weather?
 
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Old 12-20-16, 03:30 PM
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do you just have a single delta t circulator?
It seems like if the other zones are keeping warm okay, then maybe you need a separate circulator for that zone, or a proportioning valve so that when multiple zones are open, that extra long run still gets good flow... with multiple zones open, the hot water will take the easiest path, which is the shortest without proportioning valves, and then hot water will come back to the pump, causing it to reduce flow even further.

200+ is very hot for baseboard... 180 seems to be the norm.
 
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Old 12-20-16, 04:16 PM
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Typical baseboard is about 500 btu/hr/ft. So 75 feet is 37500 btu/hr. Max for 3/4 is about 40,000 BTU/hr, so you are right at the limit.

I suspect vilord is right, you are probably not getting full flow through the long run.
 
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Old 12-20-16, 05:05 PM
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was the boiler cycling on and off when trying to heat that zone?
If so not enough baseboard.

If boiler was on and never shut off then zone was/is somewhat sized properly for heat loss. And maintain around a 70F temp in that zone/room/floor..

Its 63 ft baseboard is usually make... This is actual finned tube and not the covers...

Also dust and furniture on the baseboard or in front restricts the airflow for the baseboards to work properly.Bent fins too..

550 per ft x 75 is about 41k btu which denotes a 1650 square ft room...

These #'s of 550 btu per ft are based on 4 gpm flow rates..
 
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Old 12-20-16, 07:11 PM
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Another possibility is you are getting a lot of heat loss via the bare pipe. If it is not insulated & you can get to it, I suggest insulation. Can you measure the temperature drop on that loop?
 
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Old 12-21-16, 10:03 AM
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$10 Lottery Ticket

Since no one else has suggest it try Hercules Boiler Cleaner. First time I used it on a modern copper tube system made a significant difference. For $10 is worth a try.

http://www.homedepot.com/p/1-qt-Boil...5206/100207068

PS: 180F is max water temp to avoid scaling.
 
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Old 12-30-16, 07:35 AM
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I have the boiler pipes wrapped inside the heater room. I have a chase along the middle of the basement ceiling and I can wrap those and that is a great idea. I had only wrapped the cold water pipe to cut down on sweating. Before I put a zone in the basement, I guess I thought the 40 run on pipe left unwrapped would give the basement some heat (silly me). I just purchased an infrared temp reader. Here is what I see for the first floor loop: 180 coming out of the boiler and at the air scoop but at the first floor pipe under the Honeywell zone valve (open of course and with thermostat set at 76 for a few minutes to get some readings) I only read 130 degrees. So I am at a loss about how the water can be so hot at the air scoop and a foot away be so much cooler. On the return side, I am getting 100 degrees. So the first thing is the water going into the first floor zone is so low. No other zones were open because I checked. Boiler water temp was at 180 degrees. I did use the device to measure milk in the fridge (35 degrees) and frozen food in freezer (0 degrees) but I can't say this is calibration. So why would I get so much apparent heat loss within a foot from the air scoop and expansion tank that measure 180? How could it drop 50 degrees when it goes into that first floor zone?
 
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Old 12-30-16, 07:41 AM
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The first floor is 1,200 sq feet. There is a sofa in front of half of the installed baseboard but I have it about 12 inches from the baseboard. That is a good idea to blow it out. Fins look straight. As for the boiler, we have a family room in the basement so we hear the boiler. As I see it, the boiler is on, circulating, but not "on" as in firing and heating the water (hearing air purge, then ignition of fuel and sound of boiler heating the water). What I see and hear is the boiler seems to rarely come on and off but it does circulate. It rarely comes on for longer times or frequently on and off in terms of hearing it heating the water unless it gets around zero or below...then it does come on and on more often.
 
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Old 12-30-16, 07:44 AM
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"...not getting full flow" <--would this be the pump? I changed it to a Viridian and set it to delta T and just to experiment when it was zero out recently, to speed 3. That should be a lot of umph in terms of circulation and yes, I took it back down to delta t after 30 minutes. What I did notice was after I put the aquastat up to 195 degrees, I did see some movement past 70 degrees to about 74. I put the aquastat back to 180 after that test.
 
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Old 12-30-16, 07:49 AM
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Yes it is a delta t. The zones are fine for heat calls when it is 15 degrees out. Get down to zero or cooler and the second and first floor zones, and the master bedroom zone, are not getting past 70. The basement zone is another story. That gets as hot as one would want it and within 5 minutes or so can move a degree or two up. Even if I shut off the basement zone, the other zones at zero outside just read 70 and no more. While it is not an issue because of a wood stove, when the in-laws come, and they sleep over, they like it warmer in the bedrooms and I can't make it warmer. Just shooting from the hip, I think I have about 164 feet of baseboard and the entire loops, estimated, are 175 feet second floor, 150 ft first floor, and 50 feet basement and of course the runs are long with the boiler on one side of the house, and the heat having to reach about 60 feet to get to the other side of the house then loop back the same distance plus go up a floor or two.
 

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Old 12-30-16, 07:53 AM
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Thanks. I will take a look at this.
 
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Old 12-30-16, 07:55 AM
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I don't trust IR thermometers. The reflectivity of the surface being measured can have a significant effect on the accuracy of the readings. You should certainly be able to tell the difference in 130 & 180 with your hand. At 180, it's going to be touch & ouch right now. At 130 it will take a couple of seconds between touch & ouch.

You can get foam pipe insulation at any home center. Quick & easy to install and works well.
 
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Old 12-31-16, 02:13 PM
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If the water temperatures are what you stated, I have to believe either the zone valve is not opening all the way or something is not telling the burner to fire. Pictures of the boiler & nearby piping would be a big help.
 
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Old 01-02-17, 07:48 PM
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I will post pics tomorrow but today I bled air out

Today I bled air out of the first floor loop. There was some but the temp got up to 78 on the first floor. So I thought I had all the air out but I'll see more tomorrow. I see I know very little about anything when it comes to boilers. Thank goodness for everyone's interest in helping. Thank you all.
 
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Old 01-18-17, 01:43 PM
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Well now. I checked the nozzle and it is at 1.25 80 degrees, The system is rated for a 1.5 nozzle as per the plate on the boiler (178,000 btu). So I changed the nozzle and I got much more heat out of the system and return temp is higher by ten degrees and baseboard is heating up past 70. So it seems the mystery has been solved Thanks everyone for your help and suggestions.
 
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Old 01-18-17, 04:05 PM
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If you changed the nozzle size, I strongly urge you to call a professional service person to test the combustion with instruments. Failure to do so could cause major problems including gross carbon monoxide production.
 
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Old 01-19-17, 09:05 AM
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Double check your Peerless ratings. On older boilers the GPH rating is often incorrect for newer burners.

My 60 year old Weil McLain label reads 1.80 GPH, but the label 970 sq/ft rating works out to 145,000 BTU. At 80% efficiency the nozzle would be 1.16 gph max. Am firing at .80 GPH.

If you over fire boiler you will get more BTU's, but the stack temp goes up and efficiency goes down.
 
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Old 01-29-17, 04:39 PM
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more issues here. No one commented on a 1200 sq ft house and 155k boiler even if under fired. A 60-80k boiler should do this.
 
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Old 01-30-17, 10:20 AM
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the house is not 1200 sq ft. Zone 1 is 1200 sq ft, and the house is quite a bit bigger than that.

@Dkodgis: Glad you got your problem sorted.

Agreed with Grady, if you just increase the nozzle size without tuning and increasing the airflow to match, it will likely be burning very dirty... potentially generating lots of CO, but also lots of soot which would just clog up your heat exchanger and flush your efficiency down the drain.

Also, as doughess mentions, the GPH ratings don't usually match the nozzles... My girlfriend's Burnham has a 1.6GPH rating, at 140psi, so it comes stock with a 1.3 nozzle. The 1.3 relates to 100psi of pressure, which was maybe the standard in the 1950's, but hardly any boilers still run the burner at 100psi.
 
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