Circulation pump and oil burner


  #1  
Old 10-25-04, 05:54 AM
lapplander
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Circulation pump and oil burner

Hi Everyone,

What is the most efficient way for the circulation pump and oil burner to work together? Shouldn't the circulation pump, turned on by the thermostat, stay on as the oil burner raises and keeps the water at the set temperature?

I noticed recently that the circulation pump turns on, then turns off, then the oil burner turns on, then off, then the circulation pump turns on again.

Isn' that extremely inefficient? I noticed the change after the oil burner contractor came to clean to oil burner.

Thanks for the help.

lapplander
 
  #2  
Old 10-25-04, 08:02 AM
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In a large water volume system with domestic water heated by the boiler, what you describe is what usually happens. You are correct that is it does not add comfort to the house and it is hard on the pump. When I install a conventional boiler on a system like that, I use a bypass loop around the boiler to regulate the water flow through the boiler. It allows some of the cold return water to go around (instead of through) the boiler and temper the water leaving the boiler. ***NOTE: It does NOT take hot water leaving the boiler and put it back into the return as I see it done way too many times*** It also reduces the immediate heating requirement of the boiler and matches it's capacity with the demand. The way the bypass is adjusted is to start with a cold system and close the bypass until the circulator does not cycle. Then the boilers capacity is all going toward heating the house and all radiators warm up evenly. The water temp in the boiler never drops below the temp needed for the domestic hot water and all is well. If this bypass in installed when a boiler is installed, it costs about $25. To do it later is probably $100 or more depending on the piping.

Ken
 
  #3  
Old 10-26-04, 12:55 PM
BostonB
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By-Pass Piping

Kfield,

I noticed in your last posting you mention a by-pass loop. You describe it as a pipe that bypasses the boiler. How do you know which direction the water is traveling in that pipe? Maybe I have over thought this but... water could either be traveling out of the boiler and back into the "intake" manifold (the pipe between the pumps and the intake of the boiler) or water could be traveling around the boiler. What am i missing here?

My boiler has one of these bypass pipes pipes. The pipe runs from a T on the "intake" side, lower left side of the boiler, wich is piped "down stream" of the 3 circulator pumps (pushing water to boiler) the other end is a T on the upper right output of the boiler. It has ball vavle in middle.

How should the valve be set?

B
 
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Old 10-26-04, 01:06 PM
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If your circulator is on the return, the tee for the loop should be between the circulator and the boiler. Water there will only flow one way. The farther open the valve is, the better temperature consistency you will have at all the radiators. The old rule of thumb was to use a pipe one size smaller than the supply or return. I use the same pipe size and put in a full port ball valve. Worst case is if the valve is too far open, it may take longer for the rooms to all heat up on a cold day and the boiler temperature will be at high limit. I doubt you will see that even with the valve full open but start with it, more than half open and see if the reverse aquastat stops the pump with a system full of cold water.

Ken
 
  #5  
Old 10-26-04, 01:32 PM
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If your circulator is on the return, the tee for the loop should be between the circulator and the boiler. Water there will only flow one way. The farther open the valve is, the better temperature consistency you will have at all the radiators. The old rule of thumb was to use a pipe one size smaller than the supply or return. I use the same pipe size and put in a full port ball valve. Worst case is if the valve is too far open, it may take longer for the rooms to all heat up on a cold day and the boiler temperature will be at high limit. I doubt you will see that even with the valve full open but start with it, more than half open and see if the reverse aquastat stops the pump with a system full of cold water.

Ken
 
 

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