Indoor boiler temp

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mmfan36

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Jun 4, 2008
19
north jersey
Hi guys been running a cb maxim with a 50 plate hex run to top of boiler. but my thermostat on my indoor boiler says 160-165.dont know whyis the 50 plate to small or something else not right.my maxim is set for 185 outside.thank kevin
 
A lot going on here and not much information. What is length of run from OWB to hx, what size tubing, what insulation, what size pump and gpm's? What is temp on boiler tubing when it leaves the OWB? What is temp on boiler tubing input to hx? What is temp on system side input to hx? What is temp on hx output to system? What size pump and gpm's on system side?

Very generally, my experience is that a 20 degree drop between boiler input to hx and hx output to system is not unusual, but many variables here, and an hx system can be designed to achieve a better in-out differential if that is desired. It becomes a cost/benefit issue.
 
hi i have a 009 pump on the maxim supply.running 90ft 1" thermopex in to a 5 x 12 50 plate heat exchanger.about 6 feet from hex to oil boiler with a 009 as the wrap around pump for the hex.i have 4 zones all with taco 007 on the return side. maxim set at 185. not sure of temps coming in to the hex.havent found a thermostat to put on the outside of the pipe. my plumber says the hex is undersized.but it seems there is a lot of people using smaller ones than me and don't have a problem.hope someone can help thanks kevin
 
Some thoughts, but those with more expertise will need to say more. On the OWB to hx side, I'm estimating your flow rate is 6-7 gpm's, and on the OB hx side 7-8 gpm's, based on the pump curves of an 009. 1" line also is generally is rated at about 8 gpm's maximum. You can calculate the btu's moving through the hx (estiamte) by: delta-T x gpm x 500. Example for system side of hx: if 140 in, 165 out, then delta-T=25 x 8 x 500 = 100,00 btu's.

Although my setup is different, I am using 009's on both sides of my hx with a 5 x 12 x 30 hx. Pretty typical experience for me with wood boiler input to hx from 175-200, and return to hx from system at 140, the hx supply to system will be about 15-30 higher than the return (155-170), or about a 20-25 average. At system return temp to hx of 155, the hx supply to system will be about 10-25 higher than the return (165-180),

If your OWB is putting out maximum of 185, then it is less than that 90' away at the hx, and if the other side of your hx is 160-165, I think off-hand you are doing close to as good as you can. A rough rule of thumb based on cost/benefit is that your hx output btu's will be about 80-90% of your input btu's. My experience is closer to 80% than 90%.
 
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