# Maxim 255 Temperature difference

#### Cliff DeCarlo

##### New Member
Hey everybody,

This was my first winter with my Maxim 255 outdoor pellet boiler (which replaced two indoor pellet stoves). It has been working great so far, except for really cold days (say below 10 degrees Fahrenheit). My first thought was that the boiler just didn't have enough heating capacity to heat the space. It is currently heating the first floor of my house through my existing furnace ducts (about 1800 square feet). I have a water-air heat exchanger installed in my plenum (rated at 120,000 BTU). The furnace sits outside pretty close to the house and there is about 15 feet of thermopex buried to get into the basement. Within in 3 feet of the where the thermopex enters the basement, I have a thermostatic valve installed with temperature gauges on both the feed and return sides of the 1" pex loop to the furnace.

I have the boiler temp set at the max (190 degrees F). What I have noticed is that the temp on the feed side of the thermostatic valve never gets above 172 deg F, and the return side is usually 130 deg F. I understand the loss of temp on the return side (the heat is being drawn out by the exchanger in the furnace...which is what you want). What I don't understand is how is it possible to lose almost 20 degrees of temp from the boiler to the thermostatic value which is less than 20 feet away (and 15 feet of that is thermopex which is supposed to lose only 1 degree for every 100 feet). When I have the propane burner on and measure the temp of the air coming out of the ducts in the house, it is about 20 degrees higher than when it is using the pellet boiler. I'm thinking that if I could get the temp of the water on the supply side to be what it is at the boiler that would make up the difference. I have replaced the temp guage at the thermostatic valve and taken the temp of the water in the boiler directly to rule out bad guage/temp sensor in the boiler. I'm using a Taco-007 circulator pump through about 120 feet of 1" pex (loop length). After the heating season is done, I'm planning on putting in a temp guage right at the supply side of the heat exchanger as well.

Anybody have any thoughts on why there is such a drastic temperature drop from the furnace to the temp on the supply side of the thermostatic valve?

I was thinking maybe air in the lines causing a low flow rate through the pex? I have not yet installed any air purge valves in the pex loop. Could there be something else going on?

Thanks,

Cliff

#### bob bare

##### Minister of Fire
You should have posted this in the boiler section.Perhaps a mod can move it for you.

#### Cliff DeCarlo

##### New Member
Thanks Bob...I will re-post this message in the boiler section. I wasn't sure which forum to post this...since it is not a wood boiler and not really a pellet stove either! :>