aquastat/Return temp question

[gradwell]

Thanks to all for their insite on this site over the past year. The knowledge gained has made my Econoburn install much much easier. I am a newbie to wood burning let alone the complexities of these units.

Keeping my newbie status in mind, here comes my question. First my layout. My home is new construction about 2900 sq. Ft. In-slab radiant. Additionally I have about 1500 Sq. Ft. In slab radiant out building that the Econoburn is housed. The out building is a little over 200 Ft. from the house. My system is designed with 5 zones calling for 95* water to each of the zones. No storage. I fired up the unit for the first time last week and worked out a couple of the minor kinks. Actually got the fire started and gassifying in under 10 minutes (needless to say I was pretty excited about this since I had never even started a fire before other than a camp fire). Got the kinks worked out, and intended to Fire up today for the winter. Once fired today, I gradually turned on each zone and adjusted the mixing valves for each zone accordingly. Once all zones were set, I noticed that the return temps to the boiler were coming back at 180*. This seems surprising since the water returning in each zone was between 50* and 60*. I do have piping between the supply and return at the boiler. I do not however have a termovar or danfos. Just a ball valve that I thought I could manually adjust. Even with the ball valve completely closed, i still get returns of 180*.

My biggest concern about this is that the pex supply and return are screaming hot. It actually has made the pex very pliable and i have concerns of melting it as i am not sure of the tolerances of pex.

Ok, question time.

1. Being that my system set up only calls for 95* water, is it really necessary for me to run this thing at 180*? Seems I could be more efficient and use less wood if i operate at a lower temp. If this is true, how do i change this setting, and would i also change the fan setting as well?

2. Do i need to install termovar or Danfos? Or will I get away with my manual adjustment?

In lieu of my problem, i let the fire burn out and am back to the drawing board. I already know you guys have the answers for me. Very discouraging however as I thought we were going to actually have it right on the first try. Should have known better, "nothing goes that easy"!

Thanks in advance for your help. With a little luck, i will be firing again tomorrow!

Joe

 

[jebatty]

1. Being that my system set up only calls for 95* water, is it really necessary for me to run this thing at 180*? Seems I could be more efficient and use less wood if i operate at a lower temp. If this is true, how do i change this setting, and would i also change the fan setting as well?

I think your boiler is doing what it is supposed to do, and output water at 180F sounds normal to me. What I believe is happening is that you have low heat load being transferred to your zones due to low demand, and boiler output is being bypassed back to the boiler by your mixing valves. Again, doing what they are supposed to be doing. I'm assuming your radiant zones are functioning properly. Gasifiers are most efficient when they burn "hot," so trying to achieve a burn with lower output may result in unintended adverse consequences. You didn't mention your boiler was going into idle mode, so sufficient heat is being transferred to the zones while still allowing the boiler to coast along at 180F. When heat demand increases in colder weather, you may find that output temp to drop. If heat demand is even less, your boiler may cycle into idle periods.

2. Do i need to install termovar or Danfos? Or will I get away with my manual adjustment?

Maybe not, but .... The Termovar/Danfoss advantage comes on boiler startup with cold water, allowing the boiler to quickly get up to operating temp (150-160F return water minimum), and most importantly comes when water return from system is less than 150F, when they mix hot boiler output water with system return to insure that return to boiler is always 150-160F minimum. This prevent condensation inside the boiler and also maintains heat around the firebox to sustain more efficient burns. Any system that provide this return water protection should be OK. If regardless of heat demand your return water is always 150-160F or greater, then you don't need the Termovar/Danfoss, and your manual adjustment on startup should be fine. If return is less than 150-160F and you don't want to be fiddling with your manual adjustment all the time, then get the Termovar/Danfoss or another control to provide the needed return water protection.