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[Sluggo]

Calling all mathematicians here!  Here's my problem:  About a month ago I replaced my heatmasterss 10,000 e with a 20,000.  Reason for the upgrade was the addition of a new 2800sq ft shed with 16' high ceilings.  The shed is located 200' away from my woodstove and roughly 15' lower in elevation.  I am running 1" thermopex to the shed.  I had the woodstove (800,000 btu) hooked up to just the house for the first couple of weeks.  It was relatively warm and all was good.  As soon as we put the shed online the stove started steaming a great deal but only when the fan was running.  On 170 off 180.  I currently have a taco 2400-20-owb pump located in my shed circulating the stove water.  When the shed calls for heat a grundfos does the work circulating thru the floors.  Main question is the taco pump grossly undersized and not mixing the water in my stove properly?  I have a feeling I have 220 degree water on top of my stove,180 in the middle where the aqua stat is reading,and maybe 140 on the bottom.  Thanks in advance.

[slimjim]

 Definitely sounds like a flow issue inside the boiler, Please check that you are supplying on the right lines.

[Sluggo]

Supply and returns are correct.  We even flipped the taco today to see if that changed anything but it didnt

[RSI]

Is the house still connected? If it is and adding the shed made it start steaming, I don't see how it is a low flow problem. You do have separate pumps for the house and shed?

[free heat]

Yes he does have seperate pumps for both house and shed. I was over to his house last night to check it out. I am so puzzled on what possibly is going on. I think either faulty aquastat, or not enough pump to his shop. No way a stove should steam at 170-180 range. It steams even worse when the fans kick on to force feed the fire. This stove is gonna be unbelievable when he gets this issue worked out. I pretty sure this stove could easily heat 4 homes. It's just such a mystery what is going on with the steam coming out the fill tube. We even dropped the stove to 160-170 and it still started to steam around the 166 degree range. Would air in the lines to the shop cause this? From what I saw and heard last night it doesn't appear to have any air in the lines but I could be wrong. Any advise would be great we are open ears thanks everybody.

[RSI]

There should be more circulation, not less once the loop was turned on. Are there separate ports for each loop is there a tee on inlet and outlet?

[RSI]

How is the plumbing setup in the shed? Does it just make a loop and come back? How is the floor heat tied in?

[slimjim]

OK, something has changed, perhaps the 2 lines are fighting each other for flow inside the boiler? Have you checked the actual temp of the boiler water, perhaps a bad or poorly installed/insulated sensor on the Aqua-Stat, can you check the temps at top and bottom of the unit with the circs off against what the factory Aqua-Stat is showing?

[Sluggo]

There are seperately supply and returns for the shed and house.  I really have no way of measuring the temps anywhere.  Wherever the aqua stat is located (I'm guessing the same height as the supply) it is reading the same as my maverick so I don't believe it's faulty.  For whatever reason the water in the stove just can't be getting mixed hardly at all.  I'm just a concrete guy so please tell me once this circulation issue is figured out my efficiency will increase dramatically!  Even this morning the stove was running low on wood and temps were at 145 but it was still steaming when the fan was running.  Primary loop in the shed goes about 7 feet to a heat exchanger for dhw and then returns to the stove.  If the shed is calling for heat a Grundfos pulls off the main loop until its satisfied.

[slimjim]

I just thought of something else, we at one time had an issue with boiling water at low temps on a few of our units, after looking closely we found that the vent tubes were not cut to allow the air to escape up the tube and it made an air pocket at the top of the tank, I'm not sure how Heatmaster does their vent tube but on ours there was a cut in the vent tube just below the water tank, somebody at the factory forgot to make that cut so the air could not escape resulting in overheating at low temps.

[LittleJohn]

...the shed is located 200' away from my woodstove and roughly 15' lower in elevation.  I am running 1" thermopex to the shed. 

I am not sure what the expected head pressure is in your ThermoPex, but a 400' loop [200' to and from shop], seems like it might cause a bit an on issue. 

Have you thought about having pumps between structure(s) and OWB run all the time, so see if that helps with the boiling issue??
**I personally do not do this, but it may help to keep the water in the boiler moving and reduce any stagnation.

[Sluggo]

That is what we are going to try now.  A pump between the left hand supply and a right side return. 

[Sluggo]

Well knock on wood (preferably oak or black locust) all is good in western Wisconsin!  Put a pump between an available supply and return on the stove to help circulate the water yesterday afternoon and we have no more steam!  It's only been a day but it was doing it every burn cycle before and this far no more steam!

[slimjim]

Well done