- I just finished building and firing up my gasser, and trying to get things balanced out. I built a water jacketed down draft with heat exchange. Using the RU-2001U to control the process and Steibel Eltron 3 speed circulation pump. I am finding that I have to run the pump on low to maintain temperature once set point is reached other wise it cools the water and only pumps about 50 gallons before going into heat cycle again. I also initially had an issue with once it reached set point to start pumping, the water temp would over run and put the fire into stand-by mode, I think that was just an air pocket which I have since resolved by raising the water in the storage tank. I have the temp probe mounted near the top, have considered lowering it but unsure on that one.
Total set up is the gasser water jacket holds about 100 gallons, 500 gallon dairy storage tank to store hot water with about 400 gallons in the tank. I draw to the gasser from the bottom of the horizontal tank and discharge into the center of the tank.
Any thoughts or suggested appreciated.
Dogshark
Just fired up my gasifier
- Thread starter Dogshark
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maple1
Minister of Fire
I do not have a bypass, the pump pushes tank water into the boiler under the 2nd burn chamber and I use the positive pressure to push it out the upper fitting at the top of the heat exchanger.
I had my set point at 150F with a pump launch of 145F until I got the storage tank up to temp. Then I raised the set point to 160F with a pump launch of 155F.
maple1
Minister of Fire
So that means that only cool return water from the tank is entering the boiler?
If your return water entering the boiler is much below 140 for much time at all, you will have issues. Some of which are likely the problems you were mentioning re. having to run the pump really slow to keep boiler temp up. It will also cause increased creosote condensation in the firebox which would likely increase corrosion potential of the firebox.
Most boilers run around a 20° delta T (temp increase between return water in & supply water out). So if return water is constantly low, it would struggle.
Open, as I understand it anyhow.It is unpressurized and I have both returns so that no air enters the system.
Good info and something I needed to know. I will be finishing the room to enclose the storage tank and back half of the boiler itself, so I should be able to stabilize and increase my average temp.Want to target 170 but beginning to think I may have made the water jacket on the large side being right at 100 gallons.
I was also having an issue with the return water temp from the heating loop, slow rate gave great heat transfer in the house but killed the tank temperature. With a 6GPM rate thru the radiators I have about a 40 degree drop, increased it to 12GPM I still get heat but only a 20 degree drop on return water. I have seen some diagrams, that to me make no sense, that have back to back T's (return and feed) to route return water back to the boiler. Unsure how that could work without check valves or temp mixing valves.
Starting to think that there is a balancing act you just have to figure out with each system.
I have a caleffi thermomix valve in my system that works great. It won't let anything under 140 degrees go back to the boiler. I would recommend looking them up. I paid $170 for a 1" valve but as far as return protection goes it was worth it.
maple1
Minister of Fire
Those close Ts are for a primary/secondary type of flow. Main boiler (or I guess also storage) flow goes around a main primary loop, and each load circuit pulls off what it needs via the T's & their own pumps in secondary loops. Don't think we know anything about what you have on the radiating loop, but you might need a thermostatic mixer there too to recirculate some of your return water in with the supply to it. But a 40 degree drop is very significant, at 6gpm that's like 115,000 btu/hr. Very high load - but don't know what you're heating.
I do not have much heating load on it, which is why the temperature drop caught me by surprise. I have a 24x24x8 inch coil in the air handler for the heat pump, a 3"x8"x6' radiator in the root cellar and a small cast iron radiator on the heating loop tied in series. These are controlled using the emergency heat output from the heat pump thermostat, in place of the electric heat strips. Pump rate is set at 12 gpm which gives me a 40 degree increase measured at the air vent (from 68' to 108'). The DHW flows thru the cooling plates/coils in the dairy storage tank, it is tied into the cold water feed line to the electric water heater so is only regulated by rate of use.
To be fair I was only using the temp sensor on the boiler to determine temperatures and temp lose, I will be adding a temp sensor to the tank this weekend to more accurately watch that, also failed to consider as well that the uninsulated portions of the boiler act as a very good heat sink drawing temperature down when not heating. I am discovering just how limited my understanding of thermodynamics is, quite a learning curve.
Any chance of a plumbing schematic? Doesn't have to be fancy - a cellphone picture of a sketch on a dinner napkin is way better than nothing.
If you're having trouble uploading pictures, it might help to post them to an online photo sharing site, then copy the URL of the picture itself.
If you're having trouble uploading pictures, it might help to post them to an online photo sharing site, then copy the URL of the picture itself.
maple1
Minister of Fire
I would say you definitely need return temp protection previously mentioned, for starters.
What all is insulated?
What all is insulated?
First thing I would do is plumb in someboiler water return temp protection. Is there any way to move the dhw exchanger higher in the tank, you want the hottest water in the tank for heating dhw. pics showed up good
Nice! Thanks for the picture. I'll absolutely echo the return protection and exchanger location comments. For exchangers that are drawing heat out, you need them at the top (or perhaps, vertically with cold coming in the bottom end and hot leaving at the top end).
maple1
Minister of Fire
Actually, with how effective the heat exchanger seems to function where it is now via the comments in the 'Zero Dairy' thread, that might be the best place for it. That must be a very kick-butt exchanger.
Certainly seems so, but it depends on *not* having a lot of stratification. In my tank it's pretty common to have bottom temperatures around 100. No matter how good your HX is, you're not getting a hot shower in that situation. Looks like the space heating HX is also in the bottom (if I'm understanding the system). Same comment applies, but even more of an issue for space heating because you need the highest delivery temp possible.
maple1
Minister of Fire
Yes, true - and I guess once boiler protection is in place, stratification should be even more prevalent. At least when charging. Although once my tanks are in the 120 range or so at the bottom, there is a fire going on pretty soon thereafter - then again (again), it takes a while for that 120 water at the bottom to get warmed up again. Lots of situation dependant stuff in this stuff.
I was under the impression though that the HX was only used for DHW? Clarification?
If your pump launch temp is 140 or better you should be able to draw usable media at the top of your storage fairly quickly after pump launch,no?
The pump launch is purely based on boiler temp, so it launches at 165' will run down to 145' and repeat until satified. Thus far have only been firing boiler once in the evening and once in the morning.
The HX is only used for DHW and cannot be moved, as I understand the design of these tanks the HX am using for DHW are moulded around the bottom 1/3 of the inner wall of the tank.
On pipe insulation, the tank and boiler are located in an insulated room I built at one end of the carport. Once they leave there all water lines run through a 4" non vented flexible pipe under a wood deck and thru the crawl space to the root cellar.
I have the water level 8-10" above the draw for the heating loop, temp at the top of the water is normally between 160-170' and I haven't been able to find anything without spending an arm and a leg to check the temp lower in the tank. That being said with a hot tank I get 140' DHW and the electric water heater is set at 130'.
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