outdoor reset

I would leave the boiler set point unchanged and do your outdoor reset to vary the temp of the water being delivered to the heating system instead. Ideally, you could do this on the other side of the thermal storage. In other words, mix supply and return to get the desired temp to your zones based on outdoor temp, but leave your boiler set at 180+. A wood boiler is not like a condensing gas boiler where lower BOILER temps increase efficiency - in fact, the opposite is true.

I'm not sure I see an advantage to that - wouldn't overall fuel/energy use be relatively the same?

If you didn't outdoor reset, wouldn't the effect be that when it was warmer out, it would just heat the interior to the desired temperature quicker?

one of the advantages of sending the minimum required temperature water to the distribution is that you minimize overshooting the thermostat settings. When you over heat a room because the floor or rads continue to emit heat even though the circ pumps have shut off, you are putting more heat into the room than is needed (obviously). Higher temp water sitting in the floor tubing or rads will emit more of this extra energy than lower temp water so you "waste" less fuel/energy. One big advantage of outdoor reset is that this reduced overshoot makes for a more even/consistent room temp which is more comfortable than a room that experiences wider temperature swings. To be clear, the fuel saving advantage of outdoor reset for a wood boiler is not nearly as much as it is for a gas boiler where it might make the difference between the boiler operating in a condensing mode (high -efficiency) and non-condensing (mid-efficiency). But when the comfort factor is added, I think it is something worth considering.

also wanted to mention that in wood thing's system, outdoor reset would allow his thermal storage to last longer and stratify better.

If the heat demand is met the themostat will shut off the pump to that zone,so how would you be wasting energy? When the boiler gets close to max temp along with storage the fan will slow down slowing down the burn to save wood.

I can set my max temp on my boiler at any temp i want up to 194. I can set my fan speeds also from -3 to +3 aslo my smoke gas temps.

I have rad panels and a lot of uninsulated pex in my crawl space. The way my systym is plumed the water flowes threw the pex
if the rads are calling for heat or not.
On warmer days like 45 -50 degrees I can overshoot my set temp due to transmision
losses so I have to turn my circulator off for a while. If I had an outdoor reset that would minimize this problem And save a
little wood. I plan on insulating the pex and if that don't help I will probably install a outdoor reset in the future.

sounds like there are two separate issues being talked about, sounds like most of you have boiler without storage. Tarm guy is talking about storage systems and this is were a boiler reset control is useful. As outside temps get warmer the "heated" water going to warm a space can be cooler to get the same result there fore stretching your useful storage BTU's. I have storage, currently it is 31* out when there is a call for heat in the house my re-set control will maintain 140* water going to my baseboard, when it gets colder that temp will increase up to 180*. This is what a boiler reset does. This is where I believe storage systems have the advantage over non-storage systems (shoulder season). Those of you without storage are looking for a system to keep your boilers cooler when there is little demand for heat in your house and a boiler reset won't help this. Your best bet is to have some sort of dump zone you don't mind wasting heat too our (cringe) shut down the boiler and pay the oil man (and I know we all hate that thought!).

Good luck managing your BTU's, we work way to hard to get the fuel we need to generate them and I hate like hell to see them go to waste.

Merry Christmas to all (and it is going to be a white one here in northern NH!)

Resets work well on fossil fuel.Wood is an other issue.It takes x amount of btus to heat a space if you are only putting in 140 degree water it is going to take longer to satisfy that demand than useing 180 degree water.Why would you want to take hot water and cool it down? My boiler will ramp down my fan as my tank reaches it preset temp saving wood. The cooler the water the longer the pump has to run to satisfy the zone.

You have come to the wrong conclusion henfruit. I didn't get into the details of my set up, I am running a primary/secondary setup. When a T-stat call for heat the re-set control (Tekmar 260) looks at the outside temp to determine a target temp based on a heating curve. Then it fires up the storage circ and the primary loop circ. When the primary loop reaches the Target temp it turns off the storage circ and recirculates the water in the system until it gets below the Dif set-point then the storage circ come on again. When I first put in this system I was running standard baseboard and it didn't work well, in fact eventually I did away with the re-set feature because as storage got cooler the circ did run longer. I upgraded my baseboard that was designed for 140* water and my storage last's longer and the house is warmer. I am very happy with the re-set feature now.

You never said you had low temp base board. we need to compare apples to apples.Like radiant we use a mixing valve to control the temp of the water we need to heat an area.

I bought a Tekmar boiler control to handle this exact issue.... I am using it a bit off the chart, but with wood boilers that's what you have to do....... Basically I wanted a way to turn an Alpha pump off or on based on outdoor temp. Because wood boilers aren't generally, or practically, controlled and I want to burn flat out to charge storage anyway, I decided to control my secondary panel radiator loop--the main heating for the house--like it was a boiler in itself.

I called Tekmar and verified that their controller would work in my situation. It was a bit difficult to get the technician to understand wood gasification boilers and storage WITHOUT any other source of back-up fossil fuel heat, but in the end we got there.

I'm going to be setting my Tekmar up to turn the pump on/off around 60º outdoor temp. This will help greatly in the shoulder seasons as we can have huge temp swings with warm, open-the-windows days and below freezing nights. Then, once the weather warms up for good, it will keep the pump off and when it cools down, it will kick it on. I don't have to think about it!! It might also help on those summer nights when we can occasionally dip into the 50's. I'm not quite sure how I am going to use the boiler probe feature. Ideally I wanted a set up which would monitor indoor temp as well, so that if the weather is above 60 outside, but for some reason it is only 60 in the house, and we aren't around to open windows, that the pump would keep on until an indoor set point was reached. I can't find that controller. I am thinking, however, of using the boiler probe to read the supply temp to the radiator panel zone, either from the tank, or after mix-down. I haven't figured out from the manual yet if I can use either of these temps to turn the pump (read "boiler") off if the temp drops lower than 110 in the tank--no point circulating below temp water......when I fire the boiler and the temp kicks back above 130, it could kick the pump back on.......

HeatFarmer

I use 2 Tekmar 150's to do something along those lines. I use them to decide weather to use Storage or my backup Propane boiler to provide heat into my primary loop. Both 150 measure the temp of the water leaving storage, the Tekmar that control's the storage CIRC is set for 140* and is in COOL mode, the 150 that controls the Propane is set for 138 and HEAT mode. When there is a call for heat both 150's are energized if storage is above 140* the storage CIRC keeps pumping trying to cool the storage (or until call for heat is met). If storage gets below 140 the CIR kick's off because it's job is done, if the house still calls for heat then when the STORAGE temp at the 1 1/4" supply line leaving storage reaches 138 the propane kick's on and runs until the call for heat is met.

Like you said, using control's outside of the box.

timberr said:

HeatFarmer

I use 2 Tekmar 150's to do something along those lines. I use them to decide weather to use Storage or my backup Propane boiler to provide heat into my primary loop. Both 150 measure the temp of the water leaving storage, the Tekmar that control's the storage CIRC is set for 140* and is in COOL mode, the 150 that controls the Propane is set for 138 and HEAT mode. When there is a call for heat both 150's are energized if storage is above 140* the storage CIRC keeps pumping trying to cool the storage (or until call for heat is met). If storage gets below 140 the CIR kick's off because it's job is done, if the house still calls for heat then when the STORAGE temp at the 1 1/4" supply line leaving storage reaches 138 the propane kick's on and runs until the call for heat is met.

Like you said, using control's outside of the box.

Click to expand...

Timberr,

Thanks for the ideas....I might modify my setup down the road towards this end.

sorry wood thing, didn't mean to confuse things. As I said in my original post I think the only way to deal with you problem is to not burn or create a dump zone to keep your boiler cooler. Re-setting your blower fan to a lower temp won't prevent a temp climb in your boiler if you have smoldering wood in the burn chamber, the temp will continue to climb, it may give you some more time.

Good luck I hope you find a suitable solution to your problem.