ODR for Non-Condensing

Peter_26

I am looking into adding ODR to my boiler and I like the idea of a one package product like the Taco Outdoor Reset iSeries Mixing Valve to get the job done, but I would like to know of any other products that I might consider. Does anyone have experience with these and are they reliable? Any suggestions and opinions are welcome.

Thanks,
Pete

EdTheHeaterMan

I like to see @hot_rod Bob's opinion on this stuff. He has experience with several systems
I just know that you want something that will maintain a 140° boiler water temperature on a non condensing boiler, in order to keep the ferrous metals of the boiler from cooling the flue gas too much. Flue Gas Condensation is to be avoided on non condensing boilers and the venting systems the vent to.

Peter_26

I should have added that there is a Caleffi ThermoMix on the boiler return so there is no worries of sustained flue gas condensation. I am adding a buffer tank and panel radiators and that's why I'm asking about the ODR.

Thanks Ed

hot_rod

What is the highest temperature you ever need to run the boiler for heating?
The first goal might be to get the heat emitters dialed in to run at the lowest possible SWT on design.

If in fact you need 180F or hotter, maybe ODR being able to run down to 120 or lower you would have some value. Run the tank to 180, pull down to 120 get you a 60° to leverage. If you have to run 150- 160 SWT at design , then not as much range to reset.

Whatever returns to the boiler, that 280 Thermomix will protect it. If return drops below 140F, basically all flow to the system stops and you just recirculate thru the boiler until it catches the load.

The 280 valve slowly opens to keep the boiler return adequate. It is not an on/ off protection device. It "slips the clutch" so to speak.

When a buffer tank enters the pic you have two choices. Maintain that tank at the temperature required for design condition, assume maybe 150- 160.

Or run the tank to 180 or more and pull the load via a mix valve on ODR.

Pros and cons: maintaining a 180 tank gives you more drawdown, less boiler cycles. But getting and keeping it at 180 will cost more $$ energy, and standby loss. With solar, wood, pellet we jam that tank as high as possible to get long clean burns with solid fuel, or use as much solar radiation as we can get.

Maintaining the tank at a temperature from the boiler, based on ODR limits the "use-ability" of the buffer somewhat, it reduces than big delta that is storing for you.

I've tried both logics on my various iterations of buffer tanks over the year. With one exception I always had wood fired boilers and solar thermal, I could get my buffer tank to 200F!

The exception was a single zone low temperature system with a very small load. I just used the buffer as an extension of the boiler, turning a 1.5 gallon boiler into a 7.5 gallon with a 6 gallon buffer tank, fed from a mod con non ODR.

Many of these variations were to prove out a concept Siggy would send me about tanks, ODR, micro zones, separation, etc. Hydronic tinkering as much as anything.

Peter_26

I purchased the panel radiator and oversized them so they can cover the individual room loads at 120° SWT. But since the boiler is a non-con and is still in great shape I have to work with the 140° SWT. I was thinking of changing the sensor cartridge for the ThermoMix to 130°, but didn't know if that would be pushing it. Either temp would meet the load and then some. I was thinking of keeping the delta t across the panels lower since there is no benefit in having a high delta because of the fact that the boiler is a non-con. When the boiler is changed out at some point with a mod-con then work with a higher delta t. Is my thinking not correct on the delta t?

I wanted to make sure I wasn't missing out on savings by not considering ODR, but if it means that I would end up uselessly spending more then there's no point.

hot_rod

Peter_26 said:

I purchased the panel radiator and oversized them so they can cover the individual room loads at 120° SWT. But since the boiler is a non-con and is still in great shape I have to work with the 140° SWT. I was thinking of changing the sensor cartridge for the ThermoMix to 130°, but didn't know if that would be pushing it. Either temp would meet the load and then some. I was thinking of keeping the delta t across the panels lower since there is no benefit in having a high delta because of the fact that the boiler is a non-con. When the boiler is changed out at some point with a mod-con then work with a higher delta t. Is my thinking not correct on the delta t?

I wanted to make sure I wasn't missing out on savings by not considering ODR, but if it means that I would end up uselessly spending more then there's no point.

I actually went down to the 115 temperature sensor on my 280. Remember there is an 18° hysteresis.
So 115 + 18= 133° where the bypass shuts 100%. So a 130 would probably be be safe enough.
They ship with 140° as they are sold mainly to the wood and pellet boiler manufacturers. Creosote formation is a big concern, so they tend to run a bit higher return. Gas and oil seem to run okay with 130 return.

I know what you are facing when looking at more controls or components to save how much $$ in the end.
As for optimizing the boiler efficiencies, the long run times seem to be the best operation mode.
Same thing applies, when does adding a buffer add enough efficiency gain to make it $$ worth it?.

Peter_26

I was thinking about ROI of the mixing valves and other items and it sure doesn't seem worth it sometimes, but the way fuel costs keep rising and most likely will continue to rise, every $ counts. I can't complain as this boiler system has given me no problems up to now and investing in a mod-con to save a few $ is not needed right now. I will work on tightening the envelope more than what I have done up to now, which is definitely money well spent.
The only reason for the buffer was the oversized boiler and wanting to keep it as long as possible. I'm hoping I can also benefit in the future on the buffer investment, if it lasts that long. In the end it always ends up with spending money one way or another.

Thanks for the input hot rod!

hot_rod

Peter_26 said:

I was thinking about ROI of the mixing valves and other items and it sure doesn't seem worth it sometimes, but the way fuel costs keep rising and most likely will continue to rise, every $ counts. I can't complain as this boiler system has given me no problems up to now and investing in a mod-con to save a few $ is not needed right now. I will work on tightening the envelope more than what I have done up to now, which is definitely money well spent.
The only reason for the buffer was the oversized boiler and wanting to keep it as long as possible. I'm hoping I can also benefit in the future on the buffer investment, if it lasts that long. In the end it always ends up with spending money one way or another.

Thanks for the input hot rod!

Save that buffer cost, put it in the kitty for the mod con. The modulation alone makes a mod con viable, even if it doesn't condense 100% of the time. On ODR it will condense most likely in shoulder, low demand seasons.

Peter_26

Too late on the buffer, pulled the trigger on that already!

I honestly don't like that parts on nod-cons are mostly proprietary and not off the shelf like non-condensing boilers are. The parts are harder to come by when newer models are released. I'm just not on board with them yet.

Thanks for the advice anyway.