Is it possible I just cant get enough radiant floor output and will require supplemental heating?

hot_rod

I don’t see boiler reset doing much for you If 150 is your design temperature? If you use a thermostatic return protection valve you need to run 160 as they have an 18-20 hysteresis
Then chose how much technology you want to use for the radiant mix down. A thermostatic mixer is simple, effective. Motorized valve if you want reset on the radiant portion.

TRVs are worth the time and money once you see how well the perform, comfort, energy saving potential also.

For water side longevity, use good water, add some conditioner.

ThatF_inGuyInNY

hot_rod said:

I don’t see boiler reset doing much for you If 150 is your design temperature? If you use a thermostatic return protection valve you need to run 160 as they have an 18-20 hysteresis

This is new to me. I have it currently designed with the caleffi thermoprotec with 140 cartridge. I believe these are marketed to be used to protect conventional boilers and listed with an accuracy of +/-4. Still recommend going with the 160 cartridge?

The Steam Whisperer

IIRC the ESBE thermix was not an on/off thermostat, but a variable flow so a variable bypass would maintain the rated return temperature. It's been 20 years since I used one...so you know how that goes.

The Steam Whisperer

Mad Dog_2 said:

Great Conversation.   Beautiful work Steam Whisperer!  Mad Dog

Thanks, That's was built on my driveway at my old house before I moved back to Chicago.

hot_rod

The long answer depends on a few conditions.The dewpoint of the fuel you are firing, and the CO2 of the exhaust, which depends on how the burner is tuned. The design of the boiler has something to do with it also.

The most common industry suggestions are 130 for NG, 150 for oil. The oil experts here may have an opinion, perhaps the "blended" or bio fuel oils have a different dewpoint?

I know you would not want to run much hotter than you need for design load, but with non con boilers....

So with a 140 cartridge the valve starts to open, allow some flow to the system at that 140 +or-. The valve needs to see 158F +or- to close off the bypass completely, 100% flow to
the system.

Every system behaves differently, the key it to get the boiler warmed up above dewpoint in a period, generally 10 minutes. Some low mass systems get there without any bypass help.

Other than watching your system run, recording the data, I don't have an exact answer. With a lot of number crunching based on the fluid volume, mass of the metals, building load, zoning, etc you could predict to cold run period.

My suggestion would be to try the 140, unless the oil supplier or boiler manufacturer has tighter data.

Paul Pollets

It's so much easier when you have the right control system for the boiler, in this case oil, to provide 3 temperatures...low temp, high temp and Indirect DHW. To my knowledge, only the Viessmann Vitotronic, which comes standard with most of their boilers, does this. And with correct piping and wiring diagrams. I don't want to struggle when designing or installing a system. If the system requires multiple temperatures...so be it. I don't want to spend weeks finding its sweet spot or fine tuning variables. And the design should be evident that supplemental heat is required and how much. After market controls work fine, but are more expensive than getting the boiler that comes with them.

ThatF_inGuyInNY

hot_rod said:

The long answer depends on a few conditions.The dewpoint of the fuel you are firing, and the CO2 of the exhaust, which depends on how the burner is tuned. The design of the boiler has something to do with it also.

The most common industry suggestions are 130 for NG, 150 for oil. The oil experts here may have an opinion, perhaps the "blended" or bio fuel oils have a different dewpoint?

I know you would not want to run much hotter than you need for design load, but with non con boilers....

So with a 140 cartridge the valve starts to open, allow some flow to the system at that 140 +or-. The valve needs to see 158F +or- to close off the bypass completely, 100% flow to
the system.

Every system behaves differently, the key it to get the boiler warmed up above dewpoint in a period, generally 10 minutes. Some low mass systems get there without any bypass help.

Other than watching your system run, recording the data, I don't have an exact answer. With a lot of number crunching based on the fluid volume, mass of the metals, building load, zoning, etc you could predict to cold run period.

My suggestion would be to try the 140, unless the oil supplier or boiler manufacturer has tighter data.

Not that I want to overcomplicate things but it seems like most of the problems could be solved by running the boiler at a fixed temp (say 150lo+30dif), then running all of the SW through an ODR variable speed valve then proportionally mixing down through individual dumb valves for the floors and supplemental/primary rads. Alternatively, skip the variable speed valve and run a 2-pipe buffer tank with ODR control on buffer tank temp. To me this is the only way to get both reset and boiler protection. Boiler supply stays at a high temp where oil boilers like to be and the distribution handles all of the modulating.

Im not really too concerned about efficiency gains though ODR, but I am concerned about comfort. Whats hard for me to understand is if all of this is even worth it for comfort. Maybe running a fixed high temp boiler with some kind of mix on each temp zone would be perfectly fine and im spinning my wheels for diminishing returns.

Oh yea, and I want warm floors. My wife would kill me if I did all this and the floors weren't warm.

ThatF_inGuyInNY

ThatF_inGuyInNY said:

hot_rod said:

The long answer depends on a few conditions.The dewpoint of the fuel you are firing, and the CO2 of the exhaust, which depends on how the burner is tuned. The design of the boiler has something to do with it also.

The most common industry suggestions are 130 for NG, 150 for oil. The oil experts here may have an opinion, perhaps the "blended" or bio fuel oils have a different dewpoint?

I know you would not want to run much hotter than you need for design load, but with non con boilers....

So with a 140 cartridge the valve starts to open, allow some flow to the system at that 140 +or-. The valve needs to see 158F +or- to close off the bypass completely, 100% flow to
the system.

Every system behaves differently, the key it to get the boiler warmed up above dewpoint in a period, generally 10 minutes. Some low mass systems get there without any bypass help.

Other than watching your system run, recording the data, I don't have an exact answer. With a lot of number crunching based on the fluid volume, mass of the metals, building load, zoning, etc you could predict to cold run period.

My suggestion would be to try the 140, unless the oil supplier or boiler manufacturer has tighter data.

Not that I want to overcomplicate things but it seems like most of the problems could be solved by running the boiler at a fixed temp (say 150lo+30dif), then running all of the SWT through an ODR variable speed valve then proportionally mixing down through individual dumb valves for the floors and supplemental/primary rads. Alternatively, skip the variable speed valve and run a 2-pipe buffer tank with ODR control on buffer tank temp. To me this is the only way to get both reset and boiler protection. Boiler supply stays at a high temp where oil boilers like to be and the distribution handles all of the modulating.

Im not really too concerned about efficiency gains though ODR, but I am concerned about comfort. Whats hard for me to understand is if all of this is even worth it for comfort. Maybe running a fixed high temp boiler with some kind of mix on each temp zone would be perfectly fine and im spinning my wheels for diminishing returns.

Oh yea, and I want warm floors. My wife would kill me if I did all this and the floors weren't warm.

Paul Pollets said:

It's so much easier when you have the right control system for the boiler, in this case oil, to provide 3 temperatures...low temp, high temp and Indirect DHW. To my knowledge, only the Viessmann Vitotronic, which comes standard with most of their boilers, does this. And with correct piping and wiring diagrams. I don't want to struggle when designing or installing a system. If the system requires multiple temperatures...so be it. I don't want to spend weeks finding its sweet spot or fine tuning variables. And the design should be evident that supplemental heat is required and how much. After market controls work fine, but are more expensive than getting the boiler that comes with them.

Maybe Im misunderstanding, but all of this wheel spinning always comes back to the fact that oil boilers have a narrow temp range (160-180) that they can operate efficiently and protected and any hope I have of modulating temp needs to be on the distribution side.

KC_Jones

Floors shouldn't feel warm, they should feel neutral.

Maximum comfort comes from a very narrow temperature range. If you run the radiators hot 150-180 all the time you will LOWER the comfort level from what it could be. This is because the system will call for heat, warm the space, then end the call and wait for the temperature to drop before the thermostat calls for heat again, then the cycle repeats. In other words your house is either .5-1 degree above or below set point and relatively little time at the temperature you actually want.

The goal for comfort is to run the system continuously or as close to continuously as possible. Nothing is better at accomplishing this than ODR which adjusts the supply temperature based on the needs of the house and the heat loss. So if everything is just slightly warm all the time you have maximum comfort and you don't have the temperature swings associated with a typical thermostat.

I think you are stuck on ODR being for efficiency and not realizing it's really there to maximize comfort. The efficiency just comes along for the ride.

ThatF_inGuyInNY

KC_Jones said:

Floors shouldn't feel warm, they should feel neutral.

Maximum comfort comes from a very narrow temperature range. If you run the radiators hot 150-180 all the time you will LOWER the comfort level from what it could be. This is because the system will call for heat, warm the space, then end the call and wait for the temperature to drop before the thermostat calls for heat again, then the cycle repeats. In other words your house is either .5-1 degree above or below set point and relatively little time at the temperature you actually want.

The goal for comfort is to run the system continuously or as close to continuously as possible. Nothing is better at accomplishing this than ODR which adjusts the supply temperature based on the needs of the house and the heat loss. So if everything is just slightly warm all the time you have maximum comfort and you don't have the temperature swings associated with a typical thermostat.

I think you are stuck on ODR being for efficiency and not realizing it's really there to maximize comfort. The efficiency just comes along for the ride.

I agree with all of this. The problem I guess I am trying to solve is the best way to implement ODR when the boiler cant modulate and needs to stay around 150+.

From my perspective after all this discussion there are two ways to do this.

1. Use a variable speed injection valve on the secondary loop which feeds downstream manual mixing valves on each of the temp zones which proportionally mix based on the variable valve ODR

2. Run a buffer tank with its own Tstat and an ODR curve with tank temp ranging from something like 100-150. Boiler TT is tied only to buffer tank temp (and an indirect stuck in there somewhere) Again, run manual mixing valves downstream on each temp zone.

hot_rod

Your ODR will be of limited use with that narrow operating range, but it will still help get you to constant circulation and minimize temperature swings at the rads, it that is on the priority list

TRVs come very close and add room by room adjustability, fixed boiler SWT..

If the radiant is a small % of the total load you could pull it off before the 4 way with any of the mixing choices. If it is a micro load it will short cycle the boiler regardless. But at 20% or less
I would not worry as much about boiler protection.

The beauty of a motorized 4 way is you get both functions in one valve, mixing and boiler protection, assume radiators not radiant as shown in this example

It was the go to for many years in the pre mod con day of radiant

ThatF_inGuyInNY

Ok guys, After running some calcs, crunching numbers it looks like a 4 way valve (taco iseries with outdoor reset) is my best path. One temp zone (rads) comes straight off the 4way, two go through manual mixers (basement radiant and 1st floor radiant). Primary/secondary has been scrapped as it doesnt seem to be required here. TRVs on all rads. The ODR curve adjustment and TRVs should allow me to dial in both the upstairs rads and downstairs rads.

Any issue with no circ attached to the boiler control? In this config, all circs run through a 4 way Taco switching relay with priority. I will probably turn off all features on the boiler stat (pre-purge, thermal targeting, economy, etc) and let the ODR modulate. Still not sure if I want to use a two stage for the downstairs Tstat or just jump both zones (floor/rads) in the control and dial in the supplemental heat through the TRV.


Going to finish up my 3D model, create a parts list and probably post one more time for a last minute sanity check.

Thanks for all the help, this was a great conversation

hot_rod

The boiler at fixed temperature, the 4 way modulates on ODR? Sounds workable.

Does that mix valve offer the return temperature protection. It involves a second sensor and the logic inside, I think it does, you need that function.

ThatF_inGuyInNY

hot_rod said:

The boiler at fixed temperature, the 4 way modulates on ODR? Sounds workable.

Does that mix valve offer the return temperature protection. It involves a second sensor and the logic inside, I think it does, you need that function.

it does, either 135 or 120 set through a dip switch. It will lock the boiler return wide open until the temp comes back up.

Conifer745

hot_rod said:

For water side longevity, use good water, add some conditioner.

Conditioned water from a water softener or something beyond that?