Outdoor Reset for Peerless Cast Iron Boiler

PilotPat24

Hey Guys,

Does it make sense to add an Outdoor Reset to a 25 year old Peerless WBV Oil Fired Boiler?  Any recommendations or input would be greatly appreciated.

Thanks,

Pat

SuperTech

I added outdoor reset to my Peerless WBV-03. I already had the L7224U aquastat, so I added the outdoor reset module and sensor.  You have to be careful when setting up the reset curve, you have to make sure that the return water is hot enough to avoid condensation and also make sure the stack temperature is high enough as well.  You don't want short cycles.  

PilotPat24

SuperTech said:

I added outdoor reset to my Peerless WBV-03. I already had the L7224U aquastat, so I added the outdoor reset module and sensor.  You have to be careful when setting up the reset curve, you have to make sure that the return water is hot enough to avoid condensation and also make sure the stack temperature is high enough as well.  You don't want short cycles.  

Thanks for the information. What temperature do you want to be at minimum on the return? 140F? What temperature do you want the stack temperature to be? Pat

STEVEusaPA

How many zones? Domestic hot water? What type of emitters.
I think it's going to be short cycle city without a buffer tank, or even better yet, a reverse indirect.
A 3 way (or 4 way) mixing valve should be installed to protect the boiler from lower temp return temperatures.
Depending on your location and winters, if you put a 140° minimum in the control, you'll probably be targeting that temperature most of the winter, so it will short cycle without a buffer/reverse indirect.

@SuperTech how did you make it with your set up? What's it look like when you open it up for cleaning?

PilotPat24

STEVEusaPA said:

How many zones? Domestic hot water? What type of emitters. I think it's going to be short cycle city without a buffer tank, or even better yet, a reverse indirect. A 3 way (or 4 way) mixing valve should be installed to protect the boiler from lower temp return temperatures. Depending on your location and winters, if you put a 140° minimum in the control, you'll probably be targeting that temperature most of the winter, so it will short cycle without a buffer/reverse indirect. @SuperTech how did you make it with your set up? What's it look like when you open it up for cleaning?

Hi Steve,

The boiler only provides heat.  2000 sq ft house

Slant Fin Emitters

I am on Long Island, NY

I'll take a picture of my current setup the next time I am at the house.

Pat

captainco

The important part of boiler reset is to bring the pump on and allow the water to circulate before the burner comers on. If this is done the return water can be as low as 110 degrees. Using at least a 20 degree differential should be the minimum.

PilotPat24

captainco said:

The important part of boiler reset is to bring the pump on and allow the water to circulate before the burner comers on. If this is done the return water can be as low as 110 degrees. Using at least a 20 degree differential should be the minimum.

110 degree return water temperature isn't an issue with condensation?

SuperTech

STEVEusaPA said:

How many zones? Domestic hot water? What type of emitters. I think it's going to be short cycle city without a buffer tank, or even better yet, a reverse indirect. A 3 way (or 4 way) mixing valve should be installed to protect the boiler from lower temp return temperatures. Depending on your location and winters, if you put a 140° minimum in the control, you'll probably be targeting that temperature most of the winter, so it will short cycle without a buffer/reverse indirect. @SuperTech how did you make it with your set up? What's it look like when you open it up for cleaning?

I went a little overboard on my boiler, added a reverse indirect, primary secondary piping and variable speed injection. This took care of the short cycling from the boiler being oversized and having outdoor reset. The boiler looks great on the inside, no soot or scale for years. Every year all I have to do is change my filters at the tank and burner and replace the nozzle. 

PilotPat24

SuperTech said:

STEVEusaPA said:

How many zones? Domestic hot water? What type of emitters. I think it's going to be short cycle city without a buffer tank, or even better yet, a reverse indirect. A 3 way (or 4 way) mixing valve should be installed to protect the boiler from lower temp return temperatures. Depending on your location and winters, if you put a 140° minimum in the control, you'll probably be targeting that temperature most of the winter, so it will short cycle without a buffer/reverse indirect. @SuperTech how did you make it with your set up? What's it look like when you open it up for cleaning?

I went a little overboard on my boiler, added a reverse indirect, primary secondary piping and variable speed injection. This took care of the short cycling from the boiler being oversized and having outdoor reset. The boiler looks great on the inside, no soot or scale for years. Every year all I have to do is change my filters at the tank and burner and replace the nozzle. 

Do you have a picture of your setup?

captainco

Never have had any condensation problems with 110 degree returns.

PilotPat24

captainco said:

Never have had any condensation problems with 110 degree returns.

That's great to hear!  Why does it seem from what I have been reading that some people don't recommend not having return water being less than 140 degrees do to condensation?

captainco

That is an old wives tale from poor equipment setup
Water heater have no problem taking on 50 degrees makeup water without condensation. Condensation is caused by improper firing or improper venting, not return water temperatures.

PilotPat24

captainco said:

That is an old wives tale from poor equipment setup Water heater have no problem taking on 50 degrees makeup water without condensation. Condensation is caused by improper firing or improper venting, not return water temperatures.

Totally understood.  What is the lowest return temperature that you would run?

hot_rod

Best practices say that the boiler needs to be above the dew point of the fuel with 10 minutes of running. Dew point depends on the CO 2 content of the flue gas.
For fuel oil that “industry” number has been  a “safe” 130F
Check with the oil guys here, I would not run an oil boiler with 110 return temperatures, continuously without knowing and confirming how the burner is setup.

captainco

If it takes up to 10 minutes for a boiler to reach dew point there is definitely something wrong with the equipment operation

EdTheHeaterMan

captainco said:

If it takes up to 10 minutes for a boiler to reach dew point there is definitely something wrong with the equipment operation

Agree. What might that problem be?

captainco

EdTheHeaterMan said:

captainco said:

If it takes up to 10 minutes for a boiler to reach dew point there is definitely something wrong with the equipment operation

Agree. What might that problem be?

,
Underfiring, wet flue, restricted flue, excessive house leakage would be some of the leading causes.

PilotPat24

Any recommendations on a particular outdoor reset for this application?  Much appreciated!