Do I have an outdoor reset?

josephny

I have an oil-fired Burnham hot water boiler (2 zoned) with a Resideo L7224 aquastat installed.

Does this mean I have an outdoor reset?

I've been reading about them (and watching videos) and sure sounds like an important thing to have.

But, I opened it up and I don't see any outdoor sensor.

If I don't have an outdoor reset, can I add one relatively easily (given what I do already have)?

And, if I don't have one, what does the aquastat do?

(Domestic hot water is provided by a Navien tankless.)

Thank you!

Here are some pics:

STEVEusaPA

No

josephny

Thank you.  

What would it take to add one?

Mad Dog_2

Call Burnham Tech Support on Monday.  They'll guide you. I Know the Gas Boilers have an Outdoor Reset Card that's easy to install.  Also Tekmar has many options as far as ODR...Mad Dog 🐕 

Big Ed_4

Check Tekmar controls

STEVEusaPA

I wouldn’t put one on oil. You won’t save money, you’ll short cycle and do more harm than good. Your flue pipe is the wrong gauge and the draft regulator is installed incorrectly.

hot_rod

You have a fairly limited range that you could reset water temperature in non condensing boilers. Some controls could monitor for cold return and stop the circulator   We call this bang/ bang control, not an elegant control logic

josephny

Wow! As usual, thank you guys so very much.

I watched 4 videos and read several articles that all touted the benefits of an outdoor reset -- plenty of implication that not to have one is nothing short of foolish.

So much for lay-person self-research.

However, here I am (a lay-person) getting good information and advice from all of you true experts regarding my specific environment.

Interestingly, one of the points made across all my research was that an outdoor reset reduced (ideally, eliminated) short-cycling.

If there is anything that stands out that I should or could do to improve the functionality, I'd appreciate hearing about them.

Thank you again!

Brad White

josephny said:

Wow! As usual, thank you guys so very much.

I watched 4 videos and read several articles that all touted the benefits of an outdoor reset -- plenty of implication that not to have one is nothing short of foolish.

So much for lay-person self-research.

However, here I am (a lay-person) getting good information and advice from all of you true experts regarding my specific environment.

Interestingly, one of the points made across all my research was that an outdoor reset reduced (ideally, eliminated) short-cycling.

If there is anything that stands out that I should or could do to improve the functionality, I'd appreciate hearing about them.

Thank you again!

A few thoughts-

1. You can use outdoor reset (ODR) with an oil-fired boiler, but you have to hydraulically decouple the boiler as its own circuit, from the house distribution circuit. Each by definition would have its own pump and controls.

The idea is that the boiler (any cast iron boiler, oil or gas) needs to be maintained at a higher temperature to avoid condensation, corrosion and possible thermal shock, less common but it happens and can crack a cast iron boiler. The boiler would be maintained about ten degrees F. above your required house supply temperature and the return water would be monitored and controlled with a thermal bypass to keep the boiler return coming back no lower than 130 degrees F. give or take a few degrees.

You can still vary this temperature, but it has a relatively high floor-temperature you need to maintain. You may fire the boiler to say 180F on the coldest day and to 145F on a minimal heating day. Still saves fuel.

The house-circuit would be fitted with a mixing valve, which often but not always would be a 4-way mixing valve for a CI boiler. This valve is a means to decouple the two circuits in the bargain. But the primary function is to mix hot boiler water with cooler house return water to send out water at the appropriate temperature indexed to the outside temperature.

(There are several other ways to decouple, closely-spaced tees, hydraulic separator being most common, but a modulating control valve or injection pump or other detailed means on the house side are almost always needed for best control.)

The house circuit can have a much wider temperature range, higher on colder days and maybe 85-90F on a very mild day, depending on your emitter types (radiators, coils, radiant floors, etc.)

This is how ODR works, leveraging the relationship between outside/inside temperatures (heat loss) to radiator output at various water temperatures. Marry those relationships and off you go.

2. Short Cycling: As you probably know, gas-fired condensing boilers have this ability to modulate, vary firing rate up and down to suit loads. Oil boilers, most of them have two firing rates, On and Off. This is where short cycling happens. Such a boiler takes at least two minutes usually to get to a steady state of efficiency and warm the block of iron then cools off once the boiler stops firing. You lose this with short cycling.

One common way short cycling happens is using a control strategy called a "differential". This is a varied On-point and Off-point split equally around a set point.

Say for example, you have a need for 155F supply water. That is your set point, your target. If you fire the boiler to reach that and have a two degree differential, the boiler return temperature drops to 154F and fires until it reaches 156F, with the target set point right in the middle. You might get a minute of firing time to make this happen, then it is coffee time for the boiler.

Now, WIDEN this differential to say 12 degrees. Water temperature drops to 149F, boiler fires until the water temperature rises to 161F. Same target temperature, a bit of over-firing, but you get all of that back. So you can see how differential can ease cycling. But it has nothing to do with ODR specifically.

3. Economics: You could spend several thousand dollars to make this happen, I do not mean to discuss price but order of magnitude you are not talking hundreds here to make this happen.

Is it worth it?

How long will you hold onto the house?

Is natural gas slated to be in your area and make gas-fired condensing boilers or even propane a possibility? And at what cost?

You get the idea, things to ask yourself and your family financier we know who that is...

So, not a "go do this!" encouragement, but know what and why, in rough terms.

My $0.02.

josephny

Brad White said:

josephny said:

Wow! As usual, thank you guys so very much.

I watched 4 videos and read several articles that all touted the benefits of an outdoor reset -- plenty of implication that not to have one is nothing short of foolish.

So much for lay-person self-research.

However, here I am (a lay-person) getting good information and advice from all of you true experts regarding my specific environment.

Interestingly, one of the points made across all my research was that an outdoor reset reduced (ideally, eliminated) short-cycling.

If there is anything that stands out that I should or could do to improve the functionality, I'd appreciate hearing about them.

Thank you again!

A few thoughts-

1. You can use outdoor reset (ODR) with an oil-fired boiler, but you have to hydraulically decouple the boiler as its own circuit, from the house distribution circuit. Each by definition would have its own pump and controls.

The idea is that the boiler (any cast iron boiler, oil or gas) needs to be maintained at a higher temperature to avoid condensation, corrosion and possible thermal shock, less common but it happens and can crack a cast iron boiler. The boiler would be maintained about ten degrees F. above your required house supply temperature and the return water would be monitored and controlled with a thermal bypass to keep the boiler return coming back no lower than 130 degrees F. give or take a few degrees.

You can still vary this temperature, but it has a relatively high floor-temperature you need to maintain. You may fire the boiler to say 180F on the coldest day and to 145F on a minimal heating day. Still saves fuel.

The house-circuit would be fitted with a mixing valve, which often but not always would be a 4-way mixing valve for a CI boiler. This valve is a means to decouple the two circuits in the bargain. But the primary function is to mix hot boiler water with cooler house return water to send out water at the appropriate temperature indexed to the outside temperature.

(There are several other ways to decouple, closely-spaced tees, hydraulic separator being most common, but a modulating control valve or injection pump or other detailed means on the house side are almost always needed for best control.)

The house circuit can have a much wider temperature range, higher on colder days and maybe 85-90F on a very mild day, depending on your emitter types (radiators, coils, radiant floors, etc.)

This is how ODR works, leveraging the relationship between outside/inside temperatures (heat loss) to radiator output at various water temperatures. Marry those relationships and off you go.

2. Short Cycling: As you probably know, gas-fired condensing boilers have this ability to modulate, vary firing rate up and down to suit loads. Oil boilers, most of them have two firing rates, On and Off. This is where short cycling happens. Such a boiler takes at least two minutes usually to get to a steady state of efficiency and warm the block of iron then cools off once the boiler stops firing. You lose this with short cycling.

One common way short cycling happens is using a control strategy called a "differential". This is a varied On-point and Off-point split equally around a set point.

Say for example, you have a need for 155F supply water. That is your set point, your target. If you fire the boiler to reach that and have a two degree differential, the boiler return temperature drops to 154F and fires until it reaches 156F, with the target set point right in the middle. You might get a minute of firing time to make this happen, then it is coffee time for the boiler.

Now, WIDEN this differential to say 12 degrees. Water temperature drops to 149F, boiler fires until the water temperature rises to 161F. Same target temperature, a bit of over-firing, but you get all of that back. So you can see how differential can ease cycling. But it has nothing to do with ODR specifically.

3. Economics: You could spend several thousand dollars to make this happen, I do not mean to discuss price but order of magnitude you are not talking hundreds here to make this happen.

Is it worth it?

How long will you hold onto the house?

Is natural gas slated to be in your area and make gas-fired condensing boilers or even propane a possibility? And at what cost?

You get the idea, things to ask yourself and your family financier we know who that is...

So, not a "go do this!" encouragement, but know what and why, in rough terms.

My $0.02.

Well, wow wow wow!

Again, the expertise and generousity of the members here have provided a deeper understanding of topics than I knew existed.

I'm sure you know, but I am amazed that your one, several hundred word post references so many concepts that each have a super deep body of understanding behind them.

"Hydraulic decouple," "condensation, corrosion and possible thermal shock," "maintained about ten degrees F. above," "thermal bypass," etc., etc.

I love it!!

So, here is my lay-person takaway (which, I have no doubt, is a small portion of what a person could learn from your post and probably not even substantially correct).

ODRs work by reducing the water temperature in the radiators according to the demand -- which varies in inverse correlelation to the outside temp. This happens within parameter ranges such as the floor temp of the boiler water, the max temp for the radiators, etc.

And, the goal is to maximize efficiency by reducing the short-cycleing of the boiler.

Other than reducing short-cycleing, I am not clear on what the other benefit is of reducing the delta between the water in the radiator and the water temp in the boiler.

Now that you point out that an important difference between oil and gas boilers is the ability of the gas boiler to modulate the burner, I am so much clearer on why the literature pushes the modulation capability so much.

We will never have natural gas in my area (very, very rural), but we do have LP available. In fact, the Navien hot water in the house heater is LP.

It sounds like an ODR is definetly not something I should pursue. If anything, swapping out the oil boiler for a modulating gas one would be the way to go. But, at this time, the boiler is working well and my oil usage is not too costly, so I think the economics do not warrant it.

Thank you very much!