Outdoor Reset Control

jon

I am considering having an outdoor reset control installed. I am not quite sure what the benefits are but will I see a significant benefit (comfort and/or financial) in the short or long run?

Any difference between Tekmar and Stadler Viega. Or any other companies to consider?

jon

Mike T., Swampeast MO

The lower the supply temp

the greater the resulting proportion of radiant to convective heat and the more the benefit from reset--both in comfort and economy of operation. (Not fully applicable to hydronic baseboard though.)

You're comparing "apples with oranges" by comparing radiant floor (or wall or ceiling) heat to panel radiators. Panel rads generally operate at a MUCH higher temperature than floors.

Both though can definitely benefit from reset.

While the up-front cost of radiant floor may seem high, a well-designed system is supremely comfortable. Kitchens are a notorious "trouble spot" for radiant floor as much of the available floor surface is often covered by cabinets, appliances, etc.

A "hybrid" system utilizing both floor "warming" and panel radiators is an exceptional choice.

In my opinion a natural wood floor in a kitchen is MUCH more likely to be damaged by water and UNAVOIDABLE seasonal wood movement than even "runaway" floor heating. A properly conditioned and installed natural wood floor is nearly incapable of being damaged by any reasonable radiant floor system.

While this is a personal pet peeve--if you're considering granite (or similar) countertops--put your money into fine mechanicals and you'll be MUCH happier and MORE COMFORTABLE for MUCH LONGER.

Art Pittaway

Two questions

Reset, if you have baseboard or a typical 190-170*f system reset will save you fuel and give you greater comfort. The control tries to match the heat loss curve of your building. As the out door temp goes from 10* to 60* your house needs less BTU's and the boiler will change from (i.e.) 190* to 150*. Your heaters will then put out less heat to the room and slow down the on/off cycle. Result is more even heat and greater comfort.
Radiant, is another question, wood floor shouldn't stop you from doing it unless it's 3" thick or you cant get to it from below. Even then it might be better and cheaper than the ceiling or wall. Need more information. Art

jon

Outdoor Reset Control

I have an old REPCO boiler (Model #: LA150C) and I am looking to do some plumbing upgrades. I was told by a contractor that it would be a waste of money to have installed an Outdoor Reset Control (by Tekmar for example) because the boiler can only vary the water temperature from 140-160 degrees and so that is not a large enough differential to warrant an Outdoor Reset Control. Is this true?

Steve Levine

One of the li itations of outdoor reset

is that most bolers can not have the return water temperature drop too low. Most would limit the supply water to a low of 140°F. So let's put that into a proper perspective. Most baseboard systems need about 190°F water at design conditions, cutting this to 140°F in milder weather cuts the output about 50%. That would double the on time for a zone, cleary increasing the comfort in the space. Sure, the ideal would be to approach constant on time, but without other modifications you can't do it. There are other piping and control arrangements that would allow it, such as primary secondary pumping with injection that would allow total reset range.

Art Pittaway

Is your boiler at 160* now?

If your running only 160*f now to heat your house and the heating is steady and comfortable, it may not be worth the expense. But, if your boiler is set on 180+*f and you need 180* water to heat on a design day (i.e. 0*f outside temp) then it's a good bet you could use reset to your advantage. On a day when it's 50* outside your reset control would drop the water temp and heat output from your radiators(?) and give the house a more even heat input. Art

jon

boiler temp

Wanted to answer a question from earlier. My REPCO boiler is set now at 210* f. We need to do some plumbing work including increasing the size of some pipes the circulator pump, etc. So I caannot tell what *f the boiler would be at otherwise but now it is at 210*f so my guess is that the contractor left out some details when he said it would be a waste of money to have installed an Outdoor Reset Control because the boiler can only vary the water temperature from 140-160 degrees and so that is not a large enough differential to warrant an Outdoor Reset Control.

Can you please elaborate on: Sure, the ideal would be to approach constant on time, but without other modifications you can't do it. There are other piping and control arrangements that would allow it, such as primary secondary pumping with injection that would allow total reset range.

Steve Levine

To be able

to have the zones have a constant on, you would have to be able to reset the water temperature down to almost 70 degrees. Since you can't do that directly thorugh the boiler, you would have to cycle (on/off) the zone to avoid overheating if the lowest suppyly temperature was 140 degrees... BUT.. if you use primary secondary, you have a loop through the boiler that you maintain at the highest temperature required, and you 'inject' that high temperature water into the loop feeding the radiation. If it is cold and you need high temperature water, it injects a lot. If it is mild, and you need low temeprature water, it injects a little.

There are others on the wall that can easily give you more details on how to do this.

I hope this helps.

Roger Litman

An argument against outdoor reset

If you overradiate the entire house by using a 300BTUH rating for your baseboard and the boiler has to run at a minimum of 140°, the savings of using outdoor reset are very small.You can tell what the minimum temperature that your home needs by gradually lowering the high limit and the low limit until the baseboard does not keep up with the home on a very cold night.If you need a high temperature, then outdoor reset may help.Domestic water on a tankless without storage may become a problem. Outdoor reset with an air handler with a hot water coil is usually not viable. I believe that we should be installing more radiation and smaller boilers, for maximum efficiency and comfort. Radiant systems are a different ballgame.

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