value of outdoor controller

Greg Swob

Had a debate at the office regarding the value of outdoor controllers vs. energy savings. Case in point - 14 yr. old boiler, baseboard radiant - one zone for entire small home. Owner complaint: high NG gas bills and the winter has been very mild so far. Heatloss showed that using 180 F water, the baseboard is marginally capable of handling loads. We probably need to install more, but that just isn't going to happen - elderly owner, not the best of health- physically or financially. Examined installation: operating aquastat set at 200 F, boiler aquastat set just a few degrees above that -pump into boiler (they were ALL done that way around here until lately), only air removal device is Amtrol 700 or some equivelent model # four feet from X-tank, all contolled by single T-stat, not a maintained temp a.k.a. 'hot boiler'. An older technician told me the aquastat was set that high, per his memory, because of the marginal radiation. This was the second boiler on the system and he admitted a lot of repiping should have been done. Our debate comes to: I was told the cost of installing an outdoor controller would not pay enough dividends to justify it. Any helpful opinions? Oh, yeah, before I forget - HAPPY NEW YEAR! I do have a life, but this debate has been burning on my mind and I'm looking for substantiating opinions/ advice. Thanks - Greg

Steve Eayrs

Happy New Year to you too!!!

The outdoor reset can only same money when you are able to keep the house happy at lower boiler temps.
In other words if you have to run the boiler at 180 just to keep up with the demand, then you really are not gaining anything, BUT if you could allow the boiler to run down to 140 or so and still keep up with the demand it would definitely help the fuel bill.
Even so, there would be some savings, as long as the boiler only had to run at the hottest temps in your coldest weather.
May make a big difference if there is any way you can add just a little more radiation of some sort.

Steve

heatboy

If it takes 200° water...............

to satisfy the load, that's what you need, Greg. No way around that, is there? Outdoor reset will really help this situation. With the proper set-up, the only time the system would operate at 200° is at design temperature. We all know how much noise a baseboard system makes when going from a standing water temp of 70° to 200° in several seconds! With outdoor reset, all of these issue virtually go away. Running a boiler at 200° to 180° whenever there is a call for heat assures higher fuel consumption.

Remember, you can have boiler reset, system reset or both. With boiler reset only, there is a minimum boiler temp that needs to be observed. That minimum is a direct relationship to the efficiency of the unit.

You didn't mention what type, if any, domestic hot water is produced with the boiler. That will have the biggest impact on what type of reset can be applied.

hb

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Greg Swob

Thanks for the insight

Apologies for omission: DHW is produced by a standard NG water heater. Extremely rare to find indirects used here. I feel an outdoor controller will 'lie' to the boiler often enough about what temp it needs to operate at to the point some savings will be realized. But not sure how to estimate or calculate how significant these savings could be. Agreed, 200F is needed, but only during design temp days. The rest of winter is anywhere from mild to wild around here (example- today's forcast mid 60's, Sat.'s high low 20's) Maybe Siggy's software could help calc. this? I have Writesoft and an old version of Rezcalc for loss/gain calculating available but nothing there for calculating equipment efficiency improvements, only load sizing. Thanks and best to all of you in '04. We found out we will be first time grandparents this year, it's going to be one crazy year! - Greg