Outdoor reset

Wayco Wayne_2

the Trade show at Radfest East. I got to see the Buderus condensing boiler up close. Very impressive looking and easy to service. I got into a disscussion about the fact that it had no outdoor reset availible so far and the saleman I was talking to said that with modulating boilers outdoor reset was not very helpful at lowering the gas usage. My BS control clicked in my mind, but I want to put it up for discussion. I have jobs where I can keep the water temps below condensation point for much of the season but need to go above for colder outdoor temps. To me there are going to be considerable savings by doing that. What is the reality?

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Paul Rohrs_4

Table Discussions

Wish I could have been there. Were you able to sit in on any table discussions? I would have loved to been at the table with Siggy and the "System Documentation" table.

Any other notable events? What was top dollar for Hotrods V-twin?


Regards,

PR

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Constantin

Usually....

... features found in other products are not important until your own products incorporate them. Only then do they become important. Didn't you know that? :-P

But seriously, if the GB 142 is using indoor reset, I imagine that'll work most of the time, though rooms that have high-mass emitters (slab, for example) may be marginal when there are quick changes in the weather. During periods of high insolation with lots of windows, they may overheat while sudden drops in temperature might also take a while to catch up to. OR helps avoid these issues because it anticipates future demand and modulates the output accordingly.

Another downside to no OR is the question of where the boiler will set its internal supply temperature. Between the feedback from the thermostats and the supply vs. the return temperatures, it has to decide where to set the supply and how much to fire to reach it. In other words, this is more of a closed-loop feedback system than just pure OR-control (which is pretty open-loop) - potentially a good thing with low-mass emitters. However, where to set the internal supply temperature?

However, many systems nowadays can take advantage of OR and some form of indoor reset to maximize fuel savings. Given the low cost of the electonics needed to do it, I don't see why one wouldn't have at least OR, a internal tank temperature or return temp sensor and a supply sensor. Between the thermostats, a good control program, and th ethree, you should be able to handle most, if not all, heating challenges.

I would prefer my appliance to have outdoor reset for the above reasons.