overheating with I/O reset?

mjj_2

Our hydronic heating contractor has offered us 3 choices of gas-fired boilers to heat our 2000 sq ft. 98,000 BTU/h, CI hot-water heated home. We are very reluctant to consider the Vitodens, as all parts are made in Germany/Asia, so we're leaning toward 2 locally-assembled units: Slant Fin Galaxy(82.7% AFUE) or the Vitogas-50 ECD(83.7% AFUE).

Still we were hoping to boost efficiency of these Mid-E boilers and asked about installing Outdooor reset. The contractor said he would only consider installing O. reset on large industrial structures, that residential systems often overheat with this control. Has anyone else experienced overheatng caused by I/O reset? Can I become my own Outdoor reset? Is there a formula to follow when decreasing the temp of the water?

Scooter Libby

> The contractor said

> he would only consider installing O. reset on

> large industrial structures, that residential

> systems often overheat with this control.


I've heard some stupid contractor claims in my time, but this one is a candidate for the Hall Of Shame.

But if you refuse to buy products that have foreign brand names (of course many parts are imported even when the brand is 'murrikan) then the two of you are a good match for each other.

>Can I become my own Outdoor reset?

Well, doctor or lawyer could be better, but if that's what makes you happy...

mjj_2

parts

We are not opposed to buying foreign products (Vitogas-50 is also a Viessmann). Our concerns are practical, want to make sure that parts can be replaced quickly if needed.

Bob W._3

"But if you refuse to buy products that have foreign brand names (of course many parts are imported even when the brand is 'murrikan) then the two of you are a good match for each other."

Why such a sarcastic response? Maybe the person posting would like a little help.

Unknown

That is

the type of response I would expect from someone named MooCow , who has no valid email posted .

tom_49

Id go with the highest eff. you can afford.

Outdoor reset is easily controlled, it may take a little sweaking but once you got it its great. last night for example, 35o outdoor temp, 70o indoor, boiler ( vitola, running at 109o ,HWBB,)

I run constant circ. / constant temp. ....dont even know the heats on. Try it, youll like it.

good luck.

Constantin

Some thoughts...

.... I doubt that you will find a modulating condensing boiler in the US which is wholly made in the US. Many parts come from overseas, such as heat exchangers, gas valves, burners, controls, blowers, etc. In other words, most of the value in many boilers is foreign-made. Is this a bad thing? I don't happen to think so, since Intel, Microsoft, Boeing, etc. also make a ton of money exporting their wares abroad. Trading with friendly partners is to everyone's advantage.

Are the Vitogas and the Galaxy perhaps less complicated and hence, possibly, more reliable than a Vitodens? Sure. But dropping the Vitodens on the basis of that reasoning would be foolish. According to the many posts I have read here, the Vitodens is a proven performer, with a long track record, and many happy owners and installers. Not every house is right for the Vitodens, and a efficient gas boiler in conjunction with a good control strategy might make more sense in those instances.

For example, it depends in part on the emitters in the home and the temperatures at which the emitters have to run to keep you warm on a design-day (i.e. the coldest day of the year). The cast iron you have in your home should be to your advantage, but only a calculation will show how hot the boiler will have to run to keep you happy. The Vitodens has an internal supply temperature limit of 167°F, so homes with supply temperature requirements in excess of that need not apply.

Homes in areas that do not have very high fuel costs are perhaps also better suited to have a high-efficiency but not a low-mass, modulating/condensing boiler like the Vitodens. Up here in the Northeast where natural gas is approaching $1.71 a ccf and where propane traditionally has been even more expensive, a condensing boiler will result in a payback much more quickly than in areas where gas prices are much lower.

Similarly, if your home is built in an area of the country where you heat very little, the economic case for a modulating/condensing boiler is hard to make. However, there are other, and perfectly valid, reasons to still choose a mod/con.

I am a bit surprised though that your installer seems to be confused about outdoor reset (OR) and what it does. OR will avoid precisely the kind of overheating that can happen in variable climates, and it will also save money by modulating the boiler temperature up and down as the season progresses. This leads to lower standby losses from the boiler and better efficiency. Considering the minimal cost of incorporating it (the Vitodens has it it built-in, for example) I would always select a reset controller in conjunction with a new boiler installation.

Constantin

Argh..

...double post...