Buderus Comparisions to Viessmann

Perry:

Do you know however if 6 gpm would have been adequate for reasonable emitter balance in your system?

You're also fortunate that yours was a single zone system in essentially (if not completely) original state.

Hi Andrew,

I have no idea how they derived their numbers (see below). As I stated there also, the net difference between the electrical power consumption of the least vs. the most electrically efficient mod-con gas boiler pales in comparison to the gas savings that any mod-con should produce in a well-suited home. An equivalent annual power consumption of 2 therms of gas vs. 16 therms is little to argue over when the whole heating plant can save the consumer over 30% in gas bills.

Like you, I do not think that the Vitodens is perfect for every application. Like every boiler, it has its quirks, benefits, drawbacks, etc. Thankfully, we as consumers have a wide range of boilers to chose from so that hopefully we can find the best boiler for our application.

As for the savings via VS drives, the only "data" I have seen was published by Grundfos, which made a 80% "real life" savings claim, IIRC, of a regular wet-rotor UP series pump vs. their VS Alpha Pro. The reasons have to do with flow and the ΔT's in the supply and return. The Euros don't mind a wide ΔT and anytime you can reduce flow rquirements, the electrical consumption of a pump can plummet (within reason).

Brad once posted the relationship between pump speed, electrical consumption, etc. but I do not recall it (sorry!) However, if I take a look at the super-brutes in the basement, I have 3 speeds to chose from and IIRC, the power consumption is about ½ when the pump runs on speed "Low" vs. speed "Hi". Most of the year, heat loss is low enough to allow these pumps (hopefully sized for a design day heat loss) to run at much lower speeds.

So even if the underlying pump is no more efficient than the competition under steady-state conditions, the control strategy of how the pump is used can make a big impact whenever you encounter real-life (i.e. variable loads). Look no further than the use of variable-speed technology use in AC systems, where compressors in higher-eff. units are either stepped or modulated outright, for an example.

Balance

Thanks for adding more support to the VS circ argument! LOL

Constantin

The Grundfos 3 speed isn't very proportional IIRC. I think it is 55w on low, 70 or 75w on medium and 80w or 88w on high with pretty big jumps in pumping power each step. It seems like it should be 30/70/100 based on power but it isn't. I think they use (waste) more electricty making the casing hot than what it takes to just move the water.

Like smaller capacity modulating boilers, I really think that major efficiency gains could come from much smaller and much more efficient circs. I have the feeling that many times a 70w circ on a zone, could probably be replaced by a 10w circ if they made them more efficient.

Like I said Balance

The problem with that scenario is that you have a variable burner and everything else is fixed. That high fixed component means that at some point, the marginal gains from the burner modulating back will be exceeded by the marginal inefficiencies of that fixed load being divided over less and less output. Ideally, the whole plant, stack and all would scale back but it doesn't.

Given that I'm stuck with an antique distribution system (cast iron Armstrong Monoflo knockoffs) that work best with constant circulation at a high enough velocity for the diverters to work, what possible inefficiencies do you see on my system from using a modulating boiler?

Well the laws of physics

Don't change. I am sure you noticed that the article did not tread into the electrical power consumption of the entire system. With this in mind it only stands to reason that if you can satisfy the load and keep the system or parts of the system off for 50% to 60% of the hour you can not avoid the aspect of saving energy be it gas, oil, or electricity.

Sweet I have been hyjacked again.

I take it you must be (a) not be hearing the information you want to or (b) can't substantiate your claims so you do this.

Okay I just went downstairs...

It's flatter than I thought between speeds.

60w/80w/87w

I'm guessing it uses the first 40w to heat up the case... then those numbers would be proportional to the pumping power.

Would you mind explaining PSC? Feel free to start a new thread... this is getting pretty right wing on this side.

Certainly Not From Me

nm

Just For You Uni R

I would purchase either the Bud or Viess if it fit the need. I own neither.

Welcome to the fray

Okay, nobody should be buying boilers that require twice a year servicing - if someone wishes to do that anyway that's their call but twice a year seems excessive. All heating equipment should be checked annually any way so I'm not really seeing any increased cost in that regard.

In terms of the "big ticket parts", I really don't have much knowledge and experience to give you a comprehensive answer but outside of having a blower and a computer I don't see much different, do you?

Ultimately these wall hung boilers are becoming appliances and like a new electronic clothes washer or range if it goes after 5 years, total replacement may easily be a consideration. Check out how much these things cost in Europe where they are already more like applicances than fixtures. I wish it weren't so because with good material selections and more universal computers/connections, the boiler industry could better position the hydronics industry to clearly be the superior choice against forced air (furnace lifespans appear to be getting much shorter).

$2,000 x 16% = $320 (just on your atmospheric loss numbers - btw, do you have a source for these? - it is an interesting number)

That's not a bad amount to sit aside each year as a parts or boiler replacement fund. In the meantime, if everyone burns resources more efficiently, they'll last longer.