Boilers, efficiency, on demand
Does anyone have experience with an on demand gas system for hot water and heat? It seems from the literature that the efficiency is much higher than a traditional boiler like a weil McClain CG (as much as 97% or 14% higher) and the sticker price isn’t so high on some models (Tagaki is one…
Does anyone have experience with an on demand gas system for hot water and heat? It seems from the literature that the efficiency is much higher than a traditional boiler like a weil McClain CG (as much as 97% or 14% higher) and the sticker price isn’t so high on some models (Tagaki is one maker I’ve looked into).
I’d be using the system with cast iron radiators, not radiant heat.
Hello,
I went through a lot of research a couple of years ago before we installed a Viessmann condensing (on-demand) boiler to supply our cast iron radiators and domestic hot water. It was a headache to find a plumber with experience with these systems. I got a lot of great information and guidance from http://www.heatinghelp.com/ check out the discussion board http://forums.invision.net/index.cfm?CFApp=2
In the end I couldn’t be happier with the boiler. It’s tiny, near silent, and really efficient. The Viessman isn’t cheap, our joke around here is that it’s the ‘Ferrari’ that we keep in the basement, but it will pay itself back in time, especially with the cost of fuel.
Also worth exploring are valves (can’t remember the technical name) that are installed on the radiators that create zones and equalize the water flow/heat in the house.
Good luck!
We’re thinking along the same lines, and have been looking at the Ambassador combi (Embassy is the parent company) for a combination on-demand hot water and hydronic heating. Master Plumber (or anyone else), any experience with these or similar wall mounted high efficiency boilers?
Thank you as always for all of your thoughtful and helpful comments.
I don’t recommend Weil-McLain over Buderus. Both are large corporations with good customer support. I will say that the electronics in the WM are shared with other boiler manufacturers, like Burnham, so that makes their parts and service manuals a bit more available.
On the other hand, the concept of mod-con boilers is relatively new to WM while Buderus has been making those boilers for a long, long time and have always been a leader in the high efficiency field.
What I do recommend is that you buy the one that has a reputable parts supplier and servicing contractor in the area.
Ask your GC or installing plumber about that.
Two years ago, I would’ve had a strong opinion about your proposed solar system, too. But recently there have been many changes in the way these systems work to collect and distribute energy thanks in large part to a company called Caleffi in Italy. You should probably look at their U.S. website.
I’ve installed two solar water heaters in the past year, which is encouraging, but the fact is I’m not yet the guy to ask about design strategies and concepts. Where solar is concerned, my company installs from engineering blueprints.
Good luck on your project.
Wow, well thank you for the detailed and intelligent response. I’m considering the UG-105. Do you recommend this over other boilers like the Budurus which seem to have the similar efficiencies but are cheaper?
Lastly, do have any experience with Solar Thermal heat exchangers? I’ve gotten such radically different opinions on whether having a 120 Gallon superheated water tank from a 3 panel solar array would preheat the water loop going into the boiler enough to make a contribution towards energy efficiency.
The CG-4 is an old-technology, non-condensing, cast iron, gas-fired boiler that converts the fuel it burns to usable heat at about 82% efficiency.
Not that there’s anything wrong with that.
To understand the difference between it, and any boiler of its kind, and a modulating-condensing boiler (mod-con for short) you’ll have to know the following:
A boiler contains water that is much cooler than the flame used to heat it. When that flame ignites it warms the boiler and the water inside of it but the difference in temperature creates condensation on the cast-iron, boiler-water container. We call that cast-iron container the “heat exchanger†because it exchanges heat between the flame and the boiler water.
That condensation continues to develop and collect on the heat exchanger until the water it contains reaches about 140 degrees.
All the while, until that 140 degrees is reached (could be a long time), that condensation, which in this case being a byproduct of the combustion of fuel and thus contains carbonic acid, eats away at a cast iron boiler’s surface propelling it toward failure.
We call that a non-condensing boiler because it does not handle condensation well at all.
It isn’t designed to, even though condensation is a part of life for it.
Most boilers and heating systems using this type of boiler are designed to operate at 180 degrees or more. That keeps them safe from corrosion due to condensing.
A condensing boiler’s heat exchanger is often made of materials other than cast iron: aluminum, copper, stainless steel, some alloys, etc.
These boilers are made to handle any of the corrosive properties of condensation without damage to the heat exchanger. Because they can do that, they can be incorporated into heating systems designed to work at much lower temperatures. It is for this reason they are so well-suited to work with radiant floor heating which often runs at 115 degrees or less.
A mod-con is a boiler that condenses safely but also has the ability to raise and lower the intensity of the heating flame at the same time. This is ideal because it can effectively maintain a very low and efficient boiler water temperature without damage to the system components.
In a Brooklyn brownstone they work very well because most of our homes have extremely oversized radiators anyway and lowering our operating temperatures doesn’t create a deficiency in heating ability.
Where we do run into problems is how we vent the exhaust of these boilers. They have very specific requirements and few have been able to meet our limited options.
Right now, I’ve got two types installed that have been performing extremely well in Brooklyn: the Weil-McLain Ultra and the Lochinvar Knight.
Good mod-con boilers generally cost 2-to-4 times the price of cast iron, non-condensing boilers of similar output.
If you’re going to green, stop thinking about the wallet, and start thinking about the environment. Not my rules. It’s just the way it is.
*shameless plug*
I’ve got some links on my website to quality boilers and other products here:
http://www.GatewayPlumbing.com
I guess I’d like to know what boiler you recommend for a hot water system in a brownstone with cast iron radiators. Originally when I posted I thought I had space issues and liked that condensor and hot water on demand systems are so small. It seems I don’t have as much of a space issue and so now wonder just which boiler works within my parameters. The contractor was going to get a weil Mclain CG4 which seems to be 10% less efficient than some other boilers that in a similar price class.
Any recomendations?
I do. What would you like to know?