Beudarus- Cast Iron VS. Condensing

Joe@buderus_2

It is suggested to find out what your operating temperature and delta T are before choosing a unit. Any condensing boiler will provide the higher efficiency if used in the right application. If above the the temperatures of a condensing unit, then consider a cast iron boiler with outdoor reset. It is best to consult with heating technicians who can evalute the system and offer what may work best.

andy_16

Bedarus- cast iron vs. Condensing

Renovating a 3000 sq' home appox 1700 sq' radiant, remaining area hot water coil w/ forced air.Is the additional cost for the condensing unit really worth the cost, how about life span? Any pro/cons on the install? Thanks

jeff_51

with the radiant, condensing all the way

If you are determined to install a new boiler, then go with the condensing, and I do like the Buderus

Rick Rodriguez_2

I would appreciate if you could share the reasons why you like condensing esides obvious efficientcy. How is the reliability, tech suport. I have been researching some boilers and they are stating oversizing could be a problem say you had a multi zone system and only one zone came on?

Thanks in advance
Rick

Jamie_6

Andy,

I agree with Joe! First determine your loads and the proper water temperatures to operate the radiant and the hot-water coils. Depending on what application the hot-water coils are being used (1st stage heating (primary heat source) or second stage heating (secondary heat source) your water temperatures to that appliance may be low. When we design and install radiant systems we use a 150 degree design temp on our hot-water coils for second stage heating only. This allows the house to heat comfortably above design conditions. The radiant takes care of the rest once winter sets in. Plus with a 150 degree outlet temp on a condensing boiler we are returning water back @ 130 degrees.. That way she is condensing away and taking full advantage of that high efficency piece of equipment.

By the way. We are BIG fans of the Buderus GB! Great product and tech. support.

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andy_16

Thanks for the input, the secondary heating output would be domestic hot water 2 1/2 baths 6 people in the home,I planned on using a storage tank would this set up still be efficient for the condensing setup? Called two heating companies in the area, both were'nt intrested unless the were installing the complete system. Sent plans to Roth to have the system layed out,& I would imagine the load calcs. Could you recommend anyone in the LI. NY area

Thanks

Jamie_6

Did you check "Find A Professional" on this web site?

Also, the Buderus GB is already equipped for an indirect to be used off of it.

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Constantin

Actually,

A modulating condensing boiler has an easier time with smaller loads coming on than a big single-stage boiler does. That's because the modulating/condensing boiler can reduce it's output to 20% of it's maximum, while the single-stage burner is either on or off. As a result, a properly-sized mod/con boiler will operate continuously far longer into the shoulder seasons (which predominate) than a single-stage boiler can.

There are ways to help a single-stage boiler "cope", the most widely used one is giving it a large water jacket, i.e. thermal mass. That, and preferably in conjunction with a wide outdoor reset and a mixing system, can then give you longer firing times, boosting efficiency. Yet, the thermal buffer also gives the boiler ample opportunity for standby losses, something that a low-mass mod/con boiler does not suffer from.

The more complicated things become, the more likely they are to fail, all things being equal. A mod/con certainly has more parts that can fail and some of them can be quite expensive to replace. Yet, if the heat emitters of the house allow it and the gas prices are high enough, a mod/con boiler is easily justified. Just look for all the success stories on this site where people haves saved 35%+ on their gas bills by making the switch.

As a mere homeowner and a customer of a different brand, I cannot speak to the support that Buderus gives. However, most professionals here seem to like the support they get. The only caveat seems to be supply issues, where demand is outstripping supply. However, Buderus is not alone in that conundrum, many manufacturers apparently saw their sales spike this year as fuel prices rocketed up.

Alex Giacomuzzi

Oversizing Could be a Problem

Hi Rick
You state "oversizing could be a problem" on a multi zone system with only one zone calling.

That statement would or could be true --- in many cases any time you have a heavily zoned applications. This may not apply to a lightly zoned system (as much), but it would certainly apply to systems with multiple small loads and separate feeds supplying each zone.

Taking this a step further.... and again depending on the BTU load requirements of these zones, most all boiler choices out there cast iron, condensing, condensing / modulating you name it are going to short cycle while feeding these loads. But ---- what about a 5:1 turndown, will that be the cure. Interesting thought.

In sizing a heating system ---- the boiler rating is based on your heat loss of the property. Then you either select the DOE or IBR rating closest (above) your losses. This would be for a cast iron boiler. This truly does apply to a cast iron boiler and one way to manage micro and small loads for multiple zone applications is to add water volume in one manner or another so as not to cycle the boiler as much.

Now --- how about condensing / modulating units. How should we size these and will they cycle?? This is not the same beast as the CI. Its efficiencies are primarily gained from two areas. A correctly mixed air /gas mixture and modulation ---- preferably to the lowest output.
In an application where you have minimal zoning to contend with, I would suggest "oversizing" a condensing / modulating boiler inorder to move its operation down its % loaded curve inorder to maximize efficiency. This of course assumes the emitters are sized and designed appropriately to allow for this.

But --- with several small and micro loads, this may not work so well. In fact ---- the whole system may react like a car hitting endless stop lights. Several C/M boilers start on high fire and then slowly move to a lower %. Depending on how quickly your heat demand is satisified will determine the lenght of this cycle. Shoulder seasons are even worse as you can understand.

Sorry for being so windy.... but the long and short of this is unless you are using TRV's in the separate area, try to minimize and combine where ever possible mini and micro loads. If you can not --- make sure your system design integrates them properly and you do not end up with short cycling and poor efficiencies.

By the way........ I totally agree with Joe below. Understand the application well, there are still good applications for CI and obviously for C/M. I hope CI has not been thrown out with the bath water ---.

Regards Alex

Mad Dog_2

HI Andy...............................................

I know you didn't call us. WE are on Long Island, have done several GBs and have done dozens of Buderus Cast Iron boilers as well. Give us a call or email me. Maybe we can help you. Thanks Matt Mad Dog Sweeney

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Sal Brunetto

re:

You should look at a Weil-McLain Ultra Gas condensing boiler before you make your decision. It modulates between 20 and 100% and also supports a priority zone for an indirect heater.

http://www.weil-mclain.com/FTP/Ultra 310/UltraLitw310.pdf

Sal Brunetto
Weil-McLain

[Deleted User]

well, since everyone else's bells are ringing

For the best customer support and for the most mature product, consider a call to Mr. Ed Nordstrom at Viessmann USA for a referral to the nearest trained and confident installer. THe Vitodens boiler is quite happy to provide multiple heating water temperatures as well as having DHW production capability integral to the boiler.