condensing boilers

Unknown

For what it's worth, use the domestic priority feature another poster mentions, and in my own experience whenever I do load calcs on existing baseboard, I find it can usually run at 140 or 150 max.. that's max, much lower normally.

My own house, an old farmhouse, is holding temp steady after a very cold night with a 138 max temp right now. I think under design (-5) conditions I could probably max at 150. we'll see, cold snap coming...

the modulating ability of these boilers is a big deal as well. Note their base efficiency rating (typically 92%) is not under condensing conditions.

ed m

H.E. Condensing Boilers Question

If you need say 180 degree water temp. for baseboard, or Indirect DHW, does it pay to use a condensing boiler? The way i understand it is that those boilers only reach those efficiencies on low temp applications such as radiant heat. A new house with 3 baseboard zones,3 radiant zones,and 1 DHW zone,for example would a condensing boiler even should i say condense with 180 going out and say 160 comming back i cant see how it would work.So i guess my 2 basic questions are in this scenario would it work efficiently, and is it worth the extra money.
thanks for your help just trying to get a better understanding of when it would be logical to use this type boiler other than radiant.
Eddie

Abro

But do you really need 180°?

I have el-crappo "180°" fintube. It's 22° outside and the boiler's target supply temp is 126°.

That maximum water temp should only apply to the worst outdoor temperature. Your maximum boiler temp would be for design day conditions that may only cover 6 hours in a heating season.

First, you should calculate the heatloss for your house - SlantFin has a free package. Then take 70% of that number as the true heat load (the calculated Manual J is vastly overstated). Then calculate the capacity of your rads for every 10 degree and see what supply temp comes close to generating the BTUs to match the heat load. Then subtract 10° to get a rough idea of the return temps. Ideally, most of your season would have returns under 130°. If you're in an area like me, you might only get 2 or 3 weeks where it is significantly colder than the rest of the winter (which here is close to the freezing mark). The shoulder seasons are even warmer and require even less heat for your rads. Go crunch the numbers and see if its logical to you.

ed m

DHW

will this also be the case with a indirect heater,in an existing system with a burnham direct vent boiler would it pay to use an out door sensor which also has an indirect heater. IF so what would be the easiest way to go about it.this is getting off the subject alittle but why i ask,is that when I installed my boiler 2 years ago i didnt know much about condensing boilers and we had never installed them,it seems right after i installed my boiler starting hearing about them and more costumers were intrested.In my own house i have a burnham direct vent boiler, 3 zones of baseboard,2 zones of radiant and 1 indirect DHW heater,would it pay to install an out door sensor on this system.here are some pics of my boiler. would appericiate any help,and like i said we are just starting to get inquires about installing these condensing boilers and would like to learn if they would be suitable for use, mostly new constuction homes,with b.b radiant and indirect heaters.thanks for your help i hope the pics come out ok and if any body has any suggestions on what controls i could uses i would greatly appericate it.
thanks again Eddie

ed m

DHW

wont the lower water temp effect the indirect heater.in an existing system with a burnham direct vent boiler would it pay to use an out door sensor which also has an indirect heater. IF so what would be the easiest way to go about it.this is getting off the subject alittle, but why i ask,is that when I installed my boiler 2 years ago i didnt know much about condensing boilers and we had never installed them,it seems right after i installed my boiler starting hearing about them and more costumers were intrested.In my own house i have a burnham direct vent boiler, 3 zones of baseboard,2 zones of radiant and 1 indirect DHW heater,would it pay to install an out door sensor on this system.here are some pics of my boiler. would appericiate any help,and like i said we are just starting to get inquires about installing these condensing boilers and would like to learn if they would be suitable for use, mostly new constuction homes,with b.b, radiant and indirect heaters.thanks for your help i hope the pics come out ok and if any body has any suggestions on what controls i could uses i would greatly appericate it.
thanks again Eddie

Mitch_4

Yes

Lower water temps will affect the indirect performance, but you can beat this in a couple ways.

Many modcons have 2 thermostat inputs, 1 for indirect, one for room, because you have 3 high temp zones, and 3 lower you will need a mixing valve in the heating. The 1 high temp can be connected to the indirect thermostat terminals. This over rides the lower water temps that the mod con will use in heating mode. Some mod cons are set up for Out door reset (ODR), some include it with the boiler.

Using a proportionately controlled mixing valve for the lower radiant system to maintain a target temp in that zone. Let the boiler ODR control the water temp for the baseboard so the boiler can operate in condensing mode as much as possible in heating mode, and the indirect to the seperate system, so that it will drive the boiler to the 180 mark for optimnum indirect performance.

If you did not have zones, then a condensing boiler, and ODR will do the trick as add on ODR also over ride target temps for the indirect

ed m

well as you can see my boiler is not a condensing boiler, i have a manual 3 way mixing valve set up for radiant now. if i were to use an outdoor sensor, i would have to change the mixing valve?what type of control for the low temp and high temp indirect heater would i need to use,and would it be worth it being its not a condensing boiler. Any suggestions would be appericated thanks for your help.
eddie