need some advice
#1
05-22-08, 07:02 AM
need some advice
help please! i am about to install anew boiler to replace my over fifty year old pig.
have chosen buderus with an indirect and a riello gun.
the comany i am going with suggests g-215-3.
my house is around 2200 sq. ft. (hydronic baseboard & radiators) heat loss of 50000btu hr. (according to the guy from energy kinetics)
two zones currently, but will be splitting it to three with the new install to seperate an apartment i rent out.
is the g215 too big? another company gave me a quote using the the smaller g115.
appreciate any advice....thanks
have chosen buderus with an indirect and a riello gun.
the comany i am going with suggests g-215-3.
my house is around 2200 sq. ft. (hydronic baseboard & radiators) heat loss of 50000btu hr. (according to the guy from energy kinetics)
two zones currently, but will be splitting it to three with the new install to seperate an apartment i rent out.
is the g215 too big? another company gave me a quote using the the smaller g115.
appreciate any advice....thanks
#2
05-22-08, 08:08 AM
Holy smokes... you have a small load home (50 MBH) that you want to divide into three zones and someone wants to install a 117 MBH net boiler?
You should be considering a much smaller boiler. I'd also suggest a buffer tank for a situation like yours. That will allow longer run times when only one load is calling.
Is oil the only fuel choice for you?
You should be considering a much smaller boiler. I'd also suggest a buffer tank for a situation like yours. That will allow longer run times when only one load is calling.
Is oil the only fuel choice for you?
#4
05-22-08, 09:15 AM
Any particular reason for not using the Energy Kinetics? Evidently, since you were given a heat loss by an EK dealer you were also given a quote. The post-purge feature negates the oversizing of the system and you won't have short-cycling problems.
#5
05-22-08, 09:49 AM
basically up front cost of $2200 more than the buderus.
also a lack of intrest free financing.
EK offered a 9% rate on the balance.
got intrest free for 18 months.
other than that, longevity concerns of steel vs. cast iron
and the ability to convert the buderus to gas down the road.
also a lack of intrest free financing.
EK offered a 9% rate on the balance.
got intrest free for 18 months.
other than that, longevity concerns of steel vs. cast iron
and the ability to convert the buderus to gas down the road.
#7
05-22-08, 10:24 AM
i know. big concern of mine.
but discussed with the installer and expressed the concern.
he feels it is the right choice.
what else can i do to make sure?
also possible the heat loss is not correct.
not educated enough about it.
the ek dealer said maybe 50k btu hr?
but unsure what he based it on.
the installer also came out and did a survey.
damn, there is a lot involved with this decision!!!!
but discussed with the installer and expressed the concern.
he feels it is the right choice.
what else can i do to make sure?
also possible the heat loss is not correct.
not educated enough about it.
the ek dealer said maybe 50k btu hr?
but unsure what he based it on.
the installer also came out and did a survey.
damn, there is a lot involved with this decision!!!!
#8
05-22-08, 10:45 AM
For doing a Manual J calulation you can just go to SlantFin's web site. From there, you can order the free CD or download a free copy of their heatloss calculation program.
Then use the program and calculate everything room by room. Infiltration (draftiness from outside) factors will be a bit of a guess. The heatloss number that gets calculated is itself overstated. Your true heatloss will probably be around 70% of the calculated number.
Then use the program and calculate everything room by room. Infiltration (draftiness from outside) factors will be a bit of a guess. The heatloss number that gets calculated is itself overstated. Your true heatloss will probably be around 70% of the calculated number.
#9
05-22-08, 10:46 AM
Which indirect? It is likely that although the house load may be around 50k BTU/hr, the installer is sizing for the indirect to get rated (or better...) recovery. Hence his suggestion for the 215 instead of the 115. If he's sizing the boiler for a large indirect because you've got a giant whirlpool bathtub, for instance....
You might be better off with a G115/28, or even the G115/21 if you are going with a small indirect.
There are also tricks you can use to get more effective capacity in an indirect, and can upsize or downsize depending on how the contractor figures your domestic hot water load. For example, keep the tank set for 140F and have an anti-scald tempering valve installed on the domestic output to provide ~115F at the faucets.
No matter what you choose, I very strongly recommend the Logamatic R2107 control package. This is Buderus' control for outdoor reset and other functions that will increase the overall efficiency of your system and help mitigate for the oversizing relative to the space heating load. Might cost an extra $1k for the unit and installation, but it will pay for itself in a couple years, tops. Or you could go with a control like the tekmar 260, which might be cheaper for the part but have more cost for the install. The 2107 is pretty plug-n-chug.
Heat loss of 50k BTU/hr for 2200 sf is about 23 BTU/hr/sf, which is probably within 20% of actual if your climate is cold -- e.g., design day 0-5F. If you're in a warmer climate, then the building is pretty lossy and you should also think about adding insulation and air sealing wherever possible.
You might be better off with a G115/28, or even the G115/21 if you are going with a small indirect.
There are also tricks you can use to get more effective capacity in an indirect, and can upsize or downsize depending on how the contractor figures your domestic hot water load. For example, keep the tank set for 140F and have an anti-scald tempering valve installed on the domestic output to provide ~115F at the faucets.
No matter what you choose, I very strongly recommend the Logamatic R2107 control package. This is Buderus' control for outdoor reset and other functions that will increase the overall efficiency of your system and help mitigate for the oversizing relative to the space heating load. Might cost an extra $1k for the unit and installation, but it will pay for itself in a couple years, tops. Or you could go with a control like the tekmar 260, which might be cheaper for the part but have more cost for the install. The 2107 is pretty plug-n-chug.
Heat loss of 50k BTU/hr for 2200 sf is about 23 BTU/hr/sf, which is probably within 20% of actual if your climate is cold -- e.g., design day 0-5F. If you're in a warmer climate, then the building is pretty lossy and you should also think about adding insulation and air sealing wherever possible.
#10
05-22-08, 11:22 AM
sorry.....should have mentioned
buderus s-120 indirect
and taco pc 700 outdoor reset control
the logamatic was around a thousand and was only really concerned with the outdoor reset function
taco was 300 installed
good info here by the way......very helpful to a layperson like myself....thanks
buderus s-120 indirect
and taco pc 700 outdoor reset control
the logamatic was around a thousand and was only really concerned with the outdoor reset function
taco was 300 installed
good info here by the way......very helpful to a layperson like myself....thanks
#11
05-22-08, 11:42 AM
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I have a quick method I have been using for years.
L x W x (heat factor) = BTU Load
for instance,
Your house
L x W = 2200 sq. ft.
2200 x 35 ( if new home ) = 77,000 BTU
2200 x 40 if older home, poor insulation or lots of glass) = 88,000 BTU Load
BTU load plus 25,000 for indirect heat =
New home - 77,000 + 25,000 = 102,000 BTU Load
Old home - 88,000 + 25,000 = 113,000 BTU Load
These are just quick numbers and are oversized.
The Energy Kinetic Heat loss is probably more accurate but they are selling you a way oversized boiler as the G115 puts out from 74,000 to 120,000 BTU
the G215 BTU output is 134,000 to 768,000
If you need more than the G115, I guess I haven't been in the business long enough.
L x W x (heat factor) = BTU Load
for instance,
Your house
L x W = 2200 sq. ft.
2200 x 35 ( if new home ) = 77,000 BTU
2200 x 40 if older home, poor insulation or lots of glass) = 88,000 BTU Load
BTU load plus 25,000 for indirect heat =
New home - 77,000 + 25,000 = 102,000 BTU Load
Old home - 88,000 + 25,000 = 113,000 BTU Load
These are just quick numbers and are oversized.
The Energy Kinetic Heat loss is probably more accurate but they are selling you a way oversized boiler as the G115 puts out from 74,000 to 120,000 BTU
the G215 BTU output is 134,000 to 768,000
If you need more than the G115, I guess I haven't been in the business long enough.
#12
05-22-08, 12:26 PM
Yes, the EK is sometimes a little more expensive. However, it doesn't need to use outdoor reset to achieve its high system efficiency. The post-purge at the end of a cycle also negates the effects of being a little oversized. I don't see any good reason to use a G215. Oversizing that much will probably lead to burner short cycling which definitely reduces system efficiency and could cause some sooting over a season.
As far as adding load for domestic, the average daily load is under 40,000btu so really no need to add it in.
According to a study done last year at Brookhaven National Labs under the auspisice of NORA and NYSERDA, EK had the highest system efficiency of all types of HHW system tested. That lineup included Buderus with the Logamatic and a gas-fired 95% AFUE mod/con.
As far as steel vs iron, that's an age old subject. Steel boilers can last as long or longer than cast under the same conditions. High pressure steam boilers are only made with steel.
As far as adding load for domestic, the average daily load is under 40,000btu so really no need to add it in.
According to a study done last year at Brookhaven National Labs under the auspisice of NORA and NYSERDA, EK had the highest system efficiency of all types of HHW system tested. That lineup included Buderus with the Logamatic and a gas-fired 95% AFUE mod/con.
As far as steel vs iron, that's an age old subject. Steel boilers can last as long or longer than cast under the same conditions. High pressure steam boilers are only made with steel.
#13
05-22-08, 12:58 PM
S-120 is a 32 gal indirect. The rating sheet is here
http://buderus.net/LinkClick.aspx?fi...id=175&mid=684
The G215/3 would max out the potential of this indirect, for sure (its DOE out is 117k).
If you stay with that indirect, I suggest going to the G115/28 or /21 and using the aforementioned tempering valve. Tempering down hot water gives you a reduced draw rate of the actual hot. I forget how the proportionality works, but think of it as reducing the hot draw of a 2.5 gpm showerhead to something like 2 or 1.8. You get longer use and the boiler starts the recovery cycle before the whole tank cools down.
If you go with the PC700, then you must be using a Taco -EXP switching relay or zone valve control. Since that's the case, make sure the indirect is on a priority zone, and consider getting the PC605 priority protection card, and the PC600 post-purge card. These are simple plug-ins that you could do yourself in under 4 minutes.
http://buderus.net/LinkClick.aspx?fi...id=175&mid=684
The G215/3 would max out the potential of this indirect, for sure (its DOE out is 117k).
If you stay with that indirect, I suggest going to the G115/28 or /21 and using the aforementioned tempering valve. Tempering down hot water gives you a reduced draw rate of the actual hot. I forget how the proportionality works, but think of it as reducing the hot draw of a 2.5 gpm showerhead to something like 2 or 1.8. You get longer use and the boiler starts the recovery cycle before the whole tank cools down.
If you go with the PC700, then you must be using a Taco -EXP switching relay or zone valve control. Since that's the case, make sure the indirect is on a priority zone, and consider getting the PC605 priority protection card, and the PC600 post-purge card. These are simple plug-ins that you could do yourself in under 4 minutes.
#14
05-22-08, 01:25 PM
plumbingods, your method is a very backwards step for most of the regulars here. We strongly advocate everyone doing a proper heat loss calculation. Since this is a DIY forum, we can help people "DIY" the heatloss without having to resort to methods with very questionable accuracy.
Your method almost triples my true heatloss.
Your method almost triples my true heatloss.
#15
05-22-08, 02:21 PM
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Hi everyone,
I don't want to start any problems here.
I feel I should explain myself a little further.
We were asked if we felt a Buderus G115 or a G-215/3 was the right sized boiler based on 2200 sf. with no other information about the house.
I did a quick heat loss that I know is well over that which is needed to determine which boiler I thought could do the job. I posted my quick method so people would know how I came to the answer I did. I in no way discouraged anyone from getting a proper heat loss of there house, as a matter of fact I even suggested that E. K., who's results were lower than mine, were probably more accurate than my numbers.
So basically I was saying, going with my numbers, you do not need the G215/3 boiler but could downsize to the G115 with the highest firing rate and still have plenty. Now if you use E. K. 's numbers there is even more reason not to use the G215/3
I was given this method about 20 years ago and with my experience has worked fine for me. I have even checked my numbers against other supply house heat losses and we are close. For those of you that wish to put the exact amount of heat in can listen to your customers call you at 2:00am on a 20* below zero night and the heat cant keep up. Or they want to add some heat in the basement and the customer is forced to replace the boiler because the last guy cut it so close and didn't leave a little leeway.
I am a firm believer that the older systems are way over sized but a little oversizing won't hurt. I live in the North East. Maybe that's our mentality here. Maybe down south a ways you can be a little closer. I don't know.
Once again I am not trying to offend anyone here, just stating my opinions. Take them or leave them.
Thanks for listening.
I don't want to start any problems here.
I feel I should explain myself a little further.
We were asked if we felt a Buderus G115 or a G-215/3 was the right sized boiler based on 2200 sf. with no other information about the house.
I did a quick heat loss that I know is well over that which is needed to determine which boiler I thought could do the job. I posted my quick method so people would know how I came to the answer I did. I in no way discouraged anyone from getting a proper heat loss of there house, as a matter of fact I even suggested that E. K., who's results were lower than mine, were probably more accurate than my numbers.
So basically I was saying, going with my numbers, you do not need the G215/3 boiler but could downsize to the G115 with the highest firing rate and still have plenty. Now if you use E. K. 's numbers there is even more reason not to use the G215/3
I was given this method about 20 years ago and with my experience has worked fine for me. I have even checked my numbers against other supply house heat losses and we are close. For those of you that wish to put the exact amount of heat in can listen to your customers call you at 2:00am on a 20* below zero night and the heat cant keep up. Or they want to add some heat in the basement and the customer is forced to replace the boiler because the last guy cut it so close and didn't leave a little leeway.
I am a firm believer that the older systems are way over sized but a little oversizing won't hurt. I live in the North East. Maybe that's our mentality here. Maybe down south a ways you can be a little closer. I don't know.
Once again I am not trying to offend anyone here, just stating my opinions. Take them or leave them.
Thanks for listening.
