View Full Version : natural gas boilers
05-28-2008, 04:14 PM
Hi guys, new to the forum, I was wondering if any of you are experiencing problems with condensing gas boilers.
I am converting from oil to gas (can't wait) and would need approx. 130kbtu for baseboard and indirect domestic hot water. I was told that the stainless and aluminum heat exchangers in condensing boilers were falling apart (acid build-up?). I had a plumber recommend an energy kinetics system 2000. Just wondering about opinions on that system or other recommendations? Thanks in advance Lou.
05-29-2008, 03:22 AM
I have been running my buderus for about a year now with no problems. I will let you know what it looks like after we do service some time this summer. I did see one at the supply house that was all messed up but my guess would be it was replaced under warranty and thats why it was there.
I think in europe all anyone buys is condensing boilers due to thier energy policies that actually work. Best I can tell they have a good track record over there.
If you want the most cost savings make sure the person who sets it up takes the time to read the manual and knows a little somthing about temperature set points and installing out door resets. Baseboard (especially copper tube) is not an idea heat medium for getting the boiler to be run in condensing (highest efficiency) mode. I can get mine to run in condensing mode about 75-80% of the time which has lead to huge cost savings over oil.
I will have paid for the system and be about $3500 ahead by the end of next winter, so for me anyhow the cost savings were huge
05-29-2008, 06:26 AM
Also, the grade of stainless can have an effect on corrosion. the 400-grade (I think 444) they use in Polaris won't stand up to squat, while 300-grades will generally resist corrosion far better.
05-29-2008, 07:02 AM
Big Lou do you think it wouldn't be cost effective for me to go with the condensing boiler? Because of my baseboard heat. While I haven't ever read the return temp, anytime I've touched the return piping at the boiler it was hot to the touch.
05-29-2008, 07:27 AM
Any time you can run lower water temperatures and take advantage of the extra efficiency to be gained in condensing mode you will be saving. Given the price of natural gas and issues of greenhouse gas and global warming you really need to give a high efficiency modulating/condensing gas boiler a hard look.
You need to start with a heat loss calculation for your structure and determine the amount of existing radiation. There should be btu/ft/degree tables available from the baseboard manufacture. If you are currently over radiated for your load, you can run lower water temperatures and get into condensing range. If you have outdoor reset, you can also run lower temperatures in the swing seasons when the weather is warmer and the heat loss is less.
You may be able to estimate the balance of radiation vs load by knowing your current water temperature, and how long the system runs when it is very cold outside.
05-29-2008, 07:53 AM
Older boilers typically ran at a fixed temperature. On a mild day, it might fire up and only circulate the water for a few minutes, then stop. This isn't particularly efficient. More modern systems can adjust the water temperature to the load, so on a mild day, instead of 180-degree water, it might only produce 120-degree water, and run longer. On a condensing MODULATING boiler, it can also adjust the heat output to match the load, and actually gets more efficient at these lower outputs since the heat exhanger can be more efficient.
As you lower the temperature, you also limit the maximum amount of heat you can release into the room, so on a very cold day, you may need that 180-degree water to be warm. Getting a boiler that can adjust can save money during operation that has to be reviewed against the extra costs up front to pay for the higher complexity. Reliability plays into this as well, so pick a reliable brand with good warranty and hope for the best.
05-29-2008, 03:58 PM
So, it sounds like condensing, modulating is the way to go. however it does seem like I or a Pro would have to make adjustments as the boiler runs to get the most effeciency out of it, or did I misunderstand. If so can you give me some advice on how it should be set up this way I can determine if the contractor is knowledgeable or a hack like me. The one thing I did learn from prior posts is that if the contractor doesn't set it up properly I'll be in for a nightmare. Thank you guys already for all the great advice. This is a great forum and I appreciate you guys taking the time to answer these questions. I think I've become anal in my old age and I try to get as much info as possible on anything I buy.
05-29-2008, 05:38 PM
No, the smarter boilers utilize sensors and computers to automatically adjust things. To do this properly, it needs an outdoor temperature sensor, incoming and outgoing water sensors. Then, it sees how much heat loss there is in the heating loop, checks against the outside temp, and then adjusts the boiler temp for maximum comfort and efficiency.
It does need to be set up properly, but that is what you pay a pro for. Not all of them are up to the task.
05-30-2008, 03:35 AM
my boiler has two adjustable set points that determine the slope of the line It will then automaticaly adjust along that line.
05-30-2008, 04:02 AM
A good HVAC contractor will start off with a proper heat load calculation. This involved measuring the all areas that will be exposed to the cold as well as a blower door test to determine air leakage. It can not and should no be done simply by looking at the old one or measuing the square footage of the house. If the blower door reveals your house is leaky fixing those leaks will save you far more money then new boiler.
There are two stages of set up on a new mod/con boiler one involves testing all the electronics for proper operation the other involves the the user adjustable settings.
The first one requires some special testers and training. Most of the time you can download the manual for the unit you are getting on line. I would do that and make sure the installer is performing all the pre start up tests that are out lined.
The other settings are pretty simple to adjust your self, if you can post to this board you can figure it out. On my unit they consist of a high temp shut off and two points one at 14degrees and one at 65 degrees that determine a line for out door temp vs output water temp.
I set my shut off temp to 58 so no matter what the thermostat does the boiler won't send heat. On a sunny 58 degree day my house looses very little heat and will stay warm enough from the sun. The rest of the time I just wear socks.
The two points that determine my heating temp line I did more by trial and error. we started off at 180 for my 14 degree temp. IE when its 14 out the boiler will make 180 degree water. From there on cold nights I lowered that temp untill I had the unit running 75% of the time. I may try lowering it even more this comming winter because running longer is more efficient as well as more comfortable (no temp swings). I repeated this process on the warm nights untill I no longer got enough heat transfer to warm the house
05-31-2008, 08:22 AM
Big Lou, I know you have a Buderus, but would you recommend any other manufactures? It does appear that I am going to go with a condensing/modulating boiler. I am going to post a new thread indirect or tankless for domestic in the Northeast.
Thanks again, Luigi.
05-31-2008, 10:01 AM
If you are considering a modulating HE boiler, don't even think about a tankless system...you'll get much better performance out of the boiler and indirect.
Some consider the Viessman the gold standard. They've come out with a different version that doesn't have as many bells and whistles, so I understand there are models that don't have as much of the premium price.
I also have a Buderus. I looked at Weil-McLain, but the was worried about the aluminum heat exchanger - the dealer I had install mine had not been impressed with his experiences on their Ultra version. Some have liked the Munchkin - I thought about that one as well. They've come out with their second generation version of that one since I looked. SOrt of like a new model car, they get the bugs worked out the second model year.
I've not surveyed the field for awhile, so don't know what's out there.
05-31-2008, 01:52 PM
thanks Jim, I was told that there were real problems with the aluminum heat exchangers (Ultra series). I am waiting to get a price from a contractor on the Buderus (wish me luck). Some of the additional cost will be offset by incentives from Con ED for switching to gas (God Bless their hearts).
Thanks again, Luigi
06-01-2008, 09:54 AM
I recommend that you take a look at the Triangle Tube Prestige line. They have SS heat exchangers and a good reputation. I have a TT 110 which has worked flawlessly for two heating seasons since install. They are essentially European boilers from ACV. The sizing may be wrong for you in that they have a 110 kbtuh and a 175 kbtuh, but they modulate down by about 3:1. TT also supplies a good indirect tank in tank domestic water heater. I understand that there is a new Prestige model out with a small built in domestic hot water tank and a continuous output like an on demand heater.
06-01-2008, 03:24 PM
The Buderus can modulate to 20% of max output. One reason I bought it was the local dealer, but the US facility is about 10-miles away (Londonderry, NH)...I figured if I ever did need parts, they wouldn't be too far away!
There are lots of indirect tanks out there...I ended up with a SuperStor Ultra...SS, lifetime warranty. I don't expect I'll ever need to deal with it again...maybe the T&P valve, or the tempering valve, but those are external.
Condensing boilers must be cleaned every year. All boilers should but it is very important for the high efficiency condensing boilers to be serviced every year. So add that into your calculations.