Conventional Boiler VS. Combi Hi Efficiency boiler

jinbtown

Robert_25 said:

Your situation is a great example of what can happen when a bunch of other issues are corrected along with a boiler replacement. To Jamie's point above, nothing else in your system was left as it was before when you switched to the high efficiency boiler. Just switching to the heat pump water heater probably knocked your gas bill down considerably. I am not arguing that high efficiency boilers use less fuel, just commenting on it is really tough to say how much they save because it is a rare situation where someone replaces a conventional cast iron boiler that was properly sized & maintained without making other changes to the system.

Absolutely, and I 100% agree that the old boilers were not running at peak efficiency, were probably mis-tuned, misaligned, weren't piped correctly. There was over 200k btu of cast iron boiler when we bought the house for 2200 sq ft of zone 6, which is ridiculous when heat loss calcs are some 40k odd btu. I'm sure with service and maintenance, they could have gotten to the 80% mark in steady state operation, but with propane prices at $3.48 a gallon delivered last month, and going through 1300 gallons a year previously, you can see why even 10-20% will pay this off quickly. The other deciding factor was that I got 2 quotes for tune ups and analysis on the existing boiler in the $600 range - which damn near paid for the Noble I got at a steep discount (new old stock in storage).

pecmsg

jinbtown said:

Robert_25 said:

Your situation is a great example of what can happen when a bunch of other issues are corrected along with a boiler replacement. To Jamie's point above, nothing else in your system was left as it was before when you switched to the high efficiency boiler. Just switching to the heat pump water heater probably knocked your gas bill down considerably. I am not arguing that high efficiency boilers use less fuel, just commenting on it is really tough to say how much they save because it is a rare situation where someone replaces a conventional cast iron boiler that was properly sized & maintained without making other changes to the system.

Absolutely, and I 100% agree that the old boilers were not running at peak efficiency, were probably mis-tuned, misaligned, weren't piped correctly. There was over 200k btu of cast iron boiler when we bought the house for 2200 sq ft of zone 6, which is ridiculous when heat loss calcs are some 40k odd btu. I'm sure with service and maintenance, they could have gotten to the 80% mark in steady state operation, but with propane prices at $3.48 a gallon delivered last month, and going through 1300 gallons a year previously, you can see why even 10-20% will pay this off quickly. The other deciding factor was that I got 2 quotes for tune ups and analysis on the existing boiler in the $600 range - which damn near paid for the Noble I got at a steep discount (new old stock in storage).

What about the extra expense of keeping that High Efficiency unit operating? It's tough getting a knowledgeable tech on simple units with only a few parts. Put all these extra thermistors, computers, sensers in there and that's a lot more training needed.

jinbtown

Robert_25 said:

What about the extra expense of keeping that High Efficiency unit operating? It's tough getting a knowledgeable tech on simple units with only a few parts. Put all these extra thermistors, computers, sensers in there and that's a lot more training needed.

I was a BMW master tech with high voltage hybrid certification and then a field service rep. I was the guy they called for a 6 state region when their best tech's couldn't figure it out and they needed someone to figure out a complicated diagnostic situation. Now an EE for Bosch... A modcon boiler is like a Tickle Me Elmo compared to a BMW 7 series with fiber optic buses and 4 different communications buses. I anticipate 0 extra expense, but as you said, there is necessarily more that could go wrong compared to a hulking old unit. Will definitely keep an eye on it, Lochinvar's warranty is very good. 5 years on parts, 15 years on heat exchanger.

crispa1

Well folks, got the new system installed yesterday. Bled all rads, but, installer left with it warm to touch, at 110 deg f on the system. Fired it up 4-5 deg higher then room temp so I can make sure that rads are getting up to normal operating temp. With the system at 130 deg, running over a little over 45 min. now, I have 3 rads lingering around 95-98 deg. With my old conventional boiler, these puppies were getting up to 125 easy in about 30 min at full ramp. I am new to this combi boiler. I have checked and re bled the affected rads to no avail. Any help is greatly appreciated. Also, if someone can suggest, is there something wwrong with the install aka pump location, orientation?

pecmsg

Forget the temps of the rads....Are you comfortable?

That old system would fire up run a short time and shut off. Your radiators would get hot and cool off. Your new one is Learning; what temperature water is needed to "Maintain" a certain room temperature.

If the water if flowing left to right that's fine.

The install looks Clean and neat from here.

Daveinscranton

Newbie poster here, so take with a grain of salt, although I have read the posts on this site since 2006.

Sounds like you are the mechanical type.  Good.  If you can view your new boiler as education and entertainment, even better.  I am on my second mod con as of last week.  My HTP Munchkin liked frequent cleaning.  Like every year or two.  We shall see what the Triangle Tube likes.  Near as I can tell, water quality is very important.  So is combustion analysis.  The quality of the install will make or break the mod con.  As will the fine tuning.

Had I known who to call, I personally would have hired a pro.  No clue who to call so it became a diy.  No regrets.  I cannot imagine how a mod con would make sense unless the time is taken to max out the efficiency.  The pros can probably do it quickly.  Takes me a while.

Best wishes with you new boiler.

hot_rod

Is the home maintaining temperature with that boiler temperature? If not, it needs to be increased. Is it setup on outdoor reset control? That are lots of fine tuning adjustments built into that boiler control.

crispa1

Thx for all who have shared their thoughts. I guess I have to do my homework on programming the boiler to my liking, and to get my thoughts from the old conventional boiler out of my head. Anyone who has own this combi boiler, pls feel free to chime in. I have 1 zone, and 8 cast iron rads on a 2100 sq footage home. Moderate insulation overall. Have a blessed Sunday tomorrow.

crispa1

pecmsg said:

Forget the temps of the rads....Are you comfortable?

That old system would fire up run a short time and shut off. Your radiators would get hot and cool off. Your new one is Learning; what temperature water is needed to "Maintain" a certain room temperature.

If the water if flowing left to right that's fine.

The install looks Clean and neat from here.

Yes I am comfy with hold temp setting at 68-70. As far as learning, the info that I see from the boiler MFD is 130 deg system temp, inlet and outlet about the same around 123-126. DWH iss et at 120 f max.
If you mean from one side of the rad to to the other , yes it gets warm. As per the head install tech, he said that they have been installing this NOBLE model for 5 yrs now with a 5 pct failure rate. They used to install the infamous Navean combi that kept leaking.

hot_rod

It’s nice that the boiler has so many adjustments, it can take some time, maybe a heating season to get it dialed in exactly to your liking.

 Read the manual or watch the videos at the Lochinvar site to get some ideas on fine tuning

pecmsg

crispa1 said:

pecmsg said:

Forget the temps of the rads....Are you comfortable?

That old system would fire up run a short time and shut off. Your radiators would get hot and cool off. Your new one is Learning; what temperature water is needed to "Maintain" a certain room temperature.

If the water if flowing left to right that's fine.

The install looks Clean and neat from here.

Yes I am comfy with hold temp setting at 68-70. As far as learning, the info that I see from the boiler MFD is 130 deg system temp, inlet and outlet about the same around 123-126. DWH iss et at 120 f max.
If you mean from one side of the rad to to the other , yes it gets warm. As per the head install tech, he said that they have been installing this NOBLE model for 5 yrs now with a 5 pct failure rate. They used to install the infamous Navean combi that kept leaking.

No I mean are you comfortable!