Bypass for a Buderus G115/3 boiler?

EricPeterson

https://forum.heatinghelp.com/discussion/comment/1849822#Comment_1849822

Correct - I have not installed a DirtMag, but it's on my list of things to do this summer. The Caleffi has been working fine. Last year I had the 140F element, I swapped it out this season for the 115F.

As for run times, I've not collected much data. I can tell you that, because we setback the temperature at night, that it will run for a hour or two in the morning, and also in the late afternoon (we have a daytime setback for one of the zones). I did collect some data this morning pursuant to an issue I'm having. It ran for 1h 45m. The system supply temp ranged from 68 to 150 during that time.

I should mention though that I also have an ODR (OutDoor Reset) and while the initial setpoint was 147F, that increased to 157, 167, then 170 (max) due to a "boost" function that I have enabled (raises the setpoint by 10F for every 30 minutes of constant runtime).

So "typical" depends on a lot of factors - which zone(s), setpoint, setback recovery. Bottom line though is that the system as a whole works very well, and the house is quite comfortable. I spend a lot of time by the boiler since it's right next to my workshop where I am always busy with one project or another.

—Eric

jesmed1

@EricPeterson Thanks for that feedback.

It sounds like our main difference is we have only one zone, so we have to heat 100+ gallons of water on every cold start, with the result that our water temperature doesn't get very hot except for the one long morning recovery from setback. So a Caleffi on a new boiler (when the time comes) will definitely help the return water heat up faster.

jesmed1

@hot_rod said:

"If it were my property….

Two mod cons sized to the calculated load would get you 20-1 turn down, running 90% some of the heating season. So two 80,000 btu/hr boilers could modulate from 8,000 btu/hr- 160,000 btu/hr."

Understood. That would be a great system that would definitely save us fuel $$. Unfortunately having 3 other owners with different plans for how long they may be living here makes it impossible to install an expensive system like that, because everyone may not be here long enough for the ROI. We just have to keep it simple with reasonable up-front costs that everyone can swallow.

I've asked our heating company to come out tomorrow to give us a price on a Buderus G115/4. He said he'll also give us a price on an Energy Kinetics. I know we're not allowed to discuss prices here, but I'll be interested to see what those numbers turn out to be.

hot_rod

Probably not much difference in price between a fixed output, mid efficiency and a modulation high efficiency mod con. The Buderus $ is less burner.

The mod con comes with a lot of control features ideal for your system, ODR to start. They would require a different venting system however.

20 years is not unreasonable for a properly installed and cared for quality brand mod con

jesmed1

@hot_rod

Thanks for that info. If I had known 5-10 years ago what I know now, I might have steered us in the mod-con direction, but there were a number of hurdles. We had two old oil tanks that needed replacing, so we sunk a good chunk of change into new tanks, which kind of renewed our commitment to oil. I did look into switching to gas burners 2 years ago, and that was a bust because the one plumber I could get to come give a quote on running some new gas pipe must have thought I was born yesterday from the ridiculous number he gave me. And then I couldn't get anyone to quote on installing gas burners, because everyone wanted to sell me new boilers, and then the chimney liner was going to be a big hit. So it never went anywhere. Plus I have three other owners to get on board with every decision.

In a perfect world, I would have known 10 years ago that this system is perfect for a mod-con because we could be condensing most of the time with 25% better efficiency than a cast iron boiler, and I would have been able to plan for a switch-over before the oil tanks needed replacement, and I would have known that we could direct vent through a sidewall instead of needing a stainless chimney liner, etc etc. Unfortunately I didn't know enough at the time to change course, so we are where we are, which is invested in oil and cast iron boilers.

Also, I may not be here much longer, and when I leave no one else is going to be able to/interested in making a major change in fuel source, boiler type, venting, etc. So the ship will keep heading pretty much where it's headed, towards new cast iron boilers with (hopefully) somewhat better efficiency. But I will take everything I've learned here and apply it to my next house, and maybe there I can do as you suggest.

jesmed1

Just finished up talking to the boiler sales guy from our heating oil company. I gave him a package consisting of heat loss calcs for the building, a suggested piping diagram for Buderus G115/4's with the Caleffi 280 mix valve, and a BOM for pricing.

Really good guy, knows his stuff, and has been to some of Dan Holohan's seminars, so that's a big positive. He said Dan's seminar was the only one he didn't fall asleep in (haha).

He agreed with my heat loss calcs and boiler down-sizing rationale, so it was nice not to get any pushback on downsizing as I half expected. We talked about water volume, return water temps, the rationale for a 115 degree mix valve element, etc, and he understood our low return water temp issue and said our proposed bypass piping with the 115 degree element was fine.

He's a gray-hair now who grew up installing and servicing boilers in the Boston area, first working for his dad, and later for larger oil companies. So I would rate him an A+ for knowledge and experience, which gives me confidence they would do a good job. Will expect to hear from him next week on pricing.