Hi All! First time poster here. I wanted to detail the experience I’ve had with my newly installed oil boiler, and get some of your expert insight on how I can optimize my system for further fuel efficiency. We moved away from a home that had gas heat, so I’m completely green when it comes to oil heating systems and could use a little advice.
To give you a bit of background, we recently moved into our new home last summer, in a town an hour southwest of Boston. The house has about ~2,500 sqft of living space. The previous boiler was a 35 year old Burnham V-14A, gross output 124,000 btu and net 107,000 btu. We have 4 zones (1 large zone, and 3 smaller zones). Our DHW is produced by a separate oil fired boiler (brand is Thermo-Flow, 30 gal, w/ a Beckett burner). Our oil tank is 330 gallons. Length of existing SlantFin baseboard is 163 feet. House is generally well insulated and air sealed (2x6 framing), but most of the windows are shot and are very drafty (looking to replace these soon).
When we bought the house, we knew more or less that the system was fully depreciated and on its last leg. Unfortunately for us, it was actually on its death bed. We found out early into this winter season that the heat exchanger was cracked and rotted out, and leaking out of the bottom of the system onto the basement floor (our home inspector did not catch it...rats!). Being that we were in a semi-heating emergency situation, we scrambled to pull together some quotes and get a replacement in ASAP before complete failure. As a result of not having the luxury of time to do a full heat loss analysis, I’m stuck with what I believe to be an oversized system (more on that in a bit). We ended up replacing the system with a Buderus G115ws/5 with a Logamatic R2107 control with outdoor reset. This system has a gross output of 136,000 btu and net 119,000 btu. So far everything has been working well. The burner is a Carlin EZ-1HP [based on spec sheet: firing at 1.16gph, head setting .75, pump pressure 185]. The system has 5-zone Taco ZVC405-4 relay, and a Grundfos Alpha 15-55F/LC variable speed circulator. We opted to not put in an in-direct DHW tank at the time due to budget constraints. Although we did have them install a stub out for a future indirect whenever the current tank decides to go.
I’ve done a lot of tweaking to the Logamatic settings to dial it in to the point that it barely keeps up with the heat load of our largest zone. Our installer wasn’t that knowledgeable with the Logamatic control, so it was ultimately up to me to figure that out (Buderus apparently does not provide over the phone technical support). These are the settings I’m am currently working with:
• Ref Temp: 168°
• Offset: +2°
• Heating Curves: 120° @ 50°, 149° @ 32°, 178° & 14°
So, we just had our first tank fill up today since the system was installed. Over 59 days, we went through 250.7 gallons of oil. Given that the burner operates on 1.16g/hr that puts us at around an average of 3.66 hours of burn a day using rough arithmetic. Are we getting good gas mileage on this thing or are we burning through way more oil than necessary? Is that hard to quantify if we have a separate appliance that also utilizes oil for DWH? Side note – The Logamatic still shows 0 for “Hours Run.” Any thoughts on why that meter is not working? Could it have been wired incorrectly?
Now – let’s talk boiler sizing. As it stands, I’m certain we have an oversized system and I’m sure y’all will concur. Having said that, we are planning to finish our attic in the next few years, which will add an additional 600 sqft to the load. Also, we plan on adding an indirect DHW tank down the road too. Will these additions add enough volume to system to offset the current oversized conditions? Is there a way to safely tweak the settings of the burner to downfire and generate longer burn times to curb short cycling? I’m interested to hear from you all now that I have given you the lay of the land.
General observation: Why is it that all of the HVAC pros we had come out to give us a quote recommended boilers around the same size as the one we had? Is it just pure laziness on their part to not do their due diligence with a thorough heat loss analysis to properly size the thing? Thanks in advance and apologies for the long winded post!