Which Viessmann boiler to buy?

ConnecticutYankee

Hi guys,

This will be my first post. I've been reading this forum for decades and appreciate the knowledge I've gained from all of you over the years. I’m hoping that you can help me make a decision in regard to which new boiler I should buy.

We bought a brick ranch four years ago here in Connecticut that was built in 1952. The main part of the house is 1752 square feet and is heated by cast-iron radiators. The house also has a two-story wood addition that’s an additional832 square feet and is heated by a hydro-air unit (too small @ only 31,200 btu’s)which is on its own zone. The current three-zone system has a twenty-year-old Weil-McLain Gold series pin-style oil-fired boiler that's rated @ 126,000btu's. A few months after moving in, I had a Viessmann Vitocell 300V 53-gallonindirect water tank installed - which replaced a very old indirect which was long overdue for replacement.

Unfortunately, I recently discovered a leak underneath the 275-gallon oil tank. It wasn’t much, maybe three or four ounces. The oil tank is almost 25 years old. It doesn’t seem to be happening when oil is delivered but slowly drips every few days. This might not seem like something to worry about, but the potential for a catastrophic tank failure is nothing to ignore. The replacement of the oil tank also factors into my buying decision. A new double-bottom tank from Granby will cost around $4,000.00 installed. This is why I am leaning towards a gas-fired boiler.

Fuel oil consumption is modest. We burned 900 gallons total in2024 with the thermostat set at a constant 66 degrees without any time-of-day setbacks. If you subtract the oil used for making hot water (plus the boilers internal water), the fuel used for heating is probably around 700 gallons a year. That’s both good and bad. The good is that I spend just about $ 3200.00 per year to heat my whole house at current oil prices. The bad is that the potential for saving money by replacing my old system will be minimal (let’s assume under a thousand dollars per year). The good is that as we age (currently fifty years old) we will have to raise the temperature to feel comfortable (the elderly set the thermostat as high as 75) and not suffer the increased fuel usage from our old boiler. The potential for fuel savings might be substantial if the house was indeed heated to 75 degrees (let’s assume the savings to then be several thousand dollars annually). We’d be happy with 68 degrees for the foreseeable future. We might convert the existing attached two-car garage into an in-law apartment in a few years (it’s currently unheated but would be nice to have a Modine Hot Dawg hydronic ceiling-mounted 20k btu garage heater in the meantime) which has to be factored in when sizing the boiler.

Here are the three boilers that I’m considering:

Viessmann Vitola (oldie but maybe the best oil-fired boiler ever made / new NOS units still available on the secondary market).

Viessmann Vitorond 100 (probably the best oil-fired boiler “currently” available).

Viessmann Vitocrossal 300 CU3A (Gas condensing boiler but floor mounted and has 5 stages of modulation with a high-mass water content of 13 gallons).

They have been chosen based on several criteria - but primarily durability first and energy efficiency second. For example, the Vitola could last forty years or more if properly maintained and you store a good inventory of spare parts yourself. The Vitola is also very cheap, I could buy them for $ 1500.00 a piece right now. The Vitola and Vitorond would be hooked up to a new oil tank and the Vitocrossal would burn Propane. We have a small 125-gallon propane tank next to the house currently but I would need to have a large 1000-gallon propane tank buried in the side yard if I wanted to be able to purchase propane smart when the price is lower during off-peak times. Installing an in-ground propane tank would be expensive but possibly worth it for increased curb-appeal.

I’m also a little concerned that Carrier bought Viessmann. This could eventually have negative consequences for those of us that love Viessmann products. It’s worth considering a purchase now before the brains at Carrier decide to discontinue either the Vitorond or Vitocrossal.

What are the potential benefits and/or drawbacks to thesethree boilers in your opinion(s)?

I’m looking forward to reading the replies - both good and bad. This ended up being a long write-up, my apologies!

Thank you!

Mark

offdutytech

I would say the Vitorond or the CU3A would be good choices. Both boilers are very good. The issue I've had were the CU3A would have been a great choice for a replacement boiler was ceiling height in a"Michigan" basement. Basically a glorified crawl space. I just didn't have the headroom for the boiler. The CU3A is easy to connect to a majority of piping arraignments with little modification. The CU3A is going to give you a few added features with the controls like OAT reset.

The Vitorond casting is well built, but heavy to move . We had a customer purchase one and put a waste oil burner assembly on it for his shop. I attached a pic so you can see what the casting looks like. A plus on the Vitorond would be that you can change over the burner to gas at a later date if you decide fuel oil is no longer the route you wish to go.

The question is what fuel you would like to go with now propane vs fuel oil. Factoring in the fuel oil tank replacement vs a 1000 gallon propane tank installation is sort of a wash. I would treat this as a separate bid then compare just the boiler installs. We don't discuss actual prices here. As for the Carrier acquisition of Viessman, I have not yet seen any changes in service from our Viessman rep or supply houses. It's still my go to mod con boiler choice.

mattmia2

You could also just replace the current oil burner with a gas power burner. 20 years is still pretty young for a boiler. It could leak tomorrow or it could last another 30-40 years. Without some heat loss calculations you don't know if your current boiler could pick up your loads or not. If the conversion to gas is propane it likely isn't going to be cost competitive to oil. The 125 gallon tank probably can't handle the drawdown of a boiler in winter so the new propane tank would be a significant expense. The cost of replacing the boiler is going to far exceed any fuel savings once you account for the piping and trim and labor.

Kaos

The 600gallon/year oil use puts your heat load around 30000BTU, you are oversizing by a fair bit with the Vitocrossal 300 CU3A. I would run through the math here to get your heat loss nailed down and go from there on selecting a new heat source.

https://www.greenbuildingadvisor.com/article/replacing-a-furnace-or-boiler

Oil heat has completely disappeared around me due to operating and maintaince costs.