Looking for floor mount, low output gas boiler, local installers?

stuartf

I have an 1800 sq ft home, well insulated, Manual J yields 25k Btu, fuel consumption more like 33k Btu. Considering replacing 22 year old Munchkin (80k Btu) that formerly served both sides of a duplex, now I only need a unit to heat my half.
There are three zones, #1 is hydronics in slab, upper two are fin tube.

Finding a unit that has a high enough turn down has been challenging, I have identified the Burnham (aspen and K2) and Lochnivar (with the KHB055N and KHB085N) as possibilities. I currently have an indirect for the domestic side of things and it seems best to maintain that. The problem is that I haven't been able to find local installers (Ithaca, NY) experienced in either of these product lines. My assumption is that installer experience with a particular product line is key to a no hassle install.

Any experiences with either of two two identified products (or others that might fit the bill) would be appreciated. And the two Lochnivars... both have the same low output figure but different maximum, is there a better choice here??

Hot_water_fan

The Modcons will all be about the same size: 8-10k Btu on the low end. A cast iron boiler around 40kbtu would be oversized, but might be cheap enough that doesn’t matter 

GGross

The floor mount requirement might be the tricky part here, I would lean toward the Lochinvar of the 2 brands you mentioned. Nothing against Burnham by any means, there just tend to be more people familiar with Lochinvar products than the Burnham condensing products. Triangle Tube has a floor mount boiler that they ship with a nice caleffi low loss header to make primary/secondary piping really easy, the low fire won't be quite as low as the lochinvar, but there may be some installers in your area familiar with the brand.

EdTheHeaterMan

One of the considerations is the need to produce domestic hot water. A small Utica SBV boiler has a Net rating of 36,000 BTU. This may be more than enough for the coldest day of the year, however it is not large enough to provide unlimited DHW the way that your indirect water heater is able to do if it were connected to say a 125,000 BTU or larger boiler. The indirect may be able to provide a first hour rating of over 200 gallons of hot water based on the recovery rate when connected to a large output appliance. But it can not make a small BTU appliance create more heat than the available output of the boiler it is connected to.


A 15 minute shower (teenager minimum) where your entering water temperature is around 53°F and you want to have a 115°F outlet temperature at the shower head will require at least 94,000 BTU output from the boiler. That would be a 110,000 BTU input burner on an 83% AFUE boiler. This is based on a first hour rating of your indirect being greater than or equal to 180 gallons.


First hour ratings are a measurement used for comparison of different water heaters. For example:
A Tankless gas water heater that can produce 3 gallons per minute of hot water with a 60°F temperature rise will have a first hour rating of 180 gallons. 3 GPM x 60 minutes = 180 gallons
A tank type water heater with a 40 gallon tank will produce 80% of the tank capacity plus the recover rate of the tank over a one hour period If the tank’s heater has a recovery rate of 20 gallons per hour (line an electric water heater element) then you can add 20 gallons to that total and the first hour rating is 50 Gallons.
A 40 gallon Tank type heater with a gas flame at the bottom may have a recovery rate of 80 gallons per hour, so add 80% of the tank to the 80 gallon per hour recovery and that tank has a 110 Gallon first hour rating.


Your indirect (if it is a 30 gallon) has a first hour rating of 24 gallons plus what the 36,000 BTU boiler will add to the tank. Which is about 60 gallons of hot water or a first hour rating of 86 gallons. If you are using a 3 GPM shower head then you have about 26 minutes of hot water before you start feeling cold water in the shower. If you have only one shower in your home then you should be fine. If you have two showers going at the same time, then you each get about 13 minutes before you run out.

Just sayin' you can go crazy with getting the most efficient boiler for your home and end up with about the same operating cost as the low cost boiler. You really need a much bigger home is order to have a larger savings potential.

EdTheHeaterMan

If, after reading my previous post, you believe that the recover rate of the indirect is not as important since you have only one shower on your home, then you might consider the Crown AWR Boiler by Velocity Boiler Works. Their smallest boiler is only 38,000 input with 28,000 NET output
That should be enough the heat your home and fill up your water heater. It will just take a littler longer to fill up your indirect water tank

GGross

I believe the OP currently has a munchkin installed so this would require additional install costs to install different venting

bburd

Most showerheads these days use less than 3 gallons of water per minute. The US federal maximum has been 2.5 GPM since 1992. Some states have lower requirements: 2.0 GPM in Colorado and 1.8 in California.

stuartf

We are two in the house, I shower very quickly and about half the time shower at the gym. My wife is a bit more exuberant with water, but still quite conservative. I am around 8-10 gallons for a shower my wife is probably double that. But there is always the next owner syndrome