Which Lochinvar Boiler to Choose?

Aurox

Hi all. I just purchased a house which needs a new boiler. I've done my research (a lot of it here) and went through a number of installers to find the best one. I now have an installer who I believe is the most competent around. When it comes to gas boilers, he only installs Lochinvar, which I've gathered are good boilers. Below are some details about the house.

Heated sqft: 3500
Zones: 5
Emitter type: Baseboards (total 185ft)
Heat loss calculation: ~85K BTU
Current boiler: 1983 Hydrotherm 250K BTU
New boiler (option 1): CBN135 - Lochinvar Solution 84% efficient 135K BTU
New boiler (option 2): KBN151 - Lochinvar Knight 95% efficient 150K BTU

The house is currently not very tight, but I'd like to tighten it up over the course of the next year. The difference in cost for the two boilers is $1900 and the annual maintenance is the same. I'm looking for somewhat of a trade study between these two Lochinvar boilers.

A few factors I'd like to know more about:
- Life expectancy for each
- Return on investment (worth the extra money?)
- Regular vs. high-efficiency trade off
- Cost of maintenance (outside regular annual maintenance)
- Whatever else you think is relevant

Also, a minor factor to consider, is that even though it currently only has baseboards, that might change in the future. The house is a one-story ranch (with a small basement) and the majority of the house has hardwood floors and an easy-access crawlspace with exposed subfloor to most of the main floor square footage. I hope to rework the floor plan a few years down the line and potentially install in-floor radiant heating (still only a thought). I know the in-floor radiant heating would benefit from a high-efficiency boiler. However, this would be at least 2 years down the road, if it happens at all, so this is only a minor consideration. The bedrooms are carpeted, so I would keep the baseboards in that part of the house.

Thank you all for your help. I would've been lost at trying to be an educated consumer without this website!

-Ken

Tinman

Option #3? - Lochinvar WHN155. Fire Tube heat exchanger, proven control.

Aurox

I just checked and saw I had the unit number wrong. He quoted me for the WHN155, not the KBN151.

So it's between the CBN135 and the WHN155. Sorry for the confusion.

-Ken

Gordy

Agree with Stephen, but the size choice concerns me.

IF your contractor is fully confident in his math for the heat loss calc. I would drop down to the whn 110. The DOE is 102k your heat loss is 85k. IF you plan on doing envelope upgrades I would even go to the whn 85 it's DOE is 79 k. Use the DOE if the boiler, and piping are going to be in a conditioned space.

A mod/con is going to be more efficient clawing it's way at the heat loss than being to large which will make it cycle losing efficiency.

You will find most of the time the actual heat loss real world is much less than calculated 10-15%. No one wants to get phone calls for lack of heat. You only need 460 btus a foot out of your baseboard on a design day.

Gordy

Deleted

Zman

The CBN 135 has an output of 112K/BTU.
The WHN 155 has an output of 144 K/BTU.
You have a heat loss of 85 K/BTU.
I am not sure why you aren't taking a long look at the WHN 110 at 102 K/BTU ?

I think they will have similar life expectancies.
They will both be more efficient than you present gas eating monster.
Due to the modulating ability of the WHN, I would expect it to be 15%-20% more efficient than the CBN if sized and installed correctly.

Danscrew

Aurox
Listen very close to Gordy and Zman. The most important thing is the size. The ones you are looking at are oversized why so many zones for a one story ranch? You should really thing about combining zones or just spec out the boiler for down the road when you go radiant.

Tinman

I agree with everyone on properly sizing the boiler. My eyes went right to the two choices.

Gordy

I wanted to add that a high efficiency boiler benefits from radiants lower water temps, not the radiant benefiting from a high efficiency boiler.

That is not to say base board is not a good marriage. You will use lower than 170 AWT most of the heating season even lower if your baseboard is of ample quantity. Got the type of baseboard?

Also you plan on doing under floor radiant in the future. Make sure you allow for good quality plates in that budget.

Aurox

Thank you all for the feedback. It seems the general consensus is to go with the high efficiency WHN and at the 110 size, not the 155. After the installer made the heat loss calculation, I asked him why he recommended the 155 instead of the 110. He was a bit concerned with how close the 110 was to his calculations. The house has not been tightened yet and cold Colorado winter nights can reach -20F. Therefore, he was more comfortable recommending the next size up. I'll discuss the 110 with him, since I know it's not good to oversize the boiler.

I'm not sure what type of baseboard it is (I haven't moved in yet). The installer commented that they're newer baseboards, not the originals (the house was built in 1961). That's about as much info as I have on the baseboards.

If I don't end up installing in-floor radiant heating, is it worth the extra up-front cash to install a high efficiency boiler with only baseboards?

-Ken

Zman

Ken,
What elevation are you at (you did not say anything about Colorado)?
Boilers need to be derated for altitude.
I believe the lochinvar is 2% per thousand feet.
Carl

Rich_49

Danscrew , you cannot have too many zones . One of the best features of a hydronic system is the ability to zone . Maybe this house has 3 bedrooms where all the occupants had different preferences on temp . Maybe there are exposures that regularly suffer from higher infiltration . Maybe it is zoned perfectly . Recommending cutting down the number of zones without this knowledge is silly . By the way a 3500 sf ranch is pretty damn substantial and quite conceivably could benefit from aggressive zoning if in fact 5 zones is even aggressive .
To the Op . The 110 may be a good choice , especially if you make plan to make a significant amount of DHW with it in the future but I would seriously consider Zmans recommendation of the 85 . Heat loss calcs are loaded with fudge and the fact that you have 5 zones make it a serious consideration . If 4 zones are calling at once it's enough boiler and if you sometimes see all 5 calling that would only happen for a short period of time and not be an issue .

SWEI

I'll third the recommendation on the WHN085. Do the math on your planned envelope upgrades and decide which are going to give you the fastest ROI (caulking, weatherstripping, and blown-in attic insulation generally win around here.) Heat loss calcs already include far more fudge factor than most realize. A really happy mod/con firing for hours at a time is a beautiful thing to see.

Upsize the indirect as needed to deliver what you need from the properly sized heating boiler. If your DHW demands are significant, consider pairing a tankless with the indirect.

Gordy

Carl's right the whn comes in a high altitude model for between 3000' and 12000' only, but derates 2%'for every 1000' above 3000' elevation.

That equates to 1700 btu drop in output per 2% for the whn 85, and 2200 btu drop in output for the whn 110. Depending on elevation the 85 still might be a choice

Very important information determining boiler size.

Danscrew

Rich
You have some valid points regarding zoning. I doubt much that a bedroom loop is going to have a 22,000 BTU min. For which that boiler is rated what happens when one zone calls? it short cycles now that is silly. You can have as many zones as you want as long as there above the min each and not over the max combined. You run into problems when you micro zone if its not done properly. The average Joe fails to look at the min output of the boiler and min load . Also no matter how cold it is where you live there is always a shoulder season . Dan

Gordy

Rich makes a very valid point on zoning. In a word to eliminate short cycling ......buffer tank. Or a buffer tank, boiler, and DHW all in one unit. See HTP.

One does have to look at the particular structure, rooms heat loss characteristics, and occupants habits in deciding how to zone.

SWEI

I would consider the majority of systems we encounter to be over-zoned. When we design them, we zone mostly to handle solar gain and other types of external heat (think woodstove or cook heat) and intermittent occupancy (guest wing, shop, etc.) With careful planning and balancing, room temps stay remarkably consistent.

RobG

I was wondering when Rich was going to do his HTP pitch.