What do you think of the Lochinvar Knight KHN155 gas-fired boiler?

andysaks

Hi folks -- My family just moved into a new 4-bedroom, 2-story colonial near Boston and need to replace our boiler. In order to qualify for the MassSave purchase loan program and $3,000 boiler efficiency rebate, the boiler must be at least 90% energy efficient. Our new plumber has recommended the 155,000 BTU Lochinvar knight KHN155 gas fired boiler. I can't find much information about it online, and our plumber suggested I ask here.

What do you think of this company and boiler? If you've used it, what's been your personal experience? Would you recommend it to us? Why or why not? All feedback and links to online resources are welcome and appreciated!

Thank you -
Andy S.

KC_Jones

My first thought, is this house a mansion? That's a huge boiler and unless you have a gigantic house or plan on heating with the windows and doors open it's most likely too big. I'll leave others to comment on the unit itself.

Brewbeer

I agree with Hat and KC, 155K is likely WAY too big for the house. Need to do a proper heat loss estimate for the building before you can select the proper sized boiler. Performing the heat loss estimate requires that measurements of all the walls, windows, doors, ceilings, floors, fireplaces, etc., exposed to the outside/unheated interior spaces be made, and R-vaules of walls, floors, ceilings, windows, doors, etc. be estimated to derive a heat loss estimate. It takes time to do it properly.

Also, a modulating condensing boiler may or may not be a good fit for your application, it really depends on the type and amount of radiation there is in the house.

Can you describe the house a little bit? Square feet of heated space, age/type of windows, amount of insulation, type and size of radiators, etc.

SWEI

If the house is under 3,000 square feet, I can pretty much guarantee that a KHN-085 will take care of it.

Paul48

And, another thing we hear, all the time. If the boiler is also making domestic hot water, you don't up-size the boiler, you up-size the tank.

andysaks

Hi folks - thank you very much for your quick and helpful feedback!

To answer your question, the house is...

- Garrison colonial built in 1968
- About 2300 square feet (not including an unheated basement)
- Still has its original boiler, circa 1968
- Upstairs: 4 bedrooms and 2 bathrooms
- Main floor: kitchen, living room, dining room, 4-season porch, small playroom and a guest bathroom
- All rooms use forced hot water for heat.
- All windows are original, we don't know the type. They're all reasonably tight, no major leaks. We're expecting to replace the upstairs windows in a few months, downstairs windows in a few years.
- Not sure how to answer "amount of insulation." Currently, attic and some other areas are under-insulated, other areas have full insulation. We're adding more insulation as needed next month under the MassSave insulation program based on their recent home energy audit; after that, insulation should be very solid throughout.

What do you think?

Paul48

Take advantage of as much information as MassSave is willing to generate for you. What part of Mass are you in?

andysaks

We are in Southborough. We had a MassSave audit two weeks ago and are using virtually every cost-saving program they offer!

Paul48

Did they give you any information regarding the heat loss of the structure?

andysaks

No

JohnNY

Brewbeer said:

Need to do a proper heat loss estimate for the building before you can select the proper sized boiler. Performing the heat loss estimate requires that measurements of all the walls, windows, doors, ceilings, floors, fireplaces, etc., exposed to the outside/unheated interior spaces be made, and R-vaules of walls, floors, ceilings, windows, doors, etc. be estimated to derive a heat loss estimate.

I have a quote burned into my head from a hydronics seminar given by one of the prominent hydro-geeks around here that went "No one in Europe does a heat loss calculation." then going on to say there's little point when using a modulating boiler.

It makes sense to me that some very basic info could get you close, however conservatively you'd like, then the boiler would take over from there. Where I live, 30 BTUs/sq ft works well but a proper heat loss often comes in at around 19-22 BTUs/sq ft for attached homes that heavily populate the 5 boroughs of New York City. Detached homes of quasi-modern (20 yrs-ish-old) construction do fall closer to 28-30.

andysaks

I forwarded your comments about the 085 to my plumber, and he says he completely agrees with your assessment. He says if this were a fixed output boiler, he'd be more inclined to match the heat loss of the house versus the heat absorption of the water heater, or middling the two.

However, he wants me to tell you he's sizing it based on the demand of the hot water heater along with the demand of the house. The boiler has a 10-to-1 turndown ratio, so when it's running on the low end it's running at 14,000 BTUs, vs. 10,000 BTUs for the next size down, both well below the heat loss for the house.

I don't know what any of that means, but does it change your assessment that the 085 is a better fit than the 155?

Gordy

That would be a huge demand. Stacking both loads is not necessary. DHW priority satisfies the DHW load then goes back to CH demand, if there is one. The loads are seperate.

However enlighten us to your DHW demand.

Gordy

What he is thinking is oversizing with the turndown is not a big deal. However would you buy a car with 400 hp if you will never need it

Paul48

Didn't I tell you he'd say that?

SWEI

What are you currently using to heat your domestic water?

The KHN-085 will recover at twice the rate of a conventional gas-fired tank heater. That's generally more than enough to meet all but the largest hot water demands. Unless you have four teenagers, a multi-head shower, or a huge soaker tub I would seriously doubt the need for a larger boiler.

andysaks

I'm fascinated by this discussion -- I don't understand half of it, but appreciate your passion for the topic! Please keep it coming!

To respond to the stuff I understand:

- For hot water, when we replace the boiler, we're also planning to replace the 12-year-old water heater with an Heat-Flo HF40 indirect water heater. (I requested reviews for this in a separate thread today on The Wall.) So the new boiler would be working in tandem with the HF40.

- We have no teenagers, multi-head showers, or soaker tubs; just a young daughter and two adults who all shower about once a day. No one takes baths. We run the dishwasher about every three days, and do maybe 5-8 loads of laundry a week.

SWEI

If the old water heater was a 40-50 gallon gas-fired tank, the KNH-085 paired with a 40-gallon indirect will be positively luxurious.

Zman

You don't need to add the 2 loads. The DHW is a short intermittent load which will have little or no effect on heating. This really is the whole point of an indirect with priority.

Keep in mind, electric water heaters only have about16K/BTU, gas water heaters around 32K/BTU.

The Lochinvar 85 at 78K/BTU output will heat water very quickly then immediately go back to heating the house.

NY_Rob

andysaks said:

...We have no teenagers, multi-head showers, or soaker tubs; just a young daughter and two adults who all shower about once a day. No one takes baths. We run the dishwasher about every three days, and do maybe 5-8 loads of laundry a week.

You could probably use a 30 gal indirect and still never run out of hot water.

I have two college age daughters, myself and my wife... we have a 30 gal indirect with a 80K BTU Mod-Con. When there is a call to heat the DHW tank, the boiler throws all 80K BTU's at it and it sometimes saitfies the reheating of the DHW tank while someone is still running the water in the shower!

The smallest mod-con that will work for your space heating load will have no problem satisfying your hot water demands. No need to stack/combine the loads in your boiler calculations, satisfy your home's heating requirements and the DHW requirement will automatically be met too.

andysaks

Thank you all again very much! I'm surprised (and relieved) by the consensus. Any others agree or dissent?

Gordy

The khn does come in the 55 which is down in the weeds for the ch load still as much as a conventional DHW heaters output. Just sayin.

Gordy

Cheaper unit though. A few toad skins to some is alot.

NY_Rob

Andy...
You still need to list the number of zones you presently have and the type and length of radiator (fin-tube, cast iron, etc..) in each zone and do you use a zone valve for each zone or circulator pump for each zone or a mix of the two?

Example:
Zone one- 160 ft overall length, 50ft fin-tube
Zone two- 125ft overall length, 60ft fin-tube

hot_rod

I have an oversized Loch Knight in my shop, about 1/3 larger that needed.

One interesting point is that it runs between 20 -46% fire. It amazing how much quite it is at that range compared to 80- 100%. I have to look at the display to see that it is running.

andysaks

NY_Rob said:

Andy...
You still need to list the number of zones you presently have and the type and length of radiator (fin-tube, cast iron, etc..) in each zone and do you use a zone valve for each zone or circulator pump for each zone or a mix of the two?

Example:
Zone one- 160 ft overall length, 50ft fin-tube
Zone two- 125ft overall length, 60ft fin-tube

I can tell you we have five heating zones in the house:

1. Living room / dining room / kitchen
2. Porch
3. Playroom
4. Upstairs bedrooms and bathrooms (except master bedroom)
5. Master bedroom

I'm pretty sure we use zone valves for each zone, and fin-tube radiators that look about like this:

http://www.supplyhouse.com/Slant-Fin-104003040-4-ft-Baseline-2000-Baseboard-Cover-Only?gclid=CNGAhfPxi9ECFQgFaQodCzQPZA

I don't know the overall lengths of each zone. The bedrooms are average size, and the living room, dining room, kitchen and playroom are all a bit smaller than average.

Also, if it matters, we're replacing each zone's 1968 thermostat with a programmable digital thermostat.

Sorry I can't tell you more but I hope that helps!

Andy

gschallert

NY_Rob said:

Andy...
You still need to list the number of zones you presently have and the type and length of radiator (fin-tube, cast iron, etc..) in each zone and ...

This is true. The amount of output capacity you have can determine whether a modcon is even a good fit. If you don't have the output to run the lower water temps to condense the only benefit is the modulation and unless the rebates are good enough to bring it down into the same price range as a standard CI boiler w/indirect it might not be the best choice. I faced the same choice this past fall and ended up going with CI & stainless indirect because what I saved by going with CI I can put into a ductless mini-split with heat pump for the shoulder seasons and not even have to run the hydronic CH when the heat loss would make it inefficient. This way I get new heating and cooling solutions and the best bang for my buck. I honestly think you need to slow down and assess the actual heat loss of your new house, whether a modcon is the smartest choice and whether you need to think about cooling needs in the future or if it's already outfitted. Sometimes it pays to look at the bigger picture. Just my two cents though.

NY_Rob

Short zones can be problematic for mod-cons because they reach peak efficiency at low SWT (supply water temperatures) vs. 180F SWT for conventional cast iron boilers.
If you have a micro zone like the porch for instance with maybe 15' of baseboard... there is no mod-con that could modulate down low enough to not short-cycle (hit high limit and shut off, circulate water for a few min, then fire back up again for just a few min... and repeat over and over again till the call for heat is satisfied) on that short zone.
The good news is- in some cases you can combine zones to present a larger load to the boiler so it won't short cycle.

You need to take a tape measure and measure the actual length of the fin-tube in each of your zones so as to be able to predict if short cycling will be a major problem for you.

SWEI

The preceding nine posts explain why we install systems... and not just appliances.

Gordy

Your installer needs to comprehend all that the KHN can offer your system in its control features. Biggest one is knowing, and understanding the outdoor reset feature, and how to fine tune it. Another is being able to run up to three different supply temps to different zone requirements. Quite possible not all zones need the same supply temp even though they have like emitters. Some zones could have more than enough emitter. Some maybe not enough.

Rich_49

KHN 085 will be more than sufficient in all probability . You should also check the price of the HTP SSU indirect against the HeatFlo . SSU is best in class and probably a few dollars cheaper . A 45 gallon tank heated to 140* and mixed down should be more than adequate also should you use the 085 . You really may want to interview some others also at this point .

hot_rod

Pretty much all the stainless indirect tanks include a water quality spec. If your water is outside this spec, no warranty in the event of a leak.

Perhaps that grade is better suited for chlorides, but their levels are about the same as other brands.

From the installation sheet on this tank.



It's rare to find any water supply under 100ppm, Long Island is about the lowest I have tested. I suspect chlorides in a big part of high TDS numbers. You can get a chloride specific test kit, if the city doesn't supply that info.

SWEI

hot rod said:

It's rare to find any water supply under 100ppm

100 PPM chlorides?

Things are a bit different west of the Rockies. Our Town wells averaged 12.4 PPM here in the last round of testing.

hot_rod

SWEI said:

hot rod said:

It's rare to find any water supply under 100ppm

100 PPM chlorides?

100 TDS, not sure of the chlorides.

Things are a bit different west of the Rockies. Our Town wells averaged 12.4 PPM here in the last round of testing.

SWEI

Ah, OK. ISTR LI having some chloride issues.

TDS in our Town water averages 217.

The first experiment they had us do in our college chem lab was to boil down a liter of tap water and weigh the results (800-1,000 PPM in Goleta.) Upper division chem lab did it again, but with qualitative analysis. Big bottled water business there.

hot_rod

An engineer friend worked on assembling the Saturn engine plant in NY years ago. They had a lot of problems with cam wear and breakage. Turns out the cams were heated and water quenched to harden them and the chlorides in the local water was an issue. They added DI equipment to the water quench line and the problem went away. Amazing how many thing water effects.

andysaks

Thank you all very much for your thoughtful feedback, I really appreciate it. You'll be happy to know we're going with the 085!

Have a wonderful, well-heated 2017 --

jpookie

Hey Andysaks, how did it go with your Knight 085? I'm scared to take the high efficiency plunge because research in internet is so scare. People recommend Lochinvar, Navien, Bosch and Weil and then they are equally un-recommended. Curious if your Lochinvar has been good to you for these few years. thanks.

fenkel

They are many good boilers on the market!! But a boiler is only as good as the installer that installs it.. ive seen many good boilers fail due to poor workmanship on the install..
Size your boiler to match your heat load.. then if your zones are to small to match your lowest boiler modulations, consider using a buffer tank... cutout/down the shortcycling and youll have a happy long lasting boiler system..
Also consider using deminerized water and a hydronic water conditioner as well..