The right boiler Best of the Best

Gordy

I'm living with it right now. Gagging every minute. Noisy, dry yuk.

Eastman

It just drives me crazy. The sound is all wrong. With hydronics, if you hear anything at all... it's like an aquarium sound.

Steamhead

Hatterasguy said:

njtommy said:

Literally the smallest. I know Crown makes an Aruba series that's 38,000 btus

Still too large for the heatloss...........and really marginal for DHW. The H/O will be very unhappy.

Actually, that 38K for the Crown Aruba AWR038 is the Input rating. That boiler has a Net of 28K, so it's not too far off the hypothetical 25K heat loss.

But speaking of the heat loss calculation- has anyone actually done one yet? Because if not, everyone's guessing.

Will82

> @Steamhead said:
> Literally the smallest. I know Crown makes an Aruba series that's 38,000 btus
>
> Still too large for the heatloss...........and really marginal for DHW. The H/O will be very unhappy.
>
> Actually, that 38K for the Crown Aruba AWR038 is the Input rating. That boiler has a Net of 28K, so it's not too far off the hypothetical 25K heat loss.
>
> But speaking of the heat loss calculation- has anyone actually done one yet? Because if not, everyone's guessing.

Do you have a link or a formula so I can do a heat loss do a heat loss?

Zman

Slant fin has an easy one http://www.slantfin.com/slantfin-heat-loss-calculator/

BBros

Just to add another question to the mix: Why doesn't anyone talk about recovery? It's all good that the house has 25k loss on design day, and "the boiler should run constantly for maximum efficiency" but what about power outages and other bad-day problems? If you're sizing the heat source exactly for the design load... the house could be in trouble during an emergency or even a set-back (e.g. vacation).

I've experienced homes in my area be unable to maintain or regain inside temps during extreme cold or a power failure. I would argue that some reserve btu output is valuable insurance... but I'm not the expert.

Gordy

that would be a case by case situation. Some owners rarely see if ever outages in the winter. While others it's common. Duration of outages would be next thing to consider.

However you would still be designing in a considerably larger appliance for a low percentage risk like design days.

Zman

BBros said:

Just to add another question to the mix: Why doesn't anyone talk about recovery? It's all good that the house has 25k loss on design day, and "the boiler should run constantly for maximum efficiency" but what about power outages and other bad-day problems? If you're sizing the heat source exactly for the design load... the house could be in trouble during an emergency or even a set-back (e.g. vacation).

I've experienced homes in my area be unable to maintain or regain inside temps during extreme cold or a power failure. I would argue that some reserve btu output is valuable insurance... but I'm not the expert.

I would contend that problems like this are usually related to owners expectations. Home automation t-stats have greatly reduced this problem.
Personally, I have never seen an undersized boiler. I have seen under pumped, under radiated and horribly misdesigned. Many of these where blamed on boiler sizing because if you don't have a clue, that's the easiest thing to blame it on.

Will82

So I have narrowed it down to two options just waiting for FW Webb to send me the quote.

Option A
Navien NCB-150E with primary manifold kit

Option B
Lochinvar KHN055 with a indirect 30 gallon model SITO30 or a 40 gallon SITO40

Brewbeer

I installed option B last year with the 40 gallon indirect (family of 5 here).

BBros

Glad I'm not totally out of sync. I agree about case-by-case. Here in Central/Northern Maine we have old houses and very low potential temps, combined with significant power outage occurrence and duration. Generators are common, but not widespread and they're rarely auto-transfer. Recovery remains an on going problem, and as such I think it explains partially why installers in my area tend to oversize. 2x is likely not necessary, but I haven't done the math.

Another option would be to have additional heat sources installed. Small propane or wood fired stove located in the living space that could jump start the recovery. I have this in my own home, with an added bonus that it doesn't require electricity.

Will82

Should I worry about the recovery and step it up to the NCB-180E or KHN085? The cost difference would only be a couple hundred dollars.

Zman

Will82 said:

Should I worry about the recovery and step it up to the NCB-180E or KHN085? The cost difference would only be a couple hundred dollars.

If you don't have the radiation to support the oversized boiler, the conversation just becomes that much more ridiculous....

Will82

Looks like I have 70 feet of high output. So at 800 BTUs is 56,000 BTUs which is the max for the NCB-150E Which should be plenty for baseboard for 1076 ft.² It just seems like every plumber I talk to wants to oversize.

BBros

I do not think you need to size up your boiler. 56,000 btu better be enough for that size home. If it isn't... start insulating.

My question/comments above were not meant to persuade you to a larger boiler, it was just an extension of the conversation that was happening.

njtommy

NCB-150E fits your home. Do some homework tho and make sure the installing company keeps parts instock for these boilers.

Gordy

Will82 said:

Looks like I have 70 feet of high output. So at 800 BTUs is 56,000 BTUs which is the max for the NCB-150E Which should be plenty for baseboard for 1076 ft.² It just seems like every plumber I talk to wants to oversize.

They want to up size because they don't want to do the math. Your paying no toad skins out of their wallet..... and

Paul48

@BBros
Re: Recovery
Every heat loss program available has considerable "fudge" built into it. There's a lot of smart people here, and they can come up with ways to tighten those numbers, and get it close to exact. It begs the question..........Do you shoot yourself in the foot, by doing that? Just thinnin'

Gordy

You have to look at the program designer, and the program user. Obviously if the user is a seasoned professional, and his installed systems keep coming up at 50% duty cycle at design day. Then he would assume the program is padded so long as his inputs were correct.

No heat load software designer wants someone coming back on them after using their program with a deficient install.

hot_rod

Paul48 said:

@BBros
Re: Recovery
Every heat loss program available has considerable "fudge" built into it. There's a lot of smart people here, and they can come up with ways to tighten those numbers, and get it close to exact. It begs the question..........Do you shoot yourself in the foot, by doing that? Just thinnin'

Plus the infiltration "assumption" number. That seems to be what makes or breaks load calculations more so that window wall, and ceiling calcs.

Blower door test can tighten up that input number, it is also a point in time number.

The radiant specific load calc programs have been tightened up over the years, but it is more an educated guess that proven science.

Formerly

Considering the need for dhw and the potential desire to pad the btus, why wouldn't the knight 85 be fine especially considering its ability to turn down 10:1? It would run low unless someone took a hot shower on a cold & windy day

Paul48

Now, I'm not in favor of that logic either. I posted it for topical discussion. I feel that firing rate should be taken advantage of for heating. The returns are diminishing for over-sizing for DHW, when using an indirect. The bottom for 85 may be about as low as you can get, but I don't want that logic applied to every application....and some would.

Will82

Update
Had a plumber come out today he is recommending the Navien NCB-180E but I still think it is oversized. Hey said due to the tankless he goes a little bit bigger to make sure there's no problem with the hot water demand. He also mentioned it will modulate down to 14,000 BTUs so it should not short cycle. But for some reason I still want to go with NCB-150E because it modulates down to 12,000 BTU and since it only modulate 6:1 It would modulate better from 56,000 to 12,000 BTU which I think would work better for my house vs 75,000 to 14,000 BTU if I understand the boiler specs right. And there will be 15,000 BTU I will never be able to use because my system can't handle it. What should I do?

Zman

Either of those boilers will serve you just fine.
Just pick one based on your gut and go for it.

On a side note, I have family and friends in Massachusetts. They love the expression " best of the best". They use it to describe everything from cancer hospitals to the new toaster they are purchasing. Interestingly, it is never anything better than the "average of the average" they are comparing. It's no big deal, just a strange expression, if what you intend to buy is a decent boiler that will get the job done, why not just say so?

KC_Jones

For me I feel the OP has been asking the wrong question. Do you want the best of the best boiler or do you want the best of the best system? Those are drastically different questions. You could spend hours, days, years picking a boiler and then the installer screws up the install and you have garbage.

IMHO you should put your effort into having a properly designed system and finding a proper contractor that will do it right. By what you have posted about the contractors I don't think you have found one yet.

As far as a combi, the El Camino analogy was spot on. Trying to make one device do dramatically different jobs almost never works well, there is always a sacrifice. Using the domestic hot water load for sizing makes zero sense to me.

My $0.02 worth.