Boiler/indirect-fired DHW help...

Skyline

My daughter currently has a seven years old NG Navien combi-boiler, that has been having issues. Currently, she has no heat in her house; the parts will be here tomorrow to restore the heat. The DHW does work. This is not the first time her house lost heat and she had enough and wants to replace the boiler. Her house is a two-story, atypical US house, around 2000sft with one and a half bathrooms. The heat emitters are baseboard and CI radiators, with two zones.

The contractor I trust installs Viessmann and her trusted contractor does IBC boilers. Both of the brands have boiler/indirect-fired DHW solution. Combi-boilers not excluded per se, but isn't the indirect DHW tank a better solution? Her house has a large basement, so there's no size limitation for the boiler. I don't recall, if the chimney is operational or not; the Navien intake/exhaust is on the side of the house.

I am not familiar with indirect-fired DHW tanks, any feedback on this subject would be appreciated. Cost will be a consideration, but Navien is excluded; she doesn't want that brand. Since she's a paramedic with oddball schedule, I'll be talking to contractors about their solutions. If you have experience with these and other brands, please let me know.

TIA...

Zman

I like the indirect solution, it is easier to match the heating load and there are no moving parts on the DHW side so reliability is better.
Both Viessman and IBC are solid products. If she goes with her contractor, there is less to blame on dad later in life

Jon_blaney

Watch the Youtube videos on these Navien products. There may be a warranty replacement available.

EBEBRATT-Ed

Navien is having issues.

Viessmann is considered the best by many although probably more $$ Indirect is the way to go. I don't have much IBC experience but many like them

Skyline

Zman said:

I like the indirect solution, it is easier to match the heating load and there are no moving parts on the DHW side so reliability is better.
Both Viessman and IBC are solid products. If she goes with her contractor, there is less to blame on dad later in life

Great advise @Zman, thanks!

I actually know her contractor, over a year ego he gave me a quote for replacing my non-condensing boiler. I did not like the the IBC DC33-160 combi-boiler and ended up with Viessmann 222F. Based on the quotes from over a year ego, the Viessmann had been about 30% more expensive.

As far as I know, IBC has the HC, DC, HX and SL series boilers. Out of this four, only the SL series has Stainless Steel HX, while the others have the Copper/Aluminium heat exchanger. Would that be correct?

One thing that I had noticed with her and other contractors when evaluated their company, that pretty much all of them are hard set on a their preferred series for the brand they quote/install. Most of them go for the high BTU rating of the boiler and some of them got offended, when I suggested lower BTU output boiler from the same brand and series.

Makes me wonder what her contractor will say tomorrow, when I suggest the IBC SL 20-160G3 with the INTERSTOR - BTI 40 indirect water heater. The chances are that the SL 14-115G3 would be suitable for the application, but I haven't done any calculation for heat loss, heat load, etc.

Is this combo looks ok for the application?

TIA...

JakeCK

Skyline said:

One thing that I had noticed with her and other contractors when evaluated their company, that pretty much all of them are hard set on a their preferred series for the brand they quote/install. Most of them go for the high BTU rating of the boiler and some of them got offended, when I suggested lower BTU output boiler from the same brand and series. Makes me wonder what her contractor will say tomorrow, when I suggest the IBC SL 20-160G3 with the INTERSTOR - BTI 40 indirect water heater. The chances are that the SL 14-115G3 would be suitable for the application, but I haven't done any calculation for heat loss, heat load, etc. Is this combo looks ok for the application? TIA...

If the installer doesn't base the size of the boiler on a heat loss calc walk away from them. There is no other way to size it unless its steam. Which your daughter does not have. 

The tendency of installers to stick to one brand or another is common. It simply is what they know and are comfortable with. It could also be influenced by what the supply houses have and keep parts for too.

kcopp

The SL 115G3 would be plenty big enough. Especially w a house around 2K ft2...unless there are no windows.

Skyline

@JakeCK.... Last year, five contractor had given a quote for my boiler replacement, not one of them offered heat loss calculation, even after asking for it. "Walk away" looks to be a sound advise, but one can run out of contractor in a mid-size town in a hurry. In my experience with heating contractor, they don't like people, who ask questions. It goes against their brand loyalty and familiarity of the type/size of boiler used pretty much with all of their customers...

@kcopp... Looked up the square footage at the city hall, it's 1,500sqf. Even the SL 115G3 would be more than her house needs, but probably will not get one with lower BTU ratings than that....

Dave H_2

In my opinion the one thing you are buying is 1 hour of time from a contractor. Once you are comfortable with that, the rest should fall into place.

Manufacturers don't make junk (if they knowingly do, they are typically not in business much longer) and it may come down to understanding the equipment, the installation and best practices, and serviceability. The contractors spend hours upon hours training and learning a brand/product because it also represents themselves. They don't change product/brands to easily. Don't take it too hard when they question you in regards to changing their product.

When I used to design radiant systems for people across the country, I would get that question alot and my answer was a BTU was a BTU, how you get it will depend upon the installer.

Nothing wrong with being an informed consumer, I welcome it and applaud it. Be comfortable with your installer, I think way too many forget how scary this junction is to a homeowner; homeowners have no idea what is going on in the basement and what is needed. To just plop down thousands upon thousands and hope we get a good system is very daunting. So for the installers here, remember most HO's don't know the term "Hydronics" from Hydroponics to a boiler versus a furnace. This should be partnership of sorts and all parties involved should be comfortable. You may need to kiss alot of frogs to find the prince.

Dave H.

Skyline

@Dave H_2

The thing is, that like most people, I don't have a need for plumber/ heating contractor or any other contractors for my house all the times. Especially, when you're a handyman, so to speak, and take care of the small stuff. The contractor, who installed the TriAngle Tube boiler over 20 years ego, had not been available. Hence the need to do the research for a new one and no, I didn't kiss any frogs....

Yes, contractors do have lot of training as they should, albeit it locks them in to a brand of their choice. That's one of the reasons I don't mind paying their hourly rates. Some are OK with asking questions, but most of them are not. Maybe they just didn't have time for a questions, or just don't like "educated customers".

Yes, BTU is BTU, regardless of the brand. How many BTUs one get probably does not matter as much as it used to. With today's modulating boilers with their turndown ratios, the boiler can just match the load and adjust the firing rate as needed, within limits of course,

This forum had been a great help to understand the difference between "Hydronics and Hydroponics", albeit it would be nice combining the two into one system. Keep my house warm and grow my vegetables indoors during the winter month...

JakeCK

Skyline said:

@Dave H_2
Yes, BTU is BTU, regardless of the brand. How many BTUs one get probably does not matter as much as it used to. With today's modulating boilers with their turndown ratios, the boiler can just match the load and adjust the firing rate as needed, within limits of course,

While this is kind of true with modulating heating equipment, it is still a waste to oversize it. The magic of having that turndown ratio is when it's relatively warm out and you only need a few thousand of those BTU's, the boiler can modulate down and provide a very efficient, steady, comfortable heat. For example say your house needs 50K btuh at design, but the installer just licked his finger, stuck it in the air and decided to install a 100K btuh mod-con with a 10:1 ratio. You think "Ok at design it'll just be turned down to 50% and we'll still be nice n' toasty." True except one problem. Your house is at design about 1% of the time during the heating season, the rest of the season you're well above that. If it was sized correctly at 50K btuh with a 10:1, it could fire as low as 5K btuh. That same boiler but at 100K btuh would be limited to no less than 10K. And you are paying for that with reduced comfort, more expensive equipment, and higher operating and maintenance costs.

Skyline

@All...

My daughter didn't want replace the Navien boiler at the start of the winter and we are back at it. This time, it's for real and hopefully, it'll be done in couple of weeks. Pretty much called the same companies that quoted me about 19 month ego for my boiler replacement, that had been done 18 month ego.

Interestingly, two out of three installers we had very good experience with. One of them was a OK, but the other two were excellent. It just shows, that it all depends on who one talks to at the same company. They did not mind the question and they provided very useful information.

For example, of the installer looked at the current Navien installation and stated, that the 3/4" NG gasline with flex tubing to the boiler is too small for the Navien NCB 210. He offered to replace it with 1" CI pipe directly to the boiler. According to him, that would eliminate certain error codes, where unplugging the boiler from power seemed to fix the error code. He had number of other recommendation as well.

Anyway, the finalist combi-boilers are:

• HTP
• IBC
• Locknivar
• Viessmann

Three out of four are good boilers, but I am not familiar with the HTP boilers. Does anyone had experience with the HTC boilers, combi or just boiler? I'd appreciate some advise...

TIA...

mattmia2

HTP makes good stuff. I have a UFT that is about 3 years old that the only problem I had was some odor from the insulation until i fired it up to 180. @Ironman installs a lot of HTP.

Also note that the indirect doesn't have to be from the same manufacturer as the boiler. In fact a number of other brands of indirect distributed by other boiler manufacturers appear to be rebranded HTP.

About the sizing. You may need a bigger boiler to cover the dhw demand although a larger indirect can also do it. Even though they modulate they will try to hit the setpoint as fast as possible, it will full fire until it gets near setpoint, that may lead to short cycling on mild days and it will be worse the bigger the boiler is compared to the load. There isn't a great way to communicate to the boiler that the load is small, modulate down and take longer to get to the setpoint. If it is a 50k boiler it will fire at 50k until it gets near setpoint, if it is a 100k boiler it will fire at 100k until it gets near setpoint. If it is a mild day the load may only be say 8k. At 100k it will get to setpoint and shut off very quickly.

Skyline

Thank you @mattmia2...

It's good to know, that HTP makes good boilers...

My daughter's house has one and a half bathroom that does not warrant an indirect DHW tank. It's more of a cost/benefit ratio for the given application.

The HTP boiler short cycling does not sound right. My Viessmann boiler may start out at close to 100%, but will modulate down to around 15-25% and could run for 2-5 hours depending on the outdoor temperature. Isn't that how a modulating boiler supposed to work?

Maybe I am missing something here...

hot_rod

Look for a brand or model that has ramp delay and limiting functions. The smallest mod con I could buy 50K is twice what my shop needs. The Lochinvar Knight has ramp delay,. I have it set to stay at every step for 15 minutes. Or it can be limited to 30% firing in heating mode. You still get full output for DHW

I think most 80K turn down about the same 8K on low fire. 80K should be plenty for DHW recovery, twice what a typical 40 or 50 tank style is. And at higher efficiencies.

The boiler needs to size to the largest load, in some cases that is DHW. But it depends on how you describe your DHW load.

GGross

Both of those brands are good, though IBC may be less known they have a long history with the firetube heat exchanger found in most of your residential wall hung boilers. I am very partial to Viessmann.

To answer your main question about DHW. I am in wholesale, I have been pushing contractors in my area to sell the boiler/boilermate combo as the "new" combi (yes i realize it is a traditional set-up). We have many picky customers in my area who are inevitably unhappy with on-demand DHW functionality, and the boilers and tanks are so efficient its hard to notice a fuel savings.

I have much more experience with Viessmann product. The new "E" 100 and 200 series boilers are really great, and allow the boiler mate to connect directly to the boiler eliminating an extra pump from the equation, and making for an attractive install. The 100 and 200 series each have 4 BTU sizes (the 200 has an expanded range in the "older" style), the primary difference is in the control, though the 200 series has one model that boasts a 14:1 turn down. For what it's worth I have a vitodens 100 in my home. I prefer how Viessmann handles calls for DHW, in my experience when you let them do their thing they will use a lower water temperature to heat the tank than other boilers I sell, though that feature can be modified by application.

Skyline

hot_rod said:

Look for a brand or model that has ramp delay and limiting functions. The smallest mod con I could buy 50K is twice what my shop needs. The Lochinvar Knight has ramp delay,. I have it set to stay at every step for 15 minutes. Or it can be limited to 30% firing in heating mode. You still get full output for DHW

I think most 80K turn down about the same 8K on low fire. 80K should be plenty for DHW recovery, twice what a typical 40 or 50 tank style is. And at higher efficiencies.

The boiler needs to size to the largest load, in some cases that is DHW. But it depends on how you describe your DHW load.

Lochinvar is one of the options we are evaluating...

Finding a boiler replacement for my daughter, so far all of them targeting the 199K combo-boilers. Maybe the current 210K combo-boiler makes them do that, certainly, the size of the house and DHW would be a OK with less than half of that. I didn't do a heat-loss calculation for her house, it's probably around the same as my house. In which case, an 80-120K combo-boiler would be just fine, including DHW.

Just like about two years ego, when I was looking for a boiler, the contractors don't offer heat-loss calculation. It still seems like that they look at the old boiler's BTU rating and recommend the closest BTU output boiler. Most of them only look at the boiler in the basement, while some at least looks at the windows, radiators, etc. While I did somewhat limit the BTU rating for my own house, I am hesitant to do it for my daughter's house.

GGross said:

Both of those brands are good, though IBC may be less known they have a long history with the firetube heat exchanger found in most of your residential wall hung boilers. I am very partial to Viessmann.

I am partial to my Viessmann as well, my Vitoden 222-F 125 is an awesome unit. Especially in the shoulder month to winter, the boiler modulates down 14% resulting in 17K on low fire. Even in the winter month, it seldom goes above 35%.

My daughter will probably end up a Vitoden 100W/120K BTU unit with similar turn down ratio. Its DHW delivery of 3.7 USG/min is more than enough for a single, full bathroom, there's no need for the 199K BTU's 5.3 USG/min DHW...

mattmia2

If reliability is your goal, I would go with a plain mod con and an indirect. A mod con boiler is simpler. With the indirect you have the circulator and possibly zone valves external to the boiler and they are common commodity parts that any supply house should stock a suitable replacement for. With a combi there is a diverting valve and circulator internal to the the boiler that are prone to failure and are usually proprietary to the boiler.

The combi also has an internal plate type heat exchanger to make domestic hot water that tends to scale on the domestic side and require periodic flushing with acid to descale it. The heat exchanger in an indirect is much larger and tends to have fewer issues with scaling.

The parts you field install for the indirect haven't been value engineered to make a combi come out at a certain price point, they are commodity parts that typically last for decades when properly applied.

You could easily eat up the extra cost of an indirect in a couple repairs of the combi, descaling the heat exchanger, or replacing internal circulator or diverter valve a few times.

Your capacity combi sizing has to be done for your conditions. The advertised flow is for a specific set of conditions that probably are not your conditions.
BTU/HR = 500 * GPM *Delta T

If you have municipal water in a northern climate with an incoming water temp of 35 degrees F, to produce 2 gpm of 105 degree F water you need a boiler to add:

500 * 2 GPM * 70 f Degrees = 70,000 btu/hr

for 3 gpm it is

500 * 3 GPM * 70 f Degrees = 105,000 btu/hr

Also hot water is instantly available from indirect, a combi needs to start heating water before you have hot water unless it is a model with some internal storage.

Skyline said:

Thank you @mattmia2...
The HTP boiler short cycling does not sound right. My Viessmann boiler may start out at close to 100%, but will modulate down to around 15-25% and could run for 2-5 hours depending on the outdoor temperature. Isn't that how a modulating boiler supposed to work?

The short cycling happens when the zones calling are smaller than the minimum turndown ratio. If the boiler started out with a lower fire it would have taken more time to get to the setpoint and shut off but the boiler doesn't know anything about how many zones are calling and therefore the load it is triyng to satisfy. Step modulation and limiting the DH firing rate can help a lot with this.

Skyline

@mattmia2...
If it would be my house, I would've put in an indirect DHW tank, but it is not mine. My daughter on the other hand was not convinced. The additional cost for installing an indirect was too high for her. She coudn't justify it since she had no issues with the Navian combi-boiler. She's also planning to move in 6-8 years, in which case she would not see the full benefit for having an indirect anyway.

Her hew boiler will be Lochinvar NKC199N, will be installed in ten days or so.

Jersey2

One contractor/salesman wanted me to get a NTI FTVN 199K BTU Boiler, and how he described it, I decided to get it and I impulsively signed. I didn't know what a combi boiler was. I asked him if it had a cast iron heat exchanger and he said yes. Of course now I know he was incorrect. After researching it I opted out. Practically no one has a NTI FTVN. Maybe Canadians have them.

flat_twin

Simplicity and a better shot at longevity convinced us to go with an indirect over combi. No plan to move anytime soon so the additional cost of the indirect was worth it. Very happy with that decision so far.