choosing a boiler and baseboard

dvi2020

Dear kind folks at Heating Help,

We recently bought a 100 year old two-family house in NJ, gutted it, and are re-insulating it. We're finishing the second floor small apartment first so that we can move in asap, and will finish the larger apartment next year (leaving it with bare studs for now) and the basement a few years later.

We prefer a hot water boiler with baseboard and indirect hot water tank.
Zones will be as follows:

(numbers are rounded)
Zone 1: Second floor separate apartment
400 sq-ft 10,000 BTU 20' BB
Zone 2: First floor
860 sq-ft 31,000 BTU 55' BB
Zone 3: Second floor master bedroom/bath
210 sq-ft 5,500 BTU 10.5' BB
Zone 4: Basement
600 sq-ft 30,000 BTU 51.5' BB
Optional Zone 5: Attic-closet
500 sq-ft 9,000 BTU 15' BB

Total without attic: ~ 77,000 BTU
with attic: 86,000 BTU

We decided not to go with a separate boiler for the 400 sq-ft apartment (Zone 1) because of the added cost and also so that we won't have to bother with separate gas service for that apartment. So for the first heating season, the boiler will be used for only this small space, and the rest comes later.

Our plumber asked his normal supplier what they would suggest, keeping in mind ease of service and getting parts, and they said Navien NHB 150 (with 15:1 TD) or a WM 140K CI, either one with a WM AquaPlus 55 indirect.

It would appear that they over-sized, which I understand is the "norm" and I would need to address this with them especially if I go the CI route.

He took rough measurements of the room and windows, but did not do a formal heat loss. The heat loss and baseboard lengths listed above are my best layman's attempt using the Slant Fin heat loss application.

My questions are as follows:

1. When it comes to baseboard installation (from scratch), there's limited wall-space and budget. The slant-fin app is giving lengths based on 180 degree WT. I understand it's best to oversize to reduce this temperature, but if we don't, or only do so by say, 20%, will that be enough to make a Mod Con worthwhile?

2. Given the size of the zones, would either boiler be likely to short cycle.
a. The attic will be well-insulated, but we weren't necessarily planning on heating it. However, I thought of adding some baseboard up there just to make the 5500btu zone bigger (keeping the thermostat in the bedroom). Does this help? Is it necessary?
b. During the first year using only 10,000 btu plus DHW, will even the mod con short-cycle, as even this zone will require less than this on non-design days.
c. Would using longer lengths of baseboard in the smaller zones help with short cycling or make it worse since SWT would be lower in that case?

3. Is the WM AquaPlus 55 indirect water tank a good choice for the price? The rep at WM said that this is a revised model as of this year that addresses an issue with the prior one. Not sure I like to buy a product when it's first released, but I understand that WM is a reputable company generally and it's the brand that this supplier deals with.

Anything I haven't thought of?

Thank you!
David

HVACNUT

To be honest, I didn't even finish reading your post.
Google Slant/Fin heat loss calculatior, and download the free app.
Easy to use and will give you the BTU requirements and baseboard sizes.

dvi2020

That doesn't answer any of my questions. I did just shorten my post a bit though.

KC_Jones

First I would suggest your heat loss is still high. Especially the basement, 50 btu's per sqft would be high for an upstairs with no insulation at all.
You say you are upgrading and insulating so I would expect lower numbers, how low is the question.
By your questions I think you may be thinking of things wrong. The room load is the room load, the amount of baseboard doesn't change that. So putting more baseboard into a room won't increase the load it will only lower the temperature. You can get 10,000 btu with 90° water or 180° water the amount of baseboard only changes the ratio of water temps to btu output it doesn't increase the room load. Also remember those loads are only for the coldest day, when it's not so cold out (majority of the winter) the load will be lower.

You won't like this, but it sound like you need to slow down a bit. You need a heating designer (or be your own) to lay this out. The heat loss is critical as it dictates everything in the system from baseboard to pipe sizes to pump sizing etc. Without that being right it is random guesswork, and IMHO that's being generous.

1. Yes if you don't install enough baseboard you might not be able to condense all the time, but you will be able to some of the time. How often depends on heat loss to boiler sizing.
2. Yes they will short cycle, how much again heat loss to boiler sizing. Based on the numbers you have (again I am guessing too high) they are proposing boilers that are MASSIVELY over sized. Honestly I would be finding a new contractor based on that alone.
3. I have no input on that topic

Have you tried the find a contractor on this site to find someone competent that can help? There are several good contractors and designers that work in your area.

This is one that comes to mind:
https://heatinghelp.com/find-a-contractor/detail/langans-plumbing-and-heating-llc
@Rich

Ironman

The smallest mod/con available is about 55k btu. If you attempt to connect that to only 20' of BB, it will short cycle to death. Modulation is there to match the firing rate of the boiler to the actual heat loss of the structure as it changes with outdoor temp, not to accommodate improper sizing.

Your only solution would be to add a buffer tank of sufficient size (about 40 gal) to prevent the short cycling or go with a small cast iron boiler of sufficient mass.

Zoning up a mod/con is not a good practice as this too will cause short cycling. Usually when folks do this their mind is still thinking in terms of an old CI boiler that is 100% on or off. I'd look I'd combining some of those zones and let the logic of the mod/con do its thing, or better yet...

Look at using panel rads with TRVs. Less wall space, individual control, more efficient, more astetically pleasing.

BBs are old school high temp technology. If you're stuck on using them, the look at low temp BBs like Smith's Heating Edge.

NY_Rob

+1 Ironman

If you're starting from scratch and want to go with a mod-con using baseboard take a good look at Smiths Heating Egde2 high efficiency/low-temp baseboard. If plumed correctly it's output is nearly double that of conventional fin-tube.

To get decent efficiency out of a mod-con you need it to supply low temp water to the radiators- standard fin-tube was designed to work with 180F water not 130F supply water.
Take a look at the 120F BTU output on the charts below for std fin-tube vs. Heating Edge baseboard.

leonz

Have you looked at one pipe steam with the radiators located on the interior walls to create less actual piping and pipe runs as you have everything stripped to the studs? if you have an attic for a steel expansion tank or high interior ceiling point in stairwell a gravity hot water system at the top pf the stairs would work well for both living spaces.

Piping the radiators on the interior walls reduces pipe use and allows the system to create a slow even heat for all living spaces.

Dan talks a lot about gravity hot water systems and how efficient they are as it does not require circulators to move hot water to the upper floors.
The heat rises with the hot water stand pipe and falls back down through the radiators which then heat the living space and the cooler water falls back to the boiler sump to be heated once more.

It would be well worth your while buying a copy of Classic Hydronics and Dans books about steam heat to learn more about heating before you go and spend money that you do not need to spend on hot water baseboard heat.

Ironman

The cost of running black iron piping large enough for steam, or even more for Gravity flow, would be cost prohibitive. Also, IDK if you could find a new boiler that would be able to do gravity. Certainly not a mod/con.

Then there's the expense of cast iron rads since they would be required.

dvi2020

Thank you KC_Jones for pointing out a glaring error in my Heat Loss. I failed to include insulation on the basement walls. The actual basement heat loss is half...only 15,000. That brings the total for the entire house to 71,000. I used numbers that are conservative, like glass and door factor of 0.5 and temperature spread of 0F Outdoor to 72F Indoor for Northern NJ. The real heat loss is probably less. I'm happy to have gotten your feedback that it's within reason or high if anything.

Thank you Leonz for the suggestion, but we would like to keep all of the equipment in the basement for various reasons.

Thank you Ironman and NY_Rob for the great input!

Correct me if anything I'm saying here is incorrect:
1. If I give up on the mod con idea, then I could go with a direct vent CI sized as closely as possible, let's say 75k.
-It can be kept in a sealed room in the basement.
-This would be plenty powerful enough to replenish the indirect tank while providing space heat.
-This would still be more efficient at producing DHW than a separate self-heating hot water tank, even though it requires firing up the CI throughout the year just for the tank (and this doesn't short cycle the boiler).
-I could run traditional BB using 180F at the minimum lengths to the zones as specified, or more if I desire.
-HOWEVER, the boiler will short cycle like crazy during the first season (heating only one apartment) and will continue to short cycle somewhat for the rest of it's useful life, but less so than a mod con in these conditions would, because of it's mass, and it may stand up longer to the punishment.

2. If I want to install a mod con
-I looked at the Smith's Heating Edge and they're aesthetically unpleasing. I'd don't know if it's possible to use different covers for them.
-I saw runtal tiered panel baseboards which are very pretty, and would have to see about cost. But these don't mention low temperature specifically. It gives btu specs for 140 and 180 degrees.
-Even if we install either of these alternative baseboards in sufficient lengths to reduce SWT, that still won't be enough to keep the boiler from short cycling unless I eliminate zones (undesireable), use a buffer tank (undesireable), or use one big zone with TRV's. This is true even if the boiler can turn down to 8k heating the 10k zone.
-The TRV I saw online is basically a valve. It didn't seem to specify a specific temperature like a thermostat.

NY_Rob

Small zones are a know problem w/mod-cons. Sometimes you can combine zones that have similar heatloss characteristics to form one larger zone. No current mod-con can serve a 15' zone running with 130F supply water without short cycling. A buffer tank would probably allow you to use a mod-con without short-cycling it to death. Some of the pros here have them installed in their own homes.

If you go with a CI boiler running with high supply temps, consider installing cast iron baseboard radiators like Burnham BaseRay or Gov-Board (they are identical). They retain heat like traditional cast iron radiators and will give you longer run times and less cycling.

Ironman

A TRV = thermostatic radiator valve. Thermostatic being the key word. They can be individually set to the desired temp.

Here's a panel rad with a TRV:

dvi2020

1. Does adding a buffer tank cost extra about the same to buy and install as a DHW tank? The boiler heats the water in the tank instead of heating the zones directly? Do all zones use it or just the small ones?

2. Just so I'm clear on the source of the zoning problem: Let's say the 10k zone were to have minimum baseboard lengths needing 180* and were heated with a mod con that can turn down to 10k. On the coldest days, there _won't_ necessarily be a short cycling problem and there _won't_ be much if any condensing going on. The short cycling problem would lie in the majority of the season when that zone needs _less_ than 10k for heating. And the fact that the small zones are functioning alongside the larger zones doesn't sufficiently mitigate this.

3. If we go the CI boiler route, are all the assumptions I wrote above correct?

4. Do CI BB rads cost orders-of-magnitude more than typical fin?

NY_Rob

dvi2020 said:

Does adding a buffer tank cost extra about the same to buy and install as a DHW tank?

Site rules: we don't discuss pricing.

dvi2020 said:

The boiler heats the water in the tank instead of heating the zones directly

The buffer tank provides hydraulic separation between the boiler and radiators.

dvi2020 said:

Do all zones use it or just the small ones?

All zones run through the buffer tank.

NY_Rob

dvi2020 said:

Do CI BB rads cost orders-of-magnitude more than typical fin?

My local plumbing supply house was about the same as this online supplier. Buy local no shipping charges... one 6' section weighs 90lbs!
http://www.simplyplumbing.com/catalogsearch/result/index/?limit=24&q=GOV+

NY_Rob

dvi2020 said:

Just so I'm clear on the source of the zoning problem: Let's say the 10k zone were to have minimum baseboard lengths needing 180* and were heated with a mod con that can turn down to 10k. On the coldest days, there _won't_ necessarily be a short cycling problem and there _won't_ be much if any condensing going on. The short cycling problem would lie in the majority of the season when that zone needs _less_ than 10k for heating. And the fact that the small zones are functioning alongside the larger zones doesn't sufficiently mitigate this.

Short cycling will occur any time you can't radiate as many BTU's as the boiler is supplying.
Due to the mod-con using outdoor reset to control SWT (Supply Water Temperature) you could see 180F SWT on the coldest days and 110F SWT on warmer days. Look at the radiator output charts above and calculate the BTU output of your 15ft zone with 180F and then with 110F SWT. On a boiler with a 8K BTU minimum fire rate- that 15' zone will short cycle on all but the very coldest days. In most cases, no one ever sees 180F output from their mod-con- many max out at 150F or less even at 0F or below temps... in those installs- the 15' zone would always short cycle.

If you can ensure that other zones will be active at the same time as the 15' zone (wire their zone valves together) then you can add their BTU output and you may approach the minimum needed to prevent short cycling.

Ironman

I've used electric water heaters for buffer tanks successfully. You have to pipe the system return into the bottom at the drain valve.

They're glass lined, so they should last in a closed hydronic system.

dvi2020

OK. Thank you for the clarification and thanks for the link to the CI BB rads and suggestion of electric tank.

The main drawback of simply setting up the large zone to go off whenever the small zones call is that the large space may get toastier than necessary, I suppose....on this line of thought...is the zone equipment able to be configured so that if either small zone calls on it's own, then it would open the attic zone too? (It would still be useful to heat the attic as it functions as a walk in closet; it has a permanent staircase leading to it- not just a trap door.) The additional 8.5k from the attic would bring the 5.5k zone up to 14k and the 10k zone up to 18.5k... either could still dissipate 8k almost all of the time, no?....not an acceptable solution??

Any comments on:
1. Can either a mod con, or a CI that is sealed combustion be kept in a sealed room in the basement, or do they need to interact with house air despite having dedicated in and out pipes through the wall?
2. Is indirect DHW tank still worthwhile with a traditional boiler even if heavy CI is firing all year?
3. Does a CI that is sealed combustion exist (with air tubes going out and _in_ to the boiler itself like a mod con has)?

hot_rod

Ironman said:

I've used electric water heaters for buffer tanks successfully. You have to pipe the system return into the bottom at the drain valve.



They're glass minded, so they should last in a closed hydronic system.

Yes DHW tanks can be a good way to inexpensively buffer.

I'd suggest an electric tank and use the element holes. Tall skinny type. Also a 2 pipe connection provides some nice advantages.

Find a Nibco 1" male X 1-1/2 copper adapter 604R.

Then tee into that 1-1/2 section .

NY_Rob

How about you just make three zones?
No short cycling then....


********************
Zone A: Basement
600 sq-ft / 51.5' BB
********************

********************
Zone B: First floor
860 sq-ft / 55' BB
********************

********************
Zone C: (total 45.5' of Baseboard)
Second floor master bedroom/bath
210 sq-ft / 10.5' BB
plus
Second floor separate apartment
400 sq-ft / 20' BB
plus
Optional Zone 5: Attic-closet
500 sq-ft / 15' BB
********************

dvi2020

thanks for the details of how to use a dhw as a buffer tank.

After I corrected a mistake with the basement's heat loss calc, I realized it only needs 13.3k 23'...or 15.1k 31' if I include the actual boiler room. Should I? (Is the boiler room allowed to be sealed off from the rest of the basement?) Does this make the basement zone too small?

The reason why the upper three zones can't be completely combined is that the master bedroom/bath is completely separate from the studio apartment...whereas I don't care about the exact temp in the attic. It can't work the way I proposed?

KC_Jones

Room by room heatloss, emitters are sized to that rooms heat loss. All rooms are sized using the same logic. All rooms stay the same temperature.

This is why the heatloss is absolutely critical.

To me a zone is when you want to purposely keep a room at a different temperature to keep them the same nothing beats a solid design.

You could also add balancing valves (depending on piping) to give even tighter control.

dvi2020 said:

The additional 8.5k from the attic would bring the 5.5k zone up to 14k and the 10k zone up to 18.5k... either could still dissipate 8k almost all of the time, no?....not an acceptable solution??

Remember the above numbers are on the coldest day. On a mild day you would be half that maybe less. In my area the design temp is 7, but most of the winter (southern PA) we are in the 40's so the heatloss is half the design. Looking at your numbers above that would be 5k and 9k for the proposed bigger zones. See how the short cycling can happen?

Now imagine a CI 75k boiler firing at 75k all the time and a small zone calls on a mild day with a 5k load....short cycle much? Mod con with minimum 10k would be closer.

I will also suggest you look at those numbers again. It's is agreed that those programs have some padding in them and you are going conservative and adding more padding on top of that. Accuracy is important here.

dvi2020

I visited a local Triangle Tube supplier. They're running an advertised package special: Challenger boiler (not Prestige) with Thermco indirect plus Grundfos manifold for a price much lower than the other options I was considering (less than going traditional CI route). Dealer says I should bring in my blueprints so we can recheck heat loss numbers room by room to make sure I didn't miss anything and address some of the concerns we've been discussing.

I'm partly suspicious wondering if you get what you pay for. Any experience with the Challenger boiler or Thermco indirect? The dealer comes across as genuine and was referred by someone trusted.

dvi2020

A TT seemed confident that the small zone problem could be inexpensively solved by piping the indirect to do double duty as a buffer. that zone calls would pull the boiler's water from the indirect and this shouldn't hurt hot water production. Is this something that is ever done? Could it work? Downsides? Our DHW needs are very modest at least for the next two years.

Eastman

At the bottom of this flyer one can see an example of a micro zone buffered by a Triangle Tube Comfort indirect water heater. The Comfort series has extra boiler water capacity in the water heater above and beyond their normal tank-in-tank heaters.

Link to Triangle Tube sales pdf:
https://acv.com/asset-file/f1f2f2a7cbcb4a98ae90da0a9390df22

I should add that the indirect is serving double duty as both a DWH and micro zone buffer.

dvi2020

Wow. Thanks. this setup seems like a good value that works with small zones.

Does this buffer give us permission to oversize the boiler for faster dhw recovery? (125Hs vs 105s) Strangely, the 125Hs seems to modulate lower.

At this price point, is it "too good to be true?" Any reason for concern over reliability or performance? A completely different option I'm considering is the CI boiler with condenser Williamson GWA (twin of Weil-M GV90+). I don't know if it could be setup in the same way with the comfort or another indirect doing double duty as buffer.

KC_Jones

Why do you think you need to oversize for DHW production? A standard tank water heater is 40k and generally keeps up just fine. On the "small" side you mention something 2.5 times that, which will recover no problem.

I have a standard 50 gallon gas fired water heater running at 140 and my family of 5 can take back to back showers and not run out of hot water.

How much hot water do you think you need?

Don't oversize the boiler it's something you won't be able to fix later.

dvi2020

Clarification
I'm not suggesting a 125Gal tank. The package comes with "Comfort 45" or "Comfort 55" indirect powered by either "105s" boiler or "125Hs" boiler, the 125Hs being the more powerful but whose specs say that it can modulate lower.

Eventually imagine peak of five people taking a shower in two bathrooms, two of those showers simultaneous, while two sinks going for short bursts and a washing machine.

Not sure if using indirect as buffer too, will reduce dhw recovery speed so I'm inclined to go for the 55gal and 125Hs if the buffer now eliminates short cycling anyway. Any downside?

Ironman

I've used TT indirects to supply mice zones like their diagram shows and the setup works fine for MEDIUM or LOW temp emitters. If your BBs need 180* SWT in cold weather, then you're gonna come up short.

dvi2020

Planning to oversize the emitters by about 40%. not sure what water temp this takes it to but hopefully at least less than 160?
If it comes up short, you mean the emitters won't get hot enough or the dhw will replenish too slow, or both?

Oh, zoned in this way, should the emitters still be proportionately oversized throughout the house, or now the small zones can (or should) be oversized in different proportion to rest of house?

NY_Rob

Regarding the emitters... which are you going with?

dvi2020

Regular fin. While I'd love cast iron baseboard, I can't afford it right now especially for the whole house and understand that it's best to go with the same type throughout house.

do small zones in this setup get the same water temp delivered to them as the water going to the large zones? I imagined water that would otherwise heat the tank being directed to the small zones so they would get 180* no matter.

Ironman

No, the BBs will get whatever water temp the indirect is. Probably 150* at best.

BBs typically have 1/2 their rated output at 140* SWT.

dvi2020

this is what confused me. isn't the whole standard logic that when the indirect calls for replenishment, the boiler fires to 180 temporarily. So since the boiler's outer tank is being robbed essentially, then when it's time for that water to be re-heated, it will do so at 180...unless that's the case ONLY when dhw is in use. so then there could be only occasional spikes when the supply water to BB does indeed reach 180.

So a setup like this mandates that the smaller zones get more than 40% oversize? In that case, the whole house would have to also?

Ironman

When the indirect calls for the boiler to heat it, yes, the temp can go higher. But most of the time heat is being transferred from the domestic hot water in the tank. That's the SWT that you have to design from.

In designing, you always work from worst case scenario, not best case. That's why we use the coldest night off the year for design temp instead of a 50* sunny afternoon.

dvi2020

ok. so getting enough BB to work with at _most_150* in the small zones on design day should be sufficient?
And whatever ratio that turns out to be must/should be followed through rest of house? I suppose so because in the future if ever boiler system is changed, it will be better to have whole house proportionately radiated.

Ironman

I'd use 140* for anything connected to the indirect.

The thing to remember with BB is that you must use the AVERAGE water temp for designing. At a 20* delta T (150* supply, 130* return), the AVERAGE water temp would be 140*.

dvi2020

OK.

And this setup _will_ then reduce dhw availability during heating season, so we should keep this in mind when sizing indirect and boiler?

Ironman

Not really. The micro zone isn't gonna pull that many btus.

dvi2020

two micro zones will be hooked up this way. 10k plus possibly 13k (rather than the 5k). still not that much?

NY_Rob

10K BTUs @ 140F AWT = 31ft Fin-tube
10K BTUs @ 140F AWT = 18ft Heating Edge Baseboard

13K BTUs @ 140F AWT = 41ft Fin-tube
13K BTUs @ 140F AWT = 24ft Heating Edge Baseboard

dvi2020

Thanks for the numbers NY_Rob
Correct me if I'm wrong, but Heating edge needs two independent pipe loops run for the zone to acheive these numbers, so double the copper and perhaps double the installation cost, no? Are there any showrooms in NJ/NY that actually carry it to see? The few supply shops I called (including Ferguson) hadn't heard of it. The photos of it online look like an eye sore to have in a living space.
The cast iron BB from WM looks very nice, but even if I paid extra for it 1. Could I still install regular fin in the larger zone$$? 2. I guess it doesn't really achieve the objective of lowering the AWT because the output is similar to regular fin, so I'd still need those long length$ of it, no?