A penny for your thoughts...

Constantin

... so the house is now back down to earth. After floating up to 15' over the ground (after the old foundation was demo'ed and the new basement floor was dug), the new foundation is happily carrying the old lady. On Monday, the house movers will come to remove the last beams, then we can finally install the new main beams (LVLs) and sigh relief. However, this also means that the next phase is staring at us and I hope the collective Wisdom of the Wall may come to our aid.

I performed a HVAC-Calc heat loss/heat gain calc for the house based on architectual drawings, measurements inside the house, etc. Allegedly, the design day heat loss is around 116kBTU/hr. The home was previously heated by a Williamson 230kBTU input unit which worked well despite no meaningful insulation in the place (just R-8 in the ceiling, leaky windows, etc.). So the calculated numbers do not look too outrageous.

However, I have heard folks claim that actual heat loss for a tight house heated hydronically is lower than the calcs that HVAC-Calc allegedly relies on (think foam insulation, HRV's and the like). On the other hand, Don Sleeth suggests adding a 15% safety factor to his heat loss calcs just to be sure the furnace will not generate a callback. Assuming I didn't screw up, which direction should I lean?

Next, how would I go about sizing the boiler? Should I size the boiler to the calculated heat loss by DOE output or IBR? Or, should I be extra conservative and size the boiler + 15% safety margin to the IBR output of the boiler? As best as I can tell, IBR = DOE Output x 1.15... so this would lead to the boiler being sized 30% larger than what the house allegedly calls for. And yes, we have a professional on board, but I'd like to get your opinions too.

We also had to demo the chimney as the old brick had cracked quite a bit and reconditioning via a cast-in-place flue liner was 2x more expensive than rebuilding the chimney (go figure). Considering that I want to use oil heat, what is the best permanent flue system out there?

As an additional consideration, I would prefer a flue that can handle condensation, as we may switch to a condensing gas system in the future. My builder is currently speccing out tile liner, but I have introduced him to new products before (Rub-R-Wall, drain-wall XPS, water cistern, etc.) and he's not averse to trying out my crazy ideas. What do you think I should use as a flue liner?

Paul Pollets

What's the plan?

What are your heat emitters? I've found that Calc Plus has a safety factor built in. I use it (or the SlantFin program) for radiator losses. I use the Wirsbo ADS for radiant loads. I use a stainless chimney liner for oil-fired appliances. The Buderus wall panel rads have a built-in flow circuit setter that allows fine tuning as well as the TRV head. I've never had a sizing issue problem using Calc-Plus. For obssesive folks, you can install a 4 way mix valve on the radiator circuit for precise temperature control and boiler protection.

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Constantin

Hi Paul,

Let's see if I can answer all your questions.

The house will be heated using radiant floor heat thoughout, installed above the sub-floor. The chimney is about 50' tall and we have complete freedom WRT to the material choices used within.

The actual control strategy still depends a bit on what heating system we install. It will feature outdoor reset for sure, the interior control strategy may be as simple as Danfoss TRV's + continuous circulation (with variable-speed circuit pumps).

I requested the Slant/Fin heat loss calculator but did not have any luck receiving it. They sent me a nice note though about how version 2 would be released soon. As far as I know, I ,as a mere homeowner, am not entitled to the Wirsbo ADS stuff. Perhaps my contractor has it though.

I will have to try out Firedragons software... perhaps if it and HVAC-Calc come out close to each other I will have the confidence to believe my calcs. Do I read your reply correctly in that you match the calculated heat loss with the IBR output of the boiler?

Unknown

Constantin if you e-mail

me your address I will send you a copy of the SlantFin Heat Loss CD.

Constantin

Thanks, Done!

Jed_2

> ... so the house is now back down to earth. After

> floating up to 15' over the ground (after the old

> foundation was demo'ed and the new basement floor

> was dug), the new foundation is happily carrying

> the old lady. On Monday, the house movers will

> come to remove the last beams, then we can

> finally install the new main beams (LVLs) and

> sigh relief. However, this also means that the

> next phase is staring at us and I hope the

> collective Wisdom of the Wall may come to our

> aid.

>

> I performed a HVAC-Calc heat loss/heat

> gain calc for the house based on architectual

> drawings, measurements inside the house, etc.

> Allegedly, the design day heat loss is around

> 116kBTU/hr. The home was previously heated by a

> Williamson 230kBTU input unit which worked well

> despite no meaningful insulation in the place

> (just R-8 in the ceiling, leaky windows, etc.).

> So the calculated numbers do not look too

> outrageous.

>

> However, I have heard folks claim

> that actual heat loss for a tight house heated

> hydronically is lower than the calcs that

> HVAC-Calc allegedly relies on (think foam

> insulation, HRV's and the like). On the other

> hand, Don Sleeth suggests adding a 15% safety

> factor to his heat loss calcs just to be sure the

> furnace will not generate a callback. Assuming I

> didn't screw up, which direction should I

> lean?

>

> Next, how would I go about sizing the

> boiler? Should I size the boiler to the

> calculated heat loss by DOE output or IBR? Or,

> should I be extra conservative and size the

> boiler + 15% safety margin to the IBR output of

> the boiler? As best as I can tell, IBR = DOE

> Output x 1.15... so this would lead to the boiler

> being sized 30% larger than what the house

> allegedly calls for. And yes, we have a

> professional on board, but I'd like to get your

> opinions too.

>

> We also had to demo the chimney

> as the old brick had cracked quite a bit and

> reconditioning via a cast-in-place flue liner was

> 2x more expensive than rebuilding the chimney (go

> figure). Considering that I want to use oil heat,

> what is the best permanent flue system out there?

> As an additional consideration, I would prefer a

> flue that can handle condensation, as we may

> switch to a condensing gas system in the future.

> My builder is currently speccing out tile liner,

> but I have introduced him to new products before

> (Rub-R-Wall, drain-wall XPS, water cistern, etc.)

> and he's not averse to trying out my crazy ideas.

> What do you think I should use as a flue liner?

Jed_2

Heat Loss & boiler ratings

I have a very early version of CALC-PlUS. Don't use it that much anymore. But, a heat loss calculation based on FHA circulation, IMHO, must take crackage, static pressure, and velocity, into consideration. This is forced air circulation vs. convective air circulation. There will be a higher heat loss with the forced hot air, unless the space is hermetically sealed, which requires an additional solution for consequent effects.

IBR net ratings provide 15% for circuit pipe losses and "pick up" losses. If you have radiant manifolds relatively close to the boiler- disreguard it, and size based on DOE. Or, if manifolds are multi-floored, insulate the piping (actually, insulate it regardless). DHW needs to be considered if there is a high dump load, or other large continuous demand.

That's how I approach it.

Jed

S Ebels

My three cents worth.............

RE: HVAC-CALC

I have found that this program has a safety factor built in on numerous occasions. Case&Point. This past winter we did an emergency install in an adult foster care home. I had warned the owner of the impending demise of her boiler but naturally she waited until it croaked and then called. Naturally again, it died this past January right during the stretch that didn't make it above 10* for 12 days. Naturally again, again, the old boiler managed to pack it in at about 4 PM on a Friday afternoon, she called at 7:30.

(These circumstances lead to what is commonly known as panic.)

I had done a heat loss on the residence when I had first recommended replacing the old beast and it came to a little over 109Kbtu. The only thing I had in stock was a Buderus 124 series firing at 103,000 input 87 DOE out. This is normally more than I like to give up but things being what they were, we installed it. By the time we were done the house had hit 54* and the old folks were screaming. Long story short...... the boiler ran non-stop for the first 22 hours after installation, (burner hourmeter on the 2107), the thermostats satisfied one by one and by Sunday morning the place was back up to it's normal 75*. This leads me to conclude that the program is on the conservative side. If it were right on the money the boiler would not been able to heat the house until it got above 8* outside and stayed there. The night that we put it in hit -16* and the daytime high that Saturday was 7*. You will definitely have less heat loss with a radiant floor besides. My gut feeling is that when using HVAC-CALC on a radiant floor you'll be over by 10% minimum.

RE: DOE vs IBR.

Use the DOE number. I have always done this and never had a problem. This would be especially true if your system will be constant circ. Simply put, where is the pickup factor in a system that is constantly "on"? The piping and radiation is always warm hence, there is no pickup factor.

RE: Chimneys.

Put up a nice brick or stone chimney, or what ever your choice is and install a stainless liner. This of course would be sized appropriately to match the requirements of your Vitola. Provide a drain tee at the bottom and whatever you need to allow the condensate to exit the liner itself. It will condensate. My natural gas fired Vitola will soak the liner at anything below 145* boiler temp. I will try to find the name of the company that I get mine from on Monday for you. They make liners in 316 and 304 (I think) Flexible or in sections.

Please send $.03 ASAP (G)

hr

Since the house is

already built, so to speak, I'd consider a blower door test. this will not only nail down the biggest "unknown" in the heatloss calc (infiltration) but also show you leakage points that need addressing. it's also fun to watch a blower door test performed a real jaw dropper!

Once you are comfortable with the loss figure size the boiler as close to that as possible.

Oversizing is not a big issue with mocdulating boilers if that is the ultimate goal. You'll notice they make only 4 sizes or less per brand of modulater. Whereas cast boilers are built by the sections with closer sizing.

I use the input BTU/hr, divided by the listed efficiency, personally. since we all know the published efficiency numbers are "golden"

All condensing boilers require stainless or PVC. Usually 3 or 4". Some use 2" PVC with smaller units (Polaris 100,000).

I'm not sure any atmospheric boiler of the btu range you are considering would vent into a 4" flue. except maybe some induced draft models. None with PVC however as the Munchkin and others allow.

You may pick a sidewall location for a future condensing flue, or plan on lining a tile flue with stainless when you make the switch.

I think Viessmann requires you use their double wall OEM flue. Better check into all this before you box yourself into a flueless corner

If radiant heat is your final answer, perform a heatloss calc on a radiant specfic heatloss program. If a rep, contractor or dealer can't help consider sending a plan to the factory. Some charge for a design and calc, but stand behind their numbers. Nothing wrong with doing a few different calcs.

I like Siggys heatloss calc a lot. you can download a demo at www.hydronicpros.com. i'm not sure how much you can do with the free demo.

If you are this into hydronics buy his software and Modern Hydronic Heating book. All the answers and user friendly software for tons of hydronic design are included. A smart and inexpensive investment. Heck it may be your next profession. written by an engineer in contractor "speak"

Happy heat planning.

hot rod

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Constantin

Excellent Points!

In fact, infiltration is the big bogeymanthat I have to contend with - about 1/5 of the heat loss. However, here is my dillema, what is a good infiltration rate to accept?

For example, we're getting many of the "wavy-glass" windows reconditioned by a local expert. Furthermore, we're putting Harvey Tru-Channel storms on the outside, which should slow infiltration down to a trickle. The walls will feature icenyne or closed-cell polyurethane foam insulation. The new windows are top-of-the-line double-glaze units. The chimney flues will feature Homesaver Locktops.

All appliances with the exception of the gas dryer, gas logs, and stove will be sealed combustion. The house will have at least 2 HRVs, probably Lifebreath DCS units. Old exterior doors are also getting reconditioned, the new basement has cast concrete walls. In other words, we better not have any surprises come blower-door time because the house ought to be tight by then.

Naturally, we'll still have a blower test though.

So, I am currently in the market for a typical on-off oil boiler, though the low-high-low modulating unit that Firedragon (I think) installed sounds great also. Depending on where infiltration is, the heat loss is between 104-116kBTU on the design day. In the case of Buderus offerings, right between the 115 and the 215 series. Since we are going to drive a IDWH on a primary circuit, that may swing my vote in favor of a slightly larger unit.

The chimney was planned for at 6" ID. Thanks to the above posts, I may upsize that one size to accomodate a 6" stainless flue liner and make arrangements for the condensate and all that. If we ever switch to a modulating gas boiler, I would still like to be able to use that chimney though as finding room on an exterior wall with no window conflicts may be difficult.

I loved Siggy's book, "digested" it for a while. Hence my specs for variable-speed circulators and the like. Thanks to Mike, we may even end up with Danfoss FHV TRV's for proportional control in every room of the house. Could be fun! However, I wish Siggy's software would allow more for students and the like. The current incarnation is somewhat too limited for me, though it would allow spot checks of individual rooms. That might be worth the effort.

hr

The flue

used for condensing equipment is a bit different from regular B-Vent type. All the joints and connections need to be sealed to allow the condensate to run back to the boiler. WITHOUT LEAKING! Most use a gasketed fitting and connection.

Some boiler manufactures ONLY allow their OEM vent pipe, so be sure you can install this type in the first flue you install.

Not sure you would, or could vent a condensor into a flue formerly used for an oil burner? Sounds messy at best as that acidic condensate would go after the oil deposits left behind?? All this, of course flows back to the condensor HX. Sounds like a sulfuric, high ph, black liquid mess to me

Dropping a 4" AL 29C liner down the old oil burner flue sounds iffy. Some how you need to support the vertical flue inside the old flue. That a lot of distance you mentioned.

Siggys "Modern Hydronic Heating" was built as a text book for the classes he teaches. His very first design software (dos version) was tutorialed (is that a word) by the MHH textbook.

The latest HDS version has help buttons and Siggy will happily support and answer any question regarding the program or concepts. Hard to beat that package for the cost.

I haven't seen any othey software that has injection mixing and buffer tank sizing modules. Worth the price just for those two modules!

The iceoneyne insulation will blow your socks off. I had my entire shop (pole barn/ wood truss building, metal siding and roof) sprayed with that. Beyond belief! walking around the outside and seeing where that stuff ozzed out, wow! Cut infiltration to nearly zip. I can barely hear cars pull in the drive way it insulated so well.

So I would guess weatherstrip would be your only leakage points with this insulation. After the upgrades I would calc with the low infiltration number. If possible run a blower door test before and after. this will show the value, and workmanship, of the improvements, without question.

Your largest boiler load at that point, after upgrades, may be the indirect tank for DHW! Size to it and use a reverse indirect tank as a buffer and DHW to handle any sizing error.

hot rod

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Constantin

Do you take paypal?

Seriously, thank you very much for your long and thoughtful reply. Your observations re: HVAC-calc vs. reality are certainly thought-provoking. I have since down-sized the boiler requirements by 10% and matched them to the DOE output ratings of various units. Besides, on really cold days we could always run the 20kBTU imitation-coal gas fireplace inserts to add a few BTUs to the place.

The only thing that gives me some pause is the insulation in the walls. Yes, it cuts down on infiltration significantly. Furthermore, infiltration is now about 20% of the total design-day heat loss. On the other hand, when you're dealing with full-size 2x4 lumber on 16" centers in the walls, there is a lot of opportunity for thermal bridging.

As for the flue system, I am thinking Ventinox VG/VFG or something like that. Considering that SS316Ti is good enough for the viessmann vitodens HX, it also ought to be good enough for my chimney liner. The question then is whether to go with their cast-in-place insulation system or a wrapper blanket.

Lastly, how do I best go about getting the condensate out - a drain pan in the bottom of the chimney "T"?

Constantin

Thanks for the reply!

I'm now a bit better educated in the ways of flues. The ventinox system might do the trick nicely.

I am also looking forward to getting the house well-insulated. The proof will be in the pudding if we manage to get the place to stay warm on the coldest days, even though the nameplate input capacity of the boiler will be ½ of the furnace it replaced and that it's also heating the water!

Lastly, I am now so intrigued with the other aspects of the hydronics system that I ordered Siggy's software. Should be an interesting learning curve!