Boiler/Indirect Combo Advice?


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Old 12-12-07, 09:54 PM
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Boiler/Indirect Combo Advice?

I need to decide on a hot water baseboard/domestic hot water system ASAP and am trying to sort through the options and brands.

The quick question: Lochinvar VS. Viessmann? Would you recommend one over the other as far as repair history or quality?

The more involved question:

The house is in Northern New Mexico and is just under 1500 sf, built with Structural Insulated Panels (SIPs). The walls and roof are R-41 and there are large Low-E windows for passive solar on sunny days -- we get about 300, at 7000 ft. There are 2 bathrooms.

I've had the heat loss/BTU calculations done, so we know what is needed per room. We'll be using Slant/Fin Fine/Line 30 baseboards.

My plumber has suggested a couple of options:

Rennai on-demand water heater for domestic water heating and a 90K BTU Lochinvar CBN090 copper core boiler for the baseboards.

Or: a regular water heater plus the Lochinvar.

Or: the Lochinvar Knight which I believe will be used for both the domestic and baseboard supply.

I've also looked into the Viessmann Vitogas 050 with a 53 gallon Mega-Stor indirect water heater and really was intrigued by that system.

Energy efficiency is very important as you can probably tell by the house construction choices. There will be only 1 or 2 people living at the house, so the hot water demands aren't great -- but there may be those rare times when visitors are showering in both baths or the dishwasher is competing for the hot water.

From what I've gotten from various sources the on-demand heater may not always be able to keep up, plus we have a lot of minerals in our water so the high heat will require regular maintenance for the build-up.

The cost is a factor -- can't really go high end, but if the efficiency is there, spending a bit more up front would be worth it -- as opposed to a regular water heater.

Is there a moderately priced, high efficiency solution that might work in this situation?

Thanks for reading through this and for any insight you can provide!
 
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Old 12-13-07, 07:17 AM
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Of those choices, I'd go with the Knight and an indirect for the domestic HW. IIRC, the Vitogas is a cast iron 83% efficiency boiler. Without additional piping and controls, it is more or less just another bang-bang boiler (but a very nice one, indeed). The Knight is a modulating/condensing boiler with a stainless steel heat exchanger that runs around 90+%. Modulation really gets you a lot more efficiency. It has a control package built-in, and will require a bit more thought on the piping, but if your contractor is familiar with it, then no problem.

If minerals in the water are an issue, I'd consider a tank-in-tank design for the indirect, like the Triangle Tube Phase III (www.triangletube.com). Or if you go with a coil design, go with the tank that has an easily removable and cleanable coil. IIRC, Buderus has this design.

Fin-tube baseboards will certainly be the lowest cost option for heat emitters, but they are a high-temp form of heating. If you go with them, I'd ask the contractor to try and design the space heating for as low a water temperature as you can get, to increase the efficiency of the Knight. Two ways of doing this with baseboard are to increase the length of baseboard in each room (which taken to an extreme can result in lots of baseboard and problems placing furniture), or using high-output baseboard and not increasing the length so much. There are very nice options in panel radiators (e.g., Buderus, Runtal), but then you are getting into pricier stuff. Even if you stick with the FineLine30 (I've got a house full), the Knight's modulation during non-peak demand days will get you a lot of efficiency.

Good luck.
 
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Old 12-13-07, 07:49 AM
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Thank you -- good information to consider. I'm under the gun to make the decision so getting this kind of input right now is really appreciated!
 
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Old 12-13-07, 08:42 AM
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Baseboard/indirect

As Xiphias said, the Buderus indirect is maintenance friendly. His comments about the baseboard were right on target as well. The less you have to increase the water temperature, the less energy it takes but baseboard heat emmisson falls off pretty sharply at lower water temps. I also suggest a higher capacity baseboard rather than more length of the Fineline 30.
 
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Old 12-13-07, 05:24 PM
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Panels with TRVs in all rooms except the room where you locate the t-stat - Biasi makes nice low cost good quality panel rads.

Pipe them all homerun in half-inch Pex-Al-Pex back to a simple manifold, either made or purchased.

Connect that manifold to a Triangle Tube Prestige boiler.

For DHW, I'd go with a tank-in-tank or a reverse indirect design.

You'd get great comfort, simplicity and efficiency. My one reservation with the Knight would be it the need for a very high head pump. I believe that it's HX is sourced from the same manufacturer as Munchkin and Trinity and they all need some serious pumping power. The Prestige could do all of that with just the one internal pump set on it's lowest speed. All in when heating, you'd be using whatever natural gas and about 100 watts electrical total.
 

Last edited by Who; 12-13-07 at 06:12 PM.
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Old 12-14-07, 01:14 PM
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Again, thanks for the input.

To clarify the situation, the system would be NG, and 3/4" pex tubing is already installed and divided into 3 zones. There are thermostat wires for each zone, though nothing beyond this has been decided. There is also a gas fireplace in the great room with an input of 15K to 30K BTU and an 82% (steady state) efficiency. Between using that periodically, the passive solar and the R-41 insulation, the zone heating would not be bearing the full load and at times would be supplemental. I'm hoping it would be more of a tempering, steady "base" heat to keep the temp from going too low when the other sources weren't contributing. I'm not sure if this strategy is good, but it seemed reasonable!

I wanted to look at more efficient options besides a boiler and regular hot water heater set-up (which was the contractor's initial proposal) thus all the questions.

Because of the home's small rooms, I was trying to keep the radiators low-profile, so I was leaning towards the smaller baseboard type. I haven't been able to find a higher capacity than the Slant/Fin 30s -- do you know of any that are similar to that physical size?

The Prestige looked good, but it looks like it requires a 1'' supply/return. Otherwise, it might have been a good pairing with the Buderus indirect ST 150. I've read comments on other threads here about the quality of Buderus construction and how they're manufactured in China or Taiwan. I've also heard good things about Buderus.

I really do appreciate your thoughts -- just trying to find the best products upfront to avoid problems down the line and make a good investment efficiency-wise.

FYI, I'm not sure if you've seen the recall on the Phase III, but here is some info:

Triangle Tube/Phase III

The U.S. Consumer Product Safety Commission in cooperation with Triangle Tube/Phase III has recalled 3,000 Delta Performance or Delta Performance Plus Series Combination Water Heaters due to carbon monoxide (CO) poisoning. The burner plate and flue hood seal on the water heaters can fail due to an improper seal causing a leak of flue gases and CO. This poses the risk of CO poisoning to consumers inside of the house. The water heaters were manufactured in the United States and operate on natural or propane gas. Consumers should immediately stop using the recalled water heaters.


In any case, if you have any more feedback I'm all ears! Thanks.
 

Last edited by the_tow_guy; 12-14-07 at 01:43 PM. Reason: Removed commercial link not germain to the thread.
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Old 12-14-07, 06:55 PM
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In the slantfin line, MultiPak80 is "high output" baseboard. It's an inch taller and a half inch deeper than FL/30. Puts out ~150-200 more BTUs per foot across a range of supply temps. There are other brands with which I'm not familiar.

If the baseboard is really going to be supplemental, then FL/30 is probably fine, and a mod/con would make even more sense because you will probably be running the baseboard at fairly low temps. Which brings up another point: at low supply temps baseboard becomes pretty inefficient. Baseboards work by convection -- drawing cooler air from the floor over the fins and out the top damper. At high supply temps (180F), this works great. But at lower temps (<100F) performance really starts to fall off because there's not a large enough temperature difference between the supply water and ambient air to get them to convect.

As Who said, you could go with small-profile panel radiators, but they will be more $ than SL/30. I think (actually I have no idea, but it's worth checking...) you can use the 3/4" pex to them and go down in size to the 1/2" they usually require. They would provide a more radiant form of heat and work better at low temperatures.

1" supply/return is for the near-boiler piping. You will have a header/manifold off whatever boiler you have to go from its outlet dimension (usually 1" to 1.25") to the distribution loops.

The PhaseIII recall was not on their indirects, but a gas-fired model water heater.

If your contractor is familiar with the Knight, then that might be the way to go. The Prestige from what I understand is also very well regarded. These new-fangled boilers definitely require an annual checkup, so having a good contractor familiar with your boiler is even more important.

Good luck!
 
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Old 12-14-07, 08:51 PM
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Allow me to quibble with my friends here. The heating curve for fin-tube is in my opinion actually quite linear. I have fintube and a simple straightline reset curve and it works flawlessly. If you go to Slant-Fin's web site and check the correlation between water temps and BTUs per lineal foot you'll also find it is quite linear.

If you can supply fin tube with steady well matched temps, the comfort is there in spades regardless of the outdoor temperature.

That said, if I was building new, I'd have panels. And the bulk of those panels would have TRVs so that the heat in the room stays steady regardless of whether tons of people are in the room or if there's a ton of sun shining in the room... it simply works just about as good as it gets. It's self-regulating, purely mechanical without wires, and individually controllable. Maybe some radiant for baths and kitchen, but for me, simple lower mass panels and TRVs for the bulk of the rooms. To me panels don't take nearly as much wall, pipe better and they look way way way better. With a panel you can do under a window what you'd need the better part of an outside wall if using fintube.

The one inch can be bumped up to 1" where you leave the boiler. That shouldn't be a factor... even if you left it at 1". And inch is good for 90 MBH @ 4 GPM and that's over some length.
 
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Old 12-20-07, 09:30 AM
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Once again, thank you for taking the time to respond.

I've been pretty much set on baseboards rather than panels -- just my personal choice in how they look and the visual space they take up. But I see the advantages for using them. Can TRVs be used with baseboard?

I've narrowed things down to this configuration for the 3 zones + DHW:

Lochinvar Knight 80K or 105K
Lochinvar Squire 52 gal. indirect
Slant/Fin Fine/Line 30 or MultiPak 80 Baseboard

I'm not sure of the sizing for the boiler, since my plumber said I need a 90K unit -- I'll be checking with him on this -- but I'm wondering if having some extra capacity is useful or a waste?

Here are the BTUs for the rooms based on the heat loss calcs:

Master Bedrm 4500, closet 737, bath 1267 Zone 1
Guest Bedrm 2000, bath 465, hallway 1890 Zone 2
Office 2577, Dining (supplemental) 1200 Zone 3

The great room (525 sf living rm/dining/kitchen) will be heated by a 30K gas fireplace plus it has passive solar.

The office and dining are on the south side of the house so will see the most passive solar benefits. On multiple cloudy days, the office and dining baseboard heat will be used most. The master suite also has smaller south-facing clerestory windows for passive solar.

Finally, any thoughts on how low of a temp I might be able to go with the baseboards? Between the passive solar, low-e windows and the R-41 throughout the house, I'm not sure how much the baseboards will be needing to contribute. Would I be able to set lower target temps and experiment on how low it could go or would that compromise the efficiency? Obviously it could be somewhere below 180* and definitely not lower than 120*.

If you have any input on these choices please let me know -- much appreciated!!
 
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Old 12-20-07, 10:16 AM
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When I total up your numbers it is less than 15k. Add an indirect and that is where the larger boiler comes in. I would design my baseboard for 140 providing you have the wall space. Install a mod/con boiler and indirerct. Your loads are too small for any boiler I am aware of. I would maybe consider not using 3 zones to maintain a higher efficiency. These short zones may even shortcycle a mod/con.
Ever consider a buffer tank?
 
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Old 12-20-07, 12:02 PM
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If the total load is ~15k, and the baseboards are truly supplemental, then you should probably consider a different heat source. The baseboards might only ever see a load of 5-10k. Even the lowest modulation boiler can't go there.

"Who" could list a bunch of alternatives off the top of his head, I'm sure. I'm thinking tankless water heater? Takagi? Rinnai? Thermolec? Can't remember if that's the right technology or manufacturers.

For domestic hot water, if you're not using a boiler, then in your climate I would absolutely go solar. Flat panel collectors with a small PV panel to run the pump(s). Use a 120gallon tank and you should be more than adequately supplied even through the cloudy stretches. Google around. There are packaged systems with quality components readily available. Not rocket science to install. A few key things to get right, but not alien concepts. Your plumber might even be comfortable with it. In NM, I'd guess there are a bunch of qualified solar guys.

For that matter, with a <15k load (at design!) you could easily do solar heating and DHW. Options abound.
 
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Old 12-20-07, 02:10 PM
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I'm not sure of the sizing for the boiler, since my plumber said I need a 90K unit -- I'll be checking with him on this -- but I'm wondering if having some extra capacity is useful or a waste?

Here are the BTUs for the rooms based on the heat loss calcs:

Master Bedrm 4500, closet 737, bath 1267 Zone 1
Guest Bedrm 2000, bath 465, hallway 1890 Zone 2
Office 2577, Dining (supplemental) 1200 Zone 3

The great room (525 sf living rm/dining/kitchen) will be heated by a 30K gas fireplace plus it has passive solar.
What is your plumber basing his number on?

How did you do your heatloss because it looks your gas fireplace is more than enough to heat your home?

Purely opinion here... I really like the Knight's controls from what I have seen but it's a real pump $lut. The 80 needs a Taco 011 (1.76 amps) sized pump and the 105 needs a 013 (2.0 amps) sized pump. My Prestige can handle my monoflo circuit and some radiant with just the internal 15-58 on medium speed (0.7 amps). That's piped direct which a Knight can't do... so it's just one pump drawing 80 watts. It only needs low speed (0.55 amps) to do primary secondary piping arrangements for supplying the boiler (and if I had a manifold it would work for that direct). There is very low electrical consumption with a Prestige. The Knight needs at least 2 pumps and the boiler pump is on a good chunk of the heating season. At $0.15 per kWh with the assumption that the boiler pump runs between half and all the time, each extra amp costs you $6 to $12 per month during the heating season. You might be adding a couple of amps you don't need to. Just some food for thought...
 
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Old 12-20-07, 03:24 PM
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my limited experience with the Knight

I just put in a Knight 105 - mostly DIY.

The reason for the Knight over the Buderus - local access to parts. Nobody stocks Buderus here in town and stuff has a habit of failing at the worst possible time (maybe it's just me). In fact the only mod/cons stocked here in town were the Knight and the Munchkin. Most places had no idea what I was talking about...

I have to say the unit seems fairly well built and came with a lot of detailed installation instructions. That was a dream. Lot's of controls and room for expansion. I know this wont last as long as the beast I removed but does anything last over 10 years anymore?

It's compact, quiet, and so far so good.

The temperature here jumps around a lot. It has the outdoor reset so the temp is controlled to some degree by that. It ranges from STANDBY to 100%. It seems to get up to temp and then hang around the 40% range with the current weather conditions. Adding to my situation is the fact I have standing rads and an old gravity fed system so we're talking lots of big pipes and a lot of water in the system. So, as Who describes, there's a whole lot of pumping going on even though the thing is just cruising along at 30% to 40%. The folks that did the heatloss probably oversized the thing but I will be adding DWH when my current hot water heater dies so maybe that's okay.

My only quirk has been that because of some of the weird piping that was probably great when it was a gravity feed system, there's an odd vibration you can feel in the piping to one rad. And it's totally silent - except for some reason the rad acts like an amplifier and it's focused on a small area - where my daughter's head is where she sleeps. You can only hear this low hum in an area about three feet square...

We'll see what the gas bill looks like next month, but it cant be nearly as bad as the hugely oversized 230K beast that just blew dollars out the chimney.

So that's my DIY experience with the Knight for whatever that's worth.
 
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Old 12-20-07, 03:40 PM
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The actual square footage of the house is 1360 and the heat loss calcs were done from the plans using the window sizes and U-values, the R-values of the insulation, the room sizes, etc. The gas fireplace was added afterwards in place of wood burning. I did check into solar systems at the beginning and they were between $6,000 and 12,000 just for DHW! I emailed info today to get another quote before I give up on that option.

Since everything is plumbed for baseboard, I just need a heat source to give the north and west closed off rooms additional warmth when it gets real cold.

If solar isn't affordable, I'll be back to square one, trying to figure out an appropriate, energy efficient way to heat the place. I'm wondering if you could connect an on-demand wall unit to an indirect tank and if that would be efficient or even feasible?
 
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Old 12-20-07, 06:51 PM
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Old 12-20-07, 08:18 PM
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xiphias nailed it...

You've got a tight new home. If I had a tight enough structure like you do, I'd go solar or geothermal (which is stored solar) and electric as backup. The Thermolec looks like a nice little boiler electric boiler and has outdoor reset.
 
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Old 12-20-07, 10:02 PM
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Okay -- very interesting possibilities here. Maybe a small solar system to pre-heat the water for the electric boiler? Then in the future, photo voltaic panels or more solar thermal could be added to go totally solar?

Add an indirect between the solar and the tankless?

Would it be totally wacky to have 2 tankless heaters, one electric and one gas? One for DHW and one for the baseboards? Could they be linked so that one could provide back up to the other?

Northern NM gets cold from about November to early March, but the high altitude and regular sunny days takes the edge off. The baseboard heat would be used for about 4 months just for those previously mentioned rooms -- that's why I was wondering if a 'divided' system would allow one part of the system to be idle the majority of the year.

Maybe the modulating unit would serve that purpose more effectively without another piece of equipment. I just would hate to be without heat in the middle of winter if the electricity went out. There is the gas fireplace though as back-up.

As you can tell, I'm no plumbing genius! I'm just throwing out thoughts in case these configurations have been tried before. If they make no sense, sorry -- I'm just brainstorming.

I'm running out of money to finish the house, so I'm trying to find a cost-effective solution that fits with the energy efficiency of the rest of the home's design. And if possible to lay the groundwork for future solar. Just want to invest wisely and be smart about energy use as much as possible with what I have to spend.

Thanks for the input you've all given!
 
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Old 12-20-07, 10:14 PM
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How many gallons of hot water do you figure you use in a day? Do you plan to have gas in the house for anyappliances?
 
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Old 12-20-07, 10:27 PM
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There will be gas for the range, clothes dryer, fireplace -- the mechanical room has both gas and electric hook-ups ready.

A maximum daily water usage would be 2-4 showers, 1 load of dishes, 3 loads of laundry and 2 bathroom and 2 kitchen sinks being used sporadically. Not sure how to estimate that...
 

Last edited by SWDesignrBuildr; 12-20-07 at 10:28 PM. Reason: correct numbers
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Old 12-20-07, 10:45 PM
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Hrmmm... your DHW load is there but your central heating loading is so small... which is really good, but tough to find a match since most North American houses are too big and too wasteful. Please tell us you aren't planning on having multiple zones when thye whole house is already a microload for most heating days.

I'm tempted to say a gas tankless for the DHW and maybe an electric boiler for the house?

Or maybe the smallest conventional bang bang gas boiler on the market heating a buffer tank and then draw your heat from the buffer tank. SlantFin has a 30 MBH Victory model, maybe there is something even smaller. Put full ODR on the buffer tank and a TV bypass on the boiler.
 
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Old 12-21-07, 06:58 AM
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Some WAGs. Probably worst case as it assumes all input is DHW, and they are likely on the high end for volume.

3 showers, 10 min/ea @ 2.5 gpm = 75 gal
1 dishwasher, 8 gal / load = 8 gal
3 laundry, 5 gal / load = 15 gal
2 kitchen, 4 gal /day ea = 8 gal
2 bathroom, 3 gal /day ea = 6 gal

112 gal/day. Whew. The major consideration is back-to-back(-to-back) showers. Size for that demand, I think. If you have a high-gpm custom car wash size shower, all bets are off.
 
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Old 12-21-07, 08:43 AM
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I'll try to clarify a bit since I'm sure I'm confusing the picture! You can go to this link to see a diagram of what is already plumbed for the baseboard and what the design calcs were originally:

http://www.dnahomedesign.com

Looking at the lineal feet of baseboard to be installed, it adds up to about 48 feet -- @ 610 btuh = just under 30K. Is that correct? I gave the plumber the calcs but it looks like he put in what he felt was needed for the rooms based on his experience. Changing to the gas fireplace also skewed things.

I like the plumber, but he has been busy with other jobs, hasn't given me much guidance and prefers to use only what he can get through Ferguson's. I'd switch to someone else but he has aleady done half the work and it would be difficult to have 2 plumbers trying to warrant a system if problems came up later.

In any case, Who, we WERE planning on 3 zones! 8-( The guest room/bath would only be used occasionally, and the south facing office zone has so much passive solar and is used only during the day that it didn't seem to make sense putting it with the northern rooms.

Xiphias, those load estimates are definitely worse case and would be spread over a day -- average would be about 35 or so.

Sounds like solar + elec. back-up would be the best route if I could afford it. The modulating electric, the buffer tank, the tankless all sound like workable options in some combination. The fireplace's range is 15K - 30K so maybe that should be supplemental and keep the baseboard heat steady?
 
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Old 12-21-07, 06:26 PM
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Looks like almost 2:1 overradiation everywhere except the MBR. You could run some fairly low temps (for baseboard).

The high initial cost for active solar DHW would probably pay back relatively quickly in your climate, as your production would be pretty high. If you're going to be in the house for a long time, I'd try to go for it now.

(If you weren't budget limited, solar powered radiant flooring would have been awesome in that kind of layout. Depending on floor coverings, you might have run design temps really low. Unfortunately, high-temp baseboard is about the worst thing to try with solar.)

I'd try for as small a heat source as possible. True design conditions occur maybe a couple days (even hours) per year. I'd guess you'll rarely see a total load >20k BTU/hr.
 
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Old 12-21-07, 06:43 PM
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In some ways not having the floor involved might be a good thing with the passive solar. A more responsive system might be a better match working around the solar gain.

I'll echo xiph in that it's nice that it's oversized... although I'm not really sure that term is the right term to use for radiation.
 
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Old 12-21-07, 07:01 PM
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Yeah, I looked into Warmboard and in-floor radiant heat at the beginning but the cost was prohibitive. The old part of the house was crawlspace -- I would have gone with a slab if I were starting from scratch. But I see your point with that, Who.

So, Xiphias, when you say >20k BTU/hr are you talking about a total load for the baseboards if the DHW was solar powered?

Maybe solar is the way to go, here. It was my first choice and would certainly make the most sense efficiency wise to match the rest of the design.

Thanks for helping me think through this and for sharing your expertise and experience so generously. Glad we are virtual neighbors in this amazing global village!
 
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Old 12-22-07, 06:09 AM
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Yes, Who makes an excellent point about the need for response.

~20k is probably a common total load you'll see. True design conditions are rare.
 
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Old 12-23-07, 01:23 PM
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A few more questions, if you don't mind...

So just to clarify: if I do go with solar, do you think 3 zones would still be okay?

I have the thermostat wires already in place if I use 3 zones, but would TRVs work better instead?

Looking at one of the solar estimates, there's a 4x10 AET solar collector, PV pump, and an 80 gallon Vaughn Solar SEPCO stone-lined tank -- which also seems to be able to heat the water with an electric element as a back-up. Do you think that amount of storage would cover the usage we discussed previously?

Thanks!
 
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Old 12-23-07, 06:34 PM
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On the DHW, yes. 40 ft^2 and 80 gal should cover 3-4 people out there. More resources at findsolar.com. Didn't know Vaughn made solar stuff. Looked at the sepco brochure. Not too keen on their apparently small heat exchanger, but again, that's based on 1-minute looking at a cartoon. Maybe check their ratings against other manufacturers like Stiebel-Eltron, HTProducts, etc. and ask the installer what kind of experience he's had with the Vaughn.

I'd have to think more about TRVs vs. zones with solar. And our resident TRV maven Who is AWOL. First thing would be that I believe you would not be able to use TRVs with a series loop baseboard. You need a different piping arrangement. But if you did the TRVs, modulating flow to the individual elements would potentially conserve some of the hot water stored during the day. The zones would too, but probably not as efficiently.
 
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Old 01-02-08, 08:30 PM
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Thanks Xiph for the additional input.

Just wanted to post an update on the research that I've been doing and relate another solar+electric back-up option that I've been considering. It would consist of:

-- Four 4x10 Radco Solar Collectors with copper absorber plates
-- Two Rheem Solaraid 120 gallon storage tanks/water heaters with Internal Heat exchangers and 4500 watt electric elements as back-up.
-- Drainback module
-- Flowmeter, tempering valve, pressure relief valve and expansion tank for heat exchanger loop, thermometer, all copper piping/fittings, high temperature insulation, and PVC jacketing for the insulation

This system would supply both DHW and HW for the baseboard, (separate loops of course) using the HXs to maximize the captured solar heat for both tanks. The tanks would be plumbed in series. Not entirely clear on the schematic for the system yet, but it seems like it would more than do the job. The electric back-up hopefully would not be used very much.

I know NG would be less expensive to operate, but in order to use the room that houses the mechanical room as a sleeping room, it needs to either be electric or a sealed combustion unit as far as I know.

Any thoughts?
 
 

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