Help finding the right hydronic boiler/heat source

tbrooks

Hello. I am a diy'er looking for some help. This is my first time dealing with one of these systems. I have been getting a lot of help from an engineer in the field and they have been really great. Being a novice though I have been bugging them with lots of questions, and I feel I need to find more info on my own. I do have Modern Hydronic Heating, which I read most of and have been using for reference, but there is just a lot of info in there for a novice. For some info I will be remodeling an existing home to make it into a 4 bed, 2 bath, 1300sqft single story home for myself. It will be an underfloor hydronic system. It is a framed floor with a crawlspace. I will be installing all of this myself, I'm sure that will be lots of fun! 6 zones and 10 circuits, with 1600ft of 3/8 pipe. I know that is a lot of circuits for a 1300sqft home, but long story short, it has to be that way for proper heat distribution.

My fuel of choice is Propane gas. Natural gas is not available here, and electric rates are high around here. My dream home would have a wood boiler, but this is not my dream house and my budget will not allow for that. I'm trying to keep all costs to a minimum, but I will not cheap out now, and make mistakes that will cost me more money and labor in the future.

I would like to have a combi tankless unit, but I'm not sure if that is feasible, or if I can find a model that will perform both tasks efficiently. Honestly I don't know if I can find a boiler with that high of flow rate and a low enough btu output. Of course I want a mod/con with outdoor reset. My total flow rate for my heating system will be 6.85gpm with an output of 18751btu/hr. My design temp is 111*F. I have 10 circuits, and the combined temp drops works out to 56*F (I just added them all up, I hope that I did that right).

I have searched alot for combi tankless boilers, but there are just so many out there. One thing I am not sure of is the manufacturer flow rate. Most give a flow rate listed under the dhw specs, and I'm not really sure if this is a total flow rate for the boiler, but I assume so. From what I have found (and the little that I know) I'm not sure that a single tankless boiler can supply my heating system, let alone supply dhw as well. I'm still hoping to keep my total materials cost under $5000 for my project, but I'm doubtful thats gonna happen. I was hoping somebody might have an idea of a boiler I can use or at least a better way of searching for what I need. I'm tired of reading spec sheet after spec sheet of boilers I don't believe will work.

Also I think I have decided on 2 Wilo ECO16rfc circulators in series to pump my water. Any opinion on these pumps? They seem to be midrange between taco and grundfos. I have around 20ft head hence the 2 in series. Of course all the above figures are at full design capacity, and I actually used 5*F on my design, while 15*F is the historical dbt for my area, but we had a few nights with temps below 0* this winter, and one day with a high of 17*F.

SWEI

What exactly are you trying to heat? Has anyone done a heat loss calc on the building?

20 feet of head is quite high for a residential system. How did you arrive at that number?

tbrooks

I'm heating the whole house. Yes, I have done everything by the book, literally. Room by room heat loss analysis. The head calculation was from the design calculator I used. I know it is high, but assumed that is because I have so many circuits. I also had to decrease some of my tube spacing in order to get my temperatures within 5*f of the heat source supply temp. Each bedroom has its own zone, mainly because there is a vast difference in heat loss per sqft. My bathrooms are on one zone, but they are opposite each other with an opposite exterior wall on each one, so I split that into 2 circuits so that I can have even heat distribution. The kit/lr is one large room, but the kitchen will have tile and the lr engineered hardwood. In order to keep these as one zone I had to split it into 4 circuits, as the kitchen will have 100sqft unblocked heated floor and the living room will have 300sqft. And I did lots of math for the kit/lr to make sure my calcualtions were correct. My engineer friend hasn't had a lot of time to check over my numbers, but at a glance they said everything looked right.

tbrooks

Yes, I have a propane fireplace and small wall heater that heats the entire house I'm in now and like it. But also am in a 2 bedroom 1 bath house currently. With the 4 bedroom 2 bath, and my floor plan there is really no good way to circulate the necessary heat to all the rooms, without having an individual heater in every room. I had a wood stove in the home before this as well. With a wood (and I assume a pellet stove) in a 1 story home, again the problem is heat circulation. In my previous 3 bedroom 2 bath home, with a good fireplace insert, burning 6 cords a season, majority of the time my living room was an uncomfortable 85*, but I had to have elec space heating in each of the bedrooms, costing me approx. an additional $1500 a year in heating! And I had fans going everywhere.

tbrooks

Oh and in my current house with the propane fireplace and wall heater, I still have to have a couple pedestal fans to keep the heat circulated, along with the ceiling fans

Zman

You have done some great research and are off to a good start.

A few thoughts:

You have very aggressive zoning that will make almost any boiler short cycle excessively. Rooms can be balanced by changing the amount of tubing and aluminum plates in order to prevent overheating.

Your concerns about the correct flow rates and btu's can be resolved using primary secondary piping.

Your head of 20' is too high. You are either incorrectly sizing the piping or the calcs are off. Putting high efficiency ECM's in series is not a good plan.

5 degree delta is very tight. 10 is the norm.

For a system this small you will need a boiler that will modulate way down and have significant buffer capacity.

You might look at something like this. http://www.htproducts.com/versahydro.html

@Rich is very familiar with these and may have suggestions.

You seem like a bright guy.
If you understand that raising a pound of water 1 degree F = 1 btu and you get your head around the universal hydronic formula, you do well.

Carl

tbrooks

Thank you, Carl. I have always felt, and proved to myself, there is nothing I can't do with the proper information. When I said within 5*, I meant circuit temp +/-5* of the heat source. That being my largest temp drop for any circuit is 6*. The smallest is 4*. This is because I had to adjust my temp drops, tube spacing, and pipe size in order to get my velocity above 2 and my circuit temps within +/- 5* of heat source temp, to keep from using multiple heat sources or mixing valves. Although I may need to use mixing valves anyway with my low supply temp.

Part of my problem with the zoning also is that I have share custody of 2 of my children. We switch every 3 months, so they are with me half of the winter. Their rooms have an approx heat loss of 15btu/sqft and 20btu/sqft so I can't put them on the same zone. My other 2 bedrooms have the same heat loss(one 15, one 20), but I can't put them on the same zone as the corresponding other rooms, because I need to have those rooms turned down 3 months of the winter. I can't change who gets what bedrooms as the latter 2 rooms are the master and nursery. My floor plan took alot of work to make good efficient use of all my space. I'm sure that is confusing, but its hard to explain, sorry.

I am trying to wrap my mind around all of this hydronic/radiant heating knowledge, but it has been alot to take in, to say the least. Part of the reason for my system as it is, is because I have been using a fairly simple calculator for my design, which I can see now is restricting my ability to have options that could benefit my design. I will definitely look into the primary secondary piping, and play around with my design more to see what I can do to create less head. Its just hard for me as this is all new and as I said hard to take in at once, with little prior knowledge on anything hvac. I still have a few months to figure this out, so I know I can get there with the proper help. There no people in my area experienced with hydronics, people are very backwards around here. I talked to an owner of a large local hvac company who stated hydronic floor heating is useless, I would be better to use electric radiant!

tbrooks

Well after some careful thought I have changed my mind. Carl your comments made me realize that although I can read and learn as much as I would like, without experience my system will be too complex for me to design on my own. I could do it I'm sure, but there are just too many factors, and the time it would take me to figure it out is just a waste really. Honestly I am tired of spending so much time trying to figure this out and have had many set backs. I believe it is time to save myself the headache and let someone who knows what they're doing come up with a better design. I think part of being a "bright guy" as you put it is knowing when someone else can do the job better, faster, and easier than I could!

SWEI

How long are your longest loops?

tbrooks

1 is 225ft, 2 are 94ft, 1 is 128ft, and the other 6 are around 180

jonny88

Multiple zoning is a problem I second what a previous poster said.Hit up Rich.He can advise you on HTP.That or a mod/con buffer tank etc.

RobG

Where are you located? We might know of someone who can consult for you.

Rich_49

TBrooks . Feel free to use the number below to contact me . Was unavailable yesterday for the beginning of this discussion , was sitting in a room full of dumb inspectors laughing silently as ME was trying to teach them about radiant , quite amusing . You are off to a good start but still way off track and making this too complex , referring to LR / kit , Baths , kids rooms. No need for multiple temps in this or many houses , thermostats are inexpensive and so are actuators which you already require .
Too much extra work and design and guessing to save on 3 thermostats .
Did you by some chance add all the head losses together ? This would explain the high head factor you are describing . For instance , I am now designing for a 14,300 sq ft home and the highest head loss is a remote manifold 125' from the boiler room at 6.4' . Something is amiss .

tbrooks

I am located in the southern NC mountains. Things are quite backwards up here. I'm sorta in the construction business as a handy man. I do everything, but a lot of my work is fixing problems from errors made by contractors in all fields. I have never messed much with any hvac systems, but have seen and fixed lots of obvious minor mistakes in homes by hvac contractors, and therefore don't trust any of the local ones.

Thanks for the response rich. I'm an intelligent person, but not good at speaking, so I would prefer not to call. My words never come out right lol. Typing on the computer I can fix them as go lol. I too fell that my system is over complicated. The head loss came from the calculator I was using. Maybe I put something wrong but I rechecked multiple times. It was around 16 until I started adding a pump curve to the mix. I thought with 10 circuits, 3/8 pipe, and mostly 8" spacing led me to that number. I have been planning on this being my main and only heat source, so I have been worried about having adequate heat in every room. Hence the number of zones/circuits.

Here's a rough drawing of my floor plan. I used paint to show where I had my zones divided, and included heat loss/sqft of unblocked floor. Of course I had planned no piping under the kit cabinets or appliances, and used my best guess as to how much floor would be blocked by furniture. As I said beds 1&2 will be unused for half the winter so I would like to be able to turn them off/down. Let me know what you think, or how I can better do this. Thanks

SWEI

Is that 225 foot loop using 3/8" PEX? If so, split it.

tbrooks

Oh, if you can see it, the lightly shaded walls are the existing exterior walls, the kit/lr is the addition. All the floor joists run from left to right, which is weird, they run perpendicular to the roof trusses. I planned on locating my system under the floor, with a central manifold

tbrooks

SWEI said:

Is that 225 foot loop using 3/8" PEX? If so, split it.

Yes it is, that is including leader length. I thought I could go to 250' with 3/8?

tbrooks

Well I just heard from my friend that with a small residential system, I don't need to keep my velocity above 2fps as I thought, that could change everything. Can someone recommend a level that I should stay above?

tbrooks

So I started fresh on the calculator. Put delta-t 10, and 1/2 pex, with 12" spacing. Using only # of circuits recommended by calculator. I end up with 7 circuits, 2 in the kit/lr. Most of my velocities are .7-.9, except kit/lr at 1.6. All my reynolds numbers are good. My supply temps vary from 107-139, that will have to be fixed. My flow rate is 3.87. I will have to input some more figures to get my head, and I will get all my supply temps within +/- 5* and get back to you

tbrooks

So I got my temps in check, by adjusting my pipe spacing. Got my head figure at 6.8ft, and my flow rate is now up to 4.3gpm.
Still got 1/2 pex on everything, and my velocities have not changed, they are still low. I

tbrooks

I just split my baths into 2 circuits again, for better distibution. I did reduce the pipe to 3/8 there, because the velocity dropped to .4. Now with everything re-adjusted, I am still at 4.3 gpm and 6.8ft head. My reynolds number for the baths dropped to 3654 though. Still above recommended. Just not sure on these velocity numbers

SWEI

tbrooks said:

I thought I could go to 250' with 3/8?

You can "go" almost to any number you're willing to pump. Cut it in half and re-work your math (which we're still curious about, BTW.) You'll need a lot less pump.

Rich_49

TBrooks

Don't worry too much about supply water temps from room to room . Here is the thing , if you put 105* water or for that matter 115* through an individually zoned room requiring 100* or even 90* when the surface temp reaches the required temp the stat will open and flow will cease . The room will not overheat , nor will the floor .
Bed 1 and bed 3 may very well experience different and varying heat loss numbers although on paper they are the same because they have different exposures and thus infiltration rates . One or the other will under or overheat based on T Stat placement . Same goes for the baths . Your Lr / Kit you can get away with zoning together because people in these rooms are basically active and they adjoin , place the thermostat on the wall next to the doorway to hall and you can certainly live with that quite comfortably .
Thermostats are cheap but comfort is priceless .
Another thing about radiant . Sometimes the flow is what the flow needs to be . More often than not your numbers will be in the transitional Reynolds numbers , neither turbulent or laminar but more like a PWM sort of arrangement . Your Delta T for floor radiant should be 10* and take every measure you can to insure all supply water to each circuit begins at the cold wall , this is where you will get the most heat transfer since the idea is to heat the mass of the building and build MRT . Controlling as many of these factors as you can makes predicting what and how the system will perform much easier .

tbrooks

SWEI said:

You can "go" almost to any number you're willing to pump. Cut it in half and re-work your math (which we're still curious about, BTW.) You'll need a lot less pump.

I can understand that. What is or was curious on my math? Most of it has been done by a design calculator. As I said my changes to gain velocity previously must be what caused my high head. After some searching last night I found that many residential systems have flow rates down to .5fps, so I feel much better about that.

Thanks for the input rich. On the temps I mainly wanted to lower my 3 highest, and on a side note changing them to 8" would be easier to install with joists 16" oc (in my head anyway).

Sounds like you are telling me to split my baths back into 2 zones. I combined them into one, just because its such a small amount of area, and trying to lower my number of zones. But then I split them into 2 circuits, so I could do as you said, and start each circuit at the exterior wall. Kinda defeats the purpose of combining though.

All of my delta-t's are now set to 10, except my lr/kit zone, which I had changed to 8 to lower the temp. If you think I should change it back I will.

Also I'm not sure if it makes sense or not (it does to me), but I included my master closet in my master bath circuit. Mainly because of easier calculations, but also because the mb is such a small area without an exterior wall.

Another dumb question I have is, would the supply lines running to the outside wall be considered leaders? And should leaders be insulated? Not sure if either of those questions are truly important. Considering I am working with a framed floor, I had planned on running them against the subfloor anyway, not below the joists.

Rich_49

Where is it that you want to locate your manifold ? Sometimes leaders ( YES) can be run through other interior areas or even along outside walls to other rooms . Many times this will hold a zone or a room off a call for a bit while not allowing it to become uncomfortable

tbrooks

I had planned on a central location, around where the master bedroom door is. It can really go anywhere as it will be in the crawlspace. I'm not sure if there is any reason that I can't locate all my system components under the floor, other than ease of access and possibly air entrapment issues? The only feasible place above the floor would be the laundry room, but I would rather not have it there. I could possibly fit everything in the master bath linen closet, and eliminate it a useful space, but that would be crammed in there.

tbrooks

I could also build a small lean-to off the back of the house around bedroom 2-and the bath, if need be. I wanted to locate the system in a garage on the lr end of the house, but I probably won't have the money to build the garage right now, and thats a long run to get to the far bedrooms.

SWEI

tbrooks said:

What is or was curious on my math? Most of it has been done by a design calculator.

Sorry -- I may have confused you with another recent poster who had 20 feet of head. I don't think you've actually mentioned head, but it's an important part of an iterative design process. Take a look at your numbers after splitting the 225 footer, and then look at what splitting all the 180 footers will do.

I'm not sure if it makes sense or not (it does to me), but I included my master closet in my master bath circuit. Mainly because of easier calculations, but also because the mb is such a small area without an exterior wall.

We find that an unfortunate majority of floor-heated bathrooms fail to meet owners' expectations. The first problem is limited useable floor space for tubing as you noted above. The second is that for optimal comfort, bathrooms like to be several degrees warmer than the rest of the house. We solve this by using tight tube spacing in the available floor area (typically 6") and then adding additional tubing (with plates in most cases) to the walls and/or ceiling. A fully radiant shower is a magical thing, as is a nice warm wall next to the loo.

Remote manifolds are your friend. You can feed 3-4 loops of 3/8" PEX using a 1/2" trunk line and the whole thing can tuck easily into the wall between the bedroom and the bath. This can also makes zoning simpler.

RobG

As for the bathrooms, a towel warmer and as SWEI said tubing in the floor and walls of the shower works wonders. It also helps to keep mildew away by drying the tile surfaces.

tbrooks

Thanks Swei. I had mentioned head of 20 ft, but thats all changed now. As to the bathrooms, I sort of anticipated what you were saying (by sheer luck), and I already planned my indoor temp for these rooms 2* higher. I had also planned on running my tubing under the tubs, and considered them blocked heating space. And it also worked out my bath required temps are the lowest on my plan. I'm thinking in the master, its probably a good thing that I included the closet. I can actually start the circuit in the bathroom, and end it in the closet. The other bath it will start in the tub area, so that will be the warmest part. On another note, I have made multiple towel bars, coat racks, and light fixtures from galvanized piping in the past, and plan on doing alot of that in this house. I could connect hot water to the towel bars pretty easily.

So last night, I accidently closed the calcualtor, and lost all my info. So I plugged all my numbers back in, with the bathrooms separate form the start. I also left the baths with 1/2 pipe. Now I'm getting 3.86gpm and 3.3Hft. My only concern with this is one of my baths has a velocity of .4fps and 2300RN. My other bath is .5fps and 2797. I may step these back to 3/8 pipe, what do you guys think?

Rich_49

You're done , leave it as is . Using an ECM circ you can heat your home at design using about 13 watts for the circ . These baths will ultimately receive more flow than what is stated because there is not a circ small enough to go that low . Your flow will mostly exceed those numbers , so you're good .

tbrooks

Thanks rich. I won't mess with it any more, and I got it saved as well. Any advice on a pump? I had read in the grundfos 15-55 review, that many people were replacing their faulty taco's with it, so I think I wanna stay away from taco. Then again the bumble be seems to have some good reviews, but not sure if I want a delta-t pump. From what I have read it seems that a delta-p would work better. I have also been looking at the same Wilo pump, I originally talked about above, and also grundfos up15-42f/vs or alpha 15-55. From the spec sheets it looks like the bumble bee and 15-42 modulate to the lowest level, but that 15-42 comes at a hefty price, and from the spec sheet it looks like it needs a controller? I do know that grundfos is a tried and true brand, used by many, so maybe thats the best route? And then I guess I can get back to the original questions and start looking at boilers again!

Rich_49

Look at the Taco 1816 . It has the lowest end available I believe .
Most circs get replaced by guys who are trying to make systems work better and looking for something to blame other than themselves .
Delta T and Delta P circs will work in either case , as long as the highest head segment is dealt with and the circ has enough **** to take care of it . Delta T circ will allow an Average Delta T at the boiler no matter how many zones are calling and as zones satisfy it will assist in keeping from over pumping smaller loops . Head will remain the same with the P circ if it is set up properly , if all zones are calling at a specific time both will add the needed mechanical energy required but as zones satisfy the P circ is more apt to move more fluid than necessary and narrow Delta T , The T circ watches Delta T average of all loops calling more often than not allowing cooler water back to the boiler even if it is only a couple degrees .
Either will do as I stated . If you wanted to go with Delta T the Taco 2218 that has been tested in the world and is due for release in September would be the circ to use . The Bumble Bee will be gone and is a bit louder than most appreciate .

http://www.taco-hvac.com/products/water_circulation_pumps__circulators/variable_speed_products/viridian_family/index.html

As far as boilers or heat sources as it were . You're gonna want something with a bit of mass that can be programmed to recognize the parameters of your specific system . I would suggest changing the spacing to 8" to get the SWT down to their lowest and if necessary add a couple loops .
The Versa Flame is a good boiler , don't be put off by the fact that it is 130K . It can be programmed to specific project requirements . These would be the high end for your project .
Versa Hydro is another good choice , the mass is actually your DHW and circulates water through a flat plate using variable speed pumping controlled by sensors factory installed , this allows the equivalent of a claimed 10:1 TDR . This I cannot confirm but have several of them in the world that work real good .
http://www.htproducts.com/versaflame.html
PHR130-55C (versa flame) or PHE130-55 (versa hydro)
http://www.htproducts.com/versahydro.html

If you were looking for something a bit more affordable I would tell you to look at the below combi . Better than anything that would appear comparable . It would require a hydraulic separator , can be ordered with boiler pump . No mass though so dependent on your required level of efficiency and control you could add a buffer tank ( SSU20B) , this can also act as your hydraulic separator .
http://www.htproducts.com/EFT_Combination_Floor.html

Then lastly there is the least expensive Phoenix Light Duty . You can use this as your source using 2 circs , Iseries w/ oDR and a flat plate or the Taco X pump block . You'll have the mass that you need but all these additional parts and labor bring you right to the approx. price point of the Versa Series stuff .

http://www.htproducts.com/phoenixlddocuments.html

That's what I got , hope it helps . I would use Versa Flame and set the domestic mixing valve at 105* just to get that bit of extra you'd need for simultaneous showers .

tbrooks

Thanks, wow thats a whole lot of info, much appreciated. I don't really think I have an individual loop that has more head than the others. The calculator just gives me a total head, so I'm not really sure. I'll look into it more, along with what you mentioned, and decide on a pump. Sounds like what you are saying though is that a delta-t pump is linked to the in and out of each loop, which would work alot better than what I had thought. I have all my pipes on 8" spacing already, my heat source supply temp is at 107*, and everything is right around there except my lr/kit circuit which is at 115*. Right now I've got 7 zones and 11 circuits. I'll check into those boilers as well, haven't even heard of the versa. I don't know about the 105*, my old lady takes a shower with it all the way hot, and I got our 50 gallon wh set at 130*, I don't know how she does it.

tbrooks

Just poking around, and I don't think anything with the versa name is even close to my budget. Put it this way, right now I got 17k saved up, and 3k ready to spend on my lowe's card. I've got to have about 10 huge trees dropped, beside a power line and the house, thats why I ain't doing it. Then I gotta have a new well put in, followed by a new septic. THEN I get to start construction. Which includes completely gutting the existing house. Under any other circumstances, my budget would get laughed off the planet, but other than drilling the well (I install my pump and wire), and getting the trees on the ground, everything will be done by me. And the inside of the house, other than floors, framing, elec, and plumbing will be 99% reclaimed materials. The flame looks like a neat system, but if I were to spend that much I would get a wood boiler, with a steam powered generator and go off grid completely lol. Anyway, still gotta check everything else you mentioned!

Paul48

I don't want to rain on your parade, but I've done many projects in my life. Keep these two things in mind......It's gonna take twice as long as you think, and cost twice as much. That's not specific to your jobs. It's the nature of the beast with a long list of projects. You need to prioritize or you'll run yourself into the ground, be broke and on the verge of divorce.

Rich_49

If you are interested in having a properly designed and installed system you must do certain things . If nothing in the Versa line fits your budget I would suggest looking at different technologies because the components the Versa line replaces and combines are what low load houses like yours require for proper operation and equipment protection . Maybe just an electric resistance boiler and water heater is just what you need in your situation .

RobG

Or simply an LP water heater and a flat plate heat exchanger.

tbrooks

Paul48 said:

I don't want to rain on your parade, but I've done many projects in my life. Keep these two things in mind......It's gonna take twice as long as you think, and cost twice as much. That's not specific to your jobs. It's the nature of the beast with a long list of projects. You need to prioritize or you'll run yourself into the ground, be broke and on the verge of divorce.

Believe me I know what you mean. I have been working on my planning for about 8 months now, and getting done what I can as I can. I leave the house at 7 every morning and come home at 8 at the earliest every night. The old lady already don't like, and I told her wait til we start on the house. I'll be gone before you get up and home after you go to bed.

I am trying to save as much as I can here. I actually was gonna try and use the existing lp floor furnaces, but my daughter burned herself on one so now I have this unexpected cost. The reclaimed materials are whats gonna save me, but they take more time. I can get a 15% discount at the local lumber yard so that helps some too. The house currently is completely unusable to me. It is setup like a duplex with a center dividing wall, and walls for the baths, and thats it for interior walls. I am gonna try n save as much finished sheetrock as I can which may be more of a pita, and still do things right, but we'll see. One way or another I'll get it done. I still have to have an estate sale to get rid of the PO stuff, but her kids took all the good stuff.

Rich said:

If you are interested in having a properly designed and installed system you must do certain things . If nothing in the Versa line fits your budget I would suggest looking at different technologies because the components the Versa line replaces and combines are what low load houses like yours require for proper operation and equipment protection . Maybe just an electric resistance boiler and water heater is just what you need in your situation .

I completely understand, and do not want to cut corners. That being said, like I said above, this is an unexpected cost, and I need to keep it a cheap as possible, while still doing it right , and not costing me more long term. I just can't spend half my budget on a boiler. The ones I've been looking at are in the 1-3k range, and that I can't afford, but I'd be willing to do. Anything electric I wanna stay as far as I can away from, as rates are high in this area. I haven't done much on pricing, but it seems I can get a decent boiler and the other components I need for a lot less than the price of a versa.

RobG said:

Or simply an LP water heater and a flat plate heat exchanger.

I actually have an lp water heater in storage. I got it from a vacation cabin up here, and had very minimal use, but I'm sure it was at least 10 years old when I pulled. Nothing wrong with it. Its decent size, I think maybe 60 gallons, not sure though. If nothing else it could be thermal mass, If I could find a place to put it. One reason why I had decided to get the tankless is because I have 3 daughters, and the old lady, and myself, and getting everyone showers on a school night is always a struggle. So I thought I could kill 2 birds with one stone and get a tankless boiler with dhw. If you guys think the lp wh is a good, viable option, I'll go get the specs off of it to see if it will work. I know it won't be near as efficient as a boiler

RobG

I don't know how much life a ten year old water heater has left in it. I would just buy a new one. Turn it up to 160 degrees and use mixing valves for the radiant and domestic. That will give you more volume for the domestic. Of course when you start adding up material costs you may as well just buy a combi boiler.

tbrooks

Well when I say minimal use, I mean minimal. It was used maybe 3 weeks out of the year. It sat empty for about 4-5 months in the winter, but was full the rest of the time. It was a remote off the grid cabin of a friend and I used it more then they did lol.

Like I said I don't mind paying a couple $k for a good combi unit, there's just no way I can afford something that high end.

On another note, how important is the pump curve with a variable speed pump. My system is quite small and doesn't get anywhere near most curves. It seems to me it wouldn't be an issue, but I wanted to be sure.