heat source radiant floor, dazed and confused.

Brooksi

Q; does the traditional tankless gas water heaters have a thermostat which shuts the burner off when the water is still running through it is already at a hot enough temperature.
I would like to keep my system simple. I am still very new at radiant heat and also how to use this forum so I apologize in advance for any confusion.
I would like to try to use 2- 220w = 48v electric solar panels on the roof with a solar hybrid hot water controller with MPPT (maximum power point tracking) I saw on the internet, connected to the 50 electric tank I have. I do not have the headroom in the basement for a regular 50g gas heater because of the blower I need with it, so I would like to start out with a tankless heating system (as that is what the mortgage people want to see in a tradition heat source) that is cost efficient as it would eventually be a secondary source. This has been a 2 year project. When I put the exhaust and intake pipes in 2 years ago the units I was looking at called for a 2" pipe and now most are 3" (as they go under the concrete floor to the outside they cannot be changed. I had an outdoor tankless unit to buy that was a discontinued unit yet it did not have the ability to shut off when the water was already hot as it is turned on by the flow of water.
If anyone has any resolution for me would be great.

SWEI

I'm not really sure what exactly you're asking here.

Tankless water heaters are not designed, approved, or warranted for radiant heating use. They can be made to work safely and effectively, but by the time you purchase and install everything necessary to do so, the price of a real boiler starts to look pretty reasonable.

It sounds like you have installed flue pipes which loop downward from the proposed tankless location? Condensate does not flow uphill.

Zman

I'm not sure where you are heading either. Your boiler/hotwater heater question has been asked here quite a bit. You need a boiler.
Not at all sure where you are heading with 440 watts of DC powering a heater that needs 4000 watts of AC. PV is a horribly inefficient way to heat water. They make hot water panels for that.
None of this stuff functions well when done on the cheap. I don't care what some guy with a website says....

Brooksi

thanks guys. hents why I apologize first and again now for the confusion, I had a hard time just getting back here.
Swei, it is not flue pipes as you described. There is a small 5' high and 12' by 12' wide basement in the middle of the house (the potable electric hot water tank for the house is there) and where the heat source for the floor is going and that the pex will be hooked up to the manifold. The piping is the 2" white PVC exhaust and fresh air intake piping you would use for exhaust power headed, forced air furnace, hot water tank or tankless units, and they are properly pitched so condensation does not build up and freeze at the outlet and exhausts properly, they run from the ceiling of the basement out through under the main floor to the outside.
Zman I was wondering if the electric solar panels made sense to heat up the hot water elements enough during the day to assist in keeping the water hot then rely on an additional heat source.
Ok so I will just leave out the solar panels and the tankless and give into the idea to do it right is what I want and is going to cost.
Q; would a 40g gas water heater work and approved for radiant heat.
if not,
; would the gas boiler type unit exhaust through 2" pvc and if not can it be mounted on the outside wall and insulated if needed.
; does the pex to and from the manifold from the heat source need to be 1" or can it be 3/4 as 3/4 is all I can find to easily attain without buying a role.
Pex, I have 5 runs of 150' each . 4 runs (so as to adjust flow to each room) at 12" spacing, which supply the main floor concrete and one run goes to the second floor baseboards supplying the two bedrooms. There is a gas fireplace in the main floor heating the house now. It is an old 1 and a half story, brick framed house with 1 1/2" styrofoam on the outside behind the vinyl siding and I gutted and spray foamed 2" onto the brick on the interior and added roxall insulation where I could. I have not done any heat loss calculations yet it holds its heat well and stays warm right now at these temps of 0 to -5 through the night fine and gutting it to an open concept up the stairs lets the heat flow to the second floor yet I need to solve the main heating source soon. I do realize this is old for you guys and I have a tough time navigating these computer sites and still buttoning up outside jobs before the snow so I apologize for any delay in my response but any help guiding me to a solution I do appreciate.
thanks again

Brooksi

Does anyone know how i find out if a Lennox low pressure boiler PWB-3D series model # GWB8-070E can be vented out through 2" pvc pipe.

Zman

It is understandable that you want to save yourself some money and you obviously have a strong DYI spirit.
Please, get a professional to help you with this.
The only boilers you will find that can be vented through 2" PVC will be smaller high efficiency models. The manufactures installation instructions will dictate this. Has your PVC been pressure tested? Is it solid core or cellular? There are specific details that I am sure you are not aware of.
This is not a simple "plug and play" deal. I am not being dramatic when I say that the lives of the occupants of the house are depending on the installation being 100% correct.
From the questions you are asking it is clear that you need assistance with the boiler setup.

Brooksi

Thank you Zman. As I am not set on the heating system and is why I am here for advice, i thank you for your boiler advice. The PVC which was installed was to spec for gas hot water tank unit and yes a small boiler and possible tankless heater yet use of a boiler at the time was not put into the equation fully and am realizing gradually that the 2" is not usable to all options and am unaware of solid core and cellular. It has no connections in the pipe so I did not know a pressure test was needed yet will look into that. You are right although I am new I am looking for info to figure the direction I am wanting to go before I consult that particular professional. I have talked to a few people, that all have their own different beliefs and yes many are boiler supporters. I am also getting concerns that the typical boiler being originally designed for radiators is not favoured for concrete floors as it uses concentrated heat and can fluctuate the floor heat considerably. The main reason I have done away with the gas tankless unit ideas. If indeed I can not use a boiler set up, are you against using a gas water heater. I have heard conflicting stories yet everyone does agree it supplies a more even heat to the floor. The easiest for now which would be the electric 50g hot water tank still in the basement not in use yet it has cost effective concerns and I do not know if it is approved to be used. I am going to soon have to make a decision.
I find it quite humorous I know the character Vizzini from the Princes Bride film as your posted pic. I always liked the "Im not left handed either" scene.
thanks again

Zman

The type of PVC on the exhaust is important. You should be able the read the numbers and find out which type you have. With no connections the pressure test is not needed.
You need to do a heat loss calc to find out how much heat you need.
Low water temps over a longer period of time is the key to comfortable radiant heat. A small condensing boiler sounds perfect for your application. Water heaters are used in many radiant systems. Some Jurisdictions allow them. They are not designed or rated for the application and will not perform as well, be as efficient or last as long.

"I don't mean to pry, but you don't by any chance happen to have six fingers on your right hand?" Westley: "Do you always begin conversations this way?"

Brooksi

lol. yes the 6 fingered man... Well "you" know something I don't know, and it is not just being left handed. I will check out the numbers and see what pvc is there. The small boiler was an option in my plan. I am thinking I will try to go with the small condensing boiler as you suggest, it is not a big house. I am in southern Ontario by the lake so it does not stay real cold for too long. At this point I have already drank the poison I just hope my system is immune to any issues. I have done the on line heat loss and also gave the info to a radiant installer and had conflicting readings as the installer was suggesting it would cost me 6-8 thousand $ to do it. ( I thanked him for his time) Any suggestions what brand or who to look to for the condensing boiler or just get it somewhere local.

Thanks again...

Brooksi

Hey Zman. The places that I checked, even the small boilers all have switched to 3" venting. (which is probably just a money grab to eventually have to change all the existing 2"). I know there is older models out there that take 2" (from my research 2 years ago that are now discontinued) but finding them is another time consuming adventure. I was suggested by the company i bought the pex and manifold from (heating innovations) just to go with a 6kw electric boiler in an open system, and so I am getting them to send it with the completed board for easy install. Just over two k. They also told me there are no regular hot water tank heaters that are rated for radiant heating source because he said they run more frequently than they are designed for, which to me is crazy considering a family of four would keep one working pretty steady supplying hot water more so at certain times and periodically turns on to sustain the heat in the tank. Once the floor was up to temperature it would simply do the same without ever dealing with the sudden constant running with the surge of heating cold water. This idea for my house all started with my friend putting radiant heat in his new garage. It is 60 x 100 and he heats it with a 40g propane hot water tank and he has cranked the heat at times so hot it made your feet sweat in your boots, and has been using it for 6 years with no issues other than changed his pump once (which that could be for a number of reasons as it is such a simple system, most likely air) . A real simple cheap system and runs perfect for the cost. Although I never expected my house to run on such a simple system, being just over 600sq' main floor this also should of been close to the same case. Makes me realize again how when people hold a position it is only that position that gives them knowledge, and no one does any thinking past that knowledge (like prince Humperdinck). They make it sound like it all has to be rocket science (helps pay the bills), yet it does not have to be that complicated. My buddies heating unit not including the pex cost him just over a thousand. From my research, my place could of been run off a 40g gas hot water tank vented out through the 2" pvc for app the same cost, (but that heat source is not code). I understand safety regulations are needed, but as you said "Low water temps over a longer period of time is the key to comfortable radiant heat". That is what the hot water tank does at my buddies. I googled myths of hot water tanks for radiant floors and there is more than a couple sites and to me made sense.
Your advice was solid about the boiler yet the change to 3" pvc has ended that option as the 2" vented are becoming obsolete. I would like to thank you for your time and for your help in my direction. i did not want to go electric, but perhaps all the best for future solar panels.....
Wish you and yours all the best through the holidays and the new year and may you be immune to all the poisons that may come your way....

Thanks again,

SWEI

What is your design day heat loss? Most mod/con lines have at least one small model which can be vented using 2" flue.

Brooksi

Hey Swei I do not have the heat loss calculations at hand. When they came up so different between the internet website I used and the professional I consulted ( a so called long time company) which they wanted me to spend a fortune, I unfortunately through up my hands and with it went the calculations. (I know I kept it somewhere as it is hugely time consuming). Yet it is only a small story and a half solid brick house main floor just over 600 square feet. Gutted the main floor and put in 2" foam and 5-7" concrete slab on grade floor with 12" spaced pex at 5- 150' runs (one run servicing baseboards on second floor). Upgraded windows, spray foam insulated the interior with styrofoam on the exterior so it holds its heat well. I know I should of perhaps researched more for what you are suggesting in a heat source. Yet I am realizing why this concept is so hard to get people to switch too, either too expensive, or to time consuming and conflicting ideas and ratings for a reasonably sound financial alternative for anyone to grasp. The system concept itself is not that complicated, (the powers that be complicate it to make their money, which I get). I still believe in it and I will do it with my next house. Find that fine line between safe, sufficient, rating accepted and financial feasible .
Unfortunately (I probably should have said this first) I have already ordered my electric boiler against my better judgement and paid my down payment. Should be here in 10 days. I appreciate your time in this and not sure how this site works for me to give an update down the road to you and Zman but I will. It is my belief that a more reasonable financial way to run this system is there. I would like someone to explain to me exactly why a traditional hot water tank is not rated for radiant floors besides the text book answer. As I said previously, my buddy for 6 yrs is running his whole 60x100' shop on a 40g propane hot water tank and his heat system is hardly over 1k. It is as simple system as it gets but from there you could add to it if you wanted to better suit a home, or instead of paying the big bucks for a sensored thermostat system, buy a temp laser gun and point it at the floor when you want to know what it is at (just bought one on sale for 20$). Have a great holiday season and new year.

Thanks again Swei

SWEI

http://www.slantfin.com/homeowners-page/ipadapp.html will get you close. Polystyrene (EPS or XPS foam) strong enough to put under a slab runs R-5 per inch. PolyIso starts out around 7.2 per inch, but the real R-value degrades over time.

Brooksi

I used the two inch foam recommended by the concrete guy that has the foil on one side and the green plastic on the other yet I will double check the makeup of it for future reference , and check out the website

thanks again