basic in floor system tuning

[JakeKohl]

I think you're getting too caught up with the water temperature in the tank. Laws relating to conservation of energy applies here....energy in = energy out. The size of the tank will have little effect on the system's ability to heat your floor. The amount and temperature of pre-heated water in your tank may help to slightly jump-start the system but should be ignored.

If your tank sits with no water movement and heating elements on, it's putting in 9kw of heat into the water until the thermostat reaches its set point and turns off the heating elements. When you start pumping this hot water into the slab, the heat from that water is transferred into the slab much faster than the heating element can transfer it into the water in the tank. This is OK and is normal. You will see the water temperature drop significantly as this happens. The important thing to realize here is that the heating elements are still putting heat into the water as fast as they can even though the water is at 64 degrees. After that initial charge of water is cooled, you will not see the water temperature increase much at all because of A) the volume of water in the tank and B) the amount of water flowing in and out of the tank. A "boiler" may be a little more efficient at heating this cooler water and some people think it's more effective because the discharge temperature is higher. Fact; the discharge temperature is higher because the tank is smaller on a "boiler". The amount of heat being added to the system is still only a function of the amount of wattage into the heater and the efficiency with which it is transferred to the water regardless of water temperature.

Repeating in summary: The important thing is that the heating elements are on and are putting energy (heat) into the water. Even if the water in is 65 degrees in and 65.2 degrees out you are transferring heat into the slab. A smaller boiler will see a higher temperature water output because the tank is MUCH smaller. Do not expect to see this with your hot water tank that was really meant for a different purpose.

My point is this; let it run. Mostly ignore the water temperatures (unless they get beyond safe points) and let it run for an extended period (24 hours). Don't crank up the setpoint on the water heater, it will only help with the initial charge of water that is pumped to the slab and will have practically no effect on the overall function of the system because, again, there is too much water volume in the heater for you to notice much temperature increase on the output above the actual temperature of the slab. Increased setpoint really means that the tank will be less efficient and lose more heat energy when it sits idle (temperature difference higher between the water, and surroundings). These systems will not heat the slab in 15 minutes even with a "proper" boiler. It will need to run for the better part of a day before you see a significant change.

 

[Highbeam]

Good post Jake. A 9 kw tank water heater and a 9kw electric boiler are both putting the same 9kw of heat into the slab at the same rate. Tanks are more common and easier to find second hand but the tank is of no benefit to the system.

 

[atotalnincompoop]

lots of good points there guys thanks.

 

[Dick in Wisconsin]

I've gotten a little lost.

Does the OP have water temp gauges so he can see the water temp into and out of the water heater?

Has the OP left the system on for a couple of days? Does the shop come up to the desired temp?

Jake did a very nice job of explaining everything. A 9Kw heater will only create so many BTUs. If the heat loss of your slab structure plus the building heat loss exceeds the BTUs that 9Kw of electricity creates, the temp in the building will not rise. In fact, if the outside temp goes down far enough, the temp in the building will fall.

If the 9Kw water heater does not provide enough BTUs to maintain the temp you want, get another water heater, create another zone and put more Kw's (hence BTUs) into the slab and the building. But do you have enough electricity capacity for that?

Keep us posted.

 

[atotalnincompoop]

after much research i decided to switch over to a tankless water heater type setup, i bought the ecosmart 11kw unit.
i bought one on ebay, hooked it all up and melted it down within half an hour, the tech line was great and overnighted me parts, i rebuilt it and melted it down again after a half hour use. so i sent it back and they sent me a new unit that they pretested, it lasted an hour before the melt down began.

the system is flowing and has been bled of any air. the unit is on a 60amp breaker, there are 2 hot and 1 ground wire hooked up, where could i have gone wrong? here are a couple pics of the install...

 

[atotalnincompoop]

the inline filter was just added today to catch any debris in the water, i'll go to the hardware store tonight and get a proper filter.

 

[Highbeam]

Is that all 3/4" pex? It's really foggy there.

 

[Rickcnc]

Am I missing something, do you require an expansion tank?

 

[Flexia]

It looks as if you changed your manifold out to one with flow meters. What is your flow to each loop? Maybe you dont have enough flow burning that heater out.

Sent from my SCH-I605 using Tapatalk

 

[anthony666]

lemme hit on the big reason not to use an electric hot water tank for space heating

all you guys have seen an electric kettle work .. you plug it in and three minutes later you're sipping your chai skinny latte .. now what would happen if you took the same element in the kettle and stuck it in a swimming pool ??? it would take a damn sight more than three minutes to get that sucker boiling

small radiant systems .. yea ok, might work fine .. tbut here's a fine line between the tank keeping up and the wife saying 'i told you so' and giving you that look

k .. can we put that to bed ??

 

[anthony666]

next;

is that plumbers pex or oxygen barrier heating pex ?? why the hell are you using pex anyway ??? 3/4" pex does not flow as well as 3/4" copper, all other things being equal

that unit should be thermally protected .. ie, you don't drag enough heat out of it it will shut down before it melts .. check your wiring to make sure you haven't bypassed anything

that said, that filter needs to go it's a choke .. open up the manifold and let her go full bore, see if the melt down happens again

and by 'melt down' you mean it shuts off or it actually smokes and turns into a dali painting ??

 

[atotalnincompoop]

Am I missing something, do you require an expansion tank?

THere is one, just couldnt fit it in picture

 

[atotalnincompoop]

It looks as if you changed your manifold out to one with flow meters. What is your flow to each loop? Maybe you dont have enough flow burning that heater out.

Sent from my SCH-I605 using Tapatalk

THe manifold is running with all loops wide open

 

[atotalnincompoop]

next;

is that plumbers pex or oxygen barrier heating pex ?? why the hell are you using pex anyway ??? 3/4" pex does not flow as well as 3/4" copper, all other things being equal

that unit should be thermally protected .. ie, you don't drag enough heat out of it it will shut down before it melts .. check your wiring to make sure you haven't bypassed anything

that said, that filter needs to go it's a choke .. open up the manifold and let her go full bore, see if the melt down happens again

and by 'melt down' you mean it shuts off or it actually smokes and turns into a dali painting ??

YEs, its plumbing pex, its what i had.

THe filter was added today as a temporary measure to clean junk out of the line, ill replace it tomorow with a less restrictive one.

BY melt down i mean the top of element melts then the wires burn off

 

[anthony666]

YEs, its plumbing pex, its what i had.

THe filter was added today as a temporary measure to clean junk out of the line, ill replace it tomorow with a less restrictive one.

BY melt down i mean the top of element melts then the wires burn off

what's in the floor ?? plumbing pex too ??

no filter, they're not designed for the heating temperature

if they checked it at the factory you most likely screwed up the wiring man .. but why doesn't the breaker pop ???? is it wired through a breaker ???

 

[jimgerken]

There is air in the heater. How else could it overheat? If there was water, the water would absorb huge amounts of heat, even maybe boil. I am betting there is air inside the heater.

 

[Dick in Wisconsin]

How much insulation do you have in the garage walls and roof?

 

[anthony666]

damn, now i find out we're practically related i'm gonna have to help you

lets see a closer picture of the wiring and where it melted down .. and what did the tech say about the latest melt down ?? the pump is moving water right ???

 

[Jshepard]

Is the white tubing o2 barrier?

 

[Jshepard]

4500 watt element= about 15000 btu's= not enough to heat garage. Go to power vent WH or boiler

 

[Jshepard]

How many btu's can piping handle:3/4 copper is good for 37,000 btu 1" is good for 71,000 btu 3/4 pex is about 28,000 btu

 

[pstnbly]

2" insulation down sides and around perimeter of slab extending 4' out. not under slab centre.
two schools of thought on insulating underneath slab, if the heat is on before the frost comes, the ground won't freeze there, perimeter insulation keeps frost from coming under around the edges.
sounded good to me. the other thought is everything should be done, from a builder point of view, i didn't think it was a must do.
although i'm not a heating guy, obviously

Sorry to sound nit picky, slabs need to be thermally decoupled from the earth beneath them by insulating underneath. The earth is a gigantic heat sink! Typical ground temps in heating regions range from about 50f on down. I hope everyone on this board that is looking to install radiant heat in a slab realizes the unless you like to pay to heat multiple hundreds of tons of material you will need to totally insulate your slab.

 

[atotalnincompoop]

How much insulation do you have in the garage walls and roof?

r20 wall and roof

 

[Dick in Wisconsin]

Did you get the new water heater to work yet? How are things going?

 

[Dick in Wisconsin]

Silent for over two days.

MIA

I wonder if his wife found out he spent more money on his garage buying that instant hot water machine and beat the **** out of him?

He might be lying on the garage all beat to heck.

 

[Highbeam]

There is air in the heater. How else could it overheat? If there was water, the water would absorb huge amounts of heat, even maybe boil. I am betting there is air inside the heater.

Bingo! Has to be an air pocket zapping the elements. Same thing happens in tank water heaters when you fail to fil them up first. Everything else in the "boiler" is safety protected. I suspect that the tech that is warranty replacing these isn't being told that it is being used in a heating system.

There is no reason that an electric boiler can't heat this or ANY slab it is just another fuel source and can only work if it is sized properly to meet expectations. Some of us only want freeze protection so a low btu electric boiler is sufficient. Electric can also be cheaper on a btu basis depending on prices of the other fuels. Since I don't have piped natural gas, electric resistance is my cheapest source of heat so using a gas boiler would cost extra in addition to the extra high cost of equipment.

 

[Highbeam]

How many btu's can piping handle:3/4 copper is good for 37,000 btu 1" is good for 71,000 btu 3/4 pex is about 28,000 btu

This seems crazy. I suspect that lots of assumptions are being made but not stated. I doubt it applies to every situation in the widely variable floor heating setups. Variable flow rates, variable pressures, variable temperature, etc.

 

[anthony666]

electric resistance is my cheapest source of heat

buy a chainsaw brother

 

[anthony666]

taken from the section on pipe sizing in the grundfos handbook .. sub 4 ft per sec to avoid erosion and noise, based on a 20 degree delta .. or in layman's terms, this flow chart is good for normal hydronic heating usage

copper;
1/2" - 32,000 btu
3/4" - 65,000 btu
1" - 109,000 btu
1.25" - 163,000 btu
1.5" - 229,000 btu
2" - 396,000 btu
2.5" - 750,000 btu
3" - 1,200,000 btu

pex;
3/8" - 12,000 btu
1/2" - 20,000 btu
5/8" - 40,000 btu
3/4" - 60,000 btu
1" - 95,000 btu

as you can see copper outflows pex, that's because the nominal sizing is ID and wall thickness of pex is greater than copper .. but in some cases pex is a better choice because you're not limited to 90 and 45 degree bends which really start to slow **** down like crazy when you need multiple bends

 

[Highbeam]

buy a chainsaw brother

I should have said, my cheapest non-solid fuel source. I heat with wood primarily and only have electric as back up. Two stoves running hot right now.

 

[jvitez]

Very interesting chart Anthony666. Many thanks.

Curious though: 3/4" copper is 65 Kbtu and 3/4" PEX is 60 Kbtu. Much as soldered copper piping and manifolds are sturdy and esthetically pleasing, PEX is definitely easier to work with. But would the 60 Kbtu rating still hold if you needed a whole bunch of 90° fittings? The usual fittings reduce the PEX ID, as opposed to the Uponor one which stretches the pipe.

 

[Highbeam]

taken from the section on pipe sizing in the grundfos handbook .. sub 4 ft per sec to avoid erosion and noise, based on a 20 degree delta .. or in layman's terms, this flow chart is good for normal hydronic heating usage

copper;
1/2" - 32,000 btu
3/4" - 65,000 btu
1" - 109,000 btu
1.25" - 163,000 btu
1.5" - 229,000 btu
2" - 396,000 btu
2.5" - 750,000 btu
3" - 1,200,000 btu

pex;
3/8" - 12,000 btu
1/2" - 20,000 btu
5/8" - 40,000 btu
3/4" - 60,000 btu
1" - 95,000 btu

as you can see copper outflows pex, that's because the nominal sizing is ID and wall thickness of pex is greater than copper .. but in some cases pex is a better choice because you're not limited to 90 and 45 degree bends which really start to slow **** down like crazy when you need multiple bends

So they assume a flow rate, velocity, and a temperature drop. Those are pretty dang important and variable but a good chart once you know what you are seeing. Actually great info.

 

[anthony666]

I should have said, my cheapest non-solid fuel source. I heat with wood primarily and only have electric as back up. Two stoves running hot right now.

me too, a wood stove and a wood burning insert .. wood is beautiful (i probably could have worded that better) .. but electric is definitely convenient, if you guys are getting it that cheap then more power to you (no pun intended)

 

[anthony666]

Very interesting chart Anthony666. Many thanks.

Curious though: 3/4" copper is 65 Kbtu and 3/4" PEX is 60 Kbtu. Much as soldered copper piping and manifolds are sturdy and esthetically pleasing, PEX is definitely easier to work with. But would the 60 Kbtu rating still hold if you needed a whole bunch of 90° fittings? The usual fittings reduce the PEX ID, as opposed to the Uponor one which stretches the pipe.

that's one of the big selling points of uponor/wirsbo, their fittings expand the pex and don't reduce flow due to diameter .. that and the stuff is a dream to work with .. i did a tube job at a deer farm on wednesday, i showed up and the farmer had bought watts pex instead of the uponor he was supposed to, the cold weather makes that watts stuff like wrestling dry spaghetti .. not to mention a pex slap in the ear hurts exponentially more when the temperature gets to freezing

i think the math is the same for the 90's whither it be copper or uponor pex and obviously flow drops considerably when you install a brass or plastic fitting that reduces diameter .. i remember being half awake in a classroom somewhere listening to the math but off the top of my head i can't recall it enough to post it here .. it's probably in the seigenthaler book

 

[atotalnincompoop]

Silent for over two days.

MIA

I wonder if his wife found out he spent more money on his garage buying that instant hot water machine and beat the **** out of him?

He might be lying on the garage all beat to heck.

i'm here and she has no idea

 

[atotalnincompoop]

ok, so not wanting jinx anything, here is what has happened in the last couple of days...
i picked up another replacement unit, installed it, then i replaced all the 3/4" pex with 1". turns out the guy at the hardware store down the road installs outdoor wood boilers, so i got some advice off of him.
while bleeding the system, i took the unit off its mounts and held it sideways to get every last air bubble out of it. i had been running the other units in the 130-140 degree range, this time i started out at 115 trying to not burn anything out.
i also installed a proper inline filter, 1" as well.
so far so good, it has been running since 10am yesterday. the water goes into the slab at 115 degrees and came back at 42 at first, not it is coming back at 50 degrees. so an improvement, i'm optimistic. its -29 degrees celsius (-20 f) here right now so this may take a while.

 

[wedge40]

I'm learning. How fast is the pump running? Do you have flow meters at both the input and return?

Wedge

 

[atotalnincompoop]

I'm learning. How fast is the pump running? Do you have flow meters at both the input and return?

Wedge

i've got the pump running on high, the flowmeters are on the return side of the manifold, however this is a cheap ebay special manifold, i know i have flow but they are not showing anything

 

[Dick in Wisconsin]

OP: We're all relieved you're OK!

There must have been air in the heater or in the pump. Getting the air out is really important.

Are you using that special Pex that keeps the oxygen out so you don't get "air" in the lines?

Do you have an infrared gun so you can monitor the temp of the floor in a few locations and watch it come up?

What is the temp differential between the water coming back to the heater and the floor?

 

[atotalnincompoop]

OK without jinxing anything, the system appears to be working.
It has run without incident for a couple days now. The slab has gone from 40 degrees up to 60. Its actually a nice temp in the garage., fingers crossed,