basic in floor system tuning

[atotalnincompoop]

i have been messing around with my bare bones in floor system for the past few days trying to get it running right, a couple of questions...
i'll post some pictures later...
it is a hot water tank setup, one zone, using a 4 branch manifold, all the branches are close to the same length at about 200'.
once i get it all flowing nicely, after a while it will go from all 4 branches flowing equally down to just one flowing, i have installed shut off valves on each branch trying to regulate flow, it helps but not completely.
also, do i need a pressure tank, i have an air vent located on the top of the tank, which is the highest point of the system.
thanks

 

[atotalnincompoop]

here are a couple pics

 

[Fastback]

How do you set or check pressure? I would still do an expansion, it's like $25 on line.
I think you need a better air vent, that one may be a bit small, put that one on top of that line near the pump that comes off that lower manifold,it may still help.

Is that pump pushing into the tank or pulling from it, I can't tell?

 

[atotalnincompoop]

Is that pump pushing into the tank or pulling from it, I can't tell?

its pulling it from the tank

 

[tdkkart]

Some recommendations say that the pumps should be mounted vertically, otherwise they are prone to trapping air in the pump housing and reducing their efficiency.

 

[TurnipTruck]

The pump shaft needs to be horizontal.
Definitely add a tank.

 

[randydupree]

the pump needs to be below the tank,imo.

 

[atotalnincompoop]

i reconfigured things yesterday, moved the pump to a verticle position, added a pressure tank and a pressure guage.
things worked alot better. i have one leak at the pressure tank that has been a recuring problem, but i finally found my pipe dope that was packed away in a box, so i will take care of that this morning, i'll keep you posted.

 

[atotalnincompoop]

all seems well , thanks for the knowledge
how long should it take to heat up the slab from frozen?

 

[rburke65]

Could you post a picture or 3 of the new set up for us? Thanks.

 

[atotalnincompoop]

here is an updated pic, these modifications seem to be doing the trick

anyone have any idea what the differences in temperature should be between the in and out lines?

 

[atotalnincompoop]

so after running my improved system for a while it is working better but still not up to snuff.
the water going in was 105f and the return was 65f. the thermostat was set at 65f but it never reached that, so the system never shut off. so yesterday i decided to try turning up the hot water tank, it was set at about 130f, so i cranked it up to 150f just to see what would happen...what a disaster...the tank is now making a hiss type noise as it operates, the entire system gurgles,i had hooked up the garden hose just to top things up, i thought i had most of the air out of the hose, i guess a little got into the system.
now the system will run, then when the hot water is gone from the tank, it cools everything off again. it's like the tank isn't continuing to heat the return water. could air locks be causing all this ****?

 

[Fastback]

I still dont see a good vent, that little thing may not be capable of handling the entire system.
Try a spirovent up high to purge the air, make sure the pump pulls past it and does not push past it.

What is your pump and is it rated for the Ft of head in your system? Can you speed it up?

It sounds like you have a 30º + Delta, not optimum but not uncommon. We really dont know anything about how your slab is built, what your or what your heat loss is so in reality everything here is a guess.

 

[atotalnincompoop]

****! i forgot about the bigger vent, i'll get one tomorrow
the pump is a grundfos type ups 15-42f
the system is one zone comprised of 4 equal loops
thanks

 

[atotalnincompoop]

i reset the tank to 130f this afternoon, but now i can't seem to get more than about 83f out of it.

 

[Fastback]

Did you mod the heater to strap both elements together? I have heard that it can help if you are running out of heat, some use a mixing circuit etc..

 

[atotalnincompoop]

i haven't tried that, i was getting 105f until i tried turning it up to 150f from 130f, now i'm getting 83f out of my 130f setting.

 

[Highbeam]

You could have burned out an element if you put too much air into the tank while the elements are energized. Those elements must be submerged or they will very quickly, as in seconds, melt off and cease to heat water anymore.

 

[BadgerBoilerMN]

Oh boy...

Electric water heaters are not approved for space heating, which is a good thing since they do such a poor job of it. An electric boiler makes more sense, takes up less space and cost little more. They people who sell them will even give you a passable diagram.

Your expansion tank appears to be for potable water; expensive, unnecessary and too much pressure.

I don't see a tridicator.

"Frozen" slab? You don't want to run water into a frozen slab as you could find the water in your PEX tubing frozen before it gets back to the tank.

The pump needs to be supported and should be behind the point of no pressure change.

The vent "size" has nothing to do with its effectiveness in this case.

In a small radiant floor system such as this the supply and return can come off the top.

It may take days to heat the slab, but if you don't have enough output turning up the temperature will have little if any effect.

The temperature differential will change and is base on many factors including the design water temperature, design room temperature, pipe size, pump size, etc. 10-20°F is considered average for residential work.

Please tell me you used barrier PEX.

There are resources for designing radiant floor heating systems, the first is always a proper heat load analysis.

http://www.badgerboilerservice.com/images/SampleHeatLoadAnalysis.pdf

 

[atotalnincompoop]

You could have burned out an element if you put too much air into the tank while the elements are energized. Those elements must be submerged or they will very quickly, as in seconds, melt off and cease to heat water anymore.

i replaced the upper element, has made an improvement but still only getting about 95f out of her

 

[atotalnincompoop]

Your expansion tank appears to be for potable water; expensive, unnecessary and too much pressure.

I don't see a tridicator.

The pump needs to be supported and should be behind the point of no pressure change.

i went outside this morning and found some leaves already starting to turn yellow, i'd better get back on my heating system again...

what pressure expansion tank would be better for my system?

what does the tridicator do?

should i move the expansion tank in line past the pump?

i used a 60gal water heater, it never seemed to get the water up to temperature, should i switch to a 40gal heater? i'm not going to buy an electric boiler, the "better half" is not going to let me spend too much more money

 

[Stee6043]

Badger made some very key observations. Those photo's have plenty of red flags in them. If you want a headache free setup you may want to start (over) from the beginning.

You'll find loads of threads on http://www.hearth.com/talk/ as well as http://www.radiantdesigninstitute.com/

As has been stated already that water heater you have is not setup for heating. If you ever do manage to get your setup running I suspect it will not last long.

Your pex coming out of the water heater looks to be undersized to properly feed (4) 200' zones. But it's hard to tell. I really think you should start over and clean it up a bit. There is a lot going on in your photo for what should be a pretty straight forward connection.

 

[wedge40]

what does the tridicator do?

I googled tridicator. From what I learned it's TWO gauges in one. Pressure and Temp. Whats the third function?

Wedge

 

[atotalnincompoop]

I really think you should start over and clean it up a bit.

i think i'll do that before the cold hits

anyone have any comments on the 60gal vs 40gal tank thing?

 

[Stee6043]

i think i'll do that before the cold hits

anyone have any comments on the 60gal vs 40gal tank thing?

If you're planning to use a potable hot water heater again I don't think it's going to matter. They just aren't setup for this kind of use. Have you looked at small boilers to use just for this heat zone? Are you sure they cost substantially more than the water heater you're looking at?

 

[atotalnincompoop]

how much does a small electric boiler cost?
an electric hot water heater is around $300.
if i could find one that doesn't cost too much i would probably go for it

 

[kert]

Sorry to hijack. I'm curious as to why a normal tank-type domestic water heater seems to be so unfavored for an in-floor system. I've heard several arguments and I'm not sure all of them make sense.

Water heaters can't provide enough heat - This one I can buy. Normally, electric water heaters are setup with 2 heating elements that do not operate simultaneously. If the elements are rewired to operate simultaneously, you could have 9KW, which may or may not be enough depending on heat load.

Water heaters aren't as efficient as boilers - Electric water heaters are 100% efficient as are electric boilers. Perhaps water heaters are not well insulated and will radiate heat into the room, but if that room is the same space you are trying to heat, I don't buy the argument.

Using a water heater in this fashion will significantly shorten its life - A water heater is designed to heat 55-degF or so water to 120-degF or so. In a radiant floor system, the temperature difference will be much less. Additionally, the water should be much less corrosive considering that the tubing is generally O2 barrier (which isn't beneficial in DHW as the water enters the house with O2 dissolved) and there is no chance of mineral buildup in a closed system.

Water heaters take up more space - OK that may be valid.

Boilers have fancy controls to make them operate more efficiently - I don't really buy this one again as resistance heating is 100% efficient. Maybe the heat lost to the surrounding space is the issue, but I would think this could be handled manually. Not all of us drive Cadillacs, some people have to roll their windows up manually and use a key to unlock the door.
​

 

[maxspeed96ct]

Oh boy...

Electric water heaters are not approved for space heating, which is a good thing since they do such a poor job of it. An electric boiler makes more sense, takes up less space and cost little more. They people who sell them will even give you a passable diagram.

Your expansion tank appears to be for potable water; expensive, unnecessary and too much pressure.

I don't see a tridicator.

"Frozen" slab? You don't want to run water into a frozen slab as you could find the water in your PEX tubing frozen before it gets back to the tank.

The pump needs to be supported and should be behind the point of no pressure change.

The vent "size" has nothing to do with its effectiveness in this case.

In a small radiant floor system such as this the supply and return can come off the top.

It may take days to heat the slab, but if you don't have enough output turning up the temperature will have little if any effect.

The temperature differential will change and is base on many factors including the design water temperature, design room temperature, pipe size, pump size, etc. 10-20°F is considered average for residential work.

Please tell me you used barrier PEX.

There are resources for designing radiant floor heating systems, the first is always a proper heat load analysis.

http://www.badgerboilerservice.com/images/SampleHeatLoadAnalysis.pdf

I agree with everthing but I know plenty of guys that have used water heaters for radiant heat and love it, and claim it to be efficient aswell.

And water heaters are approved to be used as a space heater in chapter 5 of the international plumbing code 2003 (which is what standard my state goes by ).

Most installers would rather sell you a boiler though because its more profit for them most of the time .

 

[Highbeam]

I see no reason that an electric water heater won't perform at least as well as an electric boiler that consumes the same wattage. The water heater will live as long as any other water heater but maybe not as long as a boiler. To properly install a water heater with both elements wired to turn on for a 9000 watt draw you would need the proper wire which would cost you.

I haven't decided on my heat source yet for my 1800 SF pole barn with 1800 LF of radiant tubes in the slab. If I can spare 9000 watts then I'll be looking for an electric boiler just for the sake of space savings and since the eboilers are cheap. If a 4500 watt heater will do it then I'll just use an unmolested water heater. Modifying the DWH elements to turn on at the same time seems to be outside of the original water heater design.

 

[Jackfre]

I think before I wired 9kw to pull in at once I'd analyze my current electrical consumption and have a conversation with the utility. It may not make any difference at all, but this is one of those look before you leap deals.

One of the reasons to use an electric boiler rather than a water heater is to be able to maintain temps. You take a tank of hot water and it gets depleted and if you not up to temp the unit grinds on but is not able to produce the operating temps needed to satisfy your demand. The smaller vol of water allows the boiler to keep up.

The comment concerning "sophisticated/fancy controls" not being needed may be right for some. If cheap is the only design goal then I guess that is right.

Contractors want to sell you a more expensive boiler because they know it is the right tool for the job. They know that if it doesn't work and they went along with the idea of putting in a cheap water heater then they are on the hook. I've seen way to many homeowners conveniently forget their demands that the contractor signed onto when everything goes into a bundle. Therefore, and to do it correctly, put in a boiler

 

[atotalnincompoop]

i'm still thinkin i can make the water heater work, it seems a lot of other people have pulled it off, i can't help think that the 60gal tank can't recover fast enough and a 40gal would be better. anyone? ...anyone?

 

[maxspeed96ct]

i'm still thinkin i can make the water heater work, it seems a lot of other people have pulled it off, i can't help think that the 60gal tank can't recover fast enough and a 40gal would be better. anyone? ...anyone?

Recovery shouldnt be an issue, since the water wont be 55 like normal cold water into a water heater, but It also depends on how long you runs are.

And remember radiant is a slow heat, you will have to maintain a certain temp in the sapce. Dont expect to turn it off and then turn it on and expect the space to be up to temp like a normal forced air or baseboard system . it takes time

Im going with natural gas 40gal and I know a guy that has used the same . But nat gas does have a higher recovery rate then elect.

Try it out and let us know how you make out.

 

[wedge40]

Recovery shouldnt be an issue, since the water wont be 55 like normal cold water into a water heater, but It also depends on how long you runs are.

And remember radiant is a slow heat, you will have to maintain a certain temp in the sapce. Dont expect to turn it off and then turn it on and expect the space to be up to temp like a normal forced air or baseboard system . it takes time

Im going with natural gas 40gal and I know a guy that has used the same . But nat gas does have a higher recovery rate then elect.

Try it out and let us know how you make out.

How big is your garage?

Wedge

 

[tdkkart]

i'm still thinkin i can make the water heater work, it seems a lot of other people have pulled it off, i can't help think that the 60gal tank can't recover fast enough and a 40gal would be better. anyone? ...anyone?

You can, maybe.
The first thing you should realize is that regardless of what size tank the water heater has, it will only have a MAX of 2 4500 watt heating elements, at least in any residential heater I've ever seen. So, even if you jumper the elements, so they both run at the same time, and supply it with 9000w worth of electricity, it can still only put out 3215btu/kilowatt, or approx. 29,000 btu's of heat.

THAT'S IT, PERIOD, NO MATTER WHAT YOU DO, you will not get any more heat.

Now, earlier you said you have approx. 800 ft of tubing, which assuming you have used 1ft/sqft of floor space, measn you have an 800 sqft garage, or approx. 20x40, or 24x32-ish. If this is the case, and assuming the building is insulated up to accepted standards, you SHOULD be OK with the water heater.

 

[atotalnincompoop]

How big is your garage?

Wedge

30x40
4 equal runs of tubing all hooked up as one zone

 

[rburke65]

Sounds ...from what I have read....that you should have had around 1200 feet of tubing. Not an expert here.

 

[atotalnincompoop]

i ran it everywhere except under the hoist, all spaced 1ft apart

 

[1949 caddyman]

Did you put insolation under the slab?

 

[atotalnincompoop]

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

 

[atotalnincompoop]

http://www.ebay.com/itm/MAXWELL-ELE...658?pt=LH_DefaultDomain_0&hash=item53eb7b3072

i was looking on ebay and saw several of these tankless boiler/heaters, would something like this work better than my tank system?