hydronic radiant floor heating issue

stuckwithbaddesign

Hoping someone here can help point me in the right direction. Maybe I'm missing something or maybe it's the design or hardware the previous owner put in, but I can't figure it out. I've talked to a couple plumbers who either didn't work on these types of systems or wanted some crazy amount of $$ to just look at it with no promises of knowing what to do to get it working.

I bought a house that has radiant heating in the basement. Sounded like a nice feature. Home inspector checked it, and mentioned how nice it'd be in the winter. In hindsight, I don't think he actually did more than make sure the circulator ran. I bought the house in spring so it wasn't used until the winter and then I couldn't get the floor to warm up at all. I did a little reading to try to figure it out, but a lot of articles/posts said to start with a drain/purge/flush of the tubing, but I didn't see how to do it with this design that wouldn't just flush only the water heater. It was a low priority with everything else I was fixing/updating, work, overseas travel, etc. So it got put on the back burner until now... I just found out I'm moving in a couple weeks for work and regardless if I rent or sell the house, this seems like something I should now get working.

I don't have any drawings or documentation of how it was installed or who did it. The water heater gets warm and the circulator runs, but as I said the floors don't warm up at all. And actually, the only part of the copper piping that I can feel any warmth is a few inches of the water heater output and just adjacent to the circulator. I checked the valves...I do have water flow to the spigot, and there is water in the water heater. They say a picture is worth 10k words, so I've attached a rough sketch of the layout and a photo. I'm thinking there is air in the system or its become clogged from the water heater sacrificial anode and/or other sentiment.

So does anyone have any suggestions? Hopefully I've just overlooked something simple. Thanks in advance.

kcopp

Need a few things.
Need to have a dedicated purge valve in the line somewhere. w a ball valve isolating it.
A 006 is too small of a circulator for a 300' loop of pex. 007 at a minimum.
Since you need to partially re-pipe it I would be adding a air scoop or Air separator and have it pump away from the expansion tank on the supply side on the set up.
The water heater, prob is not big enough to handle the output to heat the slab. 1650 watts = 5600 btu. The recovery will take days to bring that slab up to temp especially if there is no insulation under it. HOPEFULLY they insulated it w 1" foam.

Gordy

How many SF is the heated slab?

A six gal electric WH is to small. If there is no insulation under the slab the back losses probably equal the output of the water heater.

Firecontrol933

Turn it on Monday morning. Lay a nice heavy rug over a section of the floor where you're pretty sure the tubing is under. On Wednesday measure the floor surface temperature difference under the rug verses an area of the floor that isn't covered up. This will give you a VERY rough idea if what you have is even worth bothering with.

The other thing to do, on Wednesday, is measure the difference between the water temperature going into the slab and what is coming back to the water heater.

What you have may work, but the first thing with radiant slabs you must have is patience and allow the mass (tons of concrete) to warm up. Sometimes the "charge" time can be days.

Gordy

Especially if the slab is not insulated. Because then not only are you trying to heat the slab, but also the ground under it. Back losses.

5000 btus is not much to overcome this.

hot_rod

kcopp said:

Need a few things.
Need to have a dedicated purge valve in the line somewhere. w a ball valve isolating it.
A 006 is too small of a circulator for a 300' loop of pex. 007 at a minimum.
Since you need to partially re-pipe it I would be adding a air scoop or Air separator and have it pump away from the expansion tank on the supply side on the set up.
The water heater, prob is not big enough to handle the output to heat the slab. 1650 watts = 5600 btu. The recovery will take days to bring that slab up to temp especially if there is no insulation under it. HOPEFULLY they insulated it w 1" foam.


It could have a larger element in the tank. I used 6 gallon tanks with 5500 W 240v elements, giving you 18,755BTU/ hr

Remove the cover and the element will have a label or info printed on it.

stuckwithbaddesign

Thanks for the responses.

I've let it run and run and run, but the water (I think) isn't moving at all. I understand it will definitely take a while to heat. The other problem is I have no temp sensors besides the ambient air which controls the circulator or flow checks to even know for sure if its moving.

Less than 400 sq ft. I'm not sure where they ran the loops at. I would guess they did as little as possible with regards to insulation. These townhouses were built on the cheap (1980s) and everything the previous owner did was via a handy man as cheap as possible. The tile floor is only 1 to 1.5" above the concrete so I'm not sure how much they could have really fit in there.

I figured I would have to add a valve and drain and not surprised that I'd need a real air eliminator too. Is right before returning to the WH the best place to put drain? And the air scoop on the supply side right before going into the floor the best place? It would have several feet of horizontal copper for the air to go to the top. Suggestions for the scoop and eliminator? Taco scoop and hy-vent? I'd like to hold off replacing the circulator at this point if I can...these parts+plumber will add up fast enough. See additions in the red boxes. Did I understand your suggestions correctly?

Gordy

Hmmm is it possible the radiant loops are above the concrete? In other words the tubing was laid in a mud bed for the tile? When we speak of slab insulation we are talking under the concrete before its poured.

hot_rod

So many variables, it could be lack of insulation, no flow, grossly undersized heat source, burned out element, etc.

You would need to do some recording as mentioned above, either add a flow meter,some pressure gauges, record supply and return temperatures, check the current draw on the element.

Without having the room under load, it will be a bit tougher to get a performance test.

How much $$ do you want to spend if you are selling or renting the property?

stuckwithbaddesign

It is almost certainly laid in the tile mud. Sorry for the confusion. It was not original to the house and I cannot see the previous owner's handyman tearing up any of the existing slab.

I'm looking to spend just enough to get it working, not necessarily to the point of completely optimized. I do not have any tools, they've already been packed/shipped. And I just don't have the time left here to try to set up multiple visits from a plumber. I figured the quickest/cheapest way to get it done would be to order the parts and just have someone come do the install. Which is why I turned you you guys for help figuring out what I needed to do.

Gordy

My opinion is you need higher water temps than the present electric water heater can maintain trying to charge the slab. The difference in mass of say 7.5 gallons of water verses the concrete, earth below it, and tile is more than that WH can muster.

stuckwithbaddesign

I don't disagree, but the copper only gets warm for about a foot out of the WH, so I don't think the water is moving to even try to heat the floor.

kcopp

Is the pump getting power? I don't think a Taco 006 can overcome the friction loss/ head developed by 300' of 1/2 pex. Maybe i'm wrong. Wouldn't be the 1st time.....

stuckwithbaddesign

Yes, definitely getting power...I can hear it running. Not sure if it is working correctly though.

Gordy

More clues. So yes circulation seems an issue. The 006 will give flow for a 300' loop of 1/2" pex.

Is the pump quiet? If you heat the pipe after the circulator direction of flow with pump off, and water heater off then turn pump on, and carefully touch pipe to see if it cools then flow can be verified.

Also if pipe heats very quickly could be air locked.

Or take circulator apart, and verify it is turning when powered up.

Firecontrol933

Your drawing on how you think it should be resolved will work fine.... or at least let you know for sure that air isn't the issue in the tubing.

stuckwithbaddesign

Here are the parts I'm going to order. Will these work?

hot_rod

Spend a few bucks more and get a high performance air eliminator. Those old technology type of air scoops, regardless of the brand, are best used for anchoring small crafts.
They do not have a mechanism to capture and remove small micro bubbles and entrained air.

Modern hydronics need modern air elimination for top performances.

H

ere is an example of the type, many brands to chose from, this one is very service friendly.

4Johnpipe

You really want to have the circulator after the expansion tank. I cannot tell from the picture if it is pumping away. This will play havoc especially with a city pressure system

Ironman

@stuckwithbaddesign,
Jason, you've gotten some good input and I would concur that your system may be air bound. Installing a purge valve in the return would allow you to use house pressure to purge the loop.

You have an "open" system which means that every component needs to be non-ferrous. Your in-floor tubing is likely not 02 barrier either.

I'm also skeptical that the 6 gal, 5600 btu water heater can produce enough btus to properly heat the slab.

I know you don't want to invest a lot of dough, but I'd recommend that you try the purge valve and if that doesn't solve the problem, then get a pro like Dan Foley to look at it.