Concrete slab woes; need new water lines, radiant heat is leaking.

[Nitroman58]

Hello, this is my first post here. I come seeking advice from plumbing & heating pros.
My home has a leak in the hot water line. Our water bill in March was 4 times what it typically runs. Last week, I had a few local plumbing companies come out to give me a solution, and some price proposals. The general consensus is that they want to run new hot and cold water lines from the second floor boiler room to the bathrooms, kitchen, and laundry room. I was told it would take about 4 days time. Some of the plumbers prefer to work with a general contractor to open up the walls and the ceilings, while one guy felt that he did not need a contractor's assistance. I am wanting to have this work done sooner than later, but I have questions about the integrity of the radiant heat.

My other issue is, that the radiant heat on the first floor seems to have a leak in the concrete. I say this because there has been some water stains which have come up on the engineered hardwood floor.
My boiler was installed in 2008, and has an automatic water feed. As per one of the plumber's, when I shut off the automatic water line, I was told that the pressure should remain relatively constant depending on the water temperature in the boiler.
Yesterday, when I shut the boiler off, the pressure read 18 psi. After about 5 hours time, the pressure reading was 2 psi. There are 4 separate zones in the system. Two upstairs which are on baseboard hot water, and two downstairs which are using radiant heat. The older portion of the house was built in 1952, while an addition with the separate zone was sometime in the 1960's.
The radiant heat at present does do a wonderful job keeping the house warm. The floor where the kitchen meets a hallway has been ruined by water. At this point, I would not replace the flooring until I was able to resolve where the water was coming from. It could be both the domestic hot water line, and it could be the radiant heat.
There are ducts in the home for central air also.
I am not sure what would be required to convert the duct system to hot air, but we prefer to stay with some type of hot water heat.

My questions are as follows;
Can I have someone test the pressure in each zone to see if I could find which zone has the leak?
If I have to have new lines run for heat down stairs, is it possible to run the lines behind the walls?
What would be the path of heat around exterior doors?
Since I have to have areas cut open for the plumbing, should I have the heating issue resolved at the same time?
Could I use a product such as warm board R to run radiant heat in one zone? If so, would I be able to run this up to kitchen cabinets?
Any other suggestions?
Thanks

 

[Jadnashua]

Lots of questions that are really tough to answer without lots more information, much more easily available on-site to look at the situation.

At that age, it's more likely that the in-slab radiant was done with copper verses pex. How high are your ceilings? While it would be a pain, on that floor, you could abandon the in-slab stuff, and raise the slab with new stuff embedded in it (most likely pex). That would require lots of adjusting - cabinets, doors, stairs, etc. If it were just supply lines, those are fairly easy to run above the slab, but not to add or fix radiant heating in the slab...just way too many feet of it and if it's leaking in one place, likely to start leaking elsewhere soon, if there aren't already lots of small leaks. Cutting trenches in the existing slab would be really messy and expensive as you'd need LOTS of it to install new lines.

To verify it's just the zones in the slab, you'd need isolation valves (which may be there) to test, but if one of the upper floor zones were leaking, it would be fairly obvious to see water dripping somewhere. Dropping from 18-2psi does mean it's leaking in at least one place.

There are wall panel radiators, and you could install heating panels in the ceiling and/or walls verses the floor, but I think the floor is the most comfortable. Depending on the sizing of the ductwork, you could use a hydro-air arrangement (essentially, a radiator in the ductwork), to get hot air to places. Often, though, if the ductwork was optimized for cooling, it may not be either sized or with the outlets at the optimum location for heating.

 

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[Nitroman58]

The ceilings are 8 feet high, and yes the radiant heat seems to be done with copper tubing.
As for the 4 zones, there is a shut off valve on what I believe is the send line, but not the return line.
Since the hot water line is the main priority for our lives at this time, could I have that replaced first, and then address the radiant heat leak in stages, or by the zone?
Who would be the best people to call, i.e. plumbing and heating contractors, or general contractors?
I need a short and a long term solution.

 

[Jadnashua]

You should be able to isolate the radiant heating system from the potable water supply, then address your hot water situation separately. That's typically a plumber. If you want to keep the radiant (it is the most comfortable heating system generally available IMHO), a heating contractor is probably your best bet. Because it might involve lots of trades to make the accommodations, a general contractor might be useful to coordinate things, but comes at an additional cost, but then, only one guy to control the process rather than trying to do it yourself with multiple contractors. But, it depends on what and how you ultimately want to fix it. Tearing up the slab to find a leak probably isn't wise, as there is probably more than one leak, and if not, will be soon. Tearing up everything to embed new radiant on top of your existing slab is a major endeavor. ALternatives to that while keeping radiant, might be to run radiant in the ceiling and maybe walls, too. I don't think trenching for new pex lines would be feasible, but you'd have to ask (really messy!). Easiest would probably be to go with radiators or radiant panels, but it complicates things a bit if you're keeping radiant in-floor elsewhere, as they need different temperatures (the floor can't be as hot as needed for the walls most of the time). That's a fairly common situation, so there are things to help that happen and it doesn't have to be reinvented.

You really want to have a good heat load analysis done to determine what will be needed to keep the place comfortable AND economical, but the changeover is not going to be cheap. Embedded pex radiant is probably the most expensive option, but totally out of sight, out of mind, with a long lifespan.

 

[Dana]

After more than a half-century before it's first leak, don't expect it to go another half century before the next. You may be closing in on decision-time. If you can isolate the leaking zone and heat it by some other means you can probably go for years before the next leak, but it won't be decades.

If the cooling ducts and air handler are in the attic, above the insulation, forget about using them for heat distribution, even if they're insulated the efficiency losses are enormous. If they're in a basement, completely inside the pressure boundary of the house you have a shot at it, whether it's a hydro-air handler running of the existing boiler or a heat pump or something else.

Since you can probably still find this winter's fuel bill data, you can reliably use that for determining the whole-house heat load, which you won't be able to do as easily after abandoning a zone and heating it with something else. Sizing it based on the existing boiler's specifications is almost always a mistake, but you can use the existing boiler as the measuring instrument. I've posted multiple responses to threads on this site on how to do that, and more recently published blog piece on how to go about it. If you have the exact meter reading or fuel fill-up dates & quantities over this past winter, with a ZIP code for looking up design temps and weather data we could walk through yet another fuel-use heat load analysis.

 

[Nitroman58]

I had a plumbing & heating guy here last Friday. He is supposed to give me his proposal tomorrow. He was talking about using radiant panels in the kitchen, but some type of baseboard elsewhere. Something about the kitchen cabinets.
The heat is not a rush, but since the hot & cold water lines are being moved, I am trying to have both addressed at the same time. I would like to have the 2 zones pressure tested.
What is typically done around kitchen cabinets?

 

[Dana]

Did the guy on Friday gather enough information to run a Manual-J type heat load calculation, or is he punting the radiation sizing on this?

Since you're going from high thermal mass radiation (slabs) to low mass (baseboards, panel radiators), it's important to size the zone radiation to the minimum fire output of the boiler, not just the heat load.

I hope he's not proposing a miserable toe-kick heater solution under the cabinets for the kitchen...

 

[Nitroman58]

He was not specific at all. He seemed intimidated by the size of the job.
He was proposing a type of radiant panel for the kitchen, but he said it is about $25 per square foot. What is the toe kick solution?

 

[Jadnashua]

Panels come in all sorts of sizes and depending on the specific one, could go in the toe-kick, the ceiling, or an open space in the walls. Really hard to say what would work best without knowing first, how much heat the room needs to stay comfortable, and where they can be put. The size of the available area may dictate a certain type and the supply temperature required to get the needed heat into the room.

 

[Dana]

He was not specific at all. He seemed intimidated by the size of the job.
He was proposing a type of radiant panel for the kitchen, but he said it is about $25 per square foot. What is the toe kick solution?

A toe kick is a low profile hydronic coil with a blower, mounted under a cabinet. It has almost nothing going for it other than it's possible to get heat the space with it. It has both noise issues, and at condensing water temps, wind-chill issues making it a really unattractive way to go. Sure, it brings the room temperature up, but it's has human-comfort negatives. Comfort is not a temperature.

Hydronic radiant ceiling panel solutions can work in a kitchen.

What is the BTU/hr output of the boiler at it's minimum firing rate?

 

[Nitroman58]

I went with another Contractor. At this time, I do know know his plan for the kitchen. His proposal includes Haydon baseboard copper fin tubing. I would like something more attractive in the living areas. I have seen the Runtal units, which are expensive. Is there any thing else besides Runtal that some of you would recommend?

 

[Dana]

Like beauty, ugly is in the eye of the beholder. Thin profile panel radiators are more comfortable than fin-tube, and come in a variety of lengths & heights:

Some people are partial to the bi-metal or die cast aluminum convecting panel rads (popular in Eastern Europe & China, but growing in the US):

Or even the traditional 5" deep x 20" cast iron Arco SunRad type radiators that were popular up through the late 1950s before cheap fin-tube became the standard:

These can be had for cheap on the used market, but variations are still available new. (eg Burnham Radiant, or OCS Cast-Ray)

Any of the above are far more comfortable than fin-tube. Some are more architecturally appropriate than others.

 

[Nitroman58]

Thanks, I do like these! So Burnham Radiant and OCS Cast Ray so far. Any others?

 

[Dana]

Thanks, I do like these! So Burnham Radiant and OCS Cast Ray so far. Any others?

Burnham & OCS are the only two I'm aware of still selling NEW Sun-Rad type 5" x 20" flat-faced cast iron, but there are a lot of them available surplus, and they clean up easily.

It's important to size them correctly to be able to deliver the heat at the water temperatures you're running, and to achieve reasonable room-by-room temperature balance within the zone. That starts with a Manual-J or I=B=R type heat load calculation, and some analysis of water temps you've been running with the radiant floors.

Comparing it to typical fin-tube, the output every 3 - 3.5 square feet EDR is roughly equivalent to about a foot of baseboard. The 5" x 20" Sun-Rads are good for 1 square foot EDR per inch of length, and they're typically 2.25" per section.

Brand new they're pretty pricey, but once you know roughly the total EDR you need you can start checking the scrap yards & craigslist if cost is a factor. Being a couple sections (4.5") too long or too short isn't going to make a huge difference, but under or oversizing it by 25% leads to bigger room to room temperature differences. When I micro-zoned my 1920s bungalow I snagged a 26 section (58.5") and a 19 section (42.5") off Craigslist for ~$100 for the pair, and as-installed, painted to match the trim they look pretty much like they came with the place. (One I recessed into an attic room knee wall, the other is set proud of the kick board centered under a bedroom window.) If new it would have been well over a grand for the pair.

 

[Nitroman58]

I like the look of the Burnham baseboard. What does EDR mean?
Do the Sun-Rads give off the most heat?

 

[Dana]

EDR=Equivalent Direct Radiation. It has been a standard defining parameter of radiator output for over a century now. At an average water temp (AWT) of 180F most radiators deliver about 150-170 BTU/hr per square foot EDR. Fin-tube delivers about 500-600 BTU/hr per running foot @ 180F AWT, as do most 8-10" tall cast iron baseboards.

Cast iron baseboard comes in a few different heights, and is typically 3-4 sq ft EDR per foot. Burnham BaseRay is rated at 3.4 sq.ft. EDR, which is about 3.4/12"= 0.28 sq.ft. per inch, compared to the 1.0 sq. ft. per inch you get out of a SunRad. That's not surprising, since the SunRad is both taller and thicker, with more convection channels with surface area than cast iron baseboard. C.I. baseboard regularly shows up in scrap yards too, but pay attention- you need each section to have a "foot" on each end to maintain a convection channel off the floor. Sections taken out of the middle of a long run of baseboard during a demolition won't have those feet.

Panel radiators that are taller or thicker put out more heat than thin short ones. They typically are specified at a couple of AWT points, commonly 140F and 180F, but it's fine to do linear interpolations to other

You may find this radiator sizing guide useful in your estimating, particularly the AWT vs. BTU/hr per sq.ft. EDR nomograph on p.2.

If you have a condensing boiler it's useful to have enough radiation to deliver the calculated heat load in each room at an AWT of 125F, or at most 140F. At 125F you can expect 50-60 BTU/hr per square foot EDR out of cast iron, 90-100 BTU/hr @ 140F AWT. So, if the room has a design load of say, 3750 BTU/hr @ 10F (or whatever your 99% outside design temp is) you'd want at least 38 sq.ft. EDR of radiator (at 2.25" per section that's a 17 section/38" SunRad, or 11' of BaseRay) if you're planning on 140F water, or roughly twice that if planning on 125F water. As long as the ratio of radiation to calculated load is about the same on each room in the zone the room to room tempertures will track pretty closely. The lower you can get the AWT and still deliver the heat, the more condensing efficiency you'll get out of the boiler.

Most slab radiant floors run at under 100F AWT, so it'll probably be a dual-temp system (or a LOT of cast iron), but it's not unreasonable to design for 125F water on design day, in which case it will be in condensing mode at least 99% of the time. If you design for 140F it can still be set up to condense if you tweak the temps carefully, but it'll be out of condensing range 5-10% of the time (during the coldest hours of the coldest days.)

 

[Nitroman58]

The second floor has the standard copper fin baseboard on two zones. I am not sure if I would need a dual temp system.
Let me take some pictures of the kitchen area and post them.

 

[Dana]

What is the boiler behind all this?

How messy is the zone plumbing?

It may already be a 2- temp system, but we might be able to determine that with some pictures of the boiler room showing the plumbing architecture.

 

[Nitroman58]

The boiler is a Dunkirk 95M-200 gas-fired direct vent modulating hot water boiler. It was installed in 2008. There are 4 zones, 2 upstairs, 2 downstairs, east and west.

 

[Nitroman58]

In this picture, I am standing next to the chimney. The kitchen and living room are only divided by the chimney. The length of the room from here is 21.5'. The width of the room is 20.5'.