Plumbing Advice Needed - In-Floor Heat Install

reddeerguy2015 · #1 10-11-2018, 02:09 PM

Howdy all,

Looking for some advice on hooking up our in floor heat.

House is two years old and basement is roughed in for heat.

We have a 90 gallon dual purpose hot water tank that will be used for the heat source.

Been quoted between $2500 and $3500 to have someone come out and do this job, which seems astronomical to me, but who knows.

Anyways, check out the pics and let me know what I need.

I'm assuming a manifold to tie in the pex floor tubes, a pump, power source, a thermostat, some type of control box and.....??

What are the lines typically filled with in this style of application??

Have lots of room on the walls to place the manifold, on both sides of the hot water tank.

Thanks.

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Swamp hunter · #2 10-11-2018, 04:04 PM

I used propalyne glycol in mine. Put air in lines to figure out which are paired and separate pairs for supply and return. Put pump between hot outlet and supply header with pressure tank and air purge t'd in(above tank ). Cheapest way to go is put a small fractional h.p. 110v pump and let it run wild and adjust heater for desired temperature. Or you can put a stat controlling a relay for pump.and obviously tie return manifold to cold inlet on tank also with air purge.

reddeerguy2015 · #3 10-11-2018, 06:16 PM

Does anyone have any pictures of what a typical install would look like?? Or a detailed diagram ??

reddeerguy2015 · #4 10-11-2018, 07:24 PM

Okay so these three sets are paired supply and return lines (three different zones).... Now this may be a stupid question, but why do I have a 7th hose sticking out of the floor.

And this 7th hose won't accept any air at all - it's blocked.

Is the other end of the hose buried in the slab ?? Would that explain this or am I missing something??

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OldBakerHand · #5 10-11-2018, 08:19 PM

Hey I can send you pics of mine tomorrow, it's a heat exchanger ran off of the HWT. It works very well, cost was about 3k

Also the 7th line,does it go to the garage?

reddeerguy2015 · #6 10-11-2018, 08:26 PM

Okay starting to figure this out... After some digging I found this diagram.

Still uncertain why there's a 7th hose that's blocked off though...

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mked · #7 10-11-2018, 09:47 PM

7th line thats blocked could be the thermostat sensor line

reddeerguy2015 · #8 10-11-2018, 09:51 PM

Quote:

Originally Posted by mked

7th line thats blocked could be the thermostat sensor line

What the heck is that??

Or in other words....how does it work and how would it tie into this system??

mked · #9 10-11-2018, 09:56 PM

Slide the thermostat sensor end down the blocked hose as far as it will go, itll give you somewhat accurate slab temperature

reddeerguy2015 · #10 10-11-2018, 10:14 PM

Quote:

Originally Posted by mked

Slide the thermostat sensor end down the blocked hose as far as it will go, itll give you somewhat accurate slab temperature

I see... Makes sense.

Couldn't you also just put that on the return line manifold coming from the slab ??

CaberTosser · #11 10-11-2018, 10:32 PM

Quote:

Originally Posted by reddeerguy2015

I see... Makes sense.

Couldn't you also just put that on the return line manifold coming from the slab ??

Return temp does not equal slab temp. I agree one line is like a slab temp tube. You can confirm the three loops by blasting them one at a time with some compressed air and marking which is which so you can determine suppky & return and find the 'odd man out'.

reddeerguy2015 · #12 10-12-2018, 12:01 AM

Thanks for the tips.

What percentage should a guy run for the propylene glycol mix in an application like this ??

CaberTosser · #13 10-12-2018, 12:42 AM

Propylene glycol can be anywhere from 33% to 50%. Generally one gets their service tech in before the garage hits -15C so 50/50 isn't completely necessary if you are in an area that you can expect service in a reasonable time frame. I use Axiom feed tanks on all of my boiler installations, its not even an option to not use them. Don't let the installer tie it to your water lines from pressurization, doing so has a few drawbacks: a required RP-type backflow device is expensive and needs annual re-certification ($$ annually, forever); if a leak occurs and you are attached to the domestic water supply your glycol % gets watered down and freeze protection is lost. An Axiom feed tank allows visual monitoring of the reservoir level, if there's been a leak the tank level descends as its pumped into the heating system. With an Axiom I always mark the liquid level, glycol % and date on tape on the side, don't mark the tank with a Sharpie as it gets confusing with 9numeroous dates and level markings.

http://axiomind.sasktelwebhosting.com/mf200.php

reddeerguy2015 · #14 10-12-2018, 08:14 AM

Quote:

Originally Posted by CaberTosser

Propylene glycol can be anywhere from 33% to 50%. Generally one gets their service tech in before the garage hits -15C so 50/50 isn't completely necessary if you are in an area that you can expect service in a reasonable time frame. I use Axiom feed tanks on all of my boiler installations, its not even an option to not use them. Don't let the installer tie it to your water lines from pressurization, doing so has a few drawbacks: a required RP-type backflow device is expensive and needs annual re-certification ($$ annually, forever); if a leak occurs and you are attached to the domestic water supply your glycol % gets watered down and freeze protection is lost. An Axiom feed tank allows visual monitoring of the reservoir level, if there's been a leak the tank level descends as its pumped into the heating system. With an Axiom I always mark the liquid level, glycol % and date on tape on the side, don't mark the tank with a Sharpie as it gets confusing with 9numeroous dates and level markings.

http://axiomind.sasktelwebhosting.com/mf200.php

Couple questions.

- do I *need* a fill tank?? Being a closed system, save for any leaks (which would all be visible) - after the initial separation of gas from the fluid, wouldn't one just top up continually until the system is completely topped up and all air bled off??

- the system is for the basement in our house, not a cold garage.

- there is no boiler, just utilizing the (separate) coils in the combi hot water tank (there's no mixing of potable water and heating fluid).

- It's an acreage. So we wouldn't tie into the cold water inlet, as I'd want to use a distilled water/antifreeze mix vs acreage water... Ever seen the nasty stuff that grows from acreage water that's been sitting for years ?? No thanks.

OldBakerHand · #15 10-12-2018, 08:38 AM

Hey as promised these are pics of my system. This is a 100% water system. This tank does the floor heat in our 1300sq ft basement and our domestic hot water needs. The system has been in place for 4 years now and so far no issues.

Erik · #16 10-12-2018, 09:02 AM

Sorry for quick derail - and no offence to other plumbers that also give excellent advice - but I have to say that I love reading Caber's posts on plumbing. So informative and have learned a lot. Think we all owe you for the knowledge you have bestowed upon us in this forum.

Sneeze · #17 10-12-2018, 10:28 AM

I have zip experience with this but have a great deal of experience dealing with epic failures caused by junk things you buy at the store.

My first question in all of this is what happens in 10 years when the heat exchanger in the water tank fails and dumps antifreeze into your potable water supply.

Or do these water tanks have some sort of redundant safety built into them such that the fluids could never mix?

Especially with antifreeze. I think about my wife using hot water to mix baby formula. The little guy might not tell you before getting enough to loose his eyesight?

reddeerguy2015 · #18 10-12-2018, 01:00 PM

Quote:

Originally Posted by Sneeze

I have zip experience with this but have a great deal of experience dealing with epic failures caused by junk things you buy at the store.

My first question in all of this is what happens in 10 years when the heat exchanger in the water tank fails and dumps antifreeze into your potable water supply.

Or do these water tanks have some sort of redundant safety built into them such that the fluids could never mix?

Especially with antifreeze. I think about my wife using hot water to mix baby formula. The little guy might not tell you before getting enough to loose his eyesight?

- it's a steel pipe wound through the innards of the hot water tank...not exactly sure how that would fail, short of some catastrophic overpressuring event. This tank was designed for such a purpose and is essentially brand new. Cost good money too.

- this is not our potable water source. We use a separate R.O. system for ice cubes/fridge water/cooking and 19L blue water jugs for drinking water. As mentioned, it's acreage (well) water. Nobody's drinking the bath water here...

- maybe for this reason it might be a good idea to have some type of fluid level monitoring system, as caber had mentioned, even though it's a closed loop system, as a redundancy measure for such a given event ??

darren32 · #19 10-12-2018, 01:16 PM

Quote:

Originally Posted by Sneeze

I have zip experience with this but have a great deal of experience dealing with epic failures caused by junk things you buy at the store.

My first question in all of this is what happens in 10 years when the heat exchanger in the water tank fails and dumps antifreeze into your potable water supply.

Or do these water tanks have some sort of redundant safety built into them such that the fluids could never mix?

Especially with antifreeze. I think about my wife using hot water to mix baby formula. The little guy might not tell you before getting enough to loose his eyesight?

You have to use nontoxic antifreeze, you can drink the stuff.

They can definitely fail. I had 2 combicore water heaters fail before I finally switched over to a heat exchanger system. They have likely improved since then (close to 20 years ago).

Another thing to look into may be a teckmar mixing controller. I put one in (can't remember model but I can find it if you like) and it really made a big difference in the temperature control. Basically, the colder it is outside, the hotter the water it send to the slabs. Mine does it by varying the speed of the circ pump that runs the domestic side of the heat exchanger. But I think you could also just vary the speed of the pump in a system like yours and send more or less water to the slab.

I used to get pretty bad overshoot. After the pump turned off the slab kept heating the space and it would go 3 or so C above the setpoint. Now the overshoot is gone and the temperature is constant.

Anyway, I am not a plumber and I did the work a long time ago but I can get you some info if you like.

Caber, thanks for the Axiom info, my back flow device is screwed and I may switch over. Which wholesaler? Thanks

Okotok · #20 10-12-2018, 03:43 PM

Some good posts. From my days in trade school and particularly if this is only for an interior slab, 100% water gives you a significantly higher efficiency (like 20% to 25%) better than running a glycol mix. If you're running it for a snow melt system or into a garage, then a heat exchanger is your best option with glycol mix used for freeze protection. I assume the OP has a forced air system in place currently so shouldn't be a danger of the basement freezing up regardless. Things may have changed since I got my Steamfitter ticket in the mid 80s.

JimW55 · #21 10-12-2018, 03:53 PM

Hey bud,
Your heater is the manifold, put return bends on your floor lines is all you need.

reddeerguy2015 · #22 10-12-2018, 05:20 PM

Okay here's my technical diagram...

What do I need to change??

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CaberTosser · #23 10-12-2018, 07:04 PM

I've not yet seen a Bradford White heater with annexchnager coil in it, but it's possible. If that does have a coil then that diagram is functional once you remove the unnecessary PRV from that drawing.

It's better to have a set-up that allows for a more precise control of the supply water temp to the slab, generally achieved by the use of a thermostatic mixing valve.

reddeerguy2015 · #24 10-12-2018, 07:38 PM

Quote:

Originally Posted by CaberTosser

I've not yet seen a Bradford White heater with annexchnager coil in it, but it's possible. If that does have a coil then that diagram is functional once you remove the unnecessary PRV from that drawing.

It's better to have a set-up that allows for a more precise control of the supply water temp to the slab, generally achieved by the use of a thermostatic mixing valve.

Thank you, sir!

CaberTosser · #25 10-12-2018, 08:05 PM

In the instance that a water heater does not have a heat exchanger coil (the norm), then a panel like this takes care of most needs, just add a relief valve and an expansion tank:

http://tamashydronic.com/low-temp-isolation.php

reddeerguy2015 · #26 10-12-2018, 08:48 PM

Spec sheet

https://s3.amazonaws.com/bradfordwhi...csheet_547.pdf

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CaberTosser · #27 10-13-2018, 08:00 AM

Glycol was mentioned, but unless a person has a specific need for it such as a garage slab, then it’s unnecessary. A basement slab in a house that already has a furnace isn’t at risk of freezing. I have however seen a garage slab where all of the lines split at the floor when a circ pump serving the garage had seized and the homeowner drove away with the garage door wide open in very cold weather (so,etching like a broom or shovel had fallen and caused the door to bounce back when it was closing). No more slab heat for them. Mind you that was also polybutylene tubing rather than pex, but it’s not a risk worth taking.

OldBakerHand · #28 10-13-2018, 08:46 AM

Quote:

Originally Posted by CaberTosser

In the instance that a water heater does not have a heat exchanger coil (the norm), then a panel like this takes care of most needs, just add a relief valve and an expansion tank:

http://tamashydronic.com/low-temp-isolation.php

Caber, that is the exact one in my house, been using for 5 years so far and no issues

CaberTosser · #29 10-13-2018, 09:21 AM

Quote:

Originally Posted by OldBakerHand

Caber, that is the exact one in my house, been using for 5 years so far and no issues

I generally stick to boiler installations rather than utilizing water heaters due to their efficiency, flexibility and longevity (all stainless steel). The thing that concerns me about those heaters is that enamelled steel water heaters have a finite life span, I would prefer to use a stainless steel heat exchanger and then when it comes time to replace the water heater it would just be a normally priced unit rather than the more expensive model.