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Old 01-07-2010, 06:12 PM   #1
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Hydronic Radiant Floor install questions


Hi, all. First post.

I'm in the process of removing my existing ceramic floor to replace the current baseboard heat with a hydronic radiant floor system. I've got a couple of questions.

1. Currently, there is tile installed on plywood over an old t-and-g subfloor. What's the best option here? Should I remove the plywood and put the pex over the t-and-g and place sleepers between the runs? Should I route some channels in the plywood? If I have to install another layer on top of the plywood I will, but I would prefer to not gain the height. I'll be putting some backer-board on top of everything before the new tile goes in.

2. Any tips on removing baseboard radiator heat runs?

3. The PEX can take up to 180, which is the high-point for what my boiler is putting out. Can I skip the mixing valve?

Thanks!
inK

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Old 01-07-2010, 06:34 PM   #2
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Hydronic Radiant Floor install questions


pex over plywood should have adequate insulation under the floor and a radiant reflective barrier to contain and direct the heat towards the room to be warmed. In short the pex should be below this floor, then insulated with batt insulation and sealed with reflective rigid foil faced insulation.

The efficiency of the radiant system is that you only need to heat the water to 105 or so. Why waste energy making the water hotter than needed. A mixing value is still needed to adjust the desired heat to match the room's requirements. You should also consider a thermostat that integrates the indoor and outdoor temps. This allows a anticipated heat demand for cold temps and allows the radient heat to start up before the room temp calls for it. Radiant heat responds much slower.

To remove the baseboards, just close the water to those zones, cut the pipes remove the unit. If others need to be kept working on the same zone, tie a new line from the first cut to the last one.

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Old 01-09-2010, 05:40 PM   #3
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Hydronic Radiant Floor install questions


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Originally Posted by Bob Mariani View Post
The efficiency of the radiant system is that you only need to heat the water to 105 or so. Why waste energy making the water hotter than needed. A mixing value is still needed to adjust the desired heat to match the room's requirements. You should also consider a thermostat that integrates the indoor and outdoor temps. This allows a anticipated heat demand for cold temps and allows the radient heat to start up before the room temp calls for it. Radiant heat responds much slower.
Bob, I have a few questions I'm hoping you'll answer. I am attempting to retrofit an underfloor hot water radiant system to an old house (1922 construction), with approximately 900 square feet of "ground floor" living area (30' X 30'). Half of the house is carpeted (heavy pad with thick, plush carpet) and half has vinyl tile. I do have access to the floor's joist bays from the basement--the floor joists are 2 X 10 on 24" centers.

The kitchen and dining room (the area with vinyl) have had plywood or particle board installed over the original tongue and groove flooring, but I think the carpeted area has not.

My question relates to the mixing valve issue....do I need to design the system as two zones for some reason (i.e., the difference in floor construction between the area with vinyl and the area with carpeting)? I plan on using a 240V/50A electric HWOD unit to heat the water for the radiant tubing, which will be used in a closed-loop configuration, and the HWOD unit can be set to provide a very consistent output temperature, which I am hoping will eliminate the need for mixing valves.

Any help you can provide would be greatly appreciated!

Thanks in advance!

Dugly
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Old 01-09-2010, 06:42 PM   #4
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Hydronic Radiant Floor install questions


you can get by using the thermostats for this system. Only issue if you need to adjust the temps for only one zone, you cannot do it.
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Old 01-09-2010, 07:40 PM   #5
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Hydronic Radiant Floor install questions


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Originally Posted by Bob Mariani View Post
you can get by using the thermostats for this system.
Thanks for that, Bob! The company from which I am getting the underfloor tubing recommends a "floor thermostat" that apparently reads the floor temp rather than the air temp. If I go this way, do you think the floor thermostat ought to be installed in the zone with the thick pad and carpeting or in the zone with the additional plywood layer and the vinyl?

I would rather not go to a two zone system, although I could do that and use a separate HWOD unit for each zone. The only problem I foresee with that is that my hot water is a 100 amp HWOD unit and if I add two 50 amp HWOD units for the two zones of radiant heat, I'm at the 200 amp ceiling for my electrical service. In all truth, I envision this radiant heating project to be the primary heating source for the home, but not the only heating system. I'll be adding passive and active solar heating (a solarium on the south side and solar heated water to pre-heat the inlet water for the HWOD units) as well as probably some sort of wood-burning stove. There is an existing gas-fired floor furnace but I'd rather not connect to the $$ hungry natural gas company.

Thanks, again!

Dugly
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Old 01-09-2010, 10:17 PM   #6
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Hydronic Radiant Floor install questions


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Originally Posted by YerDugliness View Post

I would rather not go to a two zone system, although I could do that and use a separate HWOD unit for each zone. The only problem I foresee with that is that my hot water is a 100 amp HWOD unit and if I add two 50 amp HWOD units for the two zones of radiant heat, I'm at the 200 amp ceiling for my electrical service. .

Thanks, again!

Dugly
If you only have a 200 amp service.
Then you can't have a 100 amp HWOD and a 50 amp HWOD unit.

Since your other house hold appliances will consume enough to over load the panel.
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Old 01-09-2010, 10:57 PM   #7
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Hydronic Radiant Floor install questions


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If you only have a 200 amp service.
Then you can't have a 100 amp HWOD and a 50 amp HWOD unit.

Since your other house hold appliances will consume enough to over load the panel.
I'm a retired empty-nester bachelor, don't use very much electricity at all EXCEPT for that 100 amp HWOD unit. Most nights all you'll see is the glow of the computer screen or the TV, don't like to use the lights much, and even those are new CFL low draw bulbs (considering switching to the new ultra-efficient LED/LCD technology bulbs, a long pay-back but incredible 20 year life expectancy).

Yeah, I know what you mean, though.....it might take some very careful planning (time management) and there might be a learning curve. I wish I'd had the good sense to use two 50 amp HWOD units, one in each zone (bathroom, kitchen/laundry) rather than that 100 amp whole-house model. Oh, well, future plans include another construction project, maybe I'll re-fit the house at that time and use the high-powered monster for a different project.

Dugly
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Old 01-10-2010, 08:02 AM   #8
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Hydronic Radiant Floor install questions


The floor sensor is the correct way to adjust the temps for these systems. Place it in a room on the North side if you only want one. Two tanks is not needed. One tank with two small circulaters will give you the two zones.
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Old 01-10-2010, 09:36 AM   #9
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Hydronic Radiant Floor install questions


Thank you so much, Bob! I can see what you mean now, two zones, each with it's own circulator pump controlled by it's own floor thermometer, both connected to manifolds before and after the single HWOD unit......so simple it just hadn't occurred to me. You're Da Man !!

Thanks, again !!!

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Old 01-10-2010, 10:34 AM   #10
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Hydronic Radiant Floor install questions


hot water supply -- manifold -- zoned circulation pumps -- these are controlled by a relay which is controlled by the thermostat. pumps are on the return side.

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