baseboard elements switched to between joist 3/4 Pex tubing in an existing floor

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Old 08-08-14, 05:44 AM
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baseboard elements switched to between joist 3/4 Pex tubing in an existing floor

I currently have an older tankless gas boiler that heats baseboard elements in every room of the house. We are doing a Kitchen remodel and I would like to run 3/4 inch pex tubing with all necessary hardware in between the joists under the existing floor. the room is approximately 480 sq. feet. The question is, can I unhook the baseboard heat feed and tie the tubing into the current system where it enters the room and finish where the current system exits the room?
 
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Old 08-08-14, 06:45 AM
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Unfortunately, no, there's more to it than that.

First, you need to determine if the underfloor heat will output enough BTU to meet the heat loss of the room. For radiant heating you can't count the square footage of any floor under cabinets or appliances as 'radiator', so you need to subtract that from the square footage. What is the square footage of ONLY the exposed portion of the floor?

How many feet of baseboard are you planning on removing?

Next, your baseboard system is HIGH TEMPERATURE, meaning it maxes out around 180F. You can't run 180F water for underfloor heating, the water temperature needs to be maximum around 120F or so, and for this you need a 'mixing valve', and another pump.
 
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Old 08-08-14, 08:41 AM
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subtracting out the cabinets and appliances that leaves about 390 sq. feet of floor. The amount of baseboard element being removed is 35' and the area to be heated is over a crawlspace. my first thought was to use heating cable but the room is over the sq. footage for one zone, as I'm finding out from all the project generators apps. any suggestions would be great, as the the baseboard style doesn't leave much room for cabinet space.
 

Last edited by Schooley; 08-08-14 at 09:07 AM.
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Old 08-08-14, 09:47 AM
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Can you consider a hydronic toe space heating unit, plumbed into the existing piping below the new cabinets . . . . like a Myson Fan Convector ?
 
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Old 08-08-14, 09:48 AM
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Is that 35' only the FINNED part of the baseboard? Or is there bare pipe running inside some of the enclosure? You only need to count the actual finned part of the elements.

If it IS only the finned part, that means that you have appx 20K BTUH of heat output for your kitchen and that seems like an awful lot to me... if it is about 480 sq ft (appx), then the heating needs (using a 'rule of thumb' rather than actual heat loss estimate, which may not be completely accurate, but for example) for that room is probably more like 12K BTUH which could be met with 22' of fin-tube element. So, it's important to know if that measurement of 35' is correct or not.

Is your kitchen currently a very warm room?

Moving on, let's use the 'rule of thumb' example of 12K BTUH requirement.

Optimistically, one can get about 25 BTUH per square foot of floor space from underfloor heat. You have 390 sq ft times 25 = 9750 BTUH of heat into the room... falls a bit short of the 12K need.

Being a kitchen, you might just get away with it because there are obviously other heat producing appliances in there...

BUT, that 25 BTUH / sq ft figure is optimistic, best case. You might only get 20 ...

Have you thought about using 'kick space heaters' under the cabinets?

Beacon/Morris Residential, Commercial, Heat, Hot Water, Steam, Gas, Kickspace Heaters, Hydronic, Oil.
 
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Old 08-08-14, 01:09 PM
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the Finned area is closer to 32 feet and the kitchen has three outside walls, if that makes any difference on the heating of that area. The Kickspace heater is a great Idea NJ Trooper. My home heating scenario is based on 3 zones, one for each level, will a kickspace heater be able to run in conjunction with the other baseboard elements within that zone before and after? I also noticed that the kickspace heaters in the video look to be 1/2" pipe and my baseboards are 3/4" through out. will that make any impact on the other rooms after the Kitchen? The kitchen is the 2nd room of 5 on that particular zone. Thanks for all your help NJ Trooper it's greatly appreciated.
 
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Old 08-09-14, 09:36 AM
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Yes, three outside walls would make a difference in the heat loss of the room.

I would like to know if the kitchen is consistently warmer than the other rooms though. This would give an idea if there is the correct amount of baseboard currently installed... not exact, but an idea anyway.

In other words, if the heating in all the rooms on that zone is fairly well balanced now, you may in fact NEED that many BTU of heat emitters in that room, and if you can't output the same amount of heat by the replacement, you will end up with a cold room.

I believe that you are saying by your description that the 5 rooms of baseboard are currently piped in SERIES, into one, out and into the next, etc ?

If that's the case, then no, you don't want to connect the kickspace heaters in series with the rest of the baseboards. You have two options, one is to use a 'venturi tee' which diverts a portion of the flow. This is shown in the PDF below as "One pipe system upfeed" on page 4.

VF-075-050 - Taco VF-075-050 - 3/4" x 1/2" Copper Venturi Tee

The other option is to pipe with 'home runs' back to the boiler as shown in the diagram just below that.

http://beacon-morris.com/modules/lit...litFileID=2541

There's more installation info in this PDF

http://beacon-morris.com/modules/lit...litFileID=1871

You are probably going to need at least 2 heaters, the object being to get as close to the BTU rating of what you are removing as possible. These 2 (or more?) heaters would need to be piped off INDIVIDUAL branches from the 'main line'. You can't install a single diverter tee and feed one, then to the next in series, then back to the main line. Do this and you probably won't get enough flow (almost certainly).

A word of caution about venturi tees... they can be VERY difficult to 'bleed' the air out. The install docs show an 'air vent' at the heater. This is very often NOT ENOUGH. My advice is, in ADDITION to that MANUAL (do NOT use an 'automatic' one!) air vent, to install a FULL PORT 3/4" ball valve BETWEEN the two tees on the main line. When initially filling and purging air from the system, this valve is CLOSED in order to force ALL the flow through the heater (basically putting the heater in SERIES temporarily). Once all the air is out and flow is established, that valve is OPENED and left that way for normal operation.

I've also seen guys put a couple valves on the RETURN from the heaters, before the pipe enters the return tee, a DRAIN valve, and a FULL PORT ball valve. By closing the ball valve and opening the drain, air can be purged from the heater through a hose and bucket.

My opinion is that the valve between the tees is a better solution. You get more pressure through the heater making it easier to purge air, and no need for a bucket and hose.

The blowers in these heaters comes on automatically via a temp sensor on the piping inside the unit. When the water hits 120F the blower comes on. There is a lower temp thermostat available in the event that the heaters don't come on soon enough. (I think B/M supplies this for free for the asking)

There are other manufacturers of course, as Vermont said, Myson is another.
 
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Old 08-11-14, 07:55 AM
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Another company that makes toe kick heaters is Turbonics. Turbonics Inc., Specialists in Hydronic Heating Solutions.

I just installed (last week) one of there toe kick heaters in my kitchen remodel and have previously installed one of there floor mount fancoils. NJ Trooper is giving you excellent advice about installing a full port ball valve between the tees, it worked well for me.
 
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Old 08-17-14, 06:53 PM
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Floor warming via PEX plus a panel rad or 2 w TRVs?
 
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