Radiant heat

Glenn Sossin_2

Sorry

Drawing had some mis-labeled lines. This is correct.

Carol Lucas

Radiant heat

We recently added on an 8X10 mudroom with radiant heat in a concrete slab. We can't get the room above 65 degrees. The feed line going into the slab is 145degrees and the return line is 75 degrees! There's only about 90'of tubing in the loop. The system runs through a zone valve and a three way mixing valve. Some plumbers say we need to get rid of the zone valve, add a relay switch and a pump, others say we could leave the zone valve and just add a pump, and still others say a pump won't make any difference! HELP PLEASE!

Glenn Sossin_2

Radiant Mud Rm

It is clear you have limited water flow. Either caused by a blockage (kink or partially closed valve), air bound, or misplaced circulator. I suspect the circulator. It is probably located in the wrong spot, pushing into the tempering valve or pulling away from it. The circulator needs to be mounted in the radiant loop, not pushing/pulling to it.

Based on your description, heres what I think is happening. On a call for heat, the boiler and pump turn on sending hot water to the mixing valve. Starting out from a cold position, the hot side of the tempering valve is open letting in hot water from the boiler. As the temperature going through the mixing valve reaches its target (set point) the hot side of the tempering valve closes down. Afterall, it's job is to provide a set temperature. It the temperature of the water is too high, it closes off the hot side. If the there is no pump in the pex circuit, the water flow stops. As the water in the tempering valve cools down, the hot side opens and lets in the hot water flow again for a moment, and shuts down again. This cycle prevents water from flowing in your floor sufficiently to heat it properly.

Hope this helps you.

Glenn

Ed_26

insulation

What's under the slab?

Glenn Sossin_2

Mud Room

Sorry

I sent the diagram with some mis labled lines. This is correct.

Glenn

hr

Did the contractor

do a heat load calc for the space first? You have 80 square feet of heat emitter to cover the heating load of that space. Perhaps less if cabinets or benches are included.

The heat load calc would determine how many btus are required and if the floor space could provide that.

Was insulation used under the slab and around the exposed edges? How warm does the surface of the floor get when it is running.

It could be as simple as a flow issue, a blockage somewhere, or an under design. Either could be fixed once you determine where the problem lies.

hot rod

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Glenn Sossin_2

Sorry - Sent the drawing with some mislabled lines. This is corrected.

Glenn Sossin_2

Drawing

Sorry

I sent a drawing with some errors. Had some lines mislabled. Please use this drawing.

Uni R_3

And on the floor?

How clear is that floor area? Floor mats, benches, etc? If it's not insulated underneath, the previous poster's concern, then anything on the floor will really push the heat down. You're dropping off a lot of heat. If you aren't insulated underneath, I'd consider getting a radiator and abandoning the radiant there.

Glenn Sossin_2

Drawing

There were a few other errors regarding identification of drain cocks for purging that I caught. I believe this version is free from any errors.

Sorry

Glenn

Unknown

you can't possibly drop that much temperature in that short of a loop.

You have a flow problem. Probably should ditch the ZV and add a pump pulling from the mix valve.

Sounds like this was not put in as drawn, as it is drawn with a circ pump pulling from the tempering valve, as it should.

Weezbo

rather than reply yesterday i scrapped my post...

and considered what could induce these numbers...

here is a thought...if you have a severe leak,the ground is unstable or has extremely good drainage, no insulation,...it may be that the make up water is filling the foundation of the home or it might be being carried away from the house entirely...especially if it has some drainage or underslab plumbing drainage pipes installed in the mud room.

pressure the line...

steven E.HEAT

no Flowwwww