First hydronic floor setup - many questions

[Blk88GT]

I just finished the install on my in floor heat setup and I have a few questions. Ok, maybe a lot

Some details on my system:

2000sqft
R21 walls
R50 ceiling
2" XPS under the slab, on the side of the thickened edge and 4 feet around the building, 4" thick on the door side of the shop
7 loops of 1/2" Oxypex on 16" centers
Lion 20KW boiler
Watts needle valve manifolds
Grundfos 3 speed pump
Axiom MS 200 autofeeder

I've got a slab sensor thermostat but have yet to install it. I have the thermostat jumped out right now just to get some heat in the floor for the time being. Temperature is controlled with the aquastat on the boiler for now.

Here's where things get foggy for me:

1 - Outlet temperature - Where do most people end up for outlet temp? Right now I'm around 65-70f on the outlet and 42F on the return and I'm trying to bring the slab to temperature as slow as possible.

2 - Flow Meters - How much flow do I want through my loops? They are currently between .75-1 GPM according to the gauge.

3 - Pump speed - I'm sure there is a correlation between the needle valves and pump speed, right? Right now I've got it on medium.

Any help would be appreciated. I'm learning as I go, so go easy on me!

 

[Bondo]

1 - Outlet temperature - Where do most people end up for outlet temp? Right now I'm around 65-70f on the outlet and 42F on the return and I'm trying to bring the slab to temperature as slow as possible.

Ayuh,.... On the system I built a few years ago,..
I went with an oil boiler, 'n primary/ secondary loops...
The primary loop runs 180° for the boiler, 'n the 2ndary loops pull off mixed water at 150° to do the actual heatin' of the floors...

I'd think yer temps are Waayyy to low to heat the slab...

 

[Blk88GT]

I'm purposely keeping it low at the moment, I want to bring the slab up to temperature as slow as possible. Overnight, the slab warmed to 52F. I raised the temperature a little this morning, so I'll see what it looks like when I get home.

 

[The Boss]

You are doing it right - if the slab is relatively new, you want to notch it up a couple degrees every day so that you don't stress the concrete. Your outlet temp won't need to get much above 100 to heat the slab once it comes up to temperature as long as you are leaving it on all the time.

The system is not designed for on when you go out to work on something for a couple hours to heat the place up quickly - it's designed to keep the slab at 65-75 (or whatever you choose) for long periods of time.

My garage is about the same size as yours & I'll be using an on demand propane hot water heater to run it.

 

[tdkkart]

If you can get it you want no more than about 20-25* drop in the water temp as it passes through floor. Crank the boiler output up to about 100-110* if it will go that high, and then after the system has been running an hour or so, adjust your valving and pump speed till you get about 25* drop in the temp coming back. You may or may not be able to get there.
With decent insulation, and depending on heat load, you should only need a slab temp of 5-7* above your desired room temp, ie: a 65* slab temp should give you a 60* room temp. Also be aware that you will not need a 70* room temp to be comfortable.

 

[theoldwizard1]

Depending on what "normal" boiler output temperature is, you want the flow rate/pump speed as low as possible without the return temperature being too close to the desired slab temp.

 

[Blk88GT]

Thanks for the info guys. Once I've got it up to temp, I'll start to play with it a little more. I want to make sure I don't heat it up too quick and I think it would be pretty easy with this boiler....

 

[Blk88GT]

I'm about 82F going into the manifold, 60F coming back. Slab temp is ~70F. Ambient air temp is 62. Pump is on low speed with the loops running .5-.75 GPM.

I haven't checked the air temperature at the ceiling to see what it's like yet...

 

[The Boss]

Sounds good....I bet it feels good too!

Of all the radiant slabs I've done, the ones I enjoy most are the ones I get to work in during the winter! It's a warmth that goes right through you!

 

[anthony666]

why did you go with 16" centers ??? that's way far apart and it'll make your system struggle to keep up .. spilled milk now

don't worry about your return temps until you're at operating temp .. it should ideally be about 10 degrees of difference, but because you have a lot of space you probably won't attain that

don't worry about the amount of flow on your meters, just that they're all relatively even

once you're at operating temp turn your pump to high

 

[jlckmj]

I haven't checked the air temperature at the ceiling to see what it's like yet...

It should be about the same at the ceiling as it is at your knees. That is the great thing about in slab heat, it is even throughout the room.

Jim

 

[Blk88GT]

Jim, you're absolutely right. I went up on the scissor lift and hunt a thermometer up there yesterday and it's no different than down low. I'm pretty happy about that!

 

[Fun pain]

With his level of insulation 16" on centers will be just fine

 

[anthony666]

he's in manitoba bud .. he will be fine as long as he locks the door november to may

 

[Blk88GT]

Nothing is struggling and I've had the doors open and closed a few times. Thank you for your "input" regardless.

 

[Randy in Maine]

I have a similar set up to you and I am fine also. Actually I am more than fine..... I am happy, very comfortable, and pleased with the decisions that I made in building my shop. Putting a stereo out there has also helped make it nice.

I have been doing some carpentry and even some painting inside over the past 2 weeks, as it snows and blows outside. I keep the thermostat at 55º F and it stays right there. Putting the 2" of foam under the floor and using 2" of foam as a thermal break beetween the heated floor and the unheated walls was money well spent.

I am still hoping to heat my house AND garage for $1500 this year (500-600 gallons of propane at $2.49/gal). I think I am going to make it. 0º F here this morning and for the next while. No moquitoes and no tourists so all is well.

 

[Blk88GT]

Thanks for the info Randy. I'm not sure how much it'll be to heat, but I'll get a pretty good idea after a bill or two. I haven't used as much power as I had thought I would since they hooked up the service, I'm a happy camper so far. It was -25c outside the other night and the shop was nice and warm.

 

[anthony666]

You're "welcome"