DIY Radiant heat questions

tommygags

Hi everyone. Recently installed a closed loop radiant heat in the ceiling of my crawlspace using heat transfer plates between the joists, 1/2" hePEX. I just finished zone 1, which is total 660 sqft, 4 loops, combi water heater. 

I have 3/4" hePEX going from the return and supply to the manifold - does this need to be 1"?  Will 3/4" be ok for my zone 2, which will be 5 loops over 850 square feet?

In terms of manifold piping, does each loop need to be in reverse? First in supply should be last in return?

My Manifold does not have glass flow valves, is it needed for me to get the length of each loop to figure out which loop should get more flow?  Is it the longest circuit that should get the most flow? I have a uponor truFlow manifold jr. 

What speed setting (1-3) should I set on my circulation pump? It's a 1/25 HP pump.

I've set it up and running, 140 degrees at water heater, 130 degrees on supply manifold and 110 on return manifold. 

Thank you! This was my first heating DIY. 

Zman

I think more design info is needed.
How long are the loops? Is there a designed flow rate?
What model pump?
How long are the lines feeding the manifolds?
How is the boiler piped?
What model 3 speed circ?
Are you using outdoor reset?
Pictures are always helpful.

tommygags

Thanks! 

All loops are under 300 feet. I'll have to measure exactly, but all loops should be about within 30 feet +/- each other. The actual loops, not. Including going to and from manifold are about 250 ft each. If I am supposed to include going to and from manifold, all are probably closer to 280 feet, except the center loop, which would be 250 ft. 

Designed flow rate was 3.75 gpm. 

Lines feeding manifold are about 20-25 feet each, supply and return.

Boiler is piped with 1 inch copper.

Pumps are Grundfos UPS15-58fc, 3 speed, 1/25 HP, 115v

No outdoor reset

Zman

3/4" pex will work fine at 3.75 GPM.
With the loops within 10% of each other you can run them all at the same rate.
I wouldn't get too excited about reverse return.
You will probably need speed 3 with both zones calling.
Outdoor reset makes the system more comfortable and efficient. Run the sensor wire...
Make sure you follow the manufactures instructions especially the pressure relief valve. Don't blow your silly self up

tommygags

Thanks again for your response! Makes me feel better about this project!

I actually have that same pump for zone 2, so one pump per zone, would you suggest I lower the speed then?

Do you have an outdoor reset you recommend? I'll have to do more research on this as I just started to look it up. I have a navien combi gas tankless water heater. 

I will be using a tekmar tstat with a floor sensor as well. 


Thank you for the safety tip!! 

Zman

Speed 2 should work nicely. You may be able to run it on 1.
What model boiler do you have? Most have built in outdoor reset.

tommygags

Perfect, I'll try speed 2. The higher the speed, the higher the water temperature would travel longer, so the supply and return temps would be lower on speed 1 vs 3? Just curious.

  I have the NCB-240E

hot_rod

Should have outdoor reset onboard, do you have the manual? If not download one at their site.

tommygags

Thanks! Looks like they sell the sensor and I would program the info on the unit. 

You guys are the best!

tommygags

Based on the attached, from their manual, would you both suggest 'low mass Radiant'?  My system was designed to have the water temp at between 120-140 degrees.  Wood flooring

tommygags

Just  wanted to bump this last question up, thanks again!

hot_rod

Yep

tommygags

Thanks Bob and Zman! Appreciate all the help. Just got the sensor today. 

tommygags

Hi Bob and Zman. I just completed my 2k square foot, 2 zone system! Everything is working great, just had a question on my floor sensor temperature setting. The sensor is located below the subfloor, which is double plywood and then my wood floors. Should that subfloor sensor still be at at Max 80 degrees?  Also, should the system be running pretty much 24/7 and only have about a 5 degree tstat setting difference at night vs daytime?

Zman

I don't think that the temp of the area under the subfloor will be very telling, I think the sensor will need to be closer to the surface.
Running at low output for long cycles is great.

BTW, if you use @tommygags , the recipient gets notified.

hot_rod

You would need to, play around with settings to factor in the temperature difference below the subfloor and at the surface. So maybe 5 or so degrees warmer needed to get the surface you want.

I have carefully drilled from below, thru the sub floor to get a sensor closer to the finished floor, if that is an option.

As far as run time, the system will, should run until it meets setpoint. If it is not keeping or catching up, may need to increase SWT to the floor. The double subfloor is working against you a bit.

SuperTech

I'd avoid setting back the thermostat at night.  Find a comfortable setpoint and leave it there. Low mass radiant isnt meant to operate with setbacks usually. 

tommygags

Thanks everyone! I'll get that floor sensor closer to the bottom of the actual floor. 

Right now the sensor is showing around 88 degrees (attached to the bottom of the subfloor) and the actual temperature of my hardwood floor is around 73.

@Zman @hot_rod @SuperTech thanks for your help.  One last question: would having the subfloor (plywood) at 88 degrees be a concern? Or it's the finished Wood that shouldn't be above 80-85 degrees?

hcpatel78

That's quite amazing that you are getting 73 at floor even you have two layer of 3/4" thick plywood...Did you insulate under neath in between joist after tube and plates install in crawl space?If yes then what type of insulation and what is R value?
I am about to finish my installation and will start up my system soon. Which state(or temperature zone) are you in?
Thank you,

tommygags

Hi @hcpatel78, I have 2 zones and did not finish zone 2 with putting back the insulation, but this morning on a 20 degree morning (located outside NYC) I was getting Mid 70's on the surface floor without any insulation - SWT was lowered to 125 degrees. Now that the outside temp is 40 degrees the floor surface temp hit 80 and (subfloor plywood was 91). My other zone has its insulation back up, it varies from R-15 (mostly) to R-30 fiberglass. I also did staple up the reflective barrier over the plates as well.

hcpatel78

@tommygags Nice..I am in Northern NJ so we are probably in same temp.zone....be careful not to ruin your hardwood floor with above 80 f temp

hcpatel78

@tommygags any update after your system startup? Any fine tune of supply water temperature & effect of that etc... I just started my system and wanted to ask you about your experience...

tommygags

Hey man, haven't messed with it too much yet since it's been pretty warm out. Trying to focus on keeping my boiler in condensing mode by keeping the return water 80 degrees or less. Right now my supply is 125, but plan on lowering that to 120 to see if that gets me to the 80 return.  Need to move the sensor closer to the actual floor still and then be able to accurately set the tstat. How's your system going? 

Do you know if the plywood subfloor can handle the 80 degrees temp and it's the finished hardwood that can't? 

But already I'm loving this heat vs my forced air, so much warmer!

hcpatel78

Are you playing with flow rate to bring return water temperature around 80 F?
About plywood temperature questions, I never thought. But hard wood I am sure it can't be above 80 F for most of the hardwood flooring.

hot_rod

Certainly wood floors in a sunroom get well above 80°.

Launstein Hardwood did a lot of testing with hardwoods years ago for the RPA. The humidity is the biggest influencer of wood flooring issues.
The RPA published a Flooring Guide for years, probably still on the website.

Surface temperature has a lot to do with comfort. Above 80- 82° it can become uncomfortable, cause your feet to sweat. Some good reading here.

https://www.launstein.com/relative-humidity-and-hardwood-flooring.html

http://www.healthyheating.com/Thermal_Comfort_Working_Copy/Definitions/floor_temps.htm#.X75u1y9h2IE

hcpatel78

Very informative study....Thank you Bob,
Hiren

tommygags

Thanks @hot_rod !

tommygags

Hi, @Zman @hot_rod just wanted to send thanks again for your help! I just installed the ODR today and used the default settings for low mass. Anything you suggest I keep an eye on or just set it and forget it?

Also, wanted to see if you had any experience with the Grundfos Alpha 2 high efficiency pumps? Wonder if it's worth upgrading my Grundfos UPS15-58fc since I just installed this system and plan to use this for many years. 

Zman

The default should get you close. try turning it down to see how low you can go.
The Alpha has the same pump curve as the 15-58. It would be a nice upgrade in a zoned system.

tommygags

Thanks @Zman!  I actually have one pump per zone, if that's the case, would you recommend not getting the alpha?

Zman

I don't think the alpha is worth the money as a zone circ.

tommygags

Hi, @Zman @hot_rod hope you've been been well and safe! Another thanks for all the help last year, really enjoyed my system! I had one question:

I just realized that with the outdoor temperature reset sensor set to low mass, is good for my 1st floor radiant heat, but what about my 2nd floor forced air heat? Will this setting be too low for the forced air? Any suggestions?

Thanks!