Between joists radiant heating system new install.. Please advise..

hagani

Hello everyone,
I am new here so please don't be too hard on me.. :-)

I am in the process of planning installation of the between the joist radiant heating system in my basement just below the kitchen. It will have 2 loops 1/2 Pex with transfer plates. Each loop is approx. 200ft. Both loops will hook up to SS 3 loop manifold (I want to have an extra unused loop on the manifold just in case). Manifold looks like this one:




I have an existing baseboard heating system for the whole house that has 2 zone with two TACO 007 circulators. I planning to add another Taco 007 circulator for the floor system. So now are my questions:

1. Will be one additional Taco 007 sufficient for 2 loops total of 400ft length?
2. Do I really need a mixing valve or I can just run a supply from the boiler (approx 150F)? Whats bad about going a little hotter than recommended 120F for floor heating?

I forgot to mention that I am not a plumber or HVAC technician, but I am very handy and do most of the work in my house myself. The existing complete outdated heating system I did convert 5-7 years ago from oil to gas by myself for example.

So any help/advice/critique will be appreciated.

Thanks in advance to everyone

Ironman

Here's some recommendations:
1. I wouldn't use a cheap Chinese manifold like that: they're notorious for leaking. Leaks are the #1 enemy of any hydronic system.
2. The Taco 007 should be more than sufficient.
3. You absolutely need the mixing valve. You should never have above 120* SWT to a wood floor. The pump must be placed between the mixing valve and the manifold drawing from the mix port into the pump.

hagani

Ironman, thank you very much for your quick input on that.

Follow up questions if I might:
1. Which manifold would you recommend?
3. I have a really thick subfloor/floor in the kitchen - 3/4 tongue and groove boards (this is an old house built in 1955) then 1/4 plywood and then 12x12x1/4 thick. Will be 120F enough to heat up this thickness?

Thank again!

Ironman

Let's start from the beginning. Is the floor gonna be the sole heat source for that room/area? If so, proper design is essential to making it work. That starts with a scientific heat loss calculation to determine how many btus are needed. That is the foundation for the entire design.

Then, loop lengths, spacing, heat transfer plates, pump and pipe sizing, SWT, etc. are calculated to determine how much heat the floor can emit.

SantFin has a free app that you can download to calculate the heat loss. If you'll choose the correct construction data and enter the correct dimensions, it will do the rest.

hagani

The kitchen is 25x12 and I have a 12ft of baseboard heater SantFin type along one wall an 7ft along the other. House is old and I am sure wasn't insulated properly in 1955. Wall that has 7ft baseboard panel is exterior wall that has 2 windows and door to backyard. But 300sqft of tile floor plus granite countertops really make it cold in the kitchen.

GroundUp

As far as the chinese manifolds go, I'm going to have to respectfully disagree with Ironman. I have seen dozens of the high buck Watts, Viega, Uponor and Rehau manifolds leak like a sieve within only a couple years. That is the reason I switched to the chinese junk about 4-5 years ago, and honestly have not seen a single leak that wasn't my fault. I've got 150+ Rifeng and Bluefin manifolds in service since the switch and they've been nothing but great for me as well as several dozen systems using them that I've serviced. I wouldn't be the least bit concerned about them

hot_rod

Not many of the radiant tube folks build their own manifolds. Most are rebadged from a brass or stainless manufacturer. I suspect many stainless manifolds are made in China regardless of the sticker applied

I doubt many, if any boilers, don't have a wide selection of made in China components, especially electronic circuit boards.

China is certainly capable of building quality components if you gat a handler on their quality control.

Rifeng has been suppling PAP, fittings and manifold to many US radiant companies for a few decades now.

I would stay away from a no-name, low price product regardless of country of origin. If you buy from a "known" radiant manufacturer you should have support if ever needed.

hagani

One follow up question..

How to control temperature with between joist radiant system? Where sensor for the thermostat needs to be installed? Can someone recommend a thermostat (brand/model) for this purpose?

hot_rod

I always used the Uponor, although not this newest version. It may have been a re-labeled tekmar, shop those two brands for the features you want.

https://www.supplyhouse.com/Uponor-Wirsbo-A3100101-Heat-only-Thermostat-with-Touchscreen

It's nice to have air and sensor capability. The sensor should be under the floor, between the plates would be a good position. Install it with conduit so it can be changed or replaced some day.

hagani

Thank you Hotrod,
I also heard that sometimes sensor is being installed on the return side of the manifold but don't understand how this is should be figured out. Also do I need a programmable thermostat for radiant floor?

hot_rod

If you are using the sensor to sense floor temperature it's best to have it in or under the floor somehow. The thermostat will have an air temperature sensor.

You can use the floor sensor several ways. Set the desired air temperature, then set either a not to exceed or not to fall below temperature.

Mainly I used the floor sensor for customers that wanted warm floor even when the AC was running in the summer months, just idle the floor at around 80°F or whatever suits you. Keeping in mind it does add load to the AC system

In some case with special flooring the sensor could be a limit to prevent over-heating. Glue down vinyl flooring for example.

Floor sensors could also be used if the stat cannot, or doesn't need to be in the actual room. However with floor sensor only, the ambient temperature could over-shoot on mild days.

I use programmables only for spot heating, say a small electric zone in a room that has other heat. A home with forced air that has some radiant bathrooms for example. Warm them up before you get up and shower, etc.
Best to find the comfort zone and let the floors run without setting back in a home with radiant in living areas.

If you have a schedule that has the home empty for extended periods the wifi stats are nice for setback and monitoring when you are gone. Ecobee and others have additional sensors for use with floor systems.