Pumping Fluid and Me Do Not Work Well

[DLausche]

I'm a bit frustrated. I plumbed up my radiant floor heat system today. Used 2 Grundfos circulating pumps in series to overcome the head of the tankless water heater used to heat the fluid. I think I've got all the air bubbles out of the lines. Turn the pumps on and get 2. 9 gallons per minute circulating. I think that's a decent flow rate so where's the problem? Well, the flow rate only goes down from here. Flow drops gradually to about 0. 8 gpm or so after about 3 minutes of running and that's not enough. Maybe 2 pumps in series is not so good of an idea and I should go with one 1/12th Hp pump instead.



Oh yea, the last 4 lift pumps on my truck work terrible too. I feel I understand fluid dynamics at least fairly well, but I must really be doin something wrong.



Anyone know of a decent radiant heat plumbing design resource where I can read up and figure out what I've done wrong?



-deon

 

[daytripper63]

I'm a bit frustrated. I plumbed up my radiant floor heat system today. Used 2 Grundfos circulating pumps in series to overcome the head of the tankless water heater used to heat the fluid. I think I've got all the air bubbles out of the lines. Turn the pumps on and get 2. 9 gallons per minute circulating. I think that's a decent flow rate so where's the problem? Well, the flow rate only goes down from here. Flow drops gradually to about 0. 8 gpm or so after about 3 minutes of running and that's not enough. Maybe 2 pumps in series is not so good of an idea and I should go with one 1/12th Hp pump instead.



Oh yea, the last 4 lift pumps on my truck work terrible too. I feel I understand fluid dynamics at least fairly well, but I must really be doin something wrong.



Anyone know of a decent radiant heat plumbing design resource where I can read up and figure out what I've done wrong?



-deon

How familiar are you with radiant systems, and whos components did you use and who did the lay out plans?

And I dont think you need a 1/12 hp pump. any systems I have sold for residential application did not use that much pump

 

[DLausche]

How familiar are you with radiant systems, and whos components did you use and who did the lay out plans?

And I dont think you need a 1/12 hp pump. any systems I have sold for residential application did not use that much pump

Not very. This is my first attempt at it. I've done a fair amount of research and it does not appear to be a complicated setup. I did the tubing plans myself with LoopCAD. The manifolds, pump, expansion tank, valves, etc are all from my local Menards. I actually just figured out what my problem was. The small filter screen on the inlet of the Takagi T-KJr heater was clogged with stuff from the lines. Nothing big - just small particles that were enough to clog the filter and stop all flow. Backflushing while trying to bleed air would unclog the filter but then it would just clog again when put into normal service mode. Anyways, I'm not sure if a filter is needed or advisable on these systems. If so, I think I need a lot larger filter than this puny little one that came with the heater. For now I've removed the screen filter and the system is working good - so far.



What temp should I set the heater at? It is still on the default (122*) and I think that is a bit too high.



-Deon

 

[daytripper63]

The proper water temperature depends on the way tubing is installed and on the type of floor covering.

Tubing under a tile floor will get by with 90F to 105F water.

Adding a carpet and pad will raise the minimum temperature to 130F.

An underfloor installation with carpet will require up to 160F.

Higher temperature means lower system efficiency, I dont see many running at 160F.

Never turn your thermostat too low, you now have a very efficient heat source and by turning the homes t-stat too low or off cause you may be gone for the weekend or ? can actually cost you money or maybe just be equal, the reason is if you let it get too cold then come home and try to heat the house back up the system will use more BTUs than if it just cycled regularly to maintain a REASONABLE temp. or setback temp.

 

[daytripper63]

What type of floor do you have? Concrete ,and is the radiant in the concrete or wood with the pex pipe on top of then a filler poured over all or is it installed under a wood floor?

 

[Alphacowboy]

its in his garage, pipe was layed over 2" thick styrofoam, then I believe 3-4" of concrete over that.

 

[daytripper63]

its in his garage, pipe was layed over 2" thick styrofoam, then I believe 3-4" of concrete over that.

O. K. if its just the garage I would not worry to much about temp setbacks when not occupied, that applies more to in home radiant. Although there are times that I occupy the garage far more than the house :-laf varies between hobbies and wifes attitude:-laf

 

[DLausche]

Yep, concrete about 3. 5 inches on top of 2" pink foam board. It's my new garage/workshop area. It took 3 to 4 hours running nonstop to warm up the concrete but now it is warm in there and the heater has been off for several hours. I set the heater temp output at 110*. The water heater modulates the burner really nicely and keeps the output temp right where it is set to. I am very glad I went with this heat setup. Wow, it is nice in there. I can easily stay the night out there if/when I need to. I may set the temp a few degrees cooler than I do in the house (forced air heat) because it feels warmer because of the heat coming off the floor. I can tell it is a lot more evenly distributed.



Next year I plan on adding baseboard radiators in the Wife's garage. I'll have to replumb it then with a primary & secondary loop and mixing valve for the radiant so I can get hotter water in the baseboard loop than the radiant loop.



This is me now ->



-Deon