[Vlad]

To be reasonable or Follow your goals

For DIY projects it is very important to set your goals and keep them in mind. Your goals must be reasonable. If your priority is budget then think about pay back. Many "efficiency benefits" have pay back period of 20-50 years.

Here is my example. Few years ago I got professional heat loss calculation for my house (4200 sqft) It is over 54000 BTU. Again, it was done by professionals using very sophisticated software. Everything was taken into consideration (type of windows and area, wall insulation, roof insulation.... you name it)

Last fall I was getting ready for winter and wanted to start using radiant floor heat in a portion of my house (3000 sqft). All my calculations were based on that darn 54000 BTU heat loss. After reading this thread and many others and my drilling straggle I realized that I can't go geothermal. So I gave up (but because I am stubborn I just gave in...).

At one point I started thinking what if I go air source HP? But after reading about floor temperature required (adding floor TD, HX TD) I realized It is impossible to have that much temperature rise especially when your demand at max and outside is at low.

I have HWT which is natural gas power vented 50 gal 34000 BTU input. Considering its efficiency of I guess 70% the real useful heat output is in 24000 area or 2 ton. I knew it was kind of small for domestic HW (after long shower sometimes I can see temperature decline) and heating at the same time. So I made some changes:

1. added mixing valve. It allows to raise temperature without compromising safety (we have 2 small boys and safety is a highest priority)

2. I added second electric HWT (80 gal monster) which is used only as a storage tank. It does have one 4.5 KW heater that can be used in case of emergency.

I have good control system for radiant floor: outside temperature reset variable speed pump control few temperature sensors 12 zone manifold. This system helps keeping temperature in comfort range also it adopts to outside temperature.

Now some observations:

1. Only on coldest days HWT runs 1-3 hours at the time and takes a break !!!!!

2. I calculated gas usage based on 3 year data. Now we use even more hot water and gas drier(60000 BTU unit) (with 2 years old and 6 month old you need a lot of water)

3. On warm days HWT does nothing like before.

4. Water temperature in underfloor loop most of the time in 82F-85F range (return 5F degree lower). Only on coldest days I saw temperature going up to 92F-95F.

5. This is very cool one: our gas bill went up by about 100$ a month !!!!! For 3000 sqft it is not bad at all (remember 70% efficiency)

6. Radiant floor pump most of the time runs in low RPM range(it is controlled by speed control). Many suggestions largely oversize pump.

7. I saw many people were complaining about air problem in radiant floor. My manifold is located in basement and top floor is 20 feet higher. System runs absolutely noise free (except some humming from pumps in basement). Absolutely no problem with air (I did added air scoop and air eliminator)

Now having all this data I need to make many corrections.