Ok, we are installing a new heating system in a rental property. The old unit was an oil-fired boiler with fin-tube baseboard convection. That system was vandalized, so we start from scratch.
We are installing a gas boiler; initially propane and then to Natural Gas when the gas utility gets around to installing the gas line from the main to the house.
The home is on a slab. We are planning to utilize Viega FostaPex (Pex-Al-Pex) in a series loop configuration for each zone (2). We don't want to trench the slab, so we are open to suggestions as to the best way to run the pex tubing.
The boiler will be a cast iron New Yorker CG-D Series 20 boiler. It's rated at 37.5 BTUH 31K AHRI & 27K IBR. 82.3% Efficiency. 2.5 gallon water content. Has pre- and post-purge control. It will paired with a 50-gallon BoilerBuddy buffer tank and a SuperStor 45 gallon IDWH.
The home has a calculated heat loss of 24,672 BTUH. It will be split into 2 zones; one for the living, kitchen and dining room areas (Zone-1 13,775 BTUH) and bedrooms and bathroom (Zone-2 10,897 BTUH). Programmable thermostats will be employed for each zone. Zone valves will be employed for each zone.
Design temp is for 72-degrees on a 10-degree day. Average water temperature is 140-degrees @ 1 gpm. Zone-1 flow is 1.46 gpm and 10.32 ft head; Zone 2 is 1.06 gpm and 9.6 ft head.
An outdoor reset control will also be utilized. As this will result in return temperatures below 130-degrees at certain times, we'll need a way to control the return temps and keep them above 130-degrees. We understand Taco makes a 4-way mixing valve (IO75T4R-1) to accomplish this and Tekmar makes a 402 control which would control a mixing device, zone valves and allow for separate IDHW control utilizing different supply and differential for both the boiler and IDHW. We believe you must use Tekmar thermostats to work with this controller.
We'd appreciate a few things:
Comments on this design and ways to implement it. We don't want to install a mod-con boiler due to initial cost (~ 3K vs ~1k), life expectancy, reliability and maintenance costs.
A way to calculate how to size each successive fin-tube convector as water temperatures drop in the series of convectors. The sizing in the attachment is based on 140-degree average temperature with no consideration for diminishing temperature as the water travels in series.
A schematic diagram of this layout, if someone has a program to do so, so we can provide it to our installer.
You can find this at this link: http://www.terrylove.com/forums/index.php?threads/hydronic-system-design-boiler-piping-control.58590/#post-432722
I'll try uploading the floor plan and fin-tube convector sizes and location. Z2 R1 is Zone 2 Radiator 1 (the first in that zone series). Scale is 1/4" = 1'.