Hi guys,
Looking for some insight to my project.
Background:
Purchased a home last year which has a fairly complex heating system and after all the tinkering I have done I think it is a poor design. Have also concluded that it was very poorly maintained and installed.
So its middle of February in Alberta -30C my Original boiler (NTI TI 200 installed in 2012) goes down on low system pressure after my glycol make up tank pumped dry. Luckily with gas fireplaces on upper and lower levels the house kept warm. After hours of troubleshooting (being new to hydronics) I concluded the heat exchanger had failed.
Working hastily since I had no DWH, radiant, or forced air heat I installed a new Weil McClain boiler WMB-155h that I got a great deal on. The replacement heat exchanger for the NTI ti 200 was going to cost almost 2x as much as the new boiler not to mention that model is discontinued.
The new boiler is installed and working and I feel that downsizing the boiler was a good move since it is keeping up in the cold.
The system is piped primary/secondary with the primary loop handling priority DHW through a 40G indirect tank. The secondary loop has a fan coil and 5 radiant zones with the fan coil first to pull from it. Primary and secondary pumps are 3 speed Grundfos 26s and the 5 zone circulators are a taco 006. The fan coil is a lennox AM-30 and has its own built in taco circulator as well.
Questions:
1) The fan coil needs high water temps to be effective heating the upper level of the house. I have been running water setpoint at 150 - 160 and its working but its not allowing the return temps to be low enough for good efficiency, especially when the radiant zones are satisfied. With the outdoor reset connected the fan coil runs for ever, never reaching temp upstairs. Is there anyway to make this work properly? I feel the only way to make this system most effective and efficient is to eliminate the fan coil and install a HE forced air gas furnace. We are frozen 6-7 months of the year and its nice to be comfortable without wasting energy. The old boiler ran its whole life at high temps being poorly configured and I believe it took years off its life and wasted lots of fuel.
2) Also, when DHW is called to the indirect tank, I needed to limit the max modulation to keep the boiler from short cycling as it was overshooting the setpoint. It doesn't cycle now but will run at 170 steady until its satisfied. Even know it takes a matter of minutes to satisfy the call wouldn't it make sense to run cooler temps like 120-130 and run a little longer to make the boiler more efficient?
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