Help selecting boilers and contorls

SM

I am looking for some guidance in possible equipment selection and design schemes for my churches elementary school.

Originally built in 1966, this small school has about 10,800 sq/ft and a gym/stage area of about 4400 sq/ft. The boiler is original and is one 1MM BTU output cast iron boiler. It had an outdoor reset control originally, which modulated a bypass valve that allowed return water to bypass the boiler (varying boiler water flow). The heat emitters are baseboard, fan coil units and unit ventilators. I have a copy of the original drawings and the submittal for the emitters, which were originally, design for 200-degree water with a total load of 1MM BTU load. The gym has two AHU, which run off a thermostat, and some baseboard. Each 4 classrooms have a combination of BB and UV. However the UV does not have a stat. Teacher has to turn the UV on or off inside the cabinet. The 2 offices, clinic, storage area and restroom have BB. Cafeteria has 2 UH. Also there is a warm weather shut down which does work.

So there is no stat in the school to turn the heat on or off. The janitor runs the boiler of the limit control to adjust the temperature in the school. If he feels hot he turns it down. If he is hot he turns it up. If it is suppose to get real cold at night he turns it up. He told me that he runs the water between 100-140 degrees if it is supposed to get real cold some times he adjust the limit control to 160 degrees. I am amazed that this boiler has with stood this operation for so many years. I don’t believe the boilers built today would take this operation.

This past winter I installed a data logger on the system. And he is correct in what he says he does. I monitored RWT, SWT, and OAT. The coldest night I ever saw was 10 degrees (design is 0 degrees). And the boiler was set at 120 degrees (Sat night no school). I also notice that even on the coldest night the boiler fired for about 8 minutes and was off for 26 minutes. Never did I see the SWT above 142 degrees.

So here start my questions?

1. If I use the data form the logger to help me size the new boiler or boilers I would say that the load is 1MM/(8/34). 1MM BTU’s/(boiler ran 8 minutes out of 34 minutes (% of time boiler firing)). If I use that number I come up with 235K at 10 degrees. So at design would appear 300K should do it with 140 degree water. Is it far to use these numbers?

2. If you did go with these numbers or whatever size you decided on would it not make sense to go with 2 or 3 modulating/condensing boilers?

3. School has limited budget or should I go with 1 modulating/condensing boiler and 1 cast iron with return water protection? Say a Trinity and a WM GV?

4. One thing I have been told is that to get the gym warmed up the school gets hot, so I am looking to re-pipe so that the gym is on its own loop. Then would run the boiler primary off of OAT reset, and the gym secondary to that loop, and then possibly use a variable speed pump and controller for injection into the school loop with a feedback from a sensor in the hallway. That way I could have constant circulation has would want to minimize the possibility of freezing up a coil. Would any of this make sense? What would you recommend for controls for the multiple boiler w/outdoor reset and the injection pump with feedback from the space?

5. I plan on adding stat’s in the four classrooms to control the UV’s. This should leave the temperature control with the teacher but automate it vs. turning a switch on or off in the cabinet. I will still utilize a time clock in the boiler room that locks out the UV on the nights and weekends.

6. I think I would really like to go with 2 Ti200 and DWH for the kitchen and 4 bathrooms. However I do not think that the Trinity will accept a remote modulation signal (0-10 vdc). Is this true? Any alternatives like using a signal converter and wiring it to the terminals for the out door sensor to get it to modulate?

7. I know that there is certainly a lot of money to be saved but do not know how much as there is only one gas meter on the property and there are 5 boilers (church, priest house, convent, old school (steam heat) and the hot water boiler in the building described). We are a private school with a limited budget and I have to be able to show that this is going to be money well spent. I major factor is planning instead of a breakdown and get whatever is available for a boiler and stick it in. We already have on quote like that and I need to convince some people that is not the road we want to go down. So I am also looking for a good resource for information to document whatever the plan maybe. Tekmar has some of the info a believe I am looking for.

Thanks for the help and I imagine this will spark a lot of question?