replacing hot water heating system

Gary_9

Subject: Replacing hot water heating system

I live in Ansonia CT & have a 45 year old house with an old Burnham hot water boiler & tankless coil DHW with an Oertli replacement oil burner. There are 101 feet of copper fin-tube baseboard with one thermostat. I want to replace it with an efficient, economical system that will last well. I used www.hvac-calc.com to calculate my heat loss at 47,305 BTUH. I have done some research & selected what I think is a good system. Some professional advice would be much appreciated:

The system plan as it stands is:
Crown Freeport CT-3 three pass cast iron boiler with a Beckett AFG burner & R7184 control
Crown MS-40 stainless steel indirect DHW tank
Tekmar 260 control will allow cold start, (partial) outdoor reset, DHW post purge, DHW priority (would like DHW setback & zone purge as well)
One programmable thermostat & two standard thermostats (The three zones that will be created all currently branch off within 6 feet of the boiler.)

Several sources have advised a primary/secondary loop system to protect the boiler from the shock of initial cold water rushing in & to allow full outdoor reset. Is this really necessary &/or a significant advantage? Is full outdoor reset really only necessary for slab heating? If it is advisable, what method of mixing is wisest? I have seen three pump systems where the speed of the pump between the primary & secondary loop is varied to facilitate mixing. Other systems use a mixing valve. What is best?

If the primary/secondary loop is the way to go, it would require a different control. Anyone have advice?

The Crown DHW tank comes with an aquastat; wouldn’t it be better to have a sensor that the controller uses for feedback & decisions?

Is it any real advantage to use an outdoor air supply?

The Riello burner available for the Crown is more expensive & shows slightly better efficiency. I could not talk to or email anyone from Riello. My oil man does not like them & several other people have made comments that make them seem fussy. Are they reliable? Are parts & service readily available, or will having one limit my service company options?

Who should do the installation? I have been talking with a plumber who specializes in boilers. He proposes to do the installation & have an electrician wire the thermostats, zone valves etc. He is leading me away from the primary/secondary loop type system. I do not just want a boiler installed. I want someone who knows these advanced systems. Is there another type of professional that I should be contacting? If you are one, or know of one in my area, please contact me.

Any general observations or advice would be welcome.

Gary

Bill Nye

Gary

It sounds like you have done some research and have a good plan. It depends.

You ask a lot of good questions. I'll pick on a couple."Is it any real advantage to use an outdoor air supply?" Yes! The air has to come from some where and the oil burner is not polite and will take the air from any where it can get it. This is not opinion it is a law of physics. It will take it from around windows and doors creating drafts and infiltration of cold outside air. Conditioned air that you already paid to have heated. So yes dedicated combustion air inlet is desirable.

Riello burners are good. People who have not taken the time to learn to service them are very limited. Parts are readily available. I would not be comfortable with an oil man who doesn't like riello.

You do not have to use the aquastat that comes with the indirect if the Tekmar sensor is available.

If you do the outdoor reset you will experince a level of comfort you never had before. Near constant circulation and a warm house with no temperature swings, no expansion noise, and no drafts.

Primary / secondary piping should not add a great deal of expense to your project. Another pump and a couple of tee's. A boiler by-pass loop could help with thermal shock. BUT , if you are doing reset and constant circulation this shock issue is not a real problem.

Joe_13

The 260

can do DHW setback. It will also continue to run the circ on the indirect zone when starting the heating zone pump after DHW priority to mix some hot return water with the cooler water returning from the fin tube. You still need an aquastat on the water tank to trigger the DHW call for heat. You only get the outdoor temp sensor and you can get an optional indoor sensor for setback use. Checkout the www.tekmarcontrols.com web site for the control description.