So ive done a lot of research about this topic...talked to guys in the field....customers of mine who have converted, but still not sure about the boiler. The first one i had in mind was the Embassy Onex combi boiler. Seems to fit the bill, good temp rise on the DHW, straight forward install good price. But now im wondering if going with a Triangle Tube Solo 110 or a GB142 with 40 gallon indrect would be a better choice? Did some math on the comfort calc web site and says i could do ok with a 27 gallon. I will be adding a third zone in the basment to bring to total to 3 zones not including the indrect. Our house is 1400 SQ and 5 years old. Last person said my heat loss is around 67,000btu (this was the guy who wanted to install a EK2000 system). I like that the Onex i can program to only fire to 80,000 or what ever, but im not sure if it will be a wast to heat DHW ondemand as needed or to store it. Sorry for the long winded post... Any thoughts would be great! Ben D Cost wise the Onex is cheaper as it has a built in boiler circulator, so i would need on the pumps for the zones. The TT or GB142 run more when you add pumps, controls and a tank.

I am trying to determine the pump size and set up for an old gravity piped system. The system has an oil fired Burnham 125 btu steel boiler. The near boiler piping comes off 1 1/4" and reduces to 1", has a Taco 007 F5, and then there are three runs on two zones. One run goes to first and second floor on the front of the house and is 3" horizontal (pitched) supply and return with 3/4" runs to the radiators; the second run is on the same zone and piped the same as the first run but goes to the rear of the house first and second floors. Both runs are piped from 1" from the near boiler piping to 3". There is an added third run that is not gravity; it is 3/4" looped running to old base ray base board. The first two runs are on one 1" zone valve and the base ray zone is on a 3/4" zone valve (both zone valves are wired together so they are all working off of one zone/thermostat right now). Hot water is made separately in a gas hot water heater. I didn't measure the radiators to determine their btus, but the house is about 2000 sq feet and I am estimating that the front and rear runs have about 50k btu of heat emitters each. There was no light in the boiler room so the pictures did not come out at all. Problems: The system is not balanced at all, and with all the cold water in the large pipe and radiators, the call for heat takes almost an hour just to get the water in the system up to temperature. The circulator short cycles while the water is heated. A boiler install company did the Burnham install seven years ago and the customer lived with it until now. She is on a fixed income and looking to corrrect it without spending much money. She will consider spending a little more if there is clear fuel savings in the short term to be achieved with the corrections. She can't even afford small piping changes, so we have to pick the solution very carefully. Looking at it, we have determined that that the the size of the pump (one 007) and having a single pump for the three runs of different sizes is not right, and the 1" near boiler piping is wrong for the btus needed. If I had my way, I'd take out the 3", split the runs by floors and put them on separate zones, an outdoor reset, a mixing valve and other neat things, but the budget is not there. The plan right now is to re-pipe the near boiler piping 1 1/4" to a pump manifold and then set it up with a separate pump for each run to solve the flow issues. We were going to keep the 1" to 3" piping for front and rear runs. We figured a 007 for the 3/4 base ray zone and the front and rear runs each get a 010 pump. We were also thinking of just running it cold start to eliminate the circulator cycling issue. Questions: 1. What size pumps should we use on the 3" runs to get the water moving around properly? The water is choked down to 1" from the pump for about two feet to the 3' pipe. 2. Should we convert it to primary/secondary to deal with the volume of water and the delta T of the returns (and can we even do that within budget and have customer heat savings to recover the cost)? 3. Should we run a boiler bypass to fix the problem of the delta T of the returns, maybe even with a mixing valve? 3. Should we set it up with an oudoor reset on a budget (Tekmar is not budget friendly)? 4. Should we run it cold start (It has a 7124 with low setting disable), which will let the circulator run on call for heat regardless of kettle temperature, which will resolve the pump short cycling from the cold water return/ Delta T issue, almost simulating outdoor reset to an extent by pumping colder water through the system and heating all system water evenly rather than heating the kettle and having Delta T problems on the returns? Long thread! Thanks in advance for your input!