Advice on operation

Dave_4

given is slightly confusing as he gives 90 degrees as the initial water temp before it fired up. Surely the house was not at 90 degrees all night-so it had fired up a little earlier during the night as well. It sounds like the TT comes with the curve ODR set for 140 degrees max at the temp he had when he checked this data. That is a good max as condensing is encouraged (I assume the TT 110 is a mod/con?). Shouldn't he be checking the number of cycles too?

Eileen Olive

Advice on Boiler Operation

Have a TT 110 running. Outside temp 32*, t-stat set at 65*
Boiler fired up at 7:26 PM, water temp before start was 90*
At 7:46 Supply was 124* Return 100*
At 7:50 Supply was 130* Return 108*
At 7:55 Supply was 136* Return 114*
At 8:00 Supply was 140* Return 120*
At this point she shifted to low fire, Supply 132* Return 122* and continued running until 8:30 PM
Is this about right for the unit? All told, she ran for about an hour. It's my first mod/con boiler, so I have to ask

Brad White_191

Normal

The operation sounds normal but it all really depends on your heat loss, the radiators' sizing relative to that heat loss and of course your outdoor reset curve.

You will find over time that the initial warm-up will have a wider delta-T and this may narrow as the space warms up.

So long as the water temperature supplied to the radiators heats the place and is as low as it needs to be to do so, you are going to be OK.

Eileen Olive

Thank you Brad

Yes, the initial warm-up does take a bit longer, but the house feels fine. As for the curve on the ODR, well, I am totally unfamilliar with that. I simply mounted it per directions and wired it in to the assigned terminals on the boiler. I notice the boiler runs a good period of time circulating the cooler (130*) water, which tends to keep the house warm once warmed initially. I would like to get the most from the boiler's options and tweekings, if at all possible.

Brad White_191

To find the ideal heating curve...

Jim, I trust you calculated a proper heat loss and if not, do so. It still has value.

Once you have room by room heat losses, assess your radiators. Know the EDR or equivalent heating surface.

Divide a room's heat loss by the SF of the radiator which serves it and do this for all rooms and find the room with the lowest "radiator to heat loss" ratio. That is what will set your highest required average water temperature on the coldest day.

Say you have a room with a 5,000 BTUH heat loss and a radiator with, say, 45 EDR, or 111.1 BTUH per EDR. This means you will need about 151 degree water on average- I suspect 160 supply would do nicely.

From that information you can find tables which will tell you what that water temperature needs to be. That is as high as you need and it will drop from there as it gets warmer outside.

A little more to it, but one has to start somewhere. If you set your highest temperature too high (and you have surplus radiation), your boiler may cycle too much. You want long, slow steady burns.

Regardless of the above, play with the curve settings- drop them as low as comfort allows, waiting a day between adjustments. That is the real test. But it is good to know which of your room radiators falls short if any.

Eileen Olive

Thanks again

Thanks again, Brad. I tried once before to do a room by room heat loss calc, but the house is severely over radiated in most rooms. So I decided to go the whole house route. I see what you mean though, and I will now sit down and run a room by room calc. Eventually I intend to install TRVs on almost all the room radiators and CI baseboard. Step by step I am trying to improve this entire system as best as I can. I must admit, this new mod/com boiler is nothing like the old CI workhorses of decades past, watching & listening to it change pitch is amazing. Any suggestions or ideas I am happy to hear.

Eileen Olive

True enough

I presume the boiler had fired previously and had cooled to where the t-stat called for heat again. As for how many cycles the boiler runs during a 24-hour period, I have no clue. Nor do I know how I might find out the number of cycles and length of each heating cycle. I believe it would be very helpful to have these figures, but I do not.