WM ultra optimun run time

Tom Saggau

I have a 2100 sf house with in slab radient.
The boiler is a WM ultra too large for the house (before they brought out the smaller ones-2002).
Adjusted fan speed for high altitude and fire.
Outdoor reset installed.
One thermostat in use (had 5), 15 circuits, under 220' each, all with flow control which are used to balance heat as desired to each room.
Temps in the teens at night, good solar during the day.
Normally do not have call for heat in the day due to solar gain. Evening, intermittent. At night (in the teens) boiler will run at set point (varies by outdoor temp) all night.
Propane usage is low.
Is the unit running constantly at set point to maintain the desired building temp (70) optimum for best fuel utilization?
Thanks and Happy New Year
Tom Saggau

Unknown

If the boiler is satisfying a load above its minimum modulation and it's running constantly with low temp water, congratulations, you're in the promised land.

What you don't want is a lot of herky jerky short cycles. With 2100 square feet of slab on one zone, that isn't very likely even if the boiler is a bit oversized.

J.C.A._3

Tom,

Broken down to the bottom line..ultimate run time is 0. That is when a boiler is at its most efficient.

Next would be to use the zones to dictate the desired temps, when THEY need it. Solar gain and drop is great...but the individual rooms/zones will rely on the "master" temp controller to run the show with only THAT 1 controller. If placed somewhere that will effect the whole home....It isn't a good "representative".Overheating and non-comfort will ensue....

A good ZVC and zone valve heads on a manifold could be the answer. Get the 5 thermostats working to give the loops that need the temps, what is needed...(with the ODR...the boiler and control WILL do it)and let the pigeons fly.

Let the boiler dictate how high it runs...while letting the Zone valve heads...wired to the ZVC, control each individual zone.

I hope this makes sense .I know what I want to say...but don't know if I've conveyed the jist.... Chris

Unknown

on an oversized boiler, without syncronization, more zones can reduce boiler lifespan and efficiency by creating short cycling problems.

A buffer tank or advanced controls can bypass that issue, and outdoor reset reduces it too, but in this case I would not advocate for microzoning without something to deal with the oversized boiler's larger minimum modulation rate.

Mitch_5

Ultimate load design

is to gain as you loose so the boiler should never shut off.

Reality is another thing but if you can get the curve way down and keep the boiler running on demand days you will be more efficient. The more you start stop the more in efficient you are.

Mitch S.

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