Outdoor Boiler Reset w/Indoor Space Temperature Set Back

Chuck_20

I am little confused as to any benefits of using outdoor boiler reset with Space temperature Set Back.

Wouldn't the boiler run longer to try and bring the space to temperature during occupied times?

Does this offset the energy savings?

If not what would the percent energy saving be using this type of system individually and together?

Any information would be appreciated

RoosterBoy

setbacks with outdoor reset should be kept to a min to ovoid long catch ups. witch take longer because your running lower water temperatures.

also outdoor reset is good because with out it your burner will keep running from the time your t-stat calls for heat to the time it is satisfied. with this you can use set backs.

with out door reset you save because the burner runs just enough to keep the water at the temperature you need to heat your house on that day. i use constant circulation

good luck
Jason

Bill Nye_2

reset

You are already conserving energy by using and out door reset control. Night setback [or I prefer daytime setback] is not a real waste because you are still heating and still circulating water , only at a reduced temperature.

So, no "cold boot" when you restart to higher temp. The longer boiler cycle is negligable in this case because we are only talking about a few degrees°.

The longer boiler run time is most efficient. When you frequently stop and start a burner you produce more soot and emmissions. Steady state is the most optimum performance.

Comfort is an issue here too. I do not heat my home because I like to spend money on fuel, I heat it for the comfort of me , my family, and my pets. I work very hard for a living usually out in the elements. When I come home I want comfort , not a cold castle.

Unknown

boost

some good controls (ie. tekmar) feature a boost function which cranks up the temperature above the normal reset temp to bring the system out of setback.

Doug_7

Outdoor Boiler Reset with Indoor Space Temperature Set Back

Chuck - It may be helpful to think about how these two different methods save energy and money.

Outdoor boiler reset saves energy by reducing the temperature of your heating water in warmer weather. This avoids boiler short-cycling and lets your boiler run longer, more efficient cycles. With the heating water piping at lower temperatures, it also reduces unwanted heat losses.

Space temperature Set Back saves energy in an entirely different way. By reducing the space temperature of the house when you are away, you reduce the heat losses from the house and reduce the required heating load. The heating plant is there simply to replace the building heat losses and maintain a constant living temperature as per the thermostat setting.

If it is 70 degrees inside and 20 degrees outside, there is a 50 degree temperature difference or driving force for heat loss. If you reset the thermostat to 65 degrees, you reduce the driving force by 10% and reduce the building heat loss by 10%.

If you reduce the thermostat setting by 5 degrees for 8 hours you will save 10% on your heating requirement for about 6-7 hours because of the time required for the house to cool down and heat back up.

Yes the heating system will run harder recovering from a set-back but you will save more energy during the cool down and while running at the lower set-back temperature than you will use heating back up.

To avoid "comfort" issues, the time for full recovery needs to be gauged and allowed for - deducted from the setback time. This is why automatic set-back thermostats are the best bet - so you can set the recovery time to start sufficiently BEFORE you expect to come home, so the house will be comfortable when you arrive. Some thermostats can do this automatically.

hydronicsmike

Hello Chuck

Yes, Night Setback does make sense when used with Indoor Feedback and is efficient too. I would like to chat about that with you over the phone if thats alright. I am currently in the UK, but will return on Monday. I would be more than happy to explain why and how it is more efficient if you called me at the office on Monday at 250-545-7749, Ext. 214.

In the meantime, you can read up on tN4, our latest product line at www.tekmarcontrols.com.

Looking forward to hearing from you.

Regards,

Mike

Chuck_20

Thanks for all the responses

It sounds like the thermostat feedback control would work best for maintaining comfort and provide the quickest room temperature recovery.

Additional cost for the feedback controls would then need to be considered vs. starting the boiler earlier and increasing the runtime.

Have there been any studies to determine actual energy savings vs the additional cost for controls?

We are currently looking at installing a Taco zone control system with boiler reset, utilizing programmable thermostats for the indoor temperature control.

Thank for the Information

Doug_7

Setback Cost Savings vs Cost of Controls

There is lots of information on cost savings due to thermostat setback.

http://www.mge.com/home/saving/thermostat.htm

http://www.warmair.net/html/thermostats.htm

Cost of controls is minimal. Just use programmable electronic setback thermostats for your indoor temperature control and all the rest should look after itself.

At the start of a setback, the boiler will just see a drop in heat load and will automatically cut back or shut off. During the setback the boiler will run under reduced load. At end of the setback, the boiler will see an increase in heat load and will crank up the heat.

Don't make the controls too complicated.