A friend has radiant heat with outdoor reset.

DanHolohan

His fuel bills are high and he had a company in to do an analysis of the house and a blower-door test. They suggested that he abandon the outdoor-reset control in favor of a control that would reset solely on indoor temperature. They said he could save between 10-20% on his fuel. They don't sell the controls, or anything other than the inspection and evaluation. They just made the claim, and in writing.



Have you had any experience with changing to this sort of control, and were these the results you saw? Thanks.

CMadatMe

Not Specifically

Dan,

Haven't seen too many applications or heard of to give you an anwser. In my experience I try using set point type controls (Wirsbo 511) in every job I am involved in. If your not familiar with the control is has a floor sensor but it also has a air/indoor sensor.  I use it 100 percent of the time for kitchens and rooms with solar gain. It is a version of indoor reset but not 100 percent indoor reset.

When operating the air and slab or floor sensors concurrently, the controller calculates an on time for the Heat 1 relay to satisfy the slab or floor sensor’s requirements and on times for the Heat 1 and Heat 2 relays to satisfy the air sensor’s requirements. The controller operates the Heat 1 relay for the longer of these two on times. While the minimum slab or floor temperature is satisfied, the on times of the Heat 1 and Heat 2 relays are calculated to satisfy the air temperature requirements.



During heavy loads, the maximum slab or floor temperature setting limits the on time of the Heat 1 relay. In this situation, the Heat 2 relay may be on while the Heat 1 relay is off.



Have you seen this job? What is radiant application? What is your friend using to compare his heating bill? Is this something that has always been or something that has changed over the years? 

I can e-mail you the PDF File if you desire.

Best Regards,

DanHolohan

It's a log house

in New Hampshire. It's about 10 years old, well-built and radiant throughout. Just high fuel bills but he's not comparing it to anything other than he thinks it costs a lot. Thanks.

Steven Gronski

What water temperature is he running..........

to operate the radiant? Chris brings good points on the way the radiant is installed, slab on grade, floor panels, joist traks, staple up.You run different water temps for each application, from experiance, slab on grade is usually the lowest and staple up is the highest. He could be running water temps from 100 to 150 degrees. is the flooring consistant thru the house? all tile all wood, carpet? how many zones? how many water temps is he running? Oil or gas boiler? radiant becomes the most efficient when you can constantly have a condesating boiler. does he constantly play with the t stat or just set it and forget it? a rooms load is matched to the r values of its insulation and windows to get its btus.........if the room needs 5000 btus, its going to take what ever water temperature is required to heat the surface area of the radiation source needed to create that. I did a conversion on an existing home with no major changes in the r value of the windows and house insulation, other than the basement floor being insulated with R-13 after the joist trak was installed, and a new oil boiler was installed. The owner went from 800 gallons of oil a year to about 650 which ended up being only about a 19% less fuel consumption. people think that radiant heat is going to be half the consumption of  fuel versus conventional hydronic heating,maybe if your house is so tight than when you breath in it you suck out all the air and create a vacume......fuel consumtion is the way to judge an efficient system not cost, oil can be 2 dollars a gallon today, 4 dollars tomorrow, that creates a 100% cost difference right there with the same fuel consumption.



Steven Gronski

Unknown

Indoor Reset

Dan,



A certain Cast Iron condensing boiler preaches indoor reset. We have a few out there in application and have heard no complaints. The results have been very similar to outdoor reset. Of course with some manufactures you can get both indoor AND outdoor.



An argument for indoor reset is that it compensates for solar gain and ventilation losses. Of course a properly installed outdoor reset can do that also. I believe the answer in somewhere between Hence the comment indoor AND outdoor.



skw

Bucko

Indoor Feedback

Dan there are systems that uses indorr feedback. It changes the water temperatures according to the demand of the zone that needs the most heat and then staggers the others. I did a home where the outdoor design was 7 degrees  130 degree designwater temp. I found one time temperatures were 15 degrees outside the system was supplying 90 degree water to the home.  When you turn up a thermostat 2 degrees the water temp goes to 130 ( design temp and max.water supply due to supplimenta). This basement of this home had many halogens in it as well as the Theater and Gym. If the basement was occupied the house needed much less heat. Outdoor reset is good but house heat needs account for all of the varibles not accounted for in a typical heat loss. Yhis turn the biggest load into allmost constant circulation at minnimum supply temps.  Condensing boilers love this if you have themal mas or buffer.

Empire_2

Just a thought...

Correct me in I'm wrong, but isn't the ORC equipped with adjustable Ratio adjustments?  If so, Can he increase the water temp by increasing the degree F* rise in supply water temp as the outside air becomes cooler?  Sorry is I am not on the same wave length as you men, but I was curious.  It seems that warmer water could satisfy the space quicker with minimal boiler run time........?  



Mike T.

Charlie from wmass

It is a log cabin.

Dan in New Hampshire as in Berkshire County heat can often be maxxed out in the winter. We are talking -20 or colder design temps. I often hear from new residence in our area that they are paying far more for heat than they did in Long Island and for a smaller home here than there. Also has the boiler been tested for a clean efficient burn? Out door resets are what I would go to to save money. I know tekmar controls can also use indoor temps as feed back for the reset along with the outdoor sensor. This is to allow for quicker recovery from a deep setback though not to save fuel.

NRT_Rob

Logs

Logs do cost a lot. they aren't very good insulation and the mass effect isn't very helpful in new england.



that said, we use indoor feedback teknet 4 systems on probably 3/4 of our projects. it is a totally sweet system and in many cases it more than justifies its cost, but indoor feedback (and this is true indoor feedback) will not save 10 to 20 per cent over outdoor reset. it's about fast response, precision, and some efficiency gain, but not that much.



it has other features that do help though, like zone synchronization to manage multiple zone firings to minimize short cycling, boiler firing controls, etc.. Depending on the system, THOSE features might save 10 to 20 per cent.



if he's got multiple low mass zones, he could probably save some bucks adding a buffer tank too.



how did his blower door go? logs are tough to seal but some outfits seem to be better at it than i used to be able to count on.

John Ruhnke

RE:

Dan,

It sounds like the guys running the blower door test don't understand enough about energy efficiency. Outdoor reset will obviously save you money in fuel bills. The important thing is to reduce the water temps based on the outdoor conditions. Both indoor and outdoor reset can accomplish this. Switching from one to the other most likely won't save you money. Some controls are better then others. Stand by loss's and short cycling are a huge problems too. A good way to solve that is through post purge. A well designed control does more then just outdoor reset. Also how you program the control is very important.

I would also look at the way the radiant heating is installed. Heat does not rise. It travels in the path of least resistance. If the slab is uninsulated and there is a high water table or ledge then a lot of the heat could be traveling away underground. Also if you have a thick carpet over the top of the slab and no insulation underneath, then more heat will go down then up.