Interpreting radiant floor plan temps

sam33 · November 19

Hi,

I dug out my old floor plans for when the radiant was done and can't remember what the floor temp numbers mean. I understand the delta, BTU, and flow, but there are temp numbers such as "Floor: 71.2 F". I'm thinking that is what target water temp would be, but 71.2 seems low to me. When the system runs, it looks like 80's is low end and most of the time it's above that.

Any idea what those temps would

mean?

Dave H_2 · November 19

The design here is showing what the approximate surface temp of the floor will on a design day with thermostats set for whatever was put in for that temp.

This plan also shows what the water temperature needs to be set for 124.4F

If your floors are exceeding 80 often, which it may do this time of year because of a low heat loss, warms up outside and the floor has some extra energy, take a look at the delivered water temp.

It may also be the mixing strategy; if a fixed temp mixing valve, what is that temp set for? If modulating mix valve, what is the curve setup to?

I hope this helps

DCContrarian · November 19

What's not shown are the thermostat setpoints but you can derive them. The assumption is that heat flow will be 2BTU/square foot for every degree difference between the room temperature and the floor temperature.

So for the closet it says floor temp 71.2F, heat 6.3 Btu/hr/sf. That means a temperature difference of 3.15F, or a room temperature of 68.05F. Similarly the workout room implied temperature is at 68F, the bathroom is at 70F and the bedroom is at 68.2F.

sam33 · November 19

https://forum.heatinghelp.com/discussion/comment/1821087#Comment_1821087

Thanks! How do you calculate the 124.4F water temp?

I don't know what the mixing valves were set for. They are fixed temp. I'll have to look again, but I don't think the temps break 100F.

sam33 · November 19

https://forum.heatinghelp.com/discussion/comment/1821088#Comment_1821088

Thanks!

GGross · November 19

the calculated supply temperature is derived from all of the values that were input to the design. The design day temperature, the floor type (embedded concrete or whatever other material) and all the insulation and heat loss of the space, the room temperature setpoint, tube spacing. all of that information is set in the software, so the more accurate the numbers are in the software, the more accurate that supply temp value is. It shows the supply temperature on your plans as part of the manifold tag

should note that supply temp number is the supply temperature on design day (coldest day of the year) the rest of the year the supply temp should be lower ideally

sam33 · November 19

https://forum.heatinghelp.com/discussion/comment/1821094#Comment_1821094

Thanks. I completely missed the temp on the manifold tag. I didn't know if there was some way to back calculate it from the other numbers.

hot_rod · November 19

https://forum.heatinghelp.com/discussion/comment/1821099#Comment_1821099

Is the system working as expected? All rooms heating comfortably?

Pictures from the boiler room piping would tell how they are getting that mixed temperature.

sam33 · November 19

https://forum.heatinghelp.com/discussion/comment/1821103#Comment_1821103

I'm chasing down a problem with the DHW where the hot water fluctuates from hot to luke warm. see

https://forum.heatinghelp.com/discussion/198466/combi-bosch-zwb28-3-dhw-issues

I replaced a few parts and found a bunch of scale. Looking further, I even see some in the flow meter sight glasses on the manifolds. So then I got to wondering if the heat side was also having problems. I have noticed it somewhat colder upstairs, but didn't think much of it.

thanks

GGross · November 19

If your DHW mix valve has a screen perhaps it needs to be cleaned?

hot_rod · November 19

Thermostatic mixing valves need to be descaled from time to time, some yearly. The scale causes the spool inside to stick and not regulate accurately.

Interpreting radiant floor plan temps

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