In slab heating mixing valve

[huffdawg]

The mixing valve for the heated slab seems to send out fluctuating temps. the higher the storage temps the higher temp it sends,and the lower the storage temps the lower temps sent out.

I will get mixed temps from 130 °F to 90 °F is this normal or do I have a defective mixing valve .

Huff

 

[woodsmaster]

I think some fluctuation is normal ,but that seems excessive. Are you pulling the water threw the valve or pushing it ?

 

[jebatty]

I have a Honeywell Sparco AM series mixing valve which is nominally set to 100F, but I don't recall the boiler/storage supply temp I was at when I did the setting. In all events, over a boiler/storage supply range of 100-190F, mixed supply temp ranges between 90-110F. The table in the instruction sheet shows for a mixed setting of 99F at 140F, mix will be 97F at 120F and 103F at 180F. The range I'm getting doesn't make much difference for slab purposes.

 

[huffdawg]

I think some fluctuation is normal ,but that seems excessive. Are you pulling the water threw the valve or pushing it ?

I started out pushing it through the mixing valve but figured out that didn't work in a hurry.

But yes it has been pulling for a while .

Huff

 

[afblue]

I cant say its normal, but I can say I am not suprised. My injection mixing I get fluctuating temps on the "mixed side". I basically associate it to a hydraulic separation issue. What happens to me is when my boiler circulator is on, it constantly overshoots and tries to slow the mixing pump down. When the boiler circ is off, its constantly undershooting, and keeps trying to cycle the mixing pump to give more heat. When the boiler is maxing out the storage, the mixed side is almost uncontrollable and I have to start throttling down a balancing valve to create a hydraulic resistance to prevent the hot water from migrating to the distribution manifold becuase of the boiler circ.

 

[DaveBP]

I cant say its normal, but I can say I am not suprised. My injection mixing I get fluctuating temps on the “mixed sideâ€. I basically associate it to a hydraulic separation issue. What happens to me is when my boiler circulator is on, it constantly overshoots and tries to slow the mixing pump down. When the boiler circ is off, its constantly undershooting, and keeps trying to cycle the mixing pump to give more heat. When the boiler is maxing out the storage, the mixed side is almost uncontrollable and I have to start throttling down a balancing valve to create a hydraulic resistance to prevent the hot water from migrating to the distribution manifold becuase of the boiler circ.

If I remember my Siegenthaler correctly, that is precisely what hydraulic separators are for. Let the boiler go about its business and the distribution system go about its own business.
It's just got to make it easier to tune the system; one sub-system at a time. Independently.