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Re: Bad mixing valve
Not understanding how Cv works in a valve like that is probably why so many radiant systems slip behind as you approach design conditions.
You will often see 2 or 3 circulators connected to 3 Cv thermostatic valve!
If this attaches it is a handy spreadsheet to help understand the effect of CV. Used for design or troubleshooting.
It applies to ANY valve, zone, ball, balance.
You will often see 2 or 3 circulators connected to 3 Cv thermostatic valve!
If this attaches it is a handy spreadsheet to help understand the effect of CV. Used for design or troubleshooting.
It applies to ANY valve, zone, ball, balance.
Re: Hydronic heat not as efficient as forced air ?
The radiant gets screwed any way you compare.
If you come off radiant and go to forced air the slab carries over btus as mentioned.
If you use forced air long enough for the slab to cool. Then go to radiant the slab has to work harder to get warmed back up.
A real comparison in comfort, and efficiency. Do a complete season comparison. One year with forced air, and one with radiant. I'm assuming the forced air is for ac. Or is it supplemental to the radiant.
Then I would use the degree day per sf formula as a base line to compare.
If you come off radiant and go to forced air the slab carries over btus as mentioned.
If you use forced air long enough for the slab to cool. Then go to radiant the slab has to work harder to get warmed back up.
A real comparison in comfort, and efficiency. Do a complete season comparison. One year with forced air, and one with radiant. I'm assuming the forced air is for ac. Or is it supplemental to the radiant.
Then I would use the degree day per sf formula as a base line to compare.
Re: Believe it of not, this system is vented.
I'm pretty sure the boiler designers/engineers have taken into account the steam volume of the system in relation to the water volume of the boiler. What they can't predict is any slow returns, starving the boiler, or over-pressure forcing too much water up into the wet returns.
Where these feed tanks are needed would be in multiple building installations, with one boiler serving all of the buildings.
Dump the condensate pumps, where possible, and go with gravity!--NBC
Where these feed tanks are needed would be in multiple building installations, with one boiler serving all of the buildings.
Dump the condensate pumps, where possible, and go with gravity!--NBC
Re: Hydronic heat not as efficient as forced air ?
In reading your last post as @Rich_49 pointed out. When you turned down the radiant thermostat, and turned on the forced air the radiant slab carried part of the load for the forced air.
That heated slab will release energy for a few days.
Not a valid comparison at all.
also the boiler has to see below 130 degree return temps. If it's piped primary secondary it's possible the boiler is seeing higher temps if not pumped right.
That heated slab will release energy for a few days.
Not a valid comparison at all.
also the boiler has to see below 130 degree return temps. If it's piped primary secondary it's possible the boiler is seeing higher temps if not pumped right.
Re: Steam conversion
Anyone know how a natural gas steam boiler with radiators compares in efficiency to a natural gas forced air furnace?Warm air is terrible, yes you can get 97% combustion efficiency but that’s only when the fire is on and it’s heating, otherwise once it turns off, the heating is done.
Re: Hydronic heat not as efficient as forced air ?
Something is certainly not set up properly . The radiant slab also gave up heat to the space during your test , at least for a good period of time if the house is well insulated and air sealed . How many zones is this radiant system .T there is alot that can go wrong and it does in probably 75% of the installs , usually starts with design or lack of it , the rest comes from not understanding building science .
Re: Hydronic heat not as efficient as forced air ?
Suffice it to say that for a whole lot of reasons the comparison is completely invalid.
However, sadly, it's the kind of thing which gets published every day...
However, sadly, it's the kind of thing which gets published every day...
Re: Hydronic heat not as efficient as forced air ?
What he said^^^. Had the slab already been up to temp and provided there is at least 2" of foam underneath and around the perimeter of the slab, I find it hard to believe the radiant would take a drop more fuel than the scorched air while providing a more comfortable heat. Valid point with the DHW also. Was this boiler installed and tuned by a competent tech?
Re: Steam conversion
I agree with you completely, and yet to be fair, steam supply line losses must surpass ductwork losses, at least in my house where the risers are in the exterior wall heating up my neighborhood 😅I suspect that you are probably right -- if the ducts are properly sealed and insulated, and if the steam lines are properly insulated. But then... there's always the argument about when is a loss a loss -- if the steam pipe or duct is in a space which needs to be heated anyway, is the heat loss a loss? The argument for insulation on steam mains is much more to speed the movement of steam through the pipe on warmup, and avoiding excess condensation in what should be a dry pipe, than it is to avoid heat loss.
Re: Hydronic heat not as efficient as forced air ?
I would like to add, the OP is assuming the hydronic system was properly designed and set up.
What are your outdoor reset settings? Have you tuned them? Combi boilers most times are a compromise. To size for DHW load most times they are way oversized for the heating load, which will impact efficiency.
We would need a lot more information to even discuss this topic with respect to your system.
What are your outdoor reset settings? Have you tuned them? Combi boilers most times are a compromise. To size for DHW load most times they are way oversized for the heating load, which will impact efficiency.
We would need a lot more information to even discuss this topic with respect to your system.
