DHW mixing valve

DHW mixing valve

PostBy: Phil May On: Thu Mar 27, 2014 4:51 pm

Quick question. Do you need a check valve on the cold side of a mixing valve to stop convection in dhw use.
Phil May
 
Stoker Coal Boiler: EFM 700
Coal Size/Type: Buckwheat
Stove/Furnace Make: EFM
Stove/Furnace Model: 700

Re: DHW mixing valve

PostBy: Carbon12 On: Thu Mar 27, 2014 5:30 pm

I used a check valve on the cold water supply line to the boiler fill, cold water DHW supply and mixing valve, inclusive.

Edit: Oops, sounds confusing. I have one check valve.
Last edited by Carbon12 on Fri Mar 28, 2014 9:53 am, edited 3 times in total.
Carbon12
 
Stoker Coal Boiler: Keystoker KA-6
Coal Size/Type: Rice/Anthracite
Other Heating: Heat Pump/Forced Hot Air Oil Furnace

Re: DHW mixing valve

PostBy: lsayre On: Thu Mar 27, 2014 6:21 pm

I don't have a check valve on the cold water side of my mixing valve. Working fine for 3 years now.

I do have a check valve on my boiler water feed line.
lsayre
 
Stoker Coal Boiler: AHS S130 Coal Gun
Coal Size/Type: Stockton Anthracite Pea
Other Heating: Resistance Boiler (13 KW)


Re: DHW mixing valve

PostBy: Sting On: Thu Mar 27, 2014 8:30 pm

Phil May wrote:Quick question. Do you need a check valve on the cold side of a mixing valve to stop convection in dhw use.


no

the valve creates its own issolation
Sting
 
Other Heating: BurnHAM=NG-gas

Re: DHW mixing valve

PostBy: McGiever On: Thu Mar 27, 2014 8:31 pm

Some would use a heat trap pipe configuration instead of a check valve, but it would go on the hot side. :)
McGiever
 
Stoker Coal Boiler: AXEMAN-ANDERSON 130 "1959"
Hot Air Coal Stoker Stove: HARMAN MAGNUM
Hand Fed Coal Stove: RADIANT HOME AIR BLAST
Baseburners & Antiques: OUR GLENWOOD 111 BASEBURNER "1908"
Coal Size/Type: PEA / ANTHRACITE, NUT-STOVE / ANTHRACITE
Other Heating: Ground Source Heat Pump
Stove/Furnace Make: Hydro Heat /Mega Tek

Re: DHW mixing valve

PostBy: mozz On: Thu Mar 27, 2014 9:23 pm

I have a gate valve between the input and output of the hot water coil. Adjusted accordingly. Am i doing it wrong?
mozz
 
Stoker Coal Boiler: Axeman Anderson 1982 AA-130 Steam

Re: DHW mixing valve

PostBy: Sting On: Fri Mar 28, 2014 6:56 am

You should have used a GATE valve. but other than that....

Are you doing it wrong - in this case it doesn't depend

The answer is YES
Sting
 
Other Heating: BurnHAM=NG-gas

Re: DHW mixing valve

PostBy: mikeandgerry On: Fri Mar 28, 2014 9:18 pm

The new ones from Honeywell come with a nylon check valve built into both the hot and cold side, I guess for idiots like me who put them in wrong in the first place!

I originally mounted mine in a high location far from the boiler without a heat trap. It would on occasion deliver scalding water for a few seconds before regulating the temp which is obviously not desirable. I doubt a heat trap would have worked on my system at the boiler coil anyway with copper piping. My cold water lines got mighty hot due to conduction with a 170+ boiler. Heat traps only stop convection.

Since I mounted mine in the wrong place the first time, I moved it lower than the boiler dhw outlet and changed the supply and mixed outlet piping to pex when I re-arranged the utility room, then put in a check valve to stop the thermal transfer to the cold side (which didn't work well because it was bronze), then realized the mixing valve was encrusted and pitted, with worn o-rings and just not doing its job well, then replaced the mixing valve, then replaced a section of the copper hot supply pipe to the mixing valve to stop the conduction from the boiler dhw.

Then, and only then, did I stop all undesirable thermal transfer.

(Now I am thinking about a bronze pump to maintain a higher mixed line temperature for quicker hot water at the tap-----NOT!)
mikeandgerry
 
Stoker Coal Boiler: Axeman-Anderson Anthratube 130-M