hoping for more domestic hot water - pictures of my contraption

[Sting]

I have my doubts that I piped my DHW make up correctly --

This has served me well for several years - this year I have another woman in the house... my son is in that great sand box of the Middle East and his dear wife is with us - hot water has turned into a comodity....

I circulate to all the sinks in the house via the hot supply pipes - return to the boiler via a third "bypass" loop - and send that renewed energized DHW back to the bottom of the 50 gallon NG storage tank. Pumping is controlled with a Honeywell strap on aqua stat on the supply pipe - wired to open on temperature rise of 125 - so I never send over temp water out to the load.

Typical use - this is wonderful - I have almost instant 125 degree hot water at every tap and for the most part I have enough of it. Yet under hi or long demand - the storage tank stratification is lost by this extra pumping combined with the incursion of the replacing cold street water. I have noted 140 degree water returning from the boiler to the bottom of the storage tank - yet only 95 degree (or colder) water leaving for the load???

Under hi demand, It might be nice if I could divert some of that boiler production, going to the bottom of the tank --> directly to the house supply loop; yet keep the tap temp to code -- but at what cost and with what equipment, and how so DHW does not exceed safe code temp? --- and still rebuild the storage tank temperature when the demand is satisfied?

Thanks in advance for help and suggestions. I suppose I could just turn up the NG water heater and let it help pick up the load in hi demand. I also thought about finding a used electric water heater and piping it in series with the existing 50 gal NG heater for more storage, but am unsure if that will be a benefit or another loss.

Kind Regards
Sting

 

[stee6043]

Is it kosher to use PVC for pressure relief? Me thinks it needs to be copper or black???....

 

[Dave T]

Be carefull using your nat gas burner I see a lot of discoloration around the top on the pipes close to the chimney outlet I feel you should get a carbon monoxide detector and check your chimney flue for issues..I am a little confused by your pictures it looks like you are pumping boiler water directly into your hot water heater if this is the case that is very dangerous unless you have a domestic water coil in your boiler..Do a search on sidearm exchangers people here have used regular 1 1/4 tees with some grinding and soldered 3/4 copper pipes down the middle of them to exchange heat and not mix boiler and domestic water..Using a 3 way mixing valve will allow you to super heat the HWH and temper the output.. BEST OF LUCK TO YOUR SON ...Dave

 

[Sting]

I have though long and hard about the 3 way valve you mention TacoSteelerMan -- yes it would divert make up water to the load under hi demand - but when it is installed --will not the ability of the system to recharge storage and circulate the house system be defeated?

 

[Dave T]

I am probally in over my head commenting (due to some confusion) but the mixing valve hooks to your domestic HWH output(hot side) and your domestic HWH input (cold side) to mix the say 160 degree HWH out and the 60 degree HWH in and come out with 120 (the numbers are only for demonstration purporses) the mixing valve in this case has nothing to do with the boiler water..Dave

 

[Tony H]

It's hard to tell how all the stuff is plumbed without a diagram. The way mine is setup the boiler water runs thru a sidearm and has a mixing valve on the output to keep the water to the house at 130 but I do not have a circ in the system so no instant delivery like yours seems to be. It almost seems as if you need to somehow return the circ hot water via the cold inlet with a couple of check valves and the cold water as the secondary input. Where is your boiler to DHW heat transfered ? via ?

 

[Sting]

Thanks for the reply Tony!

System is pretty simple really -- DHW comes out the normal appliance port and goes thru the house just like a normal DHW system -- but I have a branch near each tap to a return line that congregates at the boiler -- it flows in and out of the boiler DHW leg picking up energy from there - and back via the bronze pump you see in the picture -- to be deposited in the bottom of the appliance is all started from.

Yes I could use a mixing valve -- but I cannot see the forest for the trees on how the flow would go thru the mix valve under hi demand -- yet when the system is simply circulating -- how would the tank bypass stop and the tank get recharged?

I guess this would / could work similar to some of the guys here that have large pressurized thermal storage tanks -- they draw off the tank, but when the tank grow too cold they draw directly from the boiler.

Maybe I should have the thermal mixing valve - mixing street water and water heated via the boiler as the supply to the DHW appliance -- but then the mix valve would shut down when it saw the really hot water and the tank wouldn't recharge quickly?

See what I mean -- I have though about this a lot -- but I am missing something -- most likely something simple -- maybe I am just missing how simple a mixing valve operates and could be installed in my system

 

[in hot water]

If the goal is more DHW either install a larger tank, or run the tank temperature up and install a good quality thermostatic mixing valve. Keep in mind more DHW=more $$

Insulate the tank as best as possible, and insulate all the DHW and recirc lines. Do you really need the DHW recirc? It cost heat loss and eliminates stratification as you mentioned. Maybe one of the "on demand" or thermostatic valved (Grundfos) systems for instant DHW would serve you better?

I'm curious how that Nibco (broken link removed to http://www.nibco.com/assets/Justrt.pdf) works for this purpose?

hr

 

[Sting]

Thanks for the ideas IHW.

I yes I could insulate the tank a bit more -- but the room is already its own zone -- laundry room - so it would be heated via the boiler anyway -- loss off the storage tank or the big radiator -- its all from the same source of BTU's.

My system was "contrived" to duplicate the nibco system - side benefit is it charges the storage tank and doesn't scald human pink parts - yes there is some thermal loss circulating the hot loop all the time. ( well as long as the tank needs charging and that's most of the time during season) For the most part the pipes are well insulated and what loss there is can be chalked up to the same loss as in the laundry room -- then system is in the core of the house that is already demanding BTU's from the system. It works well for me -- there is enough loss to keep hot water at the taps except on the warmest of days, and then the water is still sort of warm immediately. I don't circulate in the summer when the boiler is off.

I understand more DHW = more $$ -- Too many women under this roof to not keep enough available -- the few added pennies of expense to keep immediate hot water and enough of it is well worth price.

I need a link or a post -- to see how the guys with pressurized storage are sending storage btu's to the load - and boiler water to the load when storage is below set point.

What controls or thermostatic valve is necessary?

or am I doomed to add another tank?