Using an indirect as a dump tank

WaterPolo

From a seperate priority zone and piping it through the primary loop as a dump tank so that it heats up when ever there's a call for heat, to reduce the electricty now requried for the DHW pump.

Anybody had any experience about the relative efficiency of this. Also, the indirect has 1" outlet and inlet. That going to be a problem on a 1-1/4" primary loop?

Joe Brix

You mean buffer tank?

I don't see the value in this. First most indirects, unless it's a reverse indirect, only hold about 6 gal of boiler water. SO when a zone comes on the cold return water will start cooling the DHW you have stored, making the boiler/main circ come on to reheat everything. All this repiping to save 25 watts on a DHW pump running for 5 to 10 minutes.

Unknown

I wouldn't do it

A big question comes to mind ; What do you do for hot water in the summer months ? And you would need a tempering valve on the indirect if the heating loop raised the temp too high .

For the relatively short periods of time the indirect circ runs , it aint worth the trouble . What about using one circ and zones valves for the heat and indirect ?

mp1969

Buffer tank

I have used this in the past and it makes great sense. Use the indirect as the primary zone (it usually requires the highest temp) we call that the buffer tank and take off your secondary (lower temperature )loops off the primary loop. Need to keep the supply and return on secondary loops about 5" apart in order to keep differential temps close. Use tempering valves set to various heat requirements and you will have a system that utilizes the buffer tank to avoid short cycling of high efficiency low mass boilers. We have used this on both in-floor and retrofit systems with stand up radiators. Works great. Use a well insulated buffer tank that has low standby loss (some claim to have less than a 5 degree loss in a 24 hr period.

Good Luck!
MP 1969

P.S. Dave Viegut of Auer Steel Company in Milwaukee,Wi. has designed many systems using a buffer tank. He is known as one of the best in-floor and hydronic designers in Wisconsin.

P.P.S You have to use a higher water volume indirect like Triangle etc. in order to have a large enough water buffer!


P.P.P.S. Ron Jr. Where can you find a domestic water heater that has efficiencies in the 90s ?.It is a great way to heat domestic water all year long. Pipe insulation adds to the efficiency

mp1969

1 1/4 \"

Water Polo,
You would be best to upgrade to an 1 1/4 inlet/ outlet buffer tank to maintain proper flow. Sorry I missed that last nite (fall rush and all takes it's toll)

Mp 1969

Ron Schroeder

Hi Ron Jr,

I wouldn't suggest zoning an indirect with a zone valve. Most indirects need a lot more flow than what you can cram thru a typical zone valve. My system has it's own Taco 007 85 watt circ for the indirect and a Laing 15 watt circ for the other 14 zones.

Ron Schroeder

Unknown

15 watt circ ?

I guess you came through last years brutal winter fine ? Where do you find a circ like that ?

Yeah , the zone valve will make the indirect suffer somewhat . But it sounded like this person was concerned more with energy saving than hot water recovery .

As an aside , my old working buddy Nicky has a 50 gal. Phase 3 and 2 zones of BB on his cold start gas boiler . All 3 zones are controlled by Erie zone valves . He told me they never ran out of hot water yet , not even on the coldest of days . No priority either .