OWB DHW plumbing advice needed

[stephen44]

.... so plumbing help/advice needed please.

Looking at diagram plumbing-1.jpg - this is how the DHW is planned to be plumbed at the moment - the dealer assures me that this will produce unlimited HW - at all times even in the midst of winter

- my wife is disabled and needs a very hot 300 gallon bath a day (yes 300G - it is a 4 x 4 x 3 jacussi tub)

i am worried that when the water has been standing in the tank and the pipe that it will not be hot enough - and we would have to run off so much to re-heat, so I am wanting to put a thermostatically controlled circulating pump into the circuit.

Does diagram plumbing-2.jpg work for this - or is there a better way of doing this ?

Also by pumping my well water all the way to the OWB (150' two ways = 300') and back - will this have any significant effect on my faucet water pressure ? - it is low to begin with !

i am trying to avoid another run to the OWB - as since I have two heat exchangers as well - that means I am already running 6 pex pipes between the two - and I know I will need a water source at the OWB for refilling etc !

Please - Please - any ideas !

thanks

Stephen

 

[Nofossil]

The slug of cold water from the lines will be completely dissapated in the hot water tank.

However, there's a major safety issue with the system as drawn - you MUST have an anti-scald valve or mixing valve on the outlet of the DHW tank to limit the DHW temperature supplied to the house.

 

[stephen44]

so you are saying that i do not need a circulating pump ?


there is a mixing valve in the installation - I just didn't show it for simplicity !

 

[Nofossil]

so you are saying that i do not need a circulating pump ?


there is a mixing valve in the installation - I just didn't show it for simplicity !

As long as the OWB is hot, I don't think you'll need a circulator. However, if the DHW tank sits unused for a long time, it will cool down unless there's some other mechanism to heat it.

 

[stephen44]

I'll keep the ability to switch on the breaker for the HW element - or ' I'll set the thermostat to a lower temp so it kicks in. - haven't decided which yet.

The only standing period will be over night - the water will be used off and on during the day. Do you think there will be a noticeable temp drop in the tank overnight (it is a 2 year old well insulated tank if that help)?