Recirculating Pump Questions

I've replumbed my master bath and installed a tankless WH. Since I'm going to use this new WH to service the entire house a recirc. pump is probably in order (kitchen is 80' of copper away). I've already got part of the recirc. line in the attic running from the old location of the tank-type heater.

1. Any opinions on brand of recirculating pump?

2. Does the code allow a recirc. pump in an attic above living space? I realize pumps are usually located next to the WH, but my tankless is mounted on an outside wall.

Rick

pumpT

The code does not address the circulating pump at all. It is usually not installed in an attic since it can be prone to leaking and servicing it could be more difficult there.

You might want to think about whether recirculating from 80 ft to a kitchen from a tankless heater is a good solution.

If the recirculation flow is very low, it will not actuate the flow switch in the tankless. If it is high, you will be running hot water to the tankless supply. Many of the demands in a kitchen will not use the water in the pipe unless you run it to waste to get it hot.

You might consider whether a point-of-use heater might be a better choice for the kitchen. It will provide immediate hot water and will not waste heat that recirculation systems always do. Your A/C will have to pump that heat out of the house.

Kitchens use low and intermittent flows except for dishwashers, and the tankless will come on to resupply the POU heater when there is high flow.

Most of the tankless instructions I've read specifically say don't use a recirculating pump with them. Read the fine print and see if it is addressed; if not, suggest you talk to the tech support from the manufacturer to get them to bless or condemn it. My guess is that if you got enough flow to trigger the thing on, it would be running for many more cycles than normal, and you'd be wasting all of the energy you think you will save, and wear it out much quicker.

A recirculating pump circulates stored hot water. With a tankless heater, you don't have stored hot water, so there's nothing to circulate.

You could use an on-demand recirculating pump at the kitchen sink. This won't save any energy, but it will save 80' worth of water. I have a Chilipepper Appliance (http://www.chilipepperapp.com/) that I'm very happy with.

Taco also makes a recycling system they call d'Mand. www.taco-hvac.com . ANother is made by Gundfos. All you really need is a pump, a time-delayed off relay (adjustable) and a pushbutton to activate it for the specified time. Adjust the delay so it stays on long enough to get hot where you want it. Or, you can buy someone else's system, already engineered for you. The packaged systems include a temperature sensor to stop once hot arrives, rather than after a specific time. Either works, one is more automatic.

Thanks for the input. The Noritz 69M will work with a recirculating pump. In fact it has control circuitry built in if you choose to use this approach vs. a timer. I'm sure having a storage tank would be the preferred solution, but I really don't want to put such a tank in my attic. I'll have to think about this some more.