Hot water recirc line w/ instant water heater?

[ffmedic7]

I have an instant water heater (as backup for solar heated water) and was wondering if anyone has any experience using a hot water recirculation pump with a demand heater.
I understand that I will be circulating hot water back through the demand heater. Mine is designed to be used with preheated water, and has a modulating gas valve to turn off the flame when not needed.
I just want to hear about any other issues folks might have run into with this setup.

I do not have a return line, and have been looking into the valves that return back hot water into the cold line. Any thoughts?

Thanks and Happy Labor Day!
Matt

[jadnashua]

If you read the instructions, those that I've looked at specifically say do NOT use with a recirculator. Yours may be different.

[Gary Swart]

I believe this would overwork the on-demand heater causing early failure. There are recirculating systems that do not require a return line, but I would suggest that if at all possible you install a return line and use a recirculating pump designed to be use with a return. I have such a system in my home, and it works very well.