Insulating Hot Water Pipes

[Topzide]

Here's the unit info that I have mounted under sink.

 

[Popgadget]

I had the same issue- Rinnai combi boiler for radiant heat and hot water. Works awesome, but the wait for hot water at the kitchen sink was unbearable.
It’s the furthest from the water heater, and is in an island on a concrete floor, so the lines go under the slab insulation and radiant heat and surface in the island. They are only subterranean for about 15 feet, but coupled with the overall distance from the water heater, it was unacceptable.

Adding a return line was not really an option, so I got one of these-

https://www.supplyhouse.com/Grundfos-595926-Comfort-Valve?utm_source=google_ad&utm_medium=Shopping_Plumbing&utm_campaign=Shopping_X_Plumbing_X_SSC_New&utm_campaignid=22376725605&utm_adgroupid=175817622854&utm_targetid=pla-2435661369999&utm_product_id=595926&utm_matchtype=&utm_keyword=&utm_adtype=pla&utm_category=Plumbing&gad_source=1&gad_campaignid=22376725605&gbraid=0AAAAAD_WAyt6nqPFqVSoqt8QjzEJgHVKd&gclid=EAIaIQobChMI98ipi93EkAMV-oAiBR1LKyNXEAQYASABEgLnGfD_BwE

There is a flow switch and timer in the boiler which activates the circulator then when it senses the flow from the valve opening it stays on. If the valve is closed the pump only runs for a few seconds. I also have a timer to defeat the system overnight.

 

[IXLR8]

The house I recently purchased had a tankless water heater at one end of the house, it literally took 4 minutes to get hot water to the kitchen sink. It was 130 ft from heater to sink!! I insulated the pipes and it didn't make much difference. I installed a recirculating system, insulated the return line. I used an X-10 system to manually start/stop the recirc pump. Turn the pump on about 1 min before you need the hot water and you are good to go with unlimited hot water. My neighbor put in a recirculating system as he had the same issue with taking forever to get hot water. But he didn't put in any way to control the pump, it runs 24/7, his propane bill is sky high.