retro hot water recirc

Raylo · 03-15-2008, 04:37 AM

I installed one of those Watts systems with the pump on the HW heater outlet and a mixing cross connect valve on most remote sink. It works as advertised but I found that even with the pump off there was a lot of natural circulation, especially when the water heater cycled on. This is fine in the winter but in the summer the warm pipes would increase air conditioning load (and cost).

So I added a solenoid valve and a check valve to create a way to turn off the recirc path when not needed. Also, I connected the solenoid valve and the Watts pump to X10 appliance modules so the system can be programmed to run from the PC module or engaged manually from plug in or remote keypads.

Anyone installing one of these needs to be aware of the natural recirc potential since they don't mention it in the sales or install documentation.

Here's a couple of pics of the sink area install. Note the sharkbite fittings and check valve. These were very handy as I fiddled with the arrangement and fitment since the whole thing can easily be taken apart and reassembled over and over. Plus the fittings allow the pipe to rotate so can turn threaded connections if necessary.

**speedster123** · 03-15-2008, 05:10 AM

wouldnt just a checkvalve worked? to stop the hot water from walking?

Raylo · 03-16-2008, 07:48 AM

Yes indeed. But the hot water needs to walk to the cold side when you want it too, whether the pump is on or not. That's how these things work. The hot water flows in the hot leg from the water heater to the mixing valve at the remote sink then feeds back to the hot water heater via the cold leg and stops when it reaches the setpoint of the thermostatic mixing valve (95 deg F). Having one just one line with a check valve would render the system useless.

These systems don't come with the solenoid and check valves and I found that the natural circ potential was such that the system was always "on" whether the pump was running or not hence the need to be able to open or shut off the recirc flow path to engage it when needed and turn it off when not needed. The loop with the check valve allows cold flow to the faucet when the solenoid closes off the recirc path whilst preventing recirc through itself.

I have an overall drawing I need to convert to a .doc file and I'll post it later. This should make it clearer.

Raylo · 03-16-2008, 03:45 PM

Here's the system drawing. It really is a simple setup as supplied by Watts. in addition to the pump it's just a simple thermostatic mixing/cross connect valve (the black plastic item in the picture from the earlier post) and a couple of flex hoses. But the natural recirc effect is such that one would have warm pipes all the time. Not a problem now but will be in air conditioning season. Hence the solenoid valve to secure the recirc path when not wanted, and the spring check bypass to allow cold to flow to faucet when the solenoid valve is shut. Works like a charm. :-)

03-15-2008, 05:10 AM	#2 (permalink)
speedster123 Mentor Join Date: Oct 2006 Location: United States-New York Posts: 3,804 OS: xp pro My System	Re: retro hot water recirc wouldnt just a checkvalve worked? to stop the hot water from walking? __________________ Infection Detection and Removal Thermal Grease Instructions Bench Test Last edited by speedster123 : 03-15-2008 at 05:12 AM.

03-16-2008, 07:48 AM	#3 (permalink)
Raylo Registered User Join Date: Feb 2006 Location: Maryland, USA Posts: 215 OS: XP Desktop, Vista HP Notebook, XP Notebook	Re: retro hot water recirc Yes indeed. But the hot water needs to walk to the cold side when you want it too, whether the pump is on or not. That's how these things work. The hot water flows in the hot leg from the water heater to the mixing valve at the remote sink then feeds back to the hot water heater via the cold leg and stops when it reaches the setpoint of the thermostatic mixing valve (95 deg F). Having one just one line with a check valve would render the system useless. These systems don't come with the solenoid and check valves and I found that the natural circ potential was such that the system was always "on" whether the pump was running or not hence the need to be able to open or shut off the recirc flow path to engage it when needed and turn it off when not needed. The loop with the check valve allows cold flow to the faucet when the solenoid closes off the recirc path whilst preventing recirc through itself. I have an overall drawing I need to convert to a .doc file and I'll post it later. This should make it clearer.