Hot water recirculating system


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Old 12-22-17, 07:50 AM
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Hot water recirculating system

I see multiple ways of installing a recirculating system for hot water. I have a long house and thinking I can run a complete hot water loop, is this the preferred?
 
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Old 12-22-17, 09:13 AM
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That is the way I would do it. The pump needs a check valve at its inlet and it may come that way from the factory. Be sure to install ball valves on either side of the pump as well as unions unless the pump has flanges. You need to insulate ALL the piping, including the return piping or you will have excess heat radiated from the piping and that will significantly increase the cost of your hot water production.

The one problem is the location of the hot water sensor (thermostat) for the pump. If it is at the pump and the pump location is in an area not normally heated to the same temperature as the house you may encounter the pump running at times when the loop does not need to have the water circulated to maintain a decent interval before obtaining hot water at the tap.

Control of the pump is the biggest problem in adapting an (almost) instant hot water recirculation system to a residence. In commercial systems the pump simply runs continuously and the system losses are accepted as a cost of doing business. This works when supplying hotel rooms or many, many washrooms in an office or factory building but in a residence it can be hours between hot water usage and the continuous pumping uses a lot of energy, some for the pump but most in the heat losses in the circulating water.

Some residential systems use a time clock to only allow pump operation during hours when hot water usage may be expected. This would shut off all power to the pump during hours when everyone was away at work or school during the day and after everyone had gone to bed at night with the pump re-energized shortly before the first person rose in the morning or arrived home in the afternoon. Another method, much more complicated, would control the pump based upon room occupancy, it would start the pump the moment a person entered the bathroom or came close to the kitchen sink.
 
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Old 12-22-17, 09:17 AM
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Your diagram shows a standard method of recirculating hot water. It will increase your energy usage due to continuous losses from the piping. All the hot water piping should be insulated to reduce the losses.

Depending on the length of your piping run you could possibly use a gravity loop instead of a pump. In a gravity loop the piping is the same as shown in the diagram but does not have a pump or sensor. As water in the return pipe cools it is heavier and pushes heated water up into the hot water supply pipe. The water in the pipe may not be as hot as with a pump but it will be warmer than not having a recirculating loop. It is possible that a demand for hot water will draw it from both ends of the loop. If that causes a problem with too much cool water upon starting you might add a gravity check valve in the return loop.

You could also install a bypass loop around the pump and use it for gravity use if the pump fails or if the water temperature (say in summer) is less cold.
 

Last edited by 2john02458; 12-22-17 at 09:19 AM. Reason: typo
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Old 12-23-17, 04:18 AM
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The basement is heated and I would use a grundfos time controlled pump similar to the photo with the better foam insulation wrapped in corners and on Tís.
 
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Old 12-26-17, 04:05 AM
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I noticed that my pop-off valve is near the top portion of the tank and the photo shows it on the bottom, any issue with that?
 
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Old 12-26-17, 08:51 AM
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Thats the drain valve the picture shows. Not the relief valve...

Easier to install a pump and thermostatic valve under farthust sink IMO.. These work very well..

https://www.homedepot.com/p/Hot-Wate...5800/100426993

 
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Old 12-26-17, 08:57 AM
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Easier yes, but probably not the best in my situation as I can easily add the return line back to the tank.
 
 

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