Multiple Recirculation Pumps for Domestic Hot Water Use

[Letobrick]

Hello all,

I'm looking for any advice/comments on using multiple hot water recirculation pumps for domestic hot water systems. The intent is to use two pumps (one for each extended recirc main serving the farthest fixture at opposite wings) back to the cold water main tying to the hot water heaters (in my case, a total of 3). The concern I have is the overall performance of the recirc system when using multiple pumps (ie: will they be potentially fighting one another). I am curious if anyone out there used them in their design of the hot water recirc system.

Thanks,

 

[MikeHalloran]

I could swear I've seen it done, as much as 50 years ago, but my memory is pretty dim these days.

I don't think I've seen the hot water return directed to the cold water main, which I'd guess would eventually get you warm water in the cold water system.

How about returning the hot water loop to the top of the hot water tank?

No expertise claimed here.


Mike Halloran
Pembroke Pines, FL, USA

 

[LittleInch]

I don't understand why you don't just tie it back to the tank but so long as there are common inlets and return points, each loop should be able to work independently without impact on the other. A quick sketch of your system would be good to make sure my understanding is correct.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[PEDARRIN2]

I won't say it has never been done, but common practice is to use a single pump, sized for the longest (or most pressure loss) portion. Flow rate is based on heat loss through the insulated piping. Balancing valves are placed on the other loops to prevent short circuiting. You have to tweak the pump flow rate to account for the extra loops, but that doesn't add too much and if your piping is sized correctly, the pressure loss from the additional flow is not significant.

In a multiple pump situation, one of the pumps is going to be nearly identical to the pump in the single pump situation, so the second pump is mostly redundant. Other than the balancing valves and maybe a little bit of piping, the single pump system will be less expensive.