Grundfos Closed Loop Recirculating DHW System - Questions

Antony Upward

Hi,

I'm a homeowner.

Does anyone have any experience installing these systems who could answer the following questions...

Just about to buy the Grundfos Closed Water Recirculation - UP15-10SU7P/TLC system(http://www.grundfos.com/Web/HomeUs.nsf/Webopslag/PAVA-56TMVA) and need to check a few things...

1. We have 3/4" pipe for both the cold water and hot water - will this pump restrict the flow / lower the pressure of the water when the pump is not operating?

2. Will there be problems with this pump with the instant on hot water heaters / boilers? We have an NTI Triniti Combi T200 - www.nythermal.com. Should the pump be installed on the input or output of the boiler? Any issues with this arrangement.

3. Any problems with the pump deadheading once hot water has reached the automatic valve and it closes?

Thanks for any help..

Antony

t.speed

Grundfos hot watewr recirc pump

Having installed several of these units, the end user must NOT be sold on a system comparable to a conventional return piped system. It is a decent compromise.

The pump can operate continuously with the return valve, they call "comfort" valve, opening periodicially and/or set the timer for periodic function.

The "comfort" valve closes when the hot water reaches about 88º, not what I would call hot. But it does move hot water closer to the farthest fixture and that is the compromise. It would help if the hot water pipe was insulated too.

Another factor is how the hot water is currently distributed throughout the house. Long runs help and multiple "comfort" valves can be used too.

Keep expectations in the moderate range.



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t.speed

Grundfos recirc pump...

continuation...
recirc pumps should not be installed directly on any instantaneous water heater. Head loss through boiler is too high; a separate storage tank must be installed with the recirc pump off of that tank.

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Tom Phillips

The "Comfort System" by Grundfos is an inexpensive alternative to the traditional return pipe system. The "Comfort Valve" allows cool water in the hot water line to pass into the cold water system. The "Comfort Valve" closes when the hot water reaches 98º. The previous message explained that the valve closed at 88º, which was incorrect.

Antony Upward

Head Loss and Grundfos Comfort System

Thanks for your comments...

Could you just explain a little more your answer...

Do you mean that the recirc pump when not operating (which is most of the time) would reduce the hot water pressure too much?

Thanks

Antony

t.speed

Grundfos recirc pump

While the Grundfos recirc pump does not affect most 3/4" systems, a small amount of restriction will result when the pump is off. A by-pass, with a check valve, can easily be added to achieve maximum flow. The key problem is with the NTI. By design the head loss through that unit requires a larger circulator (Grunfos should address this issue in their literature) and that leaves the Grundfos at a disadvantage; a storage tank must be added for the recirc to work.

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Antony Upward

Final Clarification Please - Trinity Head Loss

Thanks very much for all the advice so far...really helpful.

Sorry for my ignorance...I need hopefully one final clarification...I still don't understand the head loss issue with the NTI Trinity Combi T200

The domestic hot water on the trinity is triggered with flow rates starting as low as 0.5 gpm (if I remember correctly). Are you saying that the Grundfos recirc pump can't generate that amount of pressure - so won't trigger the Trinity to start and heat the water?

Or is the head loss in the Trinity some other issue?

Thanks again for your explaination...much appreciated!

t.speed

Grundfos recirc pump

Domestic water pressure and flow rates of a circulator are two different animals. With circulator flow rates you must look at the flow restrictions of the entire length of the hot and cold lines adding fittings and the NTI and the Comfort valve.

Water pressure whether from a well or metro source provides pressures that cannot be found with most conventional circulators. The flow rates of the recirc pumps are typically at the very bottom of the scale.



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Rich Corcoran_18

Recirc solutions

Recirc solutions vary for the applications encountered. The Comfort System is designed for installation on the outlet of a tank-type water heater. The pump is optimized to work in conjunction with the patented Comfort Valve which is installed at the point of use. The pump created nearly no restriction to hot water prssure when flows are under 8gpm. At flows above 8gpm, the piping is usually larger than 1" and the pump is installed on a bypass, taking it out of the line.

This system is not intended for application on an instantaeous water heater. The pressure drop through the heat exchanger, coupled with a need for at least .5 to 1 gpm flow, requires the installation of a traditional recirc system (dedicated return line) with a pump that will deliver the minimum flow and head to satidfy the instantaneous heater and its piping network.