Hot water Recirculation Cycle Problem

Gary Lapidus · 8 Feb 2021

My house has a low pressure gravity system. It uses a Drayton Lifestyle LP722 timer w/ two HW (hot water) and CH (central heating) cycles each, and a Grundfos UPS 15-50 hot water recirculation pump. The electrics are wired into a Honeywell junction box. There two hot water loops, one for the kitchen and one for the rest of house. The two loops form at a T-junction just after the hot water cylinder top-exit, and they return and re-join at a T-junction just before the inlet to the Grundfos.
The two CH cycles work fine. The two HW cycles also "work" in that water in the cylinder is reheated. However, I only get "instant" hot water in the kitchen during the morning cycle. The Grundfos is running in the morning cycle. In the evening cycle I don't get hot water in the kitchen, just luke-warm. I do get hot water in the rest-of-house. The Grundfos does not appear to be running on the evening cycle. I'd have thought the Drayton is sending a ON signal to the pump when HW is ON, and OFF to the pump when HW is OFF. But my recirculation pump seems only ON during one of the two cycles. Any thoughts are appreciated.

Recirc2

Gary Lapidus
8 Feb 2021

Grundfos hot water recycle with two loops

Recirc1

Gary Lapidus
8 Feb 2021

Drayton and Honeywell controllers

muggles · 8 Feb 2021

Some photos of your setup would help

Gary Lapidus · 8 Feb 2021

muggles said:
Some photos of your setup would help

I appended to my post; thanks

ianmcd · 8 Feb 2021

you should have seperate controls for the circulation pump not controlled from the LP722

Gary Lapidus · 9 Feb 2021

There is one wire to the circulation pump, which leads from the Honeywell junction box. I assume there is no controller in that box. The pump itself does not appear to have any control/timer dials, and there are no other signal wires leading to the pump, e.g., from a thermocouple, so I have to conclude the control function is the LP722, i.e. the LP722 turning pump power supply on/off during the HW cycles. What am I missing?

ianmcd · 9 Feb 2021

Gary Lapidus said:
the LP722 turning pump power supply on/off during the HW cycles

It is possible that it is wired like that , but that is completely wrong if it is, just get a simple time switch wired in to power the HW pump, there are better ways but more expensive

Gary Lapidus · 9 Feb 2021

Thanks for your help on this. I know nothing about the topic but am always trying to learn.
I'm under the impression that the power to the hot water recirculation pump is a ‘switched’ Live not a ‘permanent’ Live, initiated by the LP722, and that the associated wiring is within the junction box. Further, my understanding is the ‘Switched Live’ to the pump is controlled by motorised valve(s) on the system, which in turn are controlled by thermostats (on the hot water cylinder) and the LP722 and that together they ‘activate’ the pump when there is a demand for DHW. Based on this limited understanding I don't understand how it is, as you said, "completely wrong", as that set up makes sense to me, assuming it's all working properly. I understand your point about a discrete pump timer, programmed to coincide with the LP722. That said I'd prefer to fix what I've got unless it's not possible, or "completely wrong".
This message sent with all due respect and thanks. I'm here to learn!

ianmcd · 9 Feb 2021

If you think about it, when the boiler is heating the stored HW within the Cylinder, you dont want the water being circulated throughout the pipe network,as you are just losing heat as you are trying to heat that water too you want it to get to temp than for the pump to come on, the zone valves control the system Circulator and boiler, not the HW circulator, best setup would be the HW to heat for whatever time it takes then the HW circulator to be on an individual timer and set to the times that HW is drawn, when we install them we use a PIR system , so the HW circulator only runs when someone enters a room that will neeed HW i.e. bathroom, en suite kitchen, rest of the time it is idle

Gary Lapidus · 9 Feb 2021

Okay, I see. So you're saying that while one can wire the recirculation pump to turn on and off coincident with the DHW cycles, and that seems to be how mine was set up, you're saying that it is not an efficient way to go.
PIR, I assume that's photo infra-red or motion sensor. That's a great idea. Can it be done wirelessly? I've got motion sensors for an alarm system and they terminate in a room behind the airing cupboard, although I'd think it's tricky to share those signals for a purpose other than the alarm panel.

ianmcd · 9 Feb 2021

Yes can be done wirelessly, we buy our setups here

https://www.luminite.co.uk/easyswitch/

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Hot water Recirculation Cycle Problem

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