Using my electronic timer to control a HWR system

[vetinry]

Hello everyone

This is my first post on the site but I've spent the last few evenings browsing quite a few other threads.

I recently moved into a house which needs quite a bit of work doing to it. It's substantially bigger than previous properties I've owned and initally I was very confused by the 2 hot water pipes flowing to all of the various sinks etc.
However, I think that I've now got the basics of hot water recirculation and have found the Grundfos Bronze pump in the loft.

I spent last weekend draining down the entire system because there were 10 gate valves in the loft which weren't labelled, and I needed to start putting some isolation valves onto some of the pipes where we're changing sinks.

I don't recall how noisy the pump was before, but there is definitely a hum through the hot water pipes now that the system is refilled and the pump is running continuously.

There is a timer for the bronze pump in the airing cupboard but it's not active at the minute.

We've noticed that the hot water doesn't seem to last very long if the boiler isn't on, and I wonder whether the hot water recirculation system is part of the problem.

So, I'm wondering what the best approach is.

Is the bronze pump designed to be running all the time? It was getting extremely hot and so I've switched it off at the minute.

I could just sort out the bronze pump timer but am not sure how I should set it up in terms of running times

I'm also wondering about putting a honeywell pipe stat (the high temp version rather than a frost stat) on the pipes in the utility room, which is furthest from the boiler.

From what I can see, this is the most effective way to reduce unecessary pumping of the hot water, and therefore wasted heating / electric costs.

However, the timer controls are simplistic and don't allow for different settings at weekends.

Therefore, I wondered if it's possible to use my main electronic 7 day timer to switch the bronze pump at exactly the same times that it switches the boiler for hot water, and thus enabling longer periods of running at weekends

I hope that I haven't completely confused everyone and would really appreciate any advice that is available

Many thanks

Steve

 

[Boilerman2]

Circulating water around a Hot Water secondary circuit whilst the cylinder is not being heated will deplete the hot water store temperature very quickly as you have found, I don't see a problem with wiring the Secondary pump to the "Hot water on" terminal of your CH/HW Programmer, this way the pump will circulate water only when the boiler is availible to keep the tank heated, just make sure to set the on times to suit when you regulaly draw water, as you will want the secondary pump to be active at these times

 

[vetinry]

Thanks very much for the reply.

Is the secondary pump designed to run continually? At least it does explain why there isn't ever any hot water.

I will have to thy and find a wiring diagram for the HW/CH programmer and work out where the wires run.

What do you think about putting a thermostat on a pipe at the furthest point from the cylinder so that it switches the pump off (even if it's on via a timer) when water temp is high enough at this point.

Will this further improve efficiency?

Thanks

Steve

 

[simond]

The secondary pump can run continuously but this will deplete the heat in the cylinder by distributing it all over the house, plus wasting 60w per hr or so on the pump LX.

What we normally do is get a single channel timer and run the secondary pump for around 2hrs in the morning and 2hrs in the evening at peak usage times.

For the other 20hrs keep it off.

The HW boiler timing is best brought on before the heating load rather than coincide with the secondary pump. For £40 or so it is worth getting a HW programmer and just wiring your bronze pump to it.

Regarding the pipe stat, the pipe will warm up almost immediately. Furthermore, it will call the pump on when the water is cool. Not the best idea you've probably had!

 

[Nordio]

Furthermore, it will call the pump on when the water is cool

Isn't that what a pipe stat on a secondary loop is meant to do?

 

[simond]

What is a pipe stat doing on a secondary return in a domestic environment in the first place?

 

[Nordio]

I don't know. You tell me, you're the heating engineer.
Don't wilo and grundfos have thermostats incorporated into their bronze secondary circulators?

 

[simond]

The Comfort does as an option, but it turns off when the return temp reaches a preset point.

If the cylinder is cool, the pump will run indefinitely. These are only any good where the cylinder is heated constantly, hardly a recipe for energy conservation, which is where I recall the thread started.

 

[vetinry]

Thanks again for the replies.

Simon - there is a simple timer which can operate the bronze pump - currently it isn't active but I can certainly get it to run a couple of hours morning and night.

And your explanation about not linking to the CW/ HW timer makes complete sense.

Perhaps I wasn't clear in my explanation of the pipe stat.

The primary control of the bronze pump would be the timer and so when the pump is off it is definitely off.

But as a secondary control, is there any merit in having a further control of a pipe stat at the furthest point which will then ensure that heat is only supplied to the outbound pipe to the correct temperature, rather than needing to unecessarily heat the return legs.

I'm just not sure if it would lead to any further efficiencies

Best wishes

Steve

 

[electronicsuk]

Might be an obvious point, but is all the HW pipework well insulated? It certainly wont be helping with heat loss if it isn't.

 

[vetinry]

Hi Matthew

The pipework is pretty well insulated in the loft (apart from where rats have been active) but there isn't any obvious insulation as they run down the walls under boxwork.

As I do the rooms, I shall see what I can do to improve insulation here too.

Steve

 

[vetinry]

Just a quick update
I bought a single channel version of my main honeywell HW / CH programmer and have replaced the old timer. I've set this to run for about an hour in the morning and same in the evening.

It comes on about half an hour after the boiler controller and at the minute, I'm still not getting much hot water in the sink in the bathroom that we're currently using.

Is this because an hour isn't long enough to circulate the water, or do I perhaps have air in the system?

Also, since I've removed the sink in the main kitchen and utility prior to replacing with a new kitchen, the main supply to the tanks in the loft is really noisy when it's filling back up - something that I don't believe was there before

Any ideas how to solve this?

Cheers

Steve