Hive thermostat

[darren6645]

I have a 180l flowmax thermal store, water heated by my boiler circulated by pump local to tank and returned to storage.
This store water is used to heat radiators when ch selected circulated via a second pump. I have mains pressure hot water via an internal coil in the
thermal store and blender valve, open vented system.
So to have ch on I need to have hw on as the hw selection heats the thermal store water which when ch selected warms the rads.
I've had a Hive thermostat installed with hw and ch modes all coming on and off as per schedule etc.
My old programmer wouldn't allow me to programme ch if hw wasn't programmed to be on at same time. If I clicked boost or advance on the ch it would automatically kick the hw mode in too.
The Hive I had fitted doesn't appear to do this, if the hw is off and I now turn ch on the ch circ pump runs but without the hw on I will eventually just end up circulating cold water?
I have obviously programmed the hw to be on longer than the ch so it only ever comes on when the hw is active so not really a problem but as the thermostat has a default frost protection setting that can't be overridden if that was to be reached during the night the ch pump would run, again circulating cold water?
I know the default setting is 7c and in reality if the house was going to ever get that cold I would have left hw and ch on but does this sound like it's been wired correctly?
Maybe the hive doesn't allow this type of control so the only way is to programme the hw to always be on longer than the ch programme, as I have?
Hope that long winded explanation makes sense

 

[stem]

The Hive can be configured in the same way so that the heating can't operate without the hot water being on as well. This set up is traditionally used for systems that have gravity circulation where the hot water has to be 'on' to operate the boiler and the central heating just starts the pump hence its description "Gravity-fed".

 

[darren6645]

That sounds like an easy fix, that's great news. I'd be happier knowing it's set correctly, thanks for your help I'll have a go at that now

 

[snb1]

the hive is not designed for use with a thermal store. But you can change the settings so it will work.
you need to treat the timings for the hot water to be the store reheat. Set those times to be on from 1st thing in the morning until last thing at night. Then it will all work fine.

the design of thermal store systems allows the boiler output to be smaller than normal as it is designed to be able to operate for long periods. You need to make sure that it can heat the store before there is any demand for heating. the top 2/3rds of the store is for hot water and the bottom 1/3rd for heating. Until the bottom 1/3rd is hot you don't want it trying to heat the rads. expect the boiler to take unto an hour to heat the store from cold

 

[darren6645]

snb1 are you suggesting it shouldn't be in gravity fed/part pumped setting?
In both settings and prior to the hive I have had the hw set for all day then the boiler and circ pump will kick in based on the store temp.
The ch is only ever scheduled to be on within the hw on period (previous programmer didn't allow any other way) and there's at least an hr difference in schedule on time between hw and ch on a morning this is how it's always ran.
As the hive was fitted on fully pumped setting I did observe the ch could be switched on without hw on so I assumed something wasn't correct but after switching to gravity/part pumped if both are off and the ch is boosted the hw comes on too, not what you would do in practice but that's what should happen.
My tank has a internal coil top to bottom?
Mains pressure cold water enters at the bottom, picking heat up as it passes through the tank. It leaves the tank at the top where it is mixed with cold water via a blender valve to the taps.
I think we are both on the same lines but my tank isn't as you describe above.

 

[stem]

You don't give the make of the original programmer, but if it was a standard two channel programmer with the HW channel used to heat the thermal store and the CH channel to operate the central heating, then Hive will work exactly the same as the programmer you had before.

@snb1 is quite right about the 'timings' though, the thermal store does need to be heated up in advance of any demand for central heating or hot water, but from your comments it seems you know this and have allowed for it with the settings you use.

When first available, thermal stores were often installed without a timer and were 'on' permanently and kept hot 24/7. The idea being is that the store was always fully heated and when there was no demand for CH or HW it would heat up and shut the boiler down, it's insulation keeping it toasty. However, in practice, often the boiler would kick in for a while in the middle of the night to reheat the thermal store and the noise would wake light sleepers. So timers were added to stop it preheating in the middle of the night.

If it has been working OK with a standard 2 channel programmer then I guess you will know how to set the times, and nothing will change with a move to Hive. From an electrical point of view they are both the same, they have two simple on/off switches inside, one for CH and one for HW.

 

[darren6645]

Hi, my apologies.
The original controller was a Landis&Gyr RW8270 as you say it was 2 channel one for hw to heat thermal store and the other for ch.
That programmer wouldn't physically allow you to set the ch on time outside the hw on time, as we have already said because you need the hw on to get ch.
On switching to hive I once again set the ch on time within the hw schedule, as I know this is how my systems needs to operate.
The hw is set to come on first thing in morning and last thing at night and the boiler, pump and tank stat will do there thing through out the day to maintain the temp in the thermal store
Originally the receiver was set to default mode and was operating fine, hw on maintaining temp in the store throughout the day and ch coming on when required as per schedule but only due to the times set.
I did test to see if with the hw off I asked for ch would both kick in as the old controller would do and only the ch activated so I then guessed it wasn't quite right, hence my original question.
With the default frost protection setting in hive I was concerned if temps got that low the boiler wouldn't actuality fire up when the ch kicked in.
You quickly replied and told me about the gravity setting which I did yesterday and all appers to be working correctly now.
With all off, if I boost heating both hw and ch will kick in, obviously I have only tried this with the system upto temp and to test the operation of the controller, but all seems good so far.
Appreciate the help.