Programmable thermostat

jem16

My son has a central heating system which requires the hot water to be on when the central heating is on.

This is not a great problem except for the fact that the timer switch is in a cupboard which is behind his 50" plasma TV which he would prefer not to be moving every time he wants to make an adjustment or even override it in this cold weather if someone is at home during the day - timings set to an hour in the morning and then a few hours in the evening after work. Unfortunately it's a basic timer so no different settings for weekdays and weekends.

He had a programmable thermostat fitted which was supposed to take away this problem and allow him to set different timings and different temperatures dependant on time of day and which day. Unfortunately the heating will not come on with the thermostat unless the hot water is on.

Basically this would mean leaving the hot water permanently on or at least on from 7am till 10pm so that the heating would come on as per the thermostat settings. This, of course, seems rather wasteful.

Has the thermostat been wired wrongly or is this correct for this type of system? If it is correct is there any wat around it?

DVardysShadow

jem16 wrote: »

Unfortunately the heating will not come on with the thermostat unless the hot water is on.

Basically this would mean leaving the hot water permanently on or at least on from 7am till 10pm so that the heating would come on as per the thermostat settings. This, of course, seems rather wasteful.

Has the thermostat been wired wrongly or is this correct for this type of system? If it is correct is there any wat around it?

Depends on the plumbing and wiring of his system, some systems are plumbed so that water is heated when central heating is on - and sometimes these systems are then wired with an inappropriate timer which looks like you can do more than the system is actually capable of.

Andy_WSM

jem16 wrote: »

Basically this would mean leaving the hot water permanently on or at least on from 7am till 10pm so that the heating would come on as per the thermostat settings. This, of course, seems rather wasteful.

So long as the tank is well insulated then this isn't as wasteful as it might seem. The boiler will only reheat the hot water that is used. Well insulated tanks only "lose" about 2 or 3KW of heat in a 24hr period and as long as the tank is in the house then the heat is "lost" in the form of background heating, so useful heat anyway this time of year.

jem16

Andy_WSM wrote: »

So long as the tank is well insulated then this isn't as wasteful as it might seem. The boiler will only reheat the hot water that is used. Well insulated tanks only "lose" about 2 or 3KW of heat in a 24hr period and as long as the tank is in the house then the heat is "lost" in the form of background heating, so useful heat anyway this time of year.

The tank is in the loft area but has just recemtly had extra insulation applied to both the tank and the loft itself. It's an initiative being done in his area where they pay around £90 for cavity wall insulation and then the loft area gets its insulation topped up for free.

I think he's anxious about the cost as during the summer he noticed that his gas bill was about £15pm as opposed to the £5 per month it was last year and that was just because the hot water had been left on all the time. Of course the previous summer he only had the hot water coming on for an hour in the morning and an hour at night for washing up dishes.

jamesd

It seems that he might be best looking on the possible £10 a month cost as a convenience fee that he might not fully end up paying if the improved insulation cuts the cost significantly.

marsden1002

Can;t be changed.

To have independent control of the heating and hot water, you would need an S plan system. This consists of a pump and two motorized valves. The boiler won't "fire" unless the cylinder thermostat is calling for heat ie the temperature inside the cylinder is below 65

notbritishgas

I had the same problem as your son and I did overcome it by fitting a programmable thermostat.
What I had to do was put the central heating "permanently on" on the programmer. The hot water was then left on timed which in my case is 6am to 7am.
The central heating is then controlled by the thermostat which on my Drayton digistat has 6 time/temperature periods so I can vary the temperature during the day and then put a very low temp setting for the overnight period.

jem16

notbritishgas wrote: »

What I had to do was put the central heating "permanently on" on the programmer. The hot water was then left on timed which in my case is 6am to 7am.

Unfortunately my son's system seems to be different to yours.

We knew about leaving the central heating permanently on as far as the timer is concerned. As you say the thermostat would then control it.

However his heating will not work without the hot water being on too. This means that he has to leave the hot water permanently on.

Marsdendean

For the system to work how you want it to, you will have to change certain aspects of the system. You could always move the programmer - or get a remote one then it can be placed anywhere.

IMO its pointless changing the system unless your changing the boiler & cylinder, because the cost wouldn't be worth it for the amount of time you will get from the boiler

jem16

jamesd wrote: »

It seems that he might be best looking on the possible £10 a month cost as a convenience fee that he might not fully end up paying if the improved insulation cuts the cost significantly.

He's going to monitor the costs to see how the improved insulation helps.

marsden1002 wrote: »

Can;t be changed.

To have independent control of the heating and hot water, you would need an S plan system. This consists of a pump and two motorized valves. The boiler won't "fire" unless the cylinder thermostat is calling for heat ie the temperature inside the cylinder is below 65

Presumably the system could therefore be modified? Although this may not be financially viable or possibly even not easily changed.

Marsdendean

Your correct. For the amount of time the boiler will last / how much you will save is not worth it.

Again, the boiler will only heat the cylinder when it has gone below 65. So, the wastage of gas should be minimal really. Underfloor systems work on the same principal that you leave them on all day all night and control them from a thermostat