Lower Radiator Flow for Unoccupied House

E2k

I have an unoccupied house with a combi boiler. 

I’ve set my thermostat to 14c as I want this  temperature at all times.

My Radiator flow rate on the boiler is currently set to 27c and my house maintains 14c (I have portable thermostats placed in diff rooms)

My question is should I go lower on the flow temp to save more money and are there any disadvantages to keeping the flow rate low?

Netexporter

As long as the heat is reaching all radiators then setting the pump a low as possible will save on electricity.

markin

Would you be able to monitor it remotely and go turn it up if the is a cold snap, possibly with roads blocked for days? It could take days of cold for the house to cool off and for it to become clear if the boiler can keep up or not.

I would think 35c would be a safer bet if your away for a week or 2 and cant go adjust it.

Would frost protection, usually 6c, over ride any set temp i wonder? 

FreeBear

E2k said:

I have an unoccupied house with a combi boiler. 

I’ve set my thermostat to 14c as I want this  temperature at all times.

My Radiator flow rate on the boiler is currently set to 27c and my house maintains 14c (I have portable thermostats placed in diff rooms)

My question is should I go lower on the flow temp to save more money and are there any disadvantages to keeping the flow rate low?

Are the radiators sufficiently large enough that the property heats up effectively with a sub 30°C flow temperature ?

I have modestly oversized radiators here and have tried running with a sub 40°C flow temperature. With the new (less than 6 months old) boiler, it would be ticking over for hours on end without the temperature of the house increasing. Run at a flow temperature of ~50°C, and the thermostat calls for heat for 15-20 minutes every 2-3 hours. The difference in boiler efficiency when running at 40°C (or lower) compared to 50°C is negligible, but I'm using a lot less gas with the 15-20 minute burns.

If you have a smart gas meter and access to 30min data (with the Bright app ?), I'd suggest running the heating with a flow temperature of 30°C for a few days, and then try again at 50°C - You may well find the higher temperature uses less gas and the boiler isn't cycling as much.

E2k

Netexporter said:

As long as the heat is reaching all radiators then setting the pump a low as possible will save on electricity.

All the rads are definitely warm

markin said:

Would you be able to monitor it remotely and go turn it up if the is a cold snap, possibly with roads blocked for days? It could take days of cold for the house to cool off and for it to become clear if the boiler can keep up or not.

I would think 35c would be a safer bet if your away for a week or 2 and cant go adjust it.

Would frost protection, usually 6c, over ride any set temp i wonder? 

The great thing is, it’s the house next door!

FreeBear said:

E2k said:

I have an unoccupied house with a combi boiler. 

I’ve set my thermostat to 14c as I want this  temperature at all times.

My Radiator flow rate on the boiler is currently set to 27c and my house maintains 14c (I have portable thermostats placed in diff rooms)

My question is should I go lower on the flow temp to save more money and are there any disadvantages to keeping the flow rate low?

Are the radiators sufficiently large enough that the property heats up effectively with a sub 30°C flow temperature ?

I have modestly oversized radiators here and have tried running with a sub 40°C flow temperature. With the new (less than 6 months old) boiler, it would be ticking over for hours on end without the temperature of the house increasing. Run at a flow temperature of ~50°C, and the thermostat calls for heat for 15-20 minutes every 2-3 hours. The difference in boiler efficiency when running at 40°C (or lower) compared to 50°C is negligible, but I'm using a lot less gas with the 15-20 minute burns.

If you have a smart gas meter and access to 30min data (with the Bright app ?), I'd suggest running the heating with a flow temperature of 30°C for a few days, and then try again at 50°C - You may well find the higher temperature uses less gas and the boiler isn't cycling as much.

I’ve always been lead to believe that the lower you can go the more efficiency savings.

My desired temp is 14c, the lowest I’ve ever seen in the house is 10c and that’s with the boiler off and -2 outside. 

By setting 14c on the thermostat the flow rate of 27c reaches and maintains it. I am unsure if the boiler cycles on and off as I’d have to sit by the stat to hear it click, but never found the time for it. 

I absolutely do not want my boiler cycling and for the sake of a few quid I’d rather put the flow back up to 40-50c

I am on the Shell energy App and that does give 30 minute readings, albeit a few days later. The issue is I’d have to test this theory with consistent outside temperatures? 

FreeBear

Make, model, and age of the boiler, and we can tell you what the modulation range is like.

Some of the older boilers I've looked at will modulate down to 7-8KW, whilst the latest offerings will go down as low as ~3KW. The older high output boilers would probably be cycling, where as at a lower output, it would just be ticking over.

E2k

I think it is a Baxi Duotec 2 28 GA from 2013 or so

FreeBear

E2k said:

I think it is a Baxi Duotec 2 28 GA from 2013 or so

According to the manual, 3.8 to 24KW in non-condensing mode, and 4.1 to 25.3KW in condensing mode - The latter mode being achieved by reducing the flow temperature. Anything below 50-60°C will put you in condensing mode.

E2k

FreeBear said:

E2k said:

I think it is a Baxi Duotec 2 28 GA from 2013 or so

According to the manual, 3.8 to 24KW in non-condensing mode, and 4.1 to 25.3KW in condensing mode - The latter mode being achieved by reducing the flow temperature. Anything below 50-60°C will put you in condensing mode.

At the risk of sounding like a broken record, based on that info do you reckon I should keep the central heating flow at 27c even though it’s consistently keeping a constant 14c for me or would you advise to push it up a little due to other factors such as sludge buildup or the longevity of the boiler?

QrizB

If a flow temp of 27C is working, leave it alone.

I'm a little surprised that it does work, as it suggests hugely oversized radiators, but you're the one with the data.