Hi there, thanks for your time to look at this record long post!! I work on the operational management side or a small building contracting firm. This question is for my own house setup.
We are really fortunate to have a large house, about 5,000sqft in total over 3 floors. It was built around 15 years ago by a reputable company with cavity walls and insulation plus timber double glazing etc. The heat loss is not bad from experience - so aside from peak winter - we can normally hold temperatures of 20 degrees around the house.
The house came with a little known I think 20kw Geminox boiler in the garage and 2 x unvented 200l cylinders from new in the loft. The original boiler kept breaking down plus would prioritise hot water over central heating and then be unable to cope with peak heating loads. However we had to work around the original pipework and circuits plus have not change the cyliners etc.
Around 10 years ago I replaced it with a new Worcester Bosch 40 CDI system boiler (specified by the plumber who does some work for us). Gas was something like 2.5p per kwh and for many years I did not worry about high gas consumption.
Now with gas prices so high it has come to my attention of how high our gas consumption is - it was up to 90,000kwh per annum and recently I've managed to get this down to 75,000kwh but this is still too high.
I've been studying the system and learning from online resources and Youtube videos so sorry for my basic understanding!
This is what I have currently:
Boiler set to flow 65 degrees - connected to Grundfos Alpha pump to vertical low loss header. I experimented increasing flow temperature but see below, I cannot get it to go much higher.
Two x 2 channel Honeywell programmer / timer clocks connected via a relay along with pumps below - so CH, cylinders, UF and towel rails each have a circuit.
From the low loss header we have:
1. Central heating circuit for first and second floors connected to max 12 radiators on two different zones (so 8 and 4 radiators) - controlled by a Nest thermostat and with a Grundfos Alpha pump and zone valve. My calculations suggest this should on peak load be 13-14kwh gas consumption but usually it will be around 8-9kwh.
2. Hot water cylinders x 2, each with a zone valve and connected with a Grundfos Alpha pump plus one zone valve for the circuit. These are connected with a secondary hot water brass circulator pump which is on most of the day (otherwise we lose a lot of water to get hot water). Based on my family usage and the circulator, I'd expect this to use about 30-40kwh of gas per day.
3. Underfloor heating circuit - connected with Grundfos UPS2 25-40/60 130 - zone valve for circuit and then going to two separate manifolds for the downstairs ground floor - each underfloor heated room is zone with actuator heads and room thermostats. The plumber put a JG blending valve from the low loss header flow and u/f return to ensure this circuit does not reach more than 45/50 degrees. The max demand with all circuits open I am guessing is around 19-20kwh but typically lets say 30-40% of that so maybe 8-9kwh.
4. Towel rails - with Grundfos Alpha and simply controlled on and one by the timer clock (use about 4 hours per day to heat bathrooms) - 5 towel rails - this should be 6kwh when open.
I can chart the central heating usage via the Nest app - so in peak winter to achieve around 20 degrees in the house - the circuit is open 8/9 hours. This reduces to 2/3 hours as the weather is above 7/8 degrees.
I cannot control or chart the underfloor usage. Two things I have noticed - throughout the course of the day, one of the underfloor heated rooms will be calling for heat maybe 0.5 degrees - and therefore the underfloor circuit can be on for quite a few hours a day even though it could only be one zone calling for heat. I'm experimenting overriding this with a timer function (so UF can only be on max 15 hours a day lets say). I am also trying to buy some programmable 2 wire battery room thermostats from Heatmiser.
The towel rails I can control using the timer clock.
I cannot tell how much gas the cylinders are actually using or how often the circuit is calling for heat. But if it is getting a max input flow temperature of around 50 degrees (see below) and the tanks are at 55 degrees, I wonder if this is an issue.
Another problem I wonder - using an infrared thermometer when all circuits are on - I feel like all the pump bodies on all circuits are showing a temperature of around 50 degrees (which is what the underfloor blending valve is set at) rather than 60-65 degrees which is the boiler flow. These pumps are within a couple of meters pipework from the boiler and the pipes are insulated plus in the garage, so this level of heat dropoff is confusing. I have copper pipe thermometers on the returns and they show max 40 degrees. It just got me thinking about whether it is possible the blending valve for the UF heating circuit is possibly causing the manifold to not output the true flow temperature of the boiler? So basically I am never getting 60+ degree to any circuit, but actually getting 45/50 degrees.
I've also been playing with all the pump settings to see if I notice any particular issues... but it is hard to decide the optimal CP or PP or set pressure settings for each pump. I think the CH and towel rails should be on set pressure I or II and the CH on CP (even though there are TRVs, they shouldn't be kicking in). The UF seems to work fine on setting 1 or 2.
The boiler is not cycling a lot because I put a wireless thermometer on the return to alert me when the return is above 45 degrees, and this happens rarely. The good thing is it is probably condensing all the time. However I would expect the return to rise higher when only one or two circuits are one (but it rarely does).
So a couple of novice ideas of the problem - maybe someone experienced could guide me :
1. The blending valve of the UF heating circuit is somehow affecting the low loss header to restrict the flow to 45/50 degrees all circuits i.e. UF temperature, instead of sending lets say 60+ degrees to CH, cylinders and towel rails and 45-50 degrees to UF?
2. The boiler modulation of this older boiler means it can do a minimum of 9kw output. If only one or two rooms are calling for UF heat for example, it means for many hours of the day the boiler is doing 9kw because it cannot modulate lower? So I should replace it with a more modern boiler that can modulate down to 3kwh lets say?
3. The boiler is not modulating the flow temperature well enough so it is works at max capacity too often? Recently I have range rated the boiler down to 60% to see what happens... at peak times it means the boiler is working flat out (can tell from my home hub gas consumption it is using 22kwh of gas per hour)... and so far the home is heating up ok... but this means it is going to take more hours to heat up the house (I'm experimenting so don't know the answer yet) so the net result may still be high gas consumption (i.e. more hours at lower output).
Any suggestions, ideas or thoughts would be much appreciated. I would have thought a house of this size and build should ideally not be consuming more than 30,000-40,000kw of gas per annum but maybe I am wrong.
We are really fortunate to have a large house, about 5,000sqft in total over 3 floors. It was built around 15 years ago by a reputable company with cavity walls and insulation plus timber double glazing etc. The heat loss is not bad from experience - so aside from peak winter - we can normally hold temperatures of 20 degrees around the house.
The house came with a little known I think 20kw Geminox boiler in the garage and 2 x unvented 200l cylinders from new in the loft. The original boiler kept breaking down plus would prioritise hot water over central heating and then be unable to cope with peak heating loads. However we had to work around the original pipework and circuits plus have not change the cyliners etc.
Around 10 years ago I replaced it with a new Worcester Bosch 40 CDI system boiler (specified by the plumber who does some work for us). Gas was something like 2.5p per kwh and for many years I did not worry about high gas consumption.
Now with gas prices so high it has come to my attention of how high our gas consumption is - it was up to 90,000kwh per annum and recently I've managed to get this down to 75,000kwh but this is still too high.
I've been studying the system and learning from online resources and Youtube videos so sorry for my basic understanding!
This is what I have currently:
Boiler set to flow 65 degrees - connected to Grundfos Alpha pump to vertical low loss header. I experimented increasing flow temperature but see below, I cannot get it to go much higher.
Two x 2 channel Honeywell programmer / timer clocks connected via a relay along with pumps below - so CH, cylinders, UF and towel rails each have a circuit.
From the low loss header we have:
1. Central heating circuit for first and second floors connected to max 12 radiators on two different zones (so 8 and 4 radiators) - controlled by a Nest thermostat and with a Grundfos Alpha pump and zone valve. My calculations suggest this should on peak load be 13-14kwh gas consumption but usually it will be around 8-9kwh.
2. Hot water cylinders x 2, each with a zone valve and connected with a Grundfos Alpha pump plus one zone valve for the circuit. These are connected with a secondary hot water brass circulator pump which is on most of the day (otherwise we lose a lot of water to get hot water). Based on my family usage and the circulator, I'd expect this to use about 30-40kwh of gas per day.
3. Underfloor heating circuit - connected with Grundfos UPS2 25-40/60 130 - zone valve for circuit and then going to two separate manifolds for the downstairs ground floor - each underfloor heated room is zone with actuator heads and room thermostats. The plumber put a JG blending valve from the low loss header flow and u/f return to ensure this circuit does not reach more than 45/50 degrees. The max demand with all circuits open I am guessing is around 19-20kwh but typically lets say 30-40% of that so maybe 8-9kwh.
4. Towel rails - with Grundfos Alpha and simply controlled on and one by the timer clock (use about 4 hours per day to heat bathrooms) - 5 towel rails - this should be 6kwh when open.
I can chart the central heating usage via the Nest app - so in peak winter to achieve around 20 degrees in the house - the circuit is open 8/9 hours. This reduces to 2/3 hours as the weather is above 7/8 degrees.
I cannot control or chart the underfloor usage. Two things I have noticed - throughout the course of the day, one of the underfloor heated rooms will be calling for heat maybe 0.5 degrees - and therefore the underfloor circuit can be on for quite a few hours a day even though it could only be one zone calling for heat. I'm experimenting overriding this with a timer function (so UF can only be on max 15 hours a day lets say). I am also trying to buy some programmable 2 wire battery room thermostats from Heatmiser.
The towel rails I can control using the timer clock.
I cannot tell how much gas the cylinders are actually using or how often the circuit is calling for heat. But if it is getting a max input flow temperature of around 50 degrees (see below) and the tanks are at 55 degrees, I wonder if this is an issue.
Another problem I wonder - using an infrared thermometer when all circuits are on - I feel like all the pump bodies on all circuits are showing a temperature of around 50 degrees (which is what the underfloor blending valve is set at) rather than 60-65 degrees which is the boiler flow. These pumps are within a couple of meters pipework from the boiler and the pipes are insulated plus in the garage, so this level of heat dropoff is confusing. I have copper pipe thermometers on the returns and they show max 40 degrees. It just got me thinking about whether it is possible the blending valve for the UF heating circuit is possibly causing the manifold to not output the true flow temperature of the boiler? So basically I am never getting 60+ degree to any circuit, but actually getting 45/50 degrees.
I've also been playing with all the pump settings to see if I notice any particular issues... but it is hard to decide the optimal CP or PP or set pressure settings for each pump. I think the CH and towel rails should be on set pressure I or II and the CH on CP (even though there are TRVs, they shouldn't be kicking in). The UF seems to work fine on setting 1 or 2.
The boiler is not cycling a lot because I put a wireless thermometer on the return to alert me when the return is above 45 degrees, and this happens rarely. The good thing is it is probably condensing all the time. However I would expect the return to rise higher when only one or two circuits are one (but it rarely does).
So a couple of novice ideas of the problem - maybe someone experienced could guide me :
1. The blending valve of the UF heating circuit is somehow affecting the low loss header to restrict the flow to 45/50 degrees all circuits i.e. UF temperature, instead of sending lets say 60+ degrees to CH, cylinders and towel rails and 45-50 degrees to UF?
2. The boiler modulation of this older boiler means it can do a minimum of 9kw output. If only one or two rooms are calling for UF heat for example, it means for many hours of the day the boiler is doing 9kw because it cannot modulate lower? So I should replace it with a more modern boiler that can modulate down to 3kwh lets say?
3. The boiler is not modulating the flow temperature well enough so it is works at max capacity too often? Recently I have range rated the boiler down to 60% to see what happens... at peak times it means the boiler is working flat out (can tell from my home hub gas consumption it is using 22kwh of gas per hour)... and so far the home is heating up ok... but this means it is going to take more hours to heat up the house (I'm experimenting so don't know the answer yet) so the net result may still be high gas consumption (i.e. more hours at lower output).
Any suggestions, ideas or thoughts would be much appreciated. I would have thought a house of this size and build should ideally not be consuming more than 30,000-40,000kw of gas per annum but maybe I am wrong.
