My boiler has just died. Need a hand speccing a new system!
Discussion
4 bed semi. 10 radiators (8+2 towel rails). 1 bathroom but may be adding an en-suite in the near future. Current system is vented with a cold water tank in the loft. Potterton profile system boiler was installed in 2004 and has just packed up.
1. A new system boiler is required. What brand do I choose? Which ones to avoid?
2. A new unvented 180l indirect hot water cylinder is required. What brand do I choose? Which ones to avoid?
3. A smart heating and hot water controller is required. A wireless thermostat is required. Smart TRV's are not required. Option to integrate existing electric UFH would be handy but not a deal breaker. App control would be great. Must be simple to use but have advanced functionality if required. This is my parents house and they won't be able to operate anything too complicated. I will take care of setting up advanced features and routines.
4. Is it worth moving the boiler and cylinder to the loft? It's a cold roof and I think it can get a bit draughty in there as evidenced by a lot of dust. The current boiler is in the kitchen and the cylinder is in the airing cupboard upstairs.
5. Is it worth creating heating zones? I don't see the point in having different temps in different parts of the house.
6. I read that it's good to have a system that has either weather compensation or opentherm compatibility, but not all boilers are compatible with these systems, or implement it poorly. It's not clear to me which boiler and control system is the correct one to go for, which links back to points 1 and 3.
7. Any other considerations that I haven't thought of?
1. A new system boiler is required. What brand do I choose? Which ones to avoid?
2. A new unvented 180l indirect hot water cylinder is required. What brand do I choose? Which ones to avoid?
3. A smart heating and hot water controller is required. A wireless thermostat is required. Smart TRV's are not required. Option to integrate existing electric UFH would be handy but not a deal breaker. App control would be great. Must be simple to use but have advanced functionality if required. This is my parents house and they won't be able to operate anything too complicated. I will take care of setting up advanced features and routines.
4. Is it worth moving the boiler and cylinder to the loft? It's a cold roof and I think it can get a bit draughty in there as evidenced by a lot of dust. The current boiler is in the kitchen and the cylinder is in the airing cupboard upstairs.
5. Is it worth creating heating zones? I don't see the point in having different temps in different parts of the house.
6. I read that it's good to have a system that has either weather compensation or opentherm compatibility, but not all boilers are compatible with these systems, or implement it poorly. It's not clear to me which boiler and control system is the correct one to go for, which links back to points 1 and 3.
7. Any other considerations that I haven't thought of?
Edited by rinseout on Tuesday 1st July 11:51
rinseout said:
4 bed semi. 10 radiators (8+2 towel rails). 1 bathroom but may be adding an en-suite in the near future. Current system is vented with a cold water tank in the loft. Potterton profile system boiler was installed in 2004 and has just packed up.
1. A new system boiler is required. What brand do I choose? Which ones to avoid?
2. A new unvented 180l indirect hot water cylinder is required. What brand do I choose? Which ones to avoid?
3. A smart heating and hot water controller is required. A wireless thermostat is required. Smart TRV's are not required. Option to integrate existing electric UFH would be handy but not a deal breaker. App control would be great. Must be simple to use but have advanced functionality if required. This is my parents house and they won't be able to operate anything too complicated. I will take care of setting up advanced features and routines.
4. Is it worth moving the boiler and cylinder to the loft? It's a cold roof and I think it can get a bit draughty in there as evidenced by a lot of dust. The current boiler is in the kitchen and the cylinder is in the airing cupboard upstairs.
5. Is it worth creating heating zones? I don't see the point in having different temps in different parts of the house.
5. Any other considerations that I haven't thought of?
If you've space for external control valves, pump and pressure vessel why not look at a regular boiler? Simpler and cheaper to repair. 1. A new system boiler is required. What brand do I choose? Which ones to avoid?
2. A new unvented 180l indirect hot water cylinder is required. What brand do I choose? Which ones to avoid?
3. A smart heating and hot water controller is required. A wireless thermostat is required. Smart TRV's are not required. Option to integrate existing electric UFH would be handy but not a deal breaker. App control would be great. Must be simple to use but have advanced functionality if required. This is my parents house and they won't be able to operate anything too complicated. I will take care of setting up advanced features and routines.
4. Is it worth moving the boiler and cylinder to the loft? It's a cold roof and I think it can get a bit draughty in there as evidenced by a lot of dust. The current boiler is in the kitchen and the cylinder is in the airing cupboard upstairs.
5. Is it worth creating heating zones? I don't see the point in having different temps in different parts of the house.
5. Any other considerations that I haven't thought of?
rinseout said:
A system boiler is a regular boiler as far as i'm aware?
No a system boiler will have built in valves, pressure vessel and circulating pump. Easy to instal and space saving. But a lot to pack inside the case and if anything fails a faff to strip out and little reliance on generic parts. For instance I'm cack handed but can replace an external pump, internal one and its call an engineer time.
I just replaced a regular boiler and was initially confused. My understanding is:
Regular boiler = literally just gas input, flow, and return, connections for on/off demand, and a plug. It does nothing except heat. The 3 port valves etc, filters, pumps, wiring centre/connections etc are all external.
System boiler = regular boiler + pump + possibly 3 port valves inside the box along with control hardware/wifi for stats etc.
Combi boiler = can be heat only or like mine a storage combi which is basically a system boiler + tank inside the box.
I might be wrong on all this.
Regular boiler = literally just gas input, flow, and return, connections for on/off demand, and a plug. It does nothing except heat. The 3 port valves etc, filters, pumps, wiring centre/connections etc are all external.
System boiler = regular boiler + pump + possibly 3 port valves inside the box along with control hardware/wifi for stats etc.
Combi boiler = can be heat only or like mine a storage combi which is basically a system boiler + tank inside the box.
I might be wrong on all this.
rinseout said:
I'm quite sure what you're talking about is a combi boiler. Perhaps someone else can chime in to confirm?
What you currently have is effectively a “heat only” boiler (pump separate in airing cupboard and a vented cyl with cold water store in loft as well as a F&E tank also in loft.“System Boiler” normally has pump internally and is normally set up with UVC and sealed system with expansion vessel
Upside is you get mains pressure to all hot and cold taps - because the boiler manages the pump it can control the difference between flow and return temps and modulate accordingly
“Combi boiler” is effectively a system boiler with ability to do HW on demand (lose all the tanks in loft as well as cyl in the airing cupboard - however I would not recommend a combi for a 4 bed esp if another bathroom was planned - they are normally sized for HW not for CH so when the majority of your energy used in a year (80% in my case) is CH an oversized boiler can result in more energy used.
If you are confident the existing pipework for CH, HW and CW can take mains pressure I’d go System Boiler with UVC.
If you aren’t I’d stay with heat only and keep the gravity system with a VC (vented Cyl)
Key point on boiler selection is to get one that has an excellent modulation (or turn down ratio) and size it for the heat loss of the property
I’d also be aiming to get the flow temps as low as possible to maximise condensing efficiency but your rad sizes and heat loss will ultimately determine that unless you’ve already upsized the rads
B'stard Child said:
Key point on boiler selection is to get one that has an excellent modulation (or turn down ratio) and size it for the heat loss of the property
I d also be aiming to get the flow temps as low as possible to maximise condensing efficiency but your rad sizes and heat loss will ultimately determine that unless you ve already upsized the rads
Nice. So i'm changing my heat only boiler to a system boiler. The rads are quite large so I'm confident that heat loss won't be an issue, however i'll make sure a heating engineer does the calcs. I d also be aiming to get the flow temps as low as possible to maximise condensing efficiency but your rad sizes and heat loss will ultimately determine that unless you ve already upsized the rads
Now let's turn our attention to points 1, 2, 3 and 6:
1. A new system boiler is required. What brand do I choose? Which ones to avoid?
2. A new unvented 180l indirect hot water cylinder is required. What brand do I choose? Which ones to avoid?
3. A smart heating and hot water controller is required. A wireless thermostat is required. Smart TRV's are not required. Option to integrate existing electric UFH would be handy but not a deal breaker. App control would be great. Must be simple to use but have advanced functionality if required. This is my parents house and they won't be able to operate anything too complicated. I will take care of setting up advanced features and routines.
6. I read that it's good to have a system that has either weather compensation or opentherm compatibility, but not all boilers are compatible with these systems, or implement it poorly. It's not clear to me which boiler and control system is the correct one to go for, which links back to points 1 and 3.
In my opinion, the hot water is the place to start. Questions like - How long to run a bath? What's the shower pressure / flow like? What happens to the shower if someone runs a tap somewhere else in the house? How soon can I run another bath after someone's just had one? Can everyone in the household have a hot shower in the morning? There's absolutely zero point in having efficient and cheap to run heating if it takes 45 mins to run a bath.
You need to look at the incoming cold water main - what's the flow (litres / minute) and what's the pressure. Decent pressure but poor flow (and vice versa) is a problem. If you've got decent flow and pressure (no idea what the numbers need to be), then go for a pressurised mains fed hot water cylinder and do away with the cold water tank(s) in the loft. If you haven't got decent flow and pressure then you'll either need to put in a whole house pump, or keep the cold water tanks.
As for make of boiler - Worcester Bosch are a well known reputable brand and ours has been reliable for the past 10 years. However, there are other well regarded brands such as Vaillant.
You need to look at the incoming cold water main - what's the flow (litres / minute) and what's the pressure. Decent pressure but poor flow (and vice versa) is a problem. If you've got decent flow and pressure (no idea what the numbers need to be), then go for a pressurised mains fed hot water cylinder and do away with the cold water tank(s) in the loft. If you haven't got decent flow and pressure then you'll either need to put in a whole house pump, or keep the cold water tanks.
As for make of boiler - Worcester Bosch are a well known reputable brand and ours has been reliable for the past 10 years. However, there are other well regarded brands such as Vaillant.
rinseout said:
B'stard Child said:
Key point on boiler selection is to get one that has an excellent modulation (or turn down ratio) and size it for the heat loss of the property
I d also be aiming to get the flow temps as low as possible to maximise condensing efficiency but your rad sizes and heat loss will ultimately determine that unless you ve already upsized the rads
Nice. So i'm changing my heat only boiler to a system boiler. The rads are quite large so I'm confident that heat loss won't be an issue, however i'll make sure a heating engineer does the calcs. I d also be aiming to get the flow temps as low as possible to maximise condensing efficiency but your rad sizes and heat loss will ultimately determine that unless you ve already upsized the rads
rinseout said:
Now let's turn our attention to points 1, 2, 3 and 6:
1. A new system boiler is required. What brand do I choose? Which ones to avoid?
Avoid - Ones that don't have a good modulation turn down ratio and can't run low flow temps1. A new system boiler is required. What brand do I choose? Which ones to avoid?
I made a bad choice with my previous gas boiler
it was oversized 24kW with a min of 10kW for a 7.5 kWh heat loss which after insulation improvements was a 4.5 kWh heat loss so it cycled like a t
t in the should seasons where my heat loss was more like 1.5 to 2.0 kWhincapable of running at a flow temp below 45 Deg C
My current boiler (Viessmann - 16 kW "Heat Only") is running full WC and DHWP (Domestic Hot Water Priority) is capable of running CH flow temps in the mid 20's - never went over 34 deg C last winter (but I have upsized all my rads to run low flow temps) but can do 115 litres of HW from 20 deg to 50 deg in 30 mins
rinseout said:
2. A new unvented 180l indirect hot water cylinder is required. What brand do I choose? Which ones to avoid?
One with a heating coil set up for ASHP so min 3 m2 ofcoil surface area - this means re-heat is fast even at lower flow temps on a DHWP set up rinseout said:
3. A smart heating and hot water controller is required. A wireless thermostat is required. Smart TRV's are not required. Option to integrate existing electric UFH would be handy but not a deal breaker. App control would be great. Must be simple to use but have advanced functionality if required. This is my parents house and they won't be able to operate anything too complicated. I will take care of setting up advanced features and routines.
This is tricky because functionality really depends on house usage - I went down the route of "Smart" TRV's on all rads and scheduling heating with multiple zones before I got a boiler that could do WCNow I'm removing pretty much all of that "Smart" stuff heating 24/7 with weather compensation and running the whole system as one big zone with flow rates set for each radiator/room heat loss
It really depends on usage patterns that you need.
rinseout said:
6. I read that it's good to have a system that has either weather compensation or opentherm compatibility, but not all boilers are compatible with these systems, or implement it poorly. It's not clear to me which boiler and control system is the correct one to go for, which links back to points 1 and 3.
WC and DHWP are an absolute must - Open Therm (using local weather is a good second best but an actual temp sensor on a north facing wall is in my opinion much better)omniflow said:
In my opinion, the hot water is the place to start. Questions like - How long to run a bath? What's the shower pressure / flow like? What happens to the shower if someone runs a tap somewhere else in the house? How soon can I run another bath after someone's just had one? Can everyone in the household have a hot shower in the morning? There's absolutely zero point in having efficient and cheap to run heating if it takes 45 mins to run a bath.
You need to look at the incoming cold water main - what's the flow (litres / minute) and what's the pressure. Decent pressure but poor flow (and vice versa) is a problem. If you've got decent flow and pressure (no idea what the numbers need to be), then go for a pressurised mains fed hot water cylinder and do away with the cold water tank(s) in the loft. If you haven't got decent flow and pressure then you'll either need to put in a whole house pump, or keep the cold water tanks.
As for make of boiler - Worcester Bosch are a well known reputable brand and ours has been reliable for the past 10 years. However, there are other well regarded brands such as Vaillant.
Incoming water flow and pressure are quite good. No idea of numbers, but I don't foresee an issue. Again, I will get the heating engineer to work it out when it comes to it.You need to look at the incoming cold water main - what's the flow (litres / minute) and what's the pressure. Decent pressure but poor flow (and vice versa) is a problem. If you've got decent flow and pressure (no idea what the numbers need to be), then go for a pressurised mains fed hot water cylinder and do away with the cold water tank(s) in the loft. If you haven't got decent flow and pressure then you'll either need to put in a whole house pump, or keep the cold water tanks.
As for make of boiler - Worcester Bosch are a well known reputable brand and ours has been reliable for the past 10 years. However, there are other well regarded brands such as Vaillant.
The shower is on a pump as the hot water pressure is crap. Hence the need to move away from a gravity fed system. I haven't timed it but I reckon it takes around 20 mins for the cylinder to reheat after someone has had a shower.
The heating engineer has provided quotes for Baxi and Ideal. TBH I would stick with one of these as they seem to be the most recommended from my limited research. Now it's just deciding which one is the best for my needs.
rinseout said:
Incoming water flow and pressure are quite good. No idea of numbers, but I don't foresee an issue. Again, I will get the heating engineer to work it out when it comes to it.
Get it worked out now so at least if you know what boiler type you need - Heat only, system or combirinseout said:
The shower is on a pump as the hot water pressure is crap. Hence the need to move away from a gravity fed system. I haven't timed it but I reckon it takes around 20 mins for the cylinder to reheat after someone has had a shower.
That could be improved by raising the CW tank but a pump is what most people do Both our showers are pumped because of hot water pressure however we didn't go down the route of UVC and mains pressure because our mains pressure is quite low in terms of pressure and flow (it above the min requirements but only just)
Shouldn't need to re-heat a tank after a shower unless teenage girls are involved - we have 115 litre HW tank and two of us showering twice a day, plus hand washing etc and we only heat the tank once a day 6 days out of 7 (Friday is Mrs BC's Bath night so that's the only day it gets heated twice - she likes a hot bath!!)
rinseout said:
The heating engineer has provided quotes for Baxi and Ideal. TBH I would stick with one of these as they seem to be the most recommended from my limited research. Now it's just deciding which one is the best for my needs.
What model(s) has he suggested?B'stard Child said:
Calcs for heat loss are really important - if you have gas consumption figures by month for the winter period you could use that to give a ball park understanding (provided you factor in heating by schedule or 24/7)
Now I'm removing pretty much all of that "Smart" stuff heating 24/7 with weather compensation and running the whole system as one big zone with flow rates set for each radiator/room heat loss
It really depends on usage patterns that you need.
Thanks. I'm obtaining gas consumption figures now.rinseout said:
Now let's turn our attention to points 1, 2, 3 and 6:
1. A new system boiler is required. What brand do I choose? Which ones to avoid?
Avoid - Ones that don't have a good modulation turn down ratio and can't run low flow temps1. A new system boiler is required. What brand do I choose? Which ones to avoid?
rinseout said:
2. A new unvented 180l indirect hot water cylinder is required. What brand do I choose? Which ones to avoid?
One with a heating coil set up for ASHP so min 3 m2 ofcoil surface area - this means re-heat is fast even at lower flow temps on a DHWP set up rinseout said:
3. A smart heating and hot water controller is required. A wireless thermostat is required. Smart TRV's are not required. Option to integrate existing electric UFH would be handy but not a deal breaker. App control would be great. Must be simple to use but have advanced functionality if required. This is my parents house and they won't be able to operate anything too complicated. I will take care of setting up advanced features and routines.
This is tricky because functionality really depends on house usage - I went down the route of "Smart" TRV's on all rads and scheduling heating with multiple zones before I got a boiler that could do WCNow I'm removing pretty much all of that "Smart" stuff heating 24/7 with weather compensation and running the whole system as one big zone with flow rates set for each radiator/room heat loss
It really depends on usage patterns that you need.
rinseout said:
6. I read that it's good to have a system that has either weather compensation or opentherm compatibility, but not all boilers are compatible with these systems, or implement it poorly. It's not clear to me which boiler and control system is the correct one to go for, which links back to points 1 and 3.
WC and DHWP are an absolute must - Open Therm (using local weather is a good second best but an actual temp sensor on a north facing wall is in my opinion much better)1. I've narrowed it down to Baxi and Ideal based on online recommendations. I'm not sure which one out of the two, or which models I should go for? The three choices are Baxi 800, Ideal Logic Max, and Ideal Vogue Max. Or perhaps none of these are suitable and I should go with something completely different?
2. Is that a twin coil cylinder? I had a feeling that such a setup would be more efficient if it was looped just to suck every last ounce of heat from it. Will the cheapest brand do?
3. As stated, I don't see the point in smart TRV's and multiple heating zones. A well-balanced system with manual TRV's is all that's required. Weather compensation, DHWP etc I believe are a must. I would opt with your suggestion of an external temp sensor. I just need to work out which boiler and control system is compatible.
rinseout said:
Incoming water flow and pressure are quite good. No idea of numbers, but I don't foresee an issue. Again, I will get the heating engineer to work it out when it comes to it.
B'stard Child said:
Get it worked out now so at least if you know what boiler type you need - Heat only, system or combi
Shouldn't need to re-heat a tank after a shower unless teenage girls are involved
What model(s) has he suggested?
I've got the heating engineer visiting this evening. I will pose all my question to him. This is handy so I know what to ask.Shouldn't need to re-heat a tank after a shower unless teenage girls are involved
What model(s) has he suggested?
He hasn't suggested any model numbers, simply provided a ballpark figure to change the boiler. He gave prices for Baxi and Ideal (Ideal being higher). I'll get a proper quote after he's had a look this evening.
rinseout said:
It looks like a Baxi 800 has weather compensation and DHWP. I believe both of the Ideals do too.
Something about return flow temp was mentioned and the ability to modulate?
That's one of the big advantages of a "system" boiler - it has control of the pump speed and can balance the boiler heat input with circulation flow and either ramp up/down the boiler heat input or speed up/slow down the pump speedSomething about return flow temp was mentioned and the ability to modulate?
Doesn't work so well if the boiler is oversized for the heat loss so you need to know the min boiler output compared to your heat loss.
If I had to recommend brands in no particular order it would be Atag, Vaillant, Viessmann but as far as controls are concerned a boiler is always going to perform best when the same manufactures controls are used
Third party controls like Hive, Evohome and Wiser (there are others) are rarely as good as for example Vaillant controls working with a Vaillant Boiler
Nothing technical to add from me except:
I had a troublesome boiler that (for some reason) I persisted with longer than I should have.
I asked each and every engineer which is the boiler manufacturer that they'd recommend based on reliability.
The two consistent brands that came up most recommended were Worcester Bosch & Vaillant. (In fact these were the only brands mentioned).
I did buy a Worcester Bosch & it was fine. I then moved house & bought a Vaillant and it too has been fine.
I had a troublesome boiler that (for some reason) I persisted with longer than I should have.
I asked each and every engineer which is the boiler manufacturer that they'd recommend based on reliability.
The two consistent brands that came up most recommended were Worcester Bosch & Vaillant. (In fact these were the only brands mentioned).
I did buy a Worcester Bosch & it was fine. I then moved house & bought a Vaillant and it too has been fine.
That sounds like a great idea!Gassing Station | Homes, Gardens and DIY | Top of Page | What's New | My Stuff