Hi, have been reading this website for a few years and wondered if anyone could help save me from the misery of a Combi Boiler?
I have just moved into a 1970's flat roofed bungalow and am about to have central heating fitted. If I must have a Combi boiler I will, but would very much like to avoid it. Compared to the standard open vented boiler and cylinder I grew up with I find they are unreliable, take forever to fill a bath and produce a pitiful flow of not very hot water - the temperature of which varies wildly according to the temp of the incoming main. I would also like to avoid a temperamental pressurised, unvented system due to the servicing requirements/safety/cost issues.
At first I was going to get another combination tank (like the existing Economy 7 one) but with an indirect coil, so I can heat it from a boiler and still have the immersion for backup. I had this setup in another flat and it worked really well. The flow rate wasn’t huge but at 60°C the water was hot enough that you could mix in plenty of cold and fill a bath very fast.
Unfortunately the fancy wall mounted taps I have fitted are 1.5 bar mixers – so the head is insufficient. I planned to simply fit a booster pump with flow switch, to the hot outlet on the cylinder. I have done this before on a standard vented cylinder with separate header tank and it worked fine.
Then it was pointed out that a combination cylinder only has 40l of cold storage and that a pump could suck it dry faster than it would refill. You can buy a tall Fortic F3 combination cylinder with 228l of cold and 115l hot to solve this problem. Many people online report success fitting a pump to this setup but plumbers worry about flow rates and seem wary in case anything goes wrong and they get the blame!
I also found that Range sell Kernel Plumbing Unit Model RP0779. It’s a 227L cold feed tank on top of a steel frame with a 140l cylinder underneath. All pre-plumbed with a 1.5bar Monsoon pump. They are a bit expensive but seem ideal. However, yesterday I discovered that the immersion boss is half way down the cylinder. Surely this will only heat the top half? If so would that only provide 70l of hot water? – the huge bath I have holds 231l in total.
This is an issue as I had planed get a cylinder installed, use the immersion for hot water now, then get a full boiler and rads fitted later on.
Do you think a normal combination tank with large cold storage could be pumped? I don’t have a shower or expect massive flow rates just a reasonable flow of properly hot water.
Sorry for all the questions. I suspect I will end up with a Combi boiler in the end but as you can see I'm trying hard to avoid it!
I have just moved into a 1970's flat roofed bungalow and am about to have central heating fitted. If I must have a Combi boiler I will, but would very much like to avoid it. Compared to the standard open vented boiler and cylinder I grew up with I find they are unreliable, take forever to fill a bath and produce a pitiful flow of not very hot water - the temperature of which varies wildly according to the temp of the incoming main. I would also like to avoid a temperamental pressurised, unvented system due to the servicing requirements/safety/cost issues.
At first I was going to get another combination tank (like the existing Economy 7 one) but with an indirect coil, so I can heat it from a boiler and still have the immersion for backup. I had this setup in another flat and it worked really well. The flow rate wasn’t huge but at 60°C the water was hot enough that you could mix in plenty of cold and fill a bath very fast.
Unfortunately the fancy wall mounted taps I have fitted are 1.5 bar mixers – so the head is insufficient. I planned to simply fit a booster pump with flow switch, to the hot outlet on the cylinder. I have done this before on a standard vented cylinder with separate header tank and it worked fine.
Then it was pointed out that a combination cylinder only has 40l of cold storage and that a pump could suck it dry faster than it would refill. You can buy a tall Fortic F3 combination cylinder with 228l of cold and 115l hot to solve this problem. Many people online report success fitting a pump to this setup but plumbers worry about flow rates and seem wary in case anything goes wrong and they get the blame!
I also found that Range sell Kernel Plumbing Unit Model RP0779. It’s a 227L cold feed tank on top of a steel frame with a 140l cylinder underneath. All pre-plumbed with a 1.5bar Monsoon pump. They are a bit expensive but seem ideal. However, yesterday I discovered that the immersion boss is half way down the cylinder. Surely this will only heat the top half? If so would that only provide 70l of hot water? – the huge bath I have holds 231l in total.
This is an issue as I had planed get a cylinder installed, use the immersion for hot water now, then get a full boiler and rads fitted later on.
Do you think a normal combination tank with large cold storage could be pumped? I don’t have a shower or expect massive flow rates just a reasonable flow of properly hot water.
Sorry for all the questions. I suspect I will end up with a Combi boiler in the end but as you can see I'm trying hard to avoid it!
