Suggestions for a new heating system

[Edders]

I have read some of the other threads, but they seem quite complex.

 

The house

• I have a 1970s detached house, 5 beds. 300mm insulated loft, main house walls are cavity insulated.
• Older PVC double glazed, they don't have trickle vents.
• I'm on gas mains, have a 5.5KW PV array that is on 14.5p/KW FiT.
• The boiler is an Ideal Classic, 24KW located in a kitchen cabinet
• Small VC, expansion tank in the loft for the rads.
• About 15 rads, 1900ft2 ish
• 2 bathrooms (soon to be a third) all with showers
• Stuart Turner 2.5bar shower pump
• Incoming water mains is via 15mm copper pipe, get about 12l per minute

 

Problems with the boiler 

The boiler keeps cycling, on for 30s, then off for 15s then on again, ad-infinitum.

I have flushed the system several times, used the Sentinel X400 (or something like that) ran it hot for a few days and flushed it etc. Also changed the CH pump. Seemed to make it a little better. Turning the rad temp down helped more.

The 2 port diverter valves keeping burning out the actuators, I later found that the valve is quite hard to turn with pliers and ended up leaving it open.

 

Problems with the hot water

I've got a teenage daughter, she spends forever in the bathroom washing her hair etc.

My poor VC can't cope. Pressure starts of great for the first 5 minutes, then trickles out.

 

What I'd like

• More hot water at pressure
• A boiler that works properly and be more efficient
• A hot water cylinder that has an immersion element, preferably 2 to be heated by the excess power from the PV array
• Like to relocate the boiler away from the kitchen. I do have an under stairs cupboard that may work, it's on the other side of the wall of where the current boiler is.

 

Now I've considered ASHP, though I'm not keen on the size of the unit and the noise they make. Plus I don't think it'll work too well with my current rads.

Also read that it's costing people a lot more to run. But feel free to put me right.

 

• So, traditional boiler or system boiler?
• Should I consider an unvented system, but bearing in mind the pressure isn't that high?
• When is a thermal store a good idea? (I don't have a back boiler, just mains gas and solar PV)
• Stick with a vented cylinder, but upsize it to say 250L? Any recommended that can have a couple of immersions and have very good insulation ?

 

 

[SteamyTea]

58 minutes ago, Edders said:

But feel free to put me right.

Plenty of posts showing that a properly designed system does not have the zombie myths you have heard about.

 

 

[Edders]

15 hours ago, SteamyTea said:

Plenty of posts showing that a properly designed system does not have the zombie myths you have heard about.

 

 

SteamyTea, got any good examples you can refer me to?

Everyone has their own opinions etc

[SteamyTea]

48 minutes ago, Edders said:

SteamyTea, got any good examples you can refer me to?

Everyone has their own opinions etc

@joe90, @ProDave, @Jeremy Harris (even though he is not here)

A complete housing estate just outside St. Agnes.

 

You tend to hear about the disasters, not the ones that cause no problems.

[joe90]

True I am very pleased with my ASHP but not sure it’s the answer for @Edders situation. An ASHP can only heat slowly unlike a gas or oil boiler so if high hot water consumption is needed a very large DHW would be required. It sounds like his current gas boiler is either not working properly or is inadequate for the job. I would be interested in @Nickfromwales take on this one ?.

Edited May 19, 2021 by joe90

[SteamyTea]

32 minutes ago, joe90 said:

An ASHP can only heat slowly unlike a gas or oil boiler

That is all to do with the designed output, why they are rated in kW

A kW is 1000 joules per second.  A joule is a unit of energy.

 

Specific Heat Capacity also uses joules, kJ/kg.K

 

This is why, knowing the energy needed to raise the temperature, and knowing the power you can supply, you get the time needed.

 

J/kg.K / J/s

Edited May 19, 2021 by SteamyTea