New combi install or replacement Thermal Store ?

[picbits]

Having a bit of a rethink about our current heating system. The boiler looked like it was on its last legs and the existing thermal store was starting to leak around the immersion/thermostat/pipework.

Initial plan was to scrap the thermal store and existing Potterton Prima F50 and replace with a Broag 28kw combi boiler. We only use hot water really for showers and washing up so this seemed to make sense.

Had quotes for around £1600 for the boiler, flush and installation which is bearable but having just repaired the Prima PCB, the boiler is working perfectly.

You can get a vented Albion 170L Thermal Store cylinder for around £850 delivered and its within the scope of a competent DIY'er to install so I had a rethink.

Pro's of a Combi :

Instant hot water on demand
Probably more economical than a thermal store
Gain airing cupboard space

Cons of a Combi:

Around 11L/min with a 28kw boiler, at some point we may need 2 showers operating at the same time.
More things to go wrong with it.
When it does go wrong, you lose heating plus hot water
Higher installation cost (and new outside gas pipe as we have 15mm at the moment).

Pros of a Thermal Store:

Instant hot water (if the tank is up to temperature)
30L/min water flow
Faster central heating heat up time
Diy installation possible
Backup immersion heater in case of boiler failure
Half the price of a new install
Cheaper servicing than an unvented system
If the boiler fails then a system boiler is simpler and cheaper to replace than a combi boiler.

Cons of a Thermal Store:

Less efficient as you have to keep the tank heated at 80+C so heat losses come into effect (although these are lost into the house so nothing really lost in the winter).
Lose space in airing cupboard
Three times the inhibitor required




Soooooo ..... a bit torn between the two. I'd like a combi but don't want the messing about boiling kettles of water to wash in if it fails. On a serious budget as well as I'm not getting into debt and will only spend what we have saved up. I'm quite happy to install a new cylinder - plumbing doesn't bother me in the slightest.

What are eveyone elses opinions on the above ?

Ta
Dom

 

[Deleted member 105431]

if it was my house I'd go for a high power combi such as glow worm ultracom 38cxi, stick it in the kitchen or loft and free up the airing cupboard. The gas saving will be around 30% and although the hw flow will be lower you could have 1 electric shower as a backup?

 

[BigBurner]

Pros of a Thermal Store:

Instant hot water (if the tank is up to temperature)
30L/min water flow
Faster central heating heat up time
Diy installation possible
Backup immersion heater in case of boiler failure
Half the price of a new install
Cheaper servicing than an unvented system
If the boiler fails then a system boiler is simpler and cheaper to replace than a combi boiler.

Cons of a Thermal Store:

Less efficient as you have to keep the tank heated at 80+C so heat losses come into effect (although these are lost into the house so nothing really lost in the winter).
Lose space in airing cupboard
Three times the inhibitor required

Thermals stores are NOT less efficient.hey are very efficient indeed, especially when using a heat bank version. The cylinder can be at 65-70C with a heat bank. The extra inhibitor is not a real downer. You can have a Smart pump on the CH and TRVs all around. There are many variations of thermal store/heat banks. Few people know much about them.

In your case, get the Broag 39C Combi with outside weather compensator and OpenTherm controller. You will not regret it. It will do two showers.

For backup fit an in-line electric water heater - not an electric shower. It will do one shower and a couple of taps. Not all at once but fine for backup. About £110 or so.
See:
//www.diynot.com/forums/viewtopic.php?p=1028649#1028649

A quality combi should always be the first selection. If not suitable then a heat bank.

The way energy prices are going it may be cheaper to heat via electricity. A heat bank/thermal store can heat CH & DHW. At any time a 12kW immersion can be added to heat the lot. Best have two immersion bosses. You may want to think ahead.

Quality combis do not break down a lot. Quality combis are NOT prone to failure. Quality combis can give flowrate.

 

[picbits]

Biggest problem is budget. I can just about scrape to a Broag 35C with installation but it is literally scraping it.

I'll see next week if I can bag a Broag a bit cheaper than standard retail but I'm veering towards the combi as I can make use of the airing cupboard space for another project.

 

[BigBurner]

Biggest problem is budget. I can just about scrape to a Broag 35C with installation but it is literally scraping it.

I'll see next week if I can bag a Broag a bit cheaper than standard retail but I'm veering towards the combi as I can make use of the airing cupboard space for another project.

If cash is the problem, just fit the biggest Broag combi you can - they are well, priced. Fit very cheap controls, then replace with an OpenTherm controller and outside sensor later. Also later an in-line electric water heater can be fitted in the combis DHW outlet. I would try and get the cash for the OpenTherm controller and ouside weather temperature sensor. The in-line heat can be fitted at any time - it is a separate item entirely.

 

[picbits]

Controls are sorted - I have a room stat with timer which I fitted a week ago.

I went to school with someone who is quite high up at Broag so will give him a yell next week and do some begging

 

[BigBurner]

Controls are sorted - I have a room stat with timer which I fitted a week ago.

If you get a Broag, replace the stat/timer with an OpenTherm controller and outside weather sensor, when cash is betters for you. Well worth doing.