Thinking of getting rid of Back Boiler :Advise Appreciated

[riz1]

We have a GCH system with a back boiler in the in the living room. We would like to take the chimney brest out to increase space and thus I have assumed would need to upgrade Central Heating System.

My current set-up: back-boiler; central thermostat downstairs in hallway; thermostatic valves fitted to all radiators a couple of years ago; a hot and cold water tank in the loft; power [pumped] shower.

Which is the way forward: Combi Boiler or Condenser Boiler? A.N.Other?

I assume combis are more compact? [no idea how big a condenser boiler is nor how they are fitted - small wall-mounted units or free-standing boilers?] I also have read that Condensers are more expensive to buy/install and less reliable. I understand new rules push condensers but there are "opt-outs" for unsuitability etc.

how big is a Condenser anyway and where typically would it go? which is more expensive to run?

Would any new system allow removal of the hot and cold water tanks from the Loft [but allow a power-shower to still be kept]? It would be nice for the option of a loft conversion in future as they inhibit this at present.

I have a pressure motor attached to my shower [feeds from the tanks in the loft, lives under the bathtub]; would this preclude one type of boiler over another? EDIT: I think this would not be possible with the combi I think? Any way around it?

All help appreciated!

[John Rumm]

What else about your system (other than the presence of the back boiler) would you change? Does it meet your needs currently?

That's not an "or". Just about all types of gas boiler are available in condensing versions. A Combi is one that produces hot water "on demand".

Description of the basic types:

I assume combis are more compact? [no idea how big a condenser boiler

The smallest boilers are heating only, but in fairness all types are available in small wall mounting packages. Being condensing or not does not change the size generally.

Slightly more expensive to buy - but that is changing since that is what most people are now buying. Installing is not much different from an older boiler - you need one extra connection to take the collected water to a drain. Reliability if you buy one that was designed from the ground up as a condensing boiler should be fine (compared to any other high tech boiler stuffed with electronics)

To see how things have developed since your back boiler:

is a bunch of stuff to read that may help:

To choose a new one:

is a sealed system and why you might want one: good starting point: I understand new rules push condensers but there are "opt-outs" for > unsuitability etc.

Indeed, but they are hard to satisfy, and there is no reason to try in most cases.

Same size as any other really. Condensers use less gas and hence should be cheaper to run.

See the tables here for some example sizes:

Would any new system allow removal of the hot and cold water tanks

A combi could provide hot water without the cylinder, and hot water would be at mains pressure. There are other ways of getting mains pressure hot water as well.

It would not be usable with a combi, but then again you would not need it assuming your mains pressure is ok. If you mains is not ok then neither will be a combi.

Other options for high pressure hot water:

[riz1]

types:

> > I assume combis are more compact? [no idea how big a condenser boiler

boiler:

> There is a bunch of stuff to read that may help:

one:

> Another good starting point:> > I understand new rules push condensers but there are "opt-outs" for

sizes:

> > Would any new system allow removal of the hot and cold water tanks

water:

> --

In a nutshell my current system meets my requirements just fine, barring the new considerations of redecorating and gaining space.

If I were to go for a non-combi Condensing boiler, could one of these be fitted in my loft? If that were the case I could use the install occasion to maybe more the location of the CW and HW tanks in the loft so that they do not dominate the centre of the loft and thus free-up SOME space up there that way [as opposed to getting rid altogether] and also have the space in the living room.

Liked the idea of the compactness of a combi but seems to entail a lot of other changes in terms of water feeds etc?

[John Rumm]

In which case there is no pressing need to change much other than the boiler.

Yes they can, usually helps if you have a gable end wall to hang them on. There are some other requirements to make working on the boiler safe like having a floored section, and guard rails round the loft hatch, and proper lighting.

There are other less obvious options you could go for. For example keeping your current system of tanks etc, but fitting a combi. The heating side of this would run the rads and hot water cylinder in exactly the same way as an ordinary boiler, but you also have an on demand mains pressure hot water source. This could run a nice shower, or provide quicker hot water (depending on length of pipe runs etc) to a kitchen sink etc.

If you fit a sealed system then you would also get rid of the current header tank for the central heating, leaving just the cold and hot water ones.

The main attraction of combis is they are easy to fit and don't require much in the way of support hardware, hence why many plumbers like them. Just a connection to the flow and return for the radiators, and mains cold in, with hot water out. The downside is the flow rate of hot water out of the majority of commodity boilers will not match a well implemented storage system, so baths take longer to fill[1]. Showers on the other hand are often better since you have mains hot water to play with.

[1] these are generalisations that represent "most" installations. If you go for more exotic systems like big storage combis that have an internal thermal store you can get better flow performance from them, at least for a time.

[riz1]

Many thanks for the very informative replies and links. Would it be a reasonable summary for me to think that the 2 most realistic options for me are:

1) replace the current back-boiler with a new condenser "system" boiler which would keep all my tank arrangements in the loft as-is, indeed leave the majority of the system as is but give me the chimney space in the living room? 2) replace the current back-boiler with a combi condenser boiler. Then I could again either leave the CW and HW tanks in the loft as is [but I don't really understand what purpose the HW tank serves] or else get rid of the HW tank and have mains hot water throughout and so also get rid of the noisy shower pump? This I presume would depend upon my mains pressure/flow? How is the best way to guage this?

If I wanted all-out change and wanted a new boiler and also to get rid of the CW and HW tanks in the loft [and then stump up for a loft conversion!] I would need a "sealed" system? I couldn't really follow what changes that would entail.

Finally - my gas pipes etc are currently all set up to feed my backboiler. IF I wanted the new boiler in the loft [ignoring the changes wrt flooring etc that needs] is it a lengthy job to reroute gas pipes etc etc up there?

[John Rumm]

A system condensing boiler would most likely run the heating as a sealed system. So you would lose the small heating header tank in the loft (or at least disconnect it). It would also contain the pump, so again a bit of simplification.

The least change would be with a heating only condensing boiler. Some of these can run vented rather than sealed if you want, and that would in theory mean no other changes required. However if you want to move the boiler to the loft, which is where I presume the current feed and expansion (i.e. small) header tank is, then you would find life simpler with a sealed system.

The purpose of keeping the hot water tank would be to retain the ability to rapidly fill baths. A largish 40kW combi will deliver say 16 litres per min at bath temperature. A cylinder may deliver 25 litres per min at

65 degrees C, to which you would then add say another 15 lpm from the cold to get a bath at the right temp. Hence you tanked system can fill a bath at 30 lpm, compared to the combis 16.

There are ways of getting more flow from the combis by going for those that have a built in store of water as well. However these are bigger heavier units.

Yup, if you plumbed the shower from the combis hot water output then you would have quiet mains pressure hot water.

Well the important one is really flow rate. Pressure wants to be "enough", but most combis will run on 1 bar or a little less. If you can stall the flow of mains cold water at a tap by sticking you hand over it then it might be worth measuring properly to make sure, otherwise you can assume the pressure will be ok.

To measure the flow rate, you need a stopwatch and a bucket of known capacity. Find the cold mains fed tap with best flow rate (might be the kitchen cold tap) and time it to fill the bucket. Less than 15 lpm is really a non starter for a combi. 20 lpm is marginal but ok, 25 or better ought to be fine.

Sealed systems are generally easier to use and maintain, and are a good choice when positioning header tanks above the whole system will be tricky (i.e. loft conversions - the reason I ditched my tank based system and used a combi).

The nitty gritty of converting from tanks to combi is pretty much as I described here:

From a pipework and plumbing point of view combis are simple.

Easiest way is often to just run up the outside of the house and go back in a loft level.

[Ian_m]

Or do what my mate recently had done a like for like back boiler swap. It was not possible to fit a modern condensing back boiler no where to take vent, being a mid terraced house. Nearest place at for vent at front was next to next doors front door and at back was next to his back door.(could go up as too far as well) Also there was no place for the condensate drain the backbolier being in the middle of the house. One option considered was in the kitchen, but that would have required extensive replumbing (all ceilings downstairs removed) and sacrificing one cupboard out of four in the tiny kitchen. Another option was the loft for the boiler, but due to low roof gave insufficient height + again plumbing nightmare in getting the services to the boiler.

In the end I think the 1971 Baxi Bermuda was replaced with a similar Baxi back boiler model with a fire front, left as gravity HW and pumped CH. I think it cost £2500, where as all the other options started at £5k, due to extensive building work required.

[A.Lee]

...

I did this when I moved into this house around 10 years ago. There was a horrible gas fire with a back boiler in the fireplace. We wanted an open fire, so the back boiler would have to go anyway.

Remarkbly simple to do it all. Got the quote for a combi boiler, was around £1000 fitted, using most of the existing pipework/radiators. It was moved to the opposite end of the living room, on the wall. The plumber disconnected the old back boiler and fire, and I removed them myself, and rebuilt the open fire.

The benefit of the combi was the instant(ish) hot water, with no hot water being wasted - no hot water tanks needed - that was another bonus, the cupboard with the copper cylinder and expansion tank is now a wardrobe. The gas bill dropped by around a third instantly. The shower head can be plumbed directly to the hot and cold water supply in the bathroom, as all hot water will be near to mains pressure with a combi boiler. Definitely a worthwhile change. Alan.

[bof]

In message , Ian_m writes

My dear old mum phoned the other day to say she wanted to get a new back boiler to replace the old one and when the plumber came round he said he wasn't allowed to fit them anymore. It could be my mum has got the wrong end of the stick or could be a load of porky from the plumber, or is there some restriction on the fitting of a replacement back boiler?

[Andy Hall]

It depends.

There are requirements as of April 2005 that new boilers must have a minimum efficiency. The figure has been set such that this implies the use of a condensing boiler. Even the most recent of non condensing designs and certainly back boilers just don't make it.

However.... there are some exemptions that *could* be brought into play which relate to the degree of difficulty of the installation. Note that these don't relate to whether or not it would suit an elderly lady.

There is an assessment procedure and points system for factors such as type of house, fuel, relocation, flue etc.

Have a look at

you can work out whether your mother's house and installation situation would result in a score of more than 1000 points.

If it would, then it is not a requirement to fit a condensing boiler.

I did this exercise for my parents' place a while ago. The have a BB located effectively in the centre of the house and adding everything up would result in > 1000 points.

But....

having said all of that.. your mother may also be interested in lower gas bills that fitting a condensing boiler would entail.

[bof]

Thanks for that, the issue isn't really whether it's condensing or not, more about the where it could be fitted.

Currently the boiler is behind the fireplace in the living room in the centre of a semi.

The only other realistic options would be:

in the loft, this would require a lot of new pipework then wouldn't be accessible.

possibly in the kitchen, not sure if there's enough wall space and directly above is the bath and the pipes would need to come up under this and run through the floor space of a couple of rooms.

Change the system from stored hot to a combi in the kitchen, which would have the advantage of the DHW pipes being in pretty much the right place and only the bathroom floor to come up to join to the existing CH pipework.

As it is, it looks like a back boiler direct replacement would be by far the simplest install, and as the flue would be >2m and I'm pretty sure it would need a pump or soakaway for the condensate it scores >1000.

If I was doing it for myself I think I'd go for the kitchen/combi option if there enough wall space available.

What I can't see from the form is how much more an option has the cost before you can discount it as an option. "Exceptionally high" is rather woolly.

[Ed Sirett]

Replacement back boilers are available ( and if your mother's house is a mid-terrace or flat the exemption procedure can apply).

However the cost of a new BBU+fire front starts to weigh heavily towards biting the bullet and going for the big upheaval.

[Andy Hall]

Which is why the points system is meant to address that.

590 points

Possibility and doesn't count for points. Accessible to who though?

Different room 350 points

Note that you can only count 200 points for extended flue for the possible position. In other words, if it were possible to fit it in the kitchen but still necessary to have a long flue, then it's 350 +

200points. However, if moving it from the living room to the kitchen means no long flue is necessary from the kitchen position, it's only the 350 points.

Condensate drain, same issue. If you don't need one in the new possible position, points don't count.

So... if it is possible to fit it in the kitchen, the points may only be 590 + 350 ( = 940) and a condensate pump/soakaway would have to be required for it to be exempt.

If you read the introduction, there is a set of rules for that. The assessor must work it out based on the least expensive option regardless of aesthetics while eliminating any of the positions that are unsuitable according to the list in the assessment document. That becomes the baseline cost and you can't get exemption based on cost.

However, the assessment form is filled in and self certified by the installer, so in practical terms it becomes what the installer is willing to sign. The other side of that coin is that some number of installations are inspected, and also there could be an issue down the road at the point that the house is sold.

I can completely understand the position of an older person not wanting too much disruption, and for that reason preferring to replace like with like. Mr. Prescott didn't consider that when he ran the department responsible for this legislation.

Another thing that you could do is to see how practical it is to maintain the existing boiler in good order. These are not high tech devices and it may be that that is realistic for some time to come.

[Frank Erskine]

Mr Prescott didn't consider an awful lot, apart from extracurricular legovers, and croquet during working hours at his 'company' house ...

[bof]

I added +2m flue +condensate pump for that and somehow(?) came up with >1000, which a second look says should be 890, which seems to be the max possible for a semi. So basically it looks like if you have a semi you have to have a condensing boiler.

I was reading this bit: "In exceptional circumstances it is permissible to install a non-condensing boiler instead of a condensing boiler, provided that an assessment of the property by a competent person confirms that the additional cost of installing a condensing boiler is exceptionally high". Due to the layout of the kitchen it's not certain that it's possible to fit a boiler there without a fair amount of refit, the absolute minimum is going to be relocating the cooker and fitting new work surfaces and cupboards. If the kitchen window were replaced with a smaller one it would certainly fit. So what value of additional cost counts as exceptionally high?

I don't think the disruption is necessarily an issue, it just looks like there's likely to be a vast amount of additional work (and presumably cost) not to replace like with like.

Her mind seems pretty well made up, she wants a new living room fire anyway.

Anyhow, thanks for all the info, having spoken to her again the original plumber didn't unequivocally say he couldn't fit a back boiler, and is returning at some point with a new plan.

[Andy Hall]

No you can get to > 1000 if the present position and alternatives would also result in long flue

I think that you should be able to get an exemption on that basis. There isn't a requirement to completely rip the house apart.

If she is otherwise happy with his work and he is happy to sign off the exemption, I don't see that there should be a problem.