UKC

Replacement combi boiler

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 subtle 25 Nov 2021

Ok, so my combi boiler is due to be replaced next year - however with the current trend to move away from these what do I install instead.

House is a 200 year old house, we have lived in it for 20 years, dont want to rip it apart to install things like under floor heating etc.

Further insulation would be tough to install.

So, what to do about the combi - this gives us how water and heating through the radiators.

1. Install new combi and just accept that gas prices will continue to rise

2. Install new hot water system and go to infra red heaters, thus getting rid of the hot water heating system? (although how to heat the water for showers etc?)

3. Something else?

In reply to subtle:

Pure electric heating is expensive, just don't.  IR heaters don't heat the fabric of the building so are great for e.g. Scout huts but not houses.

A heat pump with larger conventional radiators is probably the way, you don't have to go with underfloor.

In reply to subtle:

1. Nah

2. Good idea, and you can sample one room at a time with IR to see if it works for you before fully committing. Heating the fabric of the house is exactly what they do - if an IR panel is pointed at a 200yo stone wall, that wall will gently heat up, and retain that heat with the panel off. It is wet systems that heat the air by convection, which can quickly escape from poorly insulated properties. Electric showers, undercounter heaters for water (kitchen tap, etc), or reinstate a water tank with electric immersion. Then heat/charge it overnight on a low-rate tariff.

3. tepeo or Caldera, depending on house size.

4. Insulation, however tricky to install, will make any solution better.

5. Don't let the absence of your 'perfect' solution stop you from making incremental improvements, even if there is no product that immediately replicates the cost and function of your gas combi - can you replace part of the system? eg: You could keep your combi boiler for hot water to the taps only (approx. 15% of winter heat consumption), and use an electric solution for space heating only. Be that a heat pump with big ol' rads or one of these alternatives.

6. You'll get better advice from a good heating engineer visit than forum replies with limited understanding of the property and your use case

 Maggot 25 Nov 2021
In reply to George Killaspy:

7. How deep are your pockets.

 subtle 25 Nov 2021
In reply to George Killaspy:

> 2. Good idea, and you can sample one room at a time with IR to see if it works for you before fully committing. Heating the fabric of the house is exactly what they do - if an IR panel is pointed at a 200yo stone wall, that wall will gently heat up, and retain that heat with the panel off. It is wet systems that heat the air by convection, which can quickly escape from poorly insulated properties. Electric showers, undercounter heaters for water (kitchen tap, etc), or reinstate a water tank with electric immersion. Then heat/charge it overnight on a low-rate tariff.

> 3. tepeo or Caldera, depending on house size.

> 5. Don't let the absence of your 'perfect' solution stop you from making incremental improvements, even if there is no product that immediately replicates the cost and function of your gas combi - can you replace part of the system? eg: You could keep your combi boiler for hot water to the taps only (approx. 15% of winter heat consumption), and use an electric solution for space heating only. Be that a heat pump with big ol' rads or one of these alternatives.

> 6. You'll get better advice from a good heating engineer visit than forum replies with limited understanding of the property and your use case

Now, some of the above is very interesting.

Keep the combi for now, start phasing out some of the existing rads (would need to keep the wet heating going with a loop when taking rad out of the system), put in infra red heaters to see how they go over the winter - all whilst waiting for either a tepeo or caldera unit is made to substitute the combi boiler - could then revert back to wet rad system heating once they are eventually available.

Yes, I would get advice form a heating engineer, but, being cynical, they would tend to try and steer me towards their system/product whilst on here you get a more open and diverse recommendation - I can then use that as the starting point for discussions with heating engineer

In reply to George Killaspy:

Electric showers are awful.  Just no.

A tank with a pump could work, but electric heating is really, really expensive.

 mutt 25 Nov 2021
In reply to subtle:

whilst electricity is generated by gas you can't escape the cost increases. In time that will change but then the gas prices might well drop from this exceptionally high cost at present. 

Insulation and Alternative energy will isolate you from  gas and electricity prices to a degree for an relatively high initial investment. The Green homes grant is coming back so an airsource heat pump might well be possible depending on the size of your house. Also Solar hot water is easy to install but you will need to find space for a hot water cylinder. Insulation is a must. Double glazing and loft insulation as a minimum. Cavity insulation if you have cavity walls and general draft proofing are relatively easy.

alternatively go on using the combi for as long as you can. I'm sure someone will tell me/you that is suicidal but my gas boiler has been running fine since the 1990s and I'm going to keep it until either it packs up for good or some suitable sustainable heating solution is presented at reasonable cost.

Remember that space heating is about 20times the cost of water heating from the models that I have seen. More so if the heat is leaking out.

In reply to mutt:

This is a good point - what does the OP mean by "due to be replaced"?  There's little point replacing one (if it isn't an ancient non-condensing one) unless it is actually causing problems.  Hang on 5 years and heat pumps may be more affordable and the energy price situation clearer.

 tjhare1 25 Nov 2021
In reply to Neil Williams:

We were planning to but unfortunately our hand was forced when a plumber came and told us the boiler was non-compliant and disconnected it. Without time to prepare, insulate, get some modern large radiators or do underfloor, we had to go for a new combi.

Our house is like the OPs, quite old, with solid 2ft thick walls and no insulation either internally or externally. We do have a moderate amount of loft insulation and predominantly double glazed windows (though they are large sashes). We live in a conservation area so external work is a no-no. Internally, we’d rather not rip out everything and lose space in the process of fitting solid wall insulation, but might consider it on a room by room basis.

So with that said, what I think is lacking online are real-world examples of using a heat pump and not making much by way of additional major changes to an old heat-sink house. I’m hoping the UKC hive-mind might be able to give me some of this, so if you’ve installed an ASHP and not done much else to an old house, how is it? Warm enough? Most of the time? For context my house at this time of year with 2-3 hours heating in the evening is a balmy 14C daytime, increasing a few degrees to perhaps 16-18 in the evening with heating and cooking/living/etc. Averaging about 3-4 cubic metres gas per day so far this week for a 2 person house having a shower each per day.

With the assumptions above, would it be a) feasible to be adequately warm (preferably a bit more than 14c for working at my desk all day everyday…) and b) at a reasonable running cost vs current?

Post edited at 15:07
 Iamgregp 25 Nov 2021
In reply to subtle:

3. Do nothing at all.  Our combi boiler has due to be replaced for years.  Every time an engineer comes round they turn it off and put tape over it saying "do not use" but verbally tell to just carry on using it as it's fine.    

 stubbed 25 Nov 2021
In reply to tjhare1:

14 degrees is cold for working at a desk all day. Do you wear a coat all the time? I have worked from home for years and ended up with an electric radiator for the single room I worked in for when it got too cold.

 jimtitt 25 Nov 2021
In reply to subtle:

Depends on the the room available, I run pellet central heating (actually a pellet plant and a wood gasifier as well as an option but I've loads of space for the plant and fuel storage).

 tjhare1 25 Nov 2021
In reply to stubbed:

I have one of those mini oil heaters on a thermostat, but it’s obviously not an ideal solution. Aware of pricey electric heat I probs don’t ad me more than a few degrees. Tend to work with a long sleeved, jumper and keep a blanket next to me which today has spent most of the day over my legs and midriff.

In reply to George Killaspy:

 >Heating the fabric of the house is exactly what they do - if an IR panel is pointed at a 200yo stone wall, that wall will gently heat up, and retain that heat with the panel off. <

What are the downsides of IR please? Does it heat up any object it hits which which might leave some parts of the room cold and waste the heat? Might warm, convected air potentially heat up everyone in a room even if they were not directly in front of the heater?

In reply to subtle:

 I have similar problems to the OP. We have a semidetached house without cavity walls (2 bricks thick). We have a gas combi providing hot water and central heating and a gas cooker.At ground floor level the central heating water circuit runs under a suspended floor (essentially at draughty outdoor temperature which I imagine leads to considerable heat loss). Other pipes are boxed in agaist a cold, outer wall.
I've no expertise but have wondered about feasibilty of going to individual oil filled electric rads to replace existing (previous replies say this is not the way to go, IR heating has also been suggested earlier), replacing the gas combi with a central electric heater for hot water only. Also eventually replacing the gas cooker with an electric one with an induction hob. I'd rather avoid a hot water tank (sometimes unnecessarily heated water, uses up space
Some Pros.
Avoid gas entirely including gas standing charge.
Avoid the problems of water based central heating including relative simplicity of replacing individual rads. Electric water heater should last longer and be cheaper to maintain, no heat loss from underfloor pipes (though insulation could reduce this anyway).
Some Cons
Major one: 3-4 times higher cost per unit energy of electricity (likely to fall relatively in the long term?).
Higher costs of electric water heater and rads etc, possibly new wiring needed.

 CurlyStevo 25 Nov 2021
In reply to oldie:

I personally think we'll see gas prices fall from all times high and lecy stay more expensive for the life of a new combi boiler at this stage (ie 10 years or so). There is no way the government are going to make examples of people that happen to have a gas boiler any time soon tax wise.

As you say there are many problems to be solved for our old housing stock before cost effective non carbon based heating is feasible.

Post edited at 21:39
 ali k 25 Nov 2021
In reply to CurlyStevo:

> There is no way the government are going to make examples of people that happen to have a gas boiler any time soon tax wise.

Agreed. Considering the vast majority of new-build houses are STILL fitted with gas boilers it would be political suicide to do this, at least before they’re due to be replaced anyway in, what, 10yrs time?

 veteye 25 Nov 2021
In reply to subtle:

Slightly different thread than the ones that I have started in a similar subject. Interesting.

I'm currently still mulling this over, but I need time to clear some degree of belongings from the house, and garage. 

Currently, I don't have my central heating on, just trying to treat it as one up on a bothy with hot water: But I have a fan heater in my small study which retains the heat fairly well. Sometimes I heat the bathroom prior to a shower likewise. Trying to leave the central heating until December, but will I get beaten by the colder blast due in the next couple of days.      The cats are not impressed though.

In reply to subtle:

I would definitely not put in IR heaters. They were fitted to our 160 year old stone built house when we moved in, the guy we bought it from described their installation as the worst decision of his life. We gave them a go for a while, they were both ineffective and expensive to run, which is not a winning combination.

They have now been removed and after lots of investigation into alternatives we installed an oil combi (no mains gas). It still feels a bit backwards to have done this, but it is able to warm the house and I don't think anything more environmentally friendly would have done at anything approaching a reasonable price.

I'm hoping that by the time this boiler dies a viable alternative will be available. 

 Maggot 26 Nov 2021
In reply to oldie:

> At ground floor level the central heating water circuit runs under a suspended floor (essentially at draughty outdoor temperature which I imagine leads to considerable heat loss).

Easily fixed with cheap thickest spongy pipe lagging. Glue all the slits and joints for maximum effect.

In reply to subtle:

It's not going to be the popular answer here, but unless you want to spend a lot and do a lot of plumbing etc, just replace the combi as like for like as practical

You should be able to get:  combi boiler + flue kit + filler loop + strainer, for between £850 - £1,200 if you buy it from Screwfix or equivalent. Then it may be perhaps £500 - £600 for a gas-safe plumber to swap them over for you in about 1/2 a day (so 1/2 day with no hot water/heating). This all assumes simple swap out, no nasty surprises like having to reroute flue, totally new site etc etc.

If you had a large property you weren't living in and wanted to refurb/develop it then my answer would be entirely different.

 mullermn 26 Nov 2021
In reply to oldie:

> What are the downsides of IR please?

it feels like you’re under a grill. Only the side facing the heater gets the real effect, it’s quite a different sensation to being in a room full of heated air. 

In reply to oldie:

> At ground floor level the central heating water circuit runs under a suspended floor (essentially at draughty outdoor temperature which I imagine leads to considerable heat loss).

Imagine my delight when I discovered that in winter the water table is so high that the subfloor void in my old house filled up with water and the pipes under it were trying to heat not only my rads but the 20 tonnes of water under the house!

In reply to tjhare1:

> So with that said, what I think is lacking online are real-world examples of using a heat pump and not making much by way of additional major changes to an old heat-sink house. I’m hoping the UKC hive-mind might be able to give me some of this, so if you’ve installed an ASHP and not done much else to an old house, how is it? Warm enough? Most of the time? For context my house at this time of year with 2-3 hours heating in the evening is a balmy 14C daytime, increasing a few degrees to perhaps 16-18 in the evening with heating and cooking/living/etc. Averaging about 3-4 cubic metres gas per day so far this week for a 2 person house having a shower each per day.

You need to work out how much energy you're currently putting into your house - how many kW/BTU is your boiler, and how many hours is it running at full power / how much gas is being consumed?

Use the BTU calculator at https://www.theradiatorcompany.co.uk/ to see how your actual output compares to the theoretical demand and factor your calculations appropriately. don't forget, your heating demands can change over time - if you're young, don't feel the cold and are often out of the house your demands will be lower than those of a pensioner who feels the cold.

Then you need to know the output temperature of a heat pump running efficiently I've heard figures of 40-50 degrees.

Then you need to know the radiator requirements of your rooms for the relevant 'delta' the heat pump will provide - radiators are sold with heat outputs at a certain 'delta' i.e. difference in temperature between the temp of the radiator and the temp of the room.  Many radiator spec sheets will give an output based upon a delta way higher than that which a heat pump can supply.  For example, the radiator company list the outputs for a delta of 50 degrees, meaning a radiator temp of 60-70 degrees. I suspect you'll need rads double the size of the standard recommendation running for more hours in the day to give the same heating power as a traditional boiler (although running a condenser boiler efficiently means running a low output temp too).

Once you know the heat requirements of the house and the size of the radiators required to heat it you can work out the viability of a heat pump.  They're a no-brainer for new builds or people replacing floors as you can use the huge surface area and thermal store of underfloor heating to give the required heat output and take advantage of 24/7 or cheap rate running of the heat pump.

 mutt 26 Nov 2021
In reply to Toerag:

Any airsource heat pump company with model this for you. No cost involved in that as they are trying to spec which air source heat pump is needed. Bear in mind that it's more expensive to retrofit air source as gas ch operates at higher temps than underfloor. Heating so extra equipment is needed to run radiators at high enough temperatures.


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