With gas boilers potentially being banned in new homes from 2025, should we look at alternatives now

Cardew

Reed_Richards wrote: »

The boiler will set the water temperature it needs, up to a maximum of 80/85 C. That's the whole point of having a modulating boiler.

That is not my understanding of how a modulating boiler operates.

Without the weather compensation system I referred to above, I set the temperature of the water on the boiler, say 65C. The boiler then raises the temperature of water to 65C using a high output and then the output modulates down to lower power to maintain the water temperature.

Reed_Richards

It was exactly the way my modulating boiler operated. You set both the desired water temperature in the hot water tank and the desired temperature in the room with the room thermostat. Both temperatures were fully programmable so could be changed throughout the day. Both thermostats were very precise and could read to 0.1 C precision. There was also an outside thermostat which gave the boiler an indication of how hard it would have to run to raise the room temperature. If a steep temperature increase was sought then the boiler would run full-on which could raise the temperature of the water coming out the boiler to as high as 80 C or thereabouts. Once the desired room temperature and/or the desired hot water tank temperature were reached, or in fact were close to being reached, the boiler would modulate down so as not to overshoot the temperature then maintain the set temperature once it had been reached. Once a week the temperature in the hot water tank was automatically raised to about 60 C for a while to combat Legionella, enabling you to maintain a more comfortable hot water temperature the rest of the time. My boiler was made by the Dutch manufacturer Atag, taken over by Ariston a few years ago.

Cardew's system seems less sophisticated and wrong-headed because you don't want the water temperature to be as high as 65 C if you can help it.

Cardew

Reed_Richards wrote: »

It was exactly the way my modulating boiler operated. You set both the desired temperature in the hot water tank and the desired temperature of the room thermostat. Both temperatures were fully programmable so could be changed throughout the day. Both thermostats were very precise and could read to 0.1 C precision. There was also an outside thermostat which gave the boiler an indication of how hard it would have to run to raise the room temperature. If a steep temperature ncrease was sought then the boiler would run full-on which could raise the temperature of the water coming out the boiler to as high as 80 C or thereabouts. Once the desired room temperature and/or the desired hot water tank temperature were reached, or in fact were close to being reached, the boiler would modulate down so as not to overshoot the temperature then maintain the set temperature once it had been reached. Once a week the temperature in the hot water tank was automatically raised to about 60 C for a while to combat Legionella, enabling you to maintain a more comfortable hot water temperature the rest of the time. My boiler was made by the Dutch manufacturer Atag, taken over by Ariston a few years ago.

Cardew's system seems less sophisticated and wrong-headed because you don't want the water temperature to be as high as 65 C if you can help it.

We really are at cross purposes.

You state you have an outside thermostat(see in bold in your post above) May I suggest this is an outside temperature sensor and therefore you have a weather compensation system - similar to the Veissmann system referred to in Post #48 by Michaels.

As I stated in post #50 I also have weather compensation.

However Michaels in post #48 above suggested you 'Read up on Viessmann weather compensation controls*.' I have this system with a Viessmann boiler and it claims considerable savings. During the last few weeks when the heating was on for short periods in the evening the radiators were only slightly warm <40C. So I assume Viessmann know what they are doing.

* Edit
In essence the weather compensation network has an outside temperature sensor and the CH water temperature is lowered if the outside ambient temperature rises.

I explained above how this works, so you and I have the same system i.e. the water temperature varies. I pointed out that it was below 40C at times

However you have stated that the whole point of a modulating boiler is to vary the water temperature - and it isn't

The boiler will set the water temperature it needs, up to a maximum of 80/85 C. That's the whole point of having a modulating boiler.

Virtually all boilers these days are modulating and they don't automatically adjust the water temperature. It is only when a weather compensation system is fitted(i.e. an outside temperature sensor) will the boiler water temperature vary to keep the boiler in condensing mode.

Very few boilers have a weather compensation network fitted. Indeed many are incompatible with such a system. Even on the Veissmann range a couple of years ago it was only available on certain models.

Reed_Richards

Cardew wrote: »

We really are at cross purposes

Somewhat, I'm sure.

Cardew wrote: »

You state you have an outside thermostat(see in bold in your post above) May I suggest this is an outside temperature sensor and therefore you have a weather compensation system

Yes, careless use of the word thermostat on my part. In fact the one in the room and on the hot water tank were also temperature sensors which relayed their data back to the boiler rather than exercising any form of direct control.

Cardew wrote: »

- similar to the Veissmann system referred to in Post #48 by Michaels.

I did not follow that link, I'm afraid.

Cardew wrote: »

As I stated in post #50 I also have weather compensation.

I explained above how this works, so you and I have the same system i.e. the water temperature varies. I pointed out that it was below 40C at times

However you have stated that the whole point of a modulating boiler is to vary the water temperature - and it isn't

Okay, let me stop you there. Atag had a very advanced boiler when I bought my first one in 1998; it sounds as if many other manufacturers are still to catch up. The point of a condensing boiler is to have it condense. For this to happen the return water must be below a certain temperature, 55 C I think. Many older radiator systems were set-up to operate on a flow temperature of about 80 C and a return temperature of about 10 degrees less. Most radiator heat outputs are still specified on the assumption that the radiator temperature is 60 C higher than the room temperature, sometimes a 50 C value is also given grudgingly. So my problem in 1997 was how to retrofit a condensing boiler, have it condense to operate at maximum efficiency but not freeze because the water temperature in the radiators was not hot enough. Atag offered a solution where the room temperature sensor was much more precise than in those typically used. When the room reached or approached the desired temperature the boiler would modulate its output down to what it thought was necessary to maintain the room temperature, the water temperature dropped until it reached the point where condensing was possible. Thus the occupants did not freeze waiting forever for the room to reach temperature, which would have been the consequence of imposing a 65 C limit on the boiler output temperature. There was a learning algorithm to predict how much output was required and this algorithm took into account the data from the outside sensor but the fundamental purpose was nothing to do with weather compensation, it was maintaining a very constant room temperature and the system would have still managed that without the outdoor sensor, just a bit more slowly.

Cardew

Reed_Richards wrote: »

Somewhat, I'm sure.


Yes, careless use of the word thermostat on my part. In fact the one in the room and on the hot water tank were also temperature sensors which relayed their data back to the boiler rather than exercising any form of direct control.



I did not follow that link, I'm afraid.



Okay, let me stop you there. Atag had a very advanced boiler when I bought my first one in 1998; it sounds as if many other manufacturers are still to catch up.

All Atag boilers now have weather compensation and require an outside temperature sensor. I was surprised that they had weather compensation in 1998 and Atag boilers were not generally available in UK then, but they are an excellent technically advanced boiler.

From our advanced facilities in Lichtenvoorde, the Netherlands, we manufacture boilers that are trusted throughout the world.
We’ve been manufacturing boilers for almost 70 years. In 1983 we chose to focus solely on manufacturing super-efficient heating products and became active in the UK in 2001.

The issue was you correcting GA and incorrectly stating that the whole point of a modulating boiler was to alter water temperatures and it ain't!!

This is not to score a point, but left unchallenged many readers might expect their modulating boiler to automatically run at varying water temperatures.

michaels

The reason I started talking about heating circulation temps and times was from looking to switch to a heat pump.

Our system runs most of the time with the water temp at 30 degrees when outside temp is 10 degrees up to about 70 degrees water temp when the outside temp is minus 10. For me this means that we would need more/bigger rads and possibly bigger circulation pipes if the max water temp was suitable for a heat pump (is this about 45 degrees?)

Also we would either need more hot water storage or some sort of top up if again the sensible max heat pump temperature is 45 degrees.

And for all of this we need an average cop of 3.5 - 4 to make up for the gas/electricity price differential.

mmmmikey

michaels wrote: »

And for all of this we need an average cop of 3.5 - 4 to make up for the gas/electricity price differential.

Other things being equal I agree with what your saying.


But if you move to what is essentially a form of electric heating, your electricity usage pattern will change massively and be much more spread throughout the day. This will probably lead you to the position where a simple flat rate tariff is no loner the best option and you may well find that your overall electricity per kWh comes down, possibly substantially. As such your estimate of needing a COP at those levels is probably pessimistic.


Also, assuming you were to go ahead with a change to electric heating, the change of your demand for electrcity can change the economics of things like solar panels and battery panels dramatically because (a) you're demand is high enough to fully utilise these technologies, and (b) you can use any battery power to save your electricity demand when the rate is highest.


I'd agree with anyone who points out that trying to factor this in adds to the complexity massively but nevertheless I do think this is significant enough to make it worth considering as it makes a big change to the overall picture.

Reed_Richards

michaels wrote: »

For me this means that we would need more/bigger rads and possibly bigger circulation pipes if the max water temp was suitable for a heat pump (is this about 45 degrees?)

That would represent about a 25 C difference between the radiator temperature and the room temperature. Radiator outputs are usually specified on the basis that this difference is 60 C (as I mentioned earlier). That's why heat pumps are frequently paired with underfloor heating.

michaels wrote: »

Also we would either need more hot water storage or some sort of top up if again the sensible max heat pump temperature is 45 degrees.
.

I think you would need the top-up. You are obliged to heat stored hot water to 60C at least every so often as a precaution against Legionella.

GreatApe

michaels wrote: »

The reason I started talking about heating circulation temps and times was from looking to switch to a heat pump.

Our system runs most of the time with the water temp at 30 degrees when outside temp is 10 degrees up to about 70 degrees water temp when the outside temp is minus 10. For me this means that we would need more/bigger rads and possibly bigger circulation pipes if the max water temp was suitable for a heat pump (is this about 45 degrees?)

Also we would either need more hot water storage or some sort of top up if again the sensible max heat pump temperature is 45 degrees.

And for all of this we need an average cop of 3.5 - 4 to make up for the gas/electricity price differential.

For most properties the gas boiler set up already exists and a replacement boiler if necessary isn't that expensive. Compare this to the huge cost of installing a wet heat pump system which may be £15,000 and cost more to upkeep maintenance and replacement

While a COP of 3.5 - 4.0 X might make the electricity cost the same as the gas you still have that huge sunk cost Vs just keeping what's going

I think it's more realistic to mass install air to air heat pumps and just use a small tank (or instantaneous heater) for the homes shower/hot-water needs

I'm not sure what air to air heat pumps cost but they must be affordable because lots of middle income hot countries have multiple air conditioners installed which are heat pumps and if middle income countries can afford air to air heat pumps we probably can too


This could even potentially be done while keeping the gas boiler and the air to air heat pump provides base load hearting while the boiler can top up. This way if a house ideally needs 4-5 air to air heat pumps maybe 1-2 would be fine for most the heating needs with the existing gas boiler kicking in on particularly cold days.

Especially for ground mounted heat pump I can imagine companies would get very good at installing them it might be as little as a one hour job. So those might work

Perhaps the government could install for 'free' heat pumps on the 4.8 million or so social homes this would create lots and lots of companies who would get good at installing them at good prices and rapid times. But I really do think it's likely to be air to air rather than whole wet system

GreatApe

Reed_Richards wrote: »

I think you would need the top-up. You are obliged to heat stored hot water to 60C at least every so often as a precaution against Legionella.

A small tank for water needs
Air to air heat pumps for home heating needs
This mix would probably be best

The tank can be heated at night rate electric
The heat pumps on continuously during any and all times they are necessary

Air to air heat pumps especially floor standing (easier to fit and more efficient) can probably be done rapidly and at low cost for the 29 million or so existing properties. For new builds it can be a fully wet system if it makes sense.

I'm not a fan of state mega projects but perhaps this is one where they can lead with the social stock. 4.8 million or so social homes. Perhaps £3k per property to buy and install there small air to air heat pumps per property. £15 billion cost done over a 10 year period. Should create the skills and business needed to then deploy it on the other 25 million privately owned homes at affordable prices