Gas boiler lobby obstructing heatpumps

[Beelbeebub]

For whole house load any system that requires measuring walls, estimating construction, guessing air changes will always be error prone.

 

There are direct measurement methods, basically heat the room up mrleasuring the power input then let it cool down measuring the temps

 

If you could do it passively, just measuring inside and outside temps and maybe smart meter consumption data that would be good

 

Just leave the sensors in each room and one outside for a week or two and then the computer crunches the numbers and spits out some specs.

 

The big problem is these techniques only work in the winter!

[Beelbeebub]

Auto blancing trvs would be useful. Ones that can micro open/close to control the flow rather than on/off. If they were paired with a room stat, which just tweaked the weather comp'd flow up or down a bit you could balance the rooms  if that fed back to the main controller itncouod work out if the curve was too high or too low. 

 

So room stat looks at set and actual temp (plus the history) works out if the room is getting too warm because of too much flow, and then tweaks the flow down a tad. Waits a day repeats.  Goal is to get a flow rate on each room that results in the least adjustments needing to be made.

[JamesPa]

1 minute ago, Beelbeebub said:

Auto blancing trvs would be useful. Ones that can micro open/close to control the flow rather than on/off. If they were paired with a room stat, which just tweaked the weather comp'd flow up or down a bit you could balance the rooms  if that fed back to the main controller itncouod work out if the curve was too high or too low. 

 

So room stat looks at set and actual temp (plus the history) works out if the room is getting too warm because of too much flow, and then tweaks the flow down a tad. Waits a day repeats.  Goal is to get a flow rate on each room that results in the least adjustments needing to be made.

The latter was basically what I was thinking of.  Smart, or even dumb but electronic, trv actuators with alternative firmware have all the required control function.  I don't know if trv valves (by which I mean the bit that interacts directly with the water) are linear or basically on/off.  But designing a linear one isn't beyond the wit of man.  Alternatively make an adaptor to enable an electronic trv actuator with the alternative firmware fit a lockshield.

 

Working out a solution which is manufacturable and requires minimal investment by the householder is the key.  To do that you need to know more about the actual detail of plumbing components than I do.

 

Again these only really work in the heating season so some more off the wall thinking needed to find something more universally practical.  I suppose you could just automate what plumbers do (or don't do), but this balances for delta T not room T.

[Beelbeebub]

the valve bit of the trv (not the detachable head) is designed to be on/off.  it's just a flat rubber disc that pushes down on an opening.  That said it can operate as a linear valve *if* the actuator can move small amounts (total travel from on to off is around 3mm)

 

A screw actuator driven by a small motor and some fairly basic electronic would do it. Just needs to respond to "up a step" or "down a step"

 

How about this.

 

each room/zone has a thermostat with an unnumbered scale for set temp, an indication if the thermostat thinks you are at that temp or is trying to get you to that temp and two buttons for "i'm too hot" and "i'm too cold". These are just a temp sensor, basic display (could just be leds), two buttons and a wireless comms link.  This should be fairly cheap

 

Each rad has a clicky manual control knob with fine adjustment, so one click is a small change in flow rate. These should be dirt cheap.

 

The pump is set to constant pressure so each rad should stay at same flow rate regardless of others.

 

The central controller monitors zone temps and user demands for more or less heat.  it then decides if that zone needs more or less flow and puts a suggestion to the user via a screen.  "Increase zone 1 by 1 click" or "decrease zone 2 by 1 click"

 

The key part of my pitch for a very open control system is that this could be just one of many options, you wouldn't be tied into whatever systems the HP manufacturer provides.

 

One control system maker might have a complex system using variable trvs, controlling the pump output and deciding the HP flow temps with it's own web enabled AI.

 

Another might be a dumb box that takes an old school on/off hall thermostat and commands a flow temp based on the external air temp flowing into the HP.

 

Both could be interfaced easily with whichever HP is currently fitted (or any HP could be fitted and interface with the exisiting control system).

[Rob99]

32 minutes ago, Beelbeebub said:

the valve bit of the trv (not the detachable head) is designed to be on/off.  it's just a flat rubber disc that pushes down on an opening.  That said it can operate as a linear valve *if* the actuator can move small amounts (total travel from on to off is around 3mm)

 

A screw actuator driven by a small motor and some fairly basic electronic would do it. Just needs to respond to "up a step" or "down a step"

You can tick that box already........

There are proportional valve actuators already available, I'm using some with my Loxone system. They control the flow and slowly close off as the room is reaching set temperature to avoid overrun.

[JohnMo]

Now we are just getting complex for no need, balancing a system isn't rocket science, TRV's have no place except as a limit stop for room temp, so if your target is 20 set them at 22-23. If the system is balanced correctly the TRV's does nothing.  In fact a non adjustable one would be even better then a home owner couldn't mess up the smooth running of the system.

 

Flow rate is the important thing, the radiator or UFH loop delta T and flow temp from heat pump adjustments made to suit the min flow required by the HP.

[Rob99]

19 hours ago, JamesPa said:

the ability to run the flow temp for the DHW at 65/70

I expect I'll be inundated with responses (or criticised for daring to say it) but here goes.........

 

Why does anyone want stored hot water at 65/70 deg?

You can't use it safely at that temperature.

 

[Beelbeebub]

22 minutes ago, Rob99 said:

You can tick that box already........

There are proportional valve actuators already available, I'm using some with my Loxone system. They control the flow and slowly close off as the room is reaching set temperature to avoid overrun.

Could you send me some info, the only ones I've come across are big and expensive Siemens ones.

[Beelbeebub]

12 minutes ago, Rob99 said:

I expect I'll be inundated with responses (or criticised for daring to say it) but here goes.........

 

Why does anyone want stored hot water at 65/70 deg?

You can't use it safely at that temperature.

 

I agree. If designing from scratch a lower storage temp (with occasional pasteurisation cycles) would be better.

 

But this was specifically about swapping out the gas boiler with a HP unit with the minimum faff

 

Changing the water cylinder is often cited as a negative. It probably adds at least to 2k to the overall price. 

 

If you are willing to accept the efficency hit of running high (say 65C) you can leave the existing cylinder and DHW system as is.

 

The goal is to make the swap over take no longer than swapping a gas boiler.  Typically that's 2 men for a day. Maybe day and a half if you're unlucky.

 

At the mother grant is 5k, but you need to jump through hoops to get it and some of those hoops push thr overall cost up so you end up paying £7k or more after the grant.

 

Compare that with a new boiler for 2, 3k

 

And after spending double or triple, you can still end up paying more.

 

But if we made the swap cheaper. Got the price of the parts down below 5k and the labour below 2 days we could install for similar price to a gas boiler swap. That means not replacing the cylinder if we don't need to.

 

Sure, the system won't be super efficient but as long as it beats a scop of 2.5 we are ahead in terms.of CO2.

 

If there is a price guarantee scheme so you definitely won't pay more for your heating than gas I reckon uptake would shoot up.

[Rob99]

25 minutes ago, Beelbeebub said:

Could you send me some info, the only ones I've come across are big and expensive Siemens ones.

I'm using the Loxone valves so only usable with Loxone but there are others out there. I know Mohlenhoff used to do them, controlled by a 0-10v control signal.

[Rob99]

11 minutes ago, Beelbeebub said:

But this was specifically about swapping out the gas boiler with a HP unit with the minimum faff

 

Changing the water cylinder is often cited as a negative. It probably adds at least to 2k to the overall price. 

 

If you are willing to accept the efficency hit of running high (say 65C) you can leave the existing cylinder and DHW system as is.

But you still don't have to store water at 65C. There's nothing in an existing set up that says you need to.

[Beelbeebub]

34 minutes ago, Rob99 said:

But you still don't have to store water at 65C. There's nothing in an existing set up that says you need to.

No but the HX coil sizing is based on a 65C or higher water temp. If you ran lower (which you could) your heatuomtimes would be slower.

 

Of course, part of the optimisation would be to get the flow temp for heating the DHW (which is not the same as the DHW supply temp) as low as possible. It might be the slower reheat time and lower capacity of using a lower flow and DHW store temp don't impact the user, so could be used.

 

But if the HP can deliver 65C you have a much lower risk that you *have* to change the setup.

 

Note that you may still need occasional 65C flow for weekly pasteurisation cycles.

Edited July 22, 2023 by Beelbeebub

[sharpener]

3 hours ago, Rob99 said:

You can tick that box already........

There are proportional valve actuators already available, I'm using some with my Loxone system. They control the flow and slowly close off as the room is reaching set temperature to avoid overrun.

 

The electronic TRVs that are part of the Honeywell Evohome system do that also. As the room temperature approaches the setpoint you can hear the motorised valves making small adjustments to turn the flow down so there is no overshoot.

 

The main problem with it as a system is that they use a proprietary ?460MHz? signalling protocol so it will not interface with Zigbee or any of the other open standards. And they designed it with no ability to add repeaters so it is very stretched to cover a biggish house with thick stone walls.

[Lofty718]

Gas boilers can be made to be efficient but the problem is they are not, they are fitted as high temperature systems when they should be weather or load compensated.

 

A system boiler with unvented cylinder on a hot water priority can run multiple different flow temps one for DHW one for UFH and a seperate one for rads, like I have on my system.

 

I am able to run my unvented cylinder at 42c with a once in a while 60c legionella cycle.

[DougMLancs]

Absolutely- how long have we had condensing boilers now and even now they still aren’t really being pushed with weather comp. by installers or manufacturers. The amount of gas wasted… part of the reason gas installs have been quite so cheap is that they rarely are designed for efficiency. Had they been then the rads would be already reasonably suitable for transition to a HP.

[Lofty718]

Germany and Holland have it right, they design gas boilers with efficiency in mind, UFH controlled by Variable Temperature mixers rather than the crappy ones on the manifold and I believe outdoor weather sensors are mandatory in Holland or Germany (or both)

 

Here installers will install Vaillants without Vaillant controls but Nest's and run the whole system at 70c. I've even seen Viessmann installers install the 200W's that have built in weather compensation but installer it without weather comp.

 

There are some very knowledgable guys on the heating system design facebook group that try and spread the word about low temperature gas systems. I learnt a lot from there and based my system design on their practises.

[Beelbeebub]

1 hour ago, DougMLancs said:

Absolutely- how long have we had condensing boilers now and even now they still aren’t really being pushed with weather comp. by installers or manufacturers. The amount of gas wasted… part of the reason gas installs have been quite so cheap is that they rarely are designed for efficiency. Had they been then the rads would be already reasonably suitable for transition to a HP.

Yeah, the things that make a HP more efficient are also the things that make gas boilers more efficient.  If we had been pushing for higher efficiency in heating systems (rather than just higher efficiency of the heat source in the lab) we would already be most of the way there for straight HP swapovers.

 

That's partly why I like my price guarantee subsidy scheme.

 

During the proce guarantee period you'd be getting bills saying "you generated X thermal kWh which used Y electric kWh that would have cost you £Z but for the subsidy. That subsidy will reduce over time, would you like some help with reducing your electric consumption?" (QR code to stuff about low temps, new cylinders, insulation etc)

 

If the elec company has access to your thermal kWh, your HP electrical use, your flow temps and configuration and your EPC data, they could provide a really good steer on what you need to do.  For example they could work out your cops, see if your flow temps were too high so suggest weather comp or bigger rads or maybe your thermal demand was too high for your house type and they can suggest insulation.

[JamesPa]

4 hours ago, Rob99 said:

But you still don't have to store water at 65C. There's nothing in an existing set up that says you need to.

4 hours ago, Beelbeebub said:

No but the HX coil sizing is based on a 65C or higher water temp. If you ran lower (which you could) your heatuomtimes would be slower.

 

Of course, part of the optimisation would be to get the flow temp for heating the DHW (which is not the same as the DHW supply temp) as low as possible. It might be the slower reheat time and lower capacity of using a lower flow and DHW store temp don't impact the user, so could be used.

 

But if the HP can deliver 65C you have a much lower risk that you *have* to change the setup.

 

Note that you may still need occasional 65C flow for weekly pasteurisation cycles.

 

5 hours ago, Beelbeebub said:

Changing the water cylinder is often cited as a negative. It probably adds at least to 2k to the overall price. 

 

Exactly.  In a retrofit situation you need to design around what is already there as well as consider the 'ideal solution', then find a cost/performance/disruption sweet spot.  Replacing a perfectly good DHW cylinder can add a lot more than 2K to the price, because a) thats often the price of the cylinder alone if the HP manufacturers cylinder is specified (the easy option) and b) many installers will want to upgrade the primary feeds to the cylinder to 28mm, upgrade the CW feed to 22mm, and of course run the thermocouple lead, and it almost inevitably involves a lot of taking up of floorboards and uncertainty = cost.  There is also a horrible tendency to fit the HP manufacturers pre-plumbed cylinder which makes any subsequent changes even more difficult.  Then there is legionella to worry about because you are running at low temperature.  I also have a nasty suspicion is where a lot of margin is hidden.   I reckon the added cost may in practice be nearer 4k which, together with the £1200 for the MCS design fee, more than wipes out the grant. 

 

So if you can avoid doing it then its well worth considering doing so.  Running the HP at 65-70 for DHW only means that you don't have to replace the DHW cylinder and, in a typical house, might add £100 per year to the running cost without materially impacting the climate change mitigation.  The DHW cylinder upgrade can be done at a later date if needs be.  Im actually beginning to convince myself that its a no brainer.  

[JohnMo]

2 hours ago, sharpener said:

Evohome system do that also. As the room temperature approaches the setpoint you can hear the motorised valves making small adjustments

Really you are running your system too hot. The last thing you want with a heat pump is to gag the flow rate, running like that equals rubbish CoP, comprising flow rate and too higher flow temp and may need a buffer to compensate with the effect of worse CoP.

 

@Lofty718 is talking sense, managing a heat pump system with TRV's isn't.

 

[JohnMo]

5 minutes ago, JamesPa said:

Running the HP at 65-70 for DHW only means that you don't have to replace the DHW cylinder

Still don't understand why you would bother. Run a normal heat pump so your tank temp ends up at 35-40, finish it with the immersion, your overall CoP will still be around 2.5. Basically run ASHP until it trips on high temp, find the temp of cylinder on its thermostat, wind back a degree or 2. Then the ASHP will not be locked onto a never ending heating cycle. Set up some simple logic to kick the immersion into life, heat to your ideal temp, job done. If your flow and return piping gives to much pressure drop, add a pump into the return line, set pump speed just high enough to overcome system resistance, wire so that it switches on off with the 3 way valve.

[JamesPa]

13 minutes ago, JohnMo said:

Still don't understand why you would bother. Run a normal heat pump so your tank temp ends up at 35-40, finish it with the immersion, your overall CoP will still be around 2.5. Basically run ASHP until it trips on high temp, find the temp of cylinder on its thermostat, wind back a degree or 2. Then the ASHP will not be locked onto a never ending heating cycle. Set up some simple logic to kick the immersion into life, heat to your ideal temp, job done. If your flow and return piping gives to much pressure drop, add a pump into the return line, set pump speed just high enough to overcome system resistance, wire so that it switches on off with the 3 way valve.

As it happens I agree.  Now try persuading an installer to do that, no chance.  So I can do it for myself at home (but only with express planning consent) but it's not a solution for mass deployment.

Edited July 22, 2023 by JamesPa

[Beelbeebub]

3 hours ago, Lofty718 said:

Gas boilers can be made to be efficient but the problem is they are not, they are fitted as high temperature systems when they should be weather or load compensated.

 

A system boiler with unvented cylinder on a hot water priority can run multiple different flow temps one for DHW one for UFH and a seperate one for rads, like I have on my system.

 

I am able to run my unvented cylinder at 42c with a once in a while 60c legionella cycle.

sadly most are not well set up.  There are numerous old boilers kicking around that have one input (on/off) and a knob for cutout temp.  The control system is a basic timer box that turns the boiler on/off and activates the diverter valve and pump.  DHW is via simple timer, cutting out when the return temp hits the target.  CH is via timer and thermostat, again cutting out when it hits the target. The flow temp has to be 65+ anyway to sterilise the DHW and the rads are all tiny single panels, which was all they needed to be with a flow temp of 65C.  And it's microbore piping.

He won't switch when his boiler dies because he'd have to change the rads, the  plumbing etc.  And if he has a gas boiler it's cheaper to run it at high temp and accept the slightly higher gas bills.

But, if the swap were for a HP, that could deliver similar performance at the same cost, he'd go for it.

 

The trick is how to do that?

 

Same performance is an engineering problem, just need a similar flow temp and power output.  He could probably get by with 10kw at 65C.

 

Same price is a political problem - the 3.5:1 elec to gas price ratio is partially a political choice.  It's not that in other countries.  Some have gas and electric prices that are 2:1 others closer to 4:1.  Some of that is engineering (the efficiencies of gas to electric conversion, generation mix etc) but as the price cap shows, it can be controlled by policy.  If the price cap has capped elec at 20p and gas at 10p, the break even ratio for heat pumps would be really easy to hit (as it is in France and Sweden) 

 

 

 

Edited July 22, 2023 by Beelbeebub

[Beelbeebub]

52 minutes ago, JohnMo said:

Still don't understand why you would bother. Run a normal heat pump so your tank temp ends up at 35-40, finish it with the immersion, your overall CoP will still be around 2.5. Basically run ASHP until it trips on high temp, find the temp of cylinder on its thermostat, wind back a degree or 2. Then the ASHP will not be locked onto a never ending heating cycle. Set up some simple logic to kick the immersion into life, heat to your ideal temp, job done. If your flow and return piping gives to much pressure drop, add a pump into the return line, set pump speed just high enough to overcome system resistance, wire so that it switches on off with the 3 way valve.

That would also be an option, and as you point out, fairly simple to arrange. 

 

But an immersion will only ever be a COP of 1.  Even if the COP of the HP running at 65C, with defrost cycles etc is only 1.2, you are still using less electricity than an immersion. 

 

I think alot of HP thinking is still based on the old R410a systems that couldn't even hit 55C. The newer r290 units can hit a Cop of 2 at 65C and 5kw from a nominal 5kw unit.  That's gotta be better than a 3kw immersion.

[JohnMo]

5 minutes ago, Beelbeebub said:

But an immersion will only ever be a COP of 1.  Even if the COP of the HP running at 65C, with defrost cycles etc is only 1.2, you are still using less electricity than an immersion. 

 

Attached is an illustration of heating cylinder to 60, if you don't need to heat to 60, the CoP will be better. Take from -

HEAT PUMPS FOR THE HOME

Second Edition

John Cantor

[Beelbeebub]

9 minutes ago, JohnMo said:

 

Attached is an illustration of heating cylinder to 60, if you don't need to heat to 60, the CoP will be better. Take from -

HEAT PUMPS FOR THE HOME

Second Edition

John Cantor

Exactly, and yes, if you can get away with heating only to 55 or 50C then great. 

 

That's an optimisation that can occur after you've fitted the heatpump. You can dial back slowly until you hit the point you're running out of hot water.  

 

But you can only do that once you've got a HP installed.

 

The current system attempts to get your system to max efficency before install, which results in alot of upfront work, and because they add margins to make sure you aren't cold, they often end up overspeccing the system which adds a bunch of cost, and then if the system estimation has gone a bit wrong they still need up paying a bunch.

 

If we could get installs cheap and easy and allow a "running in period" to get the system right, I think we'd get alot more installs *and* probably higher efficiency at the end.

 

Maybe this analogy might help

 

NASA take no risks with their SLS. Everything is precalculated to the Nth degree. Lots of custom stuff, expensive parts all contribute to the huge cost of rockets.  Because they cost so much, they must work first time, so they spend even more time and effort making sure it works perfectly.

 

Space X (and this is in no way am endorsement of Musk) took a different route, they were happy with the first rocket just taking off then blowing up. Because of that, each rocket was cheaper. Because if that they could afford it  it to be perfect each launch. 

 

By the end they had a better system.

 

The analogy isn't perfect of course, but my point is we need to aim to just get HP's out there operating at better than 2.5 SCOP and we're winning on CO2, after that it's just tuning them over time to get more an more.efficent.

 

To do that we need to change regs and crucially remove the "bill shock risk" to allow the tuning period.

Edited July 22, 2023 by Beelbeebub