ASHP developments

[HughF]

You mean like an opentherm stat? 
 

back to my opentherm to modbus interface idea. I really should start work on that. 

[Beelbeebub]

2 hours ago, HughF said:

You mean like an opentherm stat? 
 

back to my opentherm to modbus interface idea. I really should start work on that. 

I mean it woukd be great if the industry had an open common communication bus and any thermostat could work with any heat provider.

 

Ironically the closest we have to that is the dumb "on/off" volt free contact system. It just happens to be crap at doing the clever things we want to do for better efficency and comfort!

 

And I do worry about heating control systems that rely on the Internet to operate. The market is littered with smart devices that are obsolete or crippled since the provider shut down.  That said, a function where the installer could remote diagnose and tweak the settings (say they connect it to the jtnernt before they handover and can "log in" with a password and app afterwards - function dependent on a hardware switch on the unit so the customer can block the option after a while). That might make the call back problem less of an issue. 

 

[sharpener]

On 02/01/2024 at 12:31, S2D2 said:

Somewhat unbelievably, Octopus will not install rads larger than those for a design flow temp of 50°C. So this is definitely the way they're going.

 

To qualify for the BUS grant even Octopus will have to appear to comply with MCS standard. For new builds IIRC this is 45C flow max and for retrofits 55.

 

This is probably how they will beat the independents, I have contacted 5 cos and none of them will design for flow >45C - as if I cannot be trusted to make my own capital cost v running cost decision. Current preferred choice is coming back with his Tech Dir next week and I hope to get them to re-visit the rad upgrades which are a significant part of the end price after BUS. Originally they said "do nothing for the first season and see what rad upgrades are really needed" and it would be good to get them going down that path again. Meantime I have a plan to cascade larger rads down to the smaller rooms but that doesn't save anything on the labour.

[Beelbeebub]

50 minutes ago, sharpener said:

 

To qualify for the BUS grant even Octopus will have to appear to comply with MCS standard. For new builds IIRC this is 45C flow max and for retrofits 55.

 

This is probably how they will beat the independents, I have contacted 5 cos and none of them will design for flow >45C - as if I cannot be trusted to make my own capital cost v running cost decision. Current preferred choice is coming back with his Tech Dir next week and I hope to get them to re-visit the rad upgrades which are a significant part of the end price after BUS. Originally they said "do nothing for the first season and see what rad upgrades are really needed" and it would be good to get them going down that path again. Meantime I have a plan to cascade larger rads down to the smaller rooms but that doesn't save anything on the labour.

I thought part L said 55C flow for new builds?  

 

As condensing boilers have a delta t of around 20C, this is a mean rad temp of 40C, which is equivilent to a heatpump flow/return of 42/37

 

The newer HPs eg Arotherm can start to hit Scops of greater than 3.5 at nominal 45C max flow temps. 

 

Ironically the rads can be smaller and cheaper if you design your new build for a 55C flow HP than if you use a 55C boiler! 😁 

Edited January 3 by Beelbeebub

[S2D2]

3 hours ago, sharpener said:

 

To qualify for the BUS grant even Octopus will have to appear to comply with MCS standard. For new builds IIRC this is 45C flow max and for retrofits 55.

 

This is probably how they will beat the independents, I have contacted 5 cos and none of them will design for flow >45C - as if I cannot be trusted to make my own capital cost v running cost decision. Current preferred choice is coming back with his Tech Dir next week and I hope to get them to re-visit the rad upgrades which are a significant part of the end price after BUS. Originally they said "do nothing for the first season and see what rad upgrades are really needed" and it would be good to get them going down that path again. Meantime I have a plan to cascade larger rads down to the smaller rooms but that doesn't save anything on the labour.

What really blew my mind was Octopus were proposing changing all the rads anyway to hit 50°C. The incremental cost to hit 45 or 40 would have been very small and would have been totally appropriate for my house.

 

Whatever happened to consumers paying for what they wanted? It went all the way to the head of their heat pump operation and it was a flat out "No, we won't design below 50°C".

 

Just change one text box, have the automated number crunching done and install what has been asked for provided it's within the realms of sensible, I don't see the issue.

[sharpener]

1 hour ago, Beelbeebub said:

I thought part L said 55C flow for new builds?

 

Isn't that just for boilers to ensure condensing? I thought the requirement for HPs (whether for Part L or MCS) was lower than that.

 

2 hours ago, Beelbeebub said:

As condensing boilers have a delta t of around 20C, this is a mean rad temp of 40C, which is equivilent to a heatpump flow/return of 42/37

 

Doesn't 55 flow and 20 delta T give you 35 return and an avg of 45? But I have always doubted the 20 d T, with boilers vastly oversized I don't think in many cases the modulation will turn down low enough once the system is up to temp to maintain such a high differential. Then the return temp will creep up, the rads increase their o/p, the TRVs reduce the flow even more, vicious cycle.

 

2 hours ago, sharpener said:

To qualify for the BUS grant even Octopus will have to appear to comply with MCS standard. For new builds IIRC this is 45C flow max and for retrofits 55.

 

I conflated three thoughts here, let me have another go...

1. Octopus may make a big thing of high temps from the latest HPs, but they are still limited by the rules as to how high the flow temps can be.

2. Even so they can steal a march on the independents by a willingness to sail closer to the wind than the competition.

3. However this will not be enough to avoid upgrading rads unless they were designed for the lower flow temps mandated (recently) for boilers, which in most retrofit cases they won't have been.

 

Meanwhile I have looked again at the emitter table and I think doing the full upgrades now is probably the best thing for the following reasons:

 

1. Several of the rads are significantly undersized already so in particular the landing and my study are always cold.

2. Fitting the HP will involve a clean and flush and it would be a pity to have old dirty rads still on the system afterwards.

3. There is only one rad which can plausibly be cascaded to be adequate if moved to a smaller room.

4. I could do it all myself, either piecemeal or in one hit, but either way OH  is not keen on my spending the time it would take.

[JohnMo]

9 hours ago, Beelbeebub said:

condensing boilers have a delta t of around 20C, this is a mean rad temp of 40C, which is equivilent to a heatpump flow/return of 42/37

Mine certainly didn't operate on dT20, the circulation pump just modulates to get the dT the boiler controller wants to see.  At flow temperatures of 40 to 50 the dT was the same as my heat pump - between 5 and 10.

[Beelbeebub]

57 minutes ago, JohnMo said:

Mine certainly didn't operate on dT20, the circulation pump just modulates to get the dT the boiler controller wants to see.  At flow temperatures of 40 to 50 the dT was the same as my heat pump - between 5 and 10.

I think you're right. Modern boiler controls are significantly more flexible than the early generation so can run lower dTs. 

 

The point is: the calculations for sizing the radiators assume the larger dT values (I have seen 10C as an option but at higher temps) and that HPs generally use a lower dT than boilers so the same mean radiator temp can be achieved at a (slightly) lower flow temp. 

[Beelbeebub]

8 hours ago, sharpener said:

Doesn't 55 flow and 20 delta T give you 35 return and an avg of 45?

Yeah, for some reason I had 50/30 in my head. 

 

The point is that a system designed for a boiler flow temp of X will need a slightly lower than X flow temp when run with a HP. Assuming the  various flown rates can be maintained) 

 

Personally I'd like to see the mandatory max flow temp set a bit lower, say 50C or ideally 45C. Maybe even mandatory 22mm primaries with 15mm reserved for the drops/rises to each rad. That would make straight swaps to HPs easy. 

[JamesPa]

6 minutes ago, Beelbeebub said:

Yeah, for some reason I had 50/30 in my head. 

 

The point is that a system designed for a boiler flow temp of X will need a slightly lower than X flow temp when run with a HP. Assuming the  various flown rates can be maintained) 

 

Personally I'd like to see the mandatory max flow temp set a bit lower, say 50C or ideally 45C. Maybe even mandatory 22mm primaries with 15mm reserved for the drops/rises to each rad. That would make straight swaps to HPs easy. 

I guess the reasoning was that 55 is good enough for a HP swap and guarantees condensing and to go any lower would result in push back from the industry/climate deniers/right wing press/party donors to the point where the rule risk being put on hold altogether.  Politics is the art of the possible and 55 will do, its good enough that you can reasonably swap for a HP without upgrading the space heating.  If you've designed for 55 the primaries must be large enough to operate at 55. 

 

Personally I think its an excellent compromise and much better than might have been expected given the direction of the prevailing wind.

Edited January 4 by JamesPa

[Beelbeebub]

12 minutes ago, JamesPa said:

I guess the reasoning was that 55 is good enough for a HP swap and guarantees condensing and to go any lower would result in push back from the industry/climate deniers/right wing press/party donors to the point where the rule risk being put on hold altogether.  Politics is the art of the possible and 55 will do, its good enough that you can reasonably swap for a HP without upgrading the space heating.  If you've designed for 55 the primaries must be large enough to operate at 55. 

 

Personally I think its an excellent compromise and much better than might have been expected given the direction of the prevailing wind.

I agree.

 

They could have been sneaky and mandated dT20 be used in the calculations (don't think they did) 

 

Also the 55C is the limit for HPs as well, so a shitty developer might fit a 55C system so they can get away with rads all around rather than UFH. Technically compliant but poor for SCOP. A 45C limit for HP systems would have been nice. 

 

 

Still, as you say not half bad considering 

[PhilT]

1 hour ago, JamesPa said:

I guess the reasoning was that 55 is good enough for a HP swap and guarantees condensing and to go any lower would result in push back from the industry/climate deniers/right wing press/party donors to the point where the rule risk being put on hold altogether.  Politics is the art of the possible and 55 will do, its good enough that you can reasonably swap for a HP without upgrading the space heating

Good summary, and reason to be optimistic about the potential for mass conversion. In the last couple of years I organised new boiler replacements for 3 of my relatives with existing rad installations more than 15 years old, and made sure the flow temp was set to 55degC. They do the job fine, all that happens is - longer boiler runs

[Beelbeebub]

2 hours ago, PhilT said:

Good summary, and reason to be optimistic about the potential for mass conversion. In the last couple of years I organised new boiler replacements for 3 of my relatives with existing rad installations more than 15 years old, and made sure the flow temp was set to 55degC. They do the job fine, all that happens is - longer boiler runs

If some sort of really compact heat meter and logger could be developed, with a really compact flow meter (or even an noninvasive one) that can simply be retro fitted to the boiler flow and return then we could subsidise the fitting (say it was £50 fixed fee). This would then monitor the actual heat delivered (minus DHW for combis) and also flow temps. 

 

It could then suggest what size HP is needed and also what flow temp is possible. 

 

 

[JamesPa]

2 hours ago, PhilT said:

Good summary, and reason to be optimistic about the potential for mass conversion. In the last couple of years I organised new boiler replacements for 3 of my relatives with existing rad installations more than 15 years old, and made sure the flow temp was set to 55degC. They do the job fine, all that happens is - longer boiler runs

Did the same with my boiler a couple of years ago, set FT to 55, works just fine, no plumes of steam from the flue and the house is much more comfortable.  I suspect a fair few houses are like this.

 

(In case you are wondering - my clueless, Green party run, local planning authority is blocking my installation of a heat pump - wants a sound level of 25dB(A)!)

[SteamyTea]

29 minutes ago, Beelbeebub said:

If some sort of really compact heat meter and logger could be developed, with a really compact flow meter (or even an noninvasive one) that can simply be retro fitted

I am not an expert in electronics, but I have a very cheap (from Poundland) wrist monitor.  It does heart BPM, blood oxygen levels and blood pressure.  Then it stores it until I download load it..

Now I know light can pass though the skin quite easily and 'sense' what the blood is doing, but I cannot believe that there are not sensors that can do this sort of thing though a copper pipe i.e. via sound.

@Radian is our electronics man, but not seen him about for a while.

Edited January 4 by SteamyTea

[TonyT]

You get flow sensors for measuring volume of water, i retrofitted one to the BMS of a building I manage about 10 years ago, it straps onto the pipework and needs about a metre before and after of straight pipe to minimise turbulence, it adds the flow to the other info the BMS collects.

[JohnMo]

You can get strap on ultrasonic flow meters. Tape on and insulation around two PT100 probed and a simple data logger.

 

But why bother just read the gas meter use over a 48 HR period, use the correct conversation factors convert to kWh. Get the weather data for the same time period. Log internal temp. Then subtract an allowance for DHW. Calculate kW per degree OAT. From there it's easy enough to get the heat pump size sorted out.

 

No need to reinvent the wheel. You can do all that with off the shelf Shelly (and many others) bits.

[Alan Ambrose]

>>> I cannot believe that there are not sensors that can do this sort of thing though a copper pipe i.e. via sound.

 

There are turbine ones and ultrasonic ones. They can measure flow and temperature and therefore 'heat flow'. Not cheap though, and as you might imagine, it's much harder to shine ultrasound through a copper pipe than it is to shine a LED (actually two LEDs) through your finger.

 

[Alan Ambrose]

>>> No need to reinvent the wheel.

 

If gas is your only heating and DHW source, then I guess your highest gas use day in winter minus your lowest gas use day in summer wouldn't be far from your max heat requirement.

[JamesPa]

51 minutes ago, JohnMo said:

You can get strap on ultrasonic flow meters. Tape on and insulation around two PT100 probed and a simple data logger.

 

But why bother just read the gas meter use over a 48 HR period, use the correct conversation factors convert to kWh. Get the weather data for the same time period. Log internal temp. Then subtract an allowance for DHW. Calculate kW per degree OAT. From there it's easy enough to get the heat pump size sorted out.

 

No need to reinvent the wheel. You can do all that with off the shelf Shelly (and many others) bits.

 

I wouldn't trust a 48 hour gas meter reading there are too many dynamics in this.  I would go either for the whole season (compare with degree-days) or a few weeks of smart meter readings.  But if you have a smart meter why not the whole season?

 

47 minutes ago, Alan Ambrose said:

>>> No need to reinvent the wheel.

 

If gas is your only heating and DHW source, then I guess your highest gas use day in winter minus your lowest gas use day in summer wouldn't be far from your max heat requirement.

In most houses other than passive houses no real need to subtract the summer use.  Unless you run a restaurant gas cooking use is negligible.

 

As @JohnMo says there is no need to reinvent the wheel, the  need is to convince the MCS bods to change the way they do things (or scrap MCS altogether).

Edited January 4 by JamesPa

[PhilT]

6 minutes ago, JamesPa said:

I wouldn't trust a 48 hour gas meter reading there are too many dynamics in this.

reasons being? Surprised at this - sounded like potentially a good way to size a heat pump and provide some comfort regarding a detailed heat loss calc. Say during a very cold day this month, if you could run your gas boiler for a few hours with the house in as near to steady state as you can get it - say 21 inside and -3degC average outside (or whatever are your preferred design parameters), note meter readings, ideally flow temp to get a good idea of boiler efficiency (plenty of tables/graphs around), couldn't you work out with a fair degree of accuracy the kWh supplied and hence what size heat pump you need, and wouldn't that be better than a detailed heat loss calc?

[Beelbeebub]

Yes, but using the meter readings is a viable way of doing it. 

 

Smart gas meters should record half hourly usage which would give you a good idea. Conceivably, octopus or whoever could use that to calculate what size heatpump you needed. 

 

There is a company that sticks some sensors and heaters in your house and measures heat loss directly, but it's not cheap. 

[JamesPa]

1 hour ago, PhilT said:

reasons being? Surprised at this - sounded like potentially a good way to size a heat pump and provide some comfort regarding a detailed heat loss calc. Say during a very cold day this month, if you could run your gas boiler for a few hours with the house in as near to steady state as you can get it - say 21 inside and -3degC average outside (or whatever are your preferred design parameters), note meter readings, ideally flow temp to get a good idea of boiler efficiency (plenty of tables/graphs around), couldn't you work out with a fair degree of accuracy the kWh supplied and hence what size heat pump you need, and wouldn't that be better than a detailed heat loss calc?

I think it is a good way to size a heat pump, but am cautious about relying on just 48 hrs only because houses respond quite slowly to changes in ambient and have a significant thermal mass.  Thus any reading over that short a period is subject to considerable error.   I find mine (1930 solid walls, suspended floors plus partial IWI and about 30% more modern extension) takes two or three days to fully stabilise in times when the outside air temperature is pretty constant, and when the OAT is varying wildly I doubt equilibrium is ever achieved.  To put some numbers on it, there is evidence on another forum that the heat capacity of the fabric of a 3-4bedroom 150-200 sqm house is 10-20kW/deg C, which is significant in comparison the the heat loss.  So any measurement needs to be done over enough time to take out fabric heat capacity effects.   

 

Having said that I suspect a 48hr reading is still better than the GIGO spreadsheet method and I would guess that its highly likely that (say) a week of half hourly meter readings with IAT and OAT and a suitable correlation engine would suffice.  Still easily doable, as I have said several times on this forum I cant believe Octopus aren't already working on it, they have all the data and seem to like using it.

 

For my money its smart meter readings first, consumption over a period second, and spreadsheets as a very poor third.  Pity MCS (more or less) insist on exactly the opposite.

 

On a positive note things do change.  Two years ago, if you were to believe this forum and others, buffer tanks were 'necessary', now they are 'to be avoided unless absolutely needed'.  55C was an absolute no-no and now its actively being discussed. 

 

That just leaves two big 'practice' problems to crack namely: the GIGO spreadsheet and the insistence on replacing DHW tanks.  I might also throw in the nonsense of the rigid application of the guidance (not the letter) of G3 if the only heat source is a heat pump, but @JohnMo will kill me if I do that!😊

Edited January 4 by JamesPa

[JohnMo]

13 minutes ago, JamesPa said:

might also throw in the nonsense of the rigid application of the guidance (not the letter) of G3 if the only heat source is a heat pump, but @JohnMo will kill me if I do that!

The way around that is to do similar to RED heat pumps, and use a modified version of the Harlequin vented cylinder (way bigger coils than standard), it also does not require an overhead tank, as the DHW is produced via a coil, so pretty similar to thermal store. No access to drains is needed, pipe to from heating coil, cold in hot out.

[JohnMo]

18 minutes ago, JamesPa said:

just 48 hrs

Was just a random number picked, but as you point out longer would be better. If you have a smart meter, half the jobs done already.