Nick1c

Vaillant high(er) temperature ASHP?

Recommended Posts

@Nick Laslett  What I plan to do is divert PV to ASHP indirectly via battery so as to get round the instability of PV required to run a ASHP. This allows you to take advantage of ASHP COP rather than just using immersion heater.  (This might seem over-engineered for a summers day when there is plenty of PV generation, it's in spring/autumn with shorter days where it's more valuable)

 

In practice this would mean firing the ASHP up for n minutes if:
- UVC temp < x
- PV generation over last m minutes  > y
- Battery Charge > z

 

It's not true PV diversion, but would have roughly the same effect and by using the battery as a buffer gets around the instability of PV, and by turning ASHP on for a mininum time of it stops the ASHP cycling as much. 

 

This is just theoretical for now but don't see why It shouldn't work..

 

 

 

Share this post


Link to post
Share on other sites

BTW. The "Vaillant high(er) temperature ASHP'"'s that were the subject of this thread have now been available for a few weeks.   If anyone gets one, please report back!

 

- Monobloc

- MCS approved

- Max 75C

- 3.5/7/10/12 kW versions.

- SCOP of up to 5 @35C,  3.6 @55C

Share this post


Link to post
Share on other sites
1 hour ago, Nickfromwales said:

If it's injected straight into the CU and not delivered through a diverter the PV will power anything and everything, when generation is sufficient of course.

What does this mean Nick? I thought all PV had to go through a diverter before it was used in the house?TIA

Share this post


Link to post
Share on other sites
Posted (edited)
21 minutes ago, Pete said:

I thought all PV had to go through a diverter before it was used in the house?TIA

 

No, your are thinking 'Inverter',   which turns D.C. into A.C.. A diverter is a device which redirects electricity which would otherwise be exported to another load (usually an immersion heater)

Edited by A_L
typo
  • Thanks 1

Share this post


Link to post
Share on other sites

PV goes through an INVERTER to turn it into 230v ac sycnchronised with the mains frequency and phase so anything in the house can use it.

 

A PV diverter is a separate device that detects if more power is being generated than the house is using (so power is being exported to the grid) and instead sends some power to the immersion heater so no or little power is exported.

 

You can't sent power from a PV diverter directly to anything elecronic as it is genearlly bursts of power pulse width modulated.  but what you can di is what I do, in the summer I time the ASHP so it does not come on to heat the hot water until mid morning, when there is a high probability of there being a decent amount of pv generation, so it is more likely it will use PV generated power and import less or none from the grid.

 

  • Like 1
  • Thanks 1

Share this post


Link to post
Share on other sites
1 hour ago, Pete said:

What does this mean Nick? I thought all PV had to go through a diverter before it was used in the house?TIA

As above.

Inverter to take DC to AC, diverter to send it to specific loads at specific times etc.

1 hour ago, ProDave said:

You can't sent power from a PV diverter directly to anything electronic as it is generally bursts of power pulse width modulated. 

Yes. The reason a Sunamp has a mains 230v feed from the CU for the controller, and then a separate feed to the immersion ( via a contactor on the controller PCB which operates as a gate ). Lots of electricians were getting this wrong early on and some ended up blowing the SA controllers up.

Share this post


Link to post
Share on other sites

So there is a cursory mention of cooling in the Valliant aroTHERM docs I've so far seen but the supplier I'm in contact with not yet answered question as to whether they will install and commission a new system with the cooling function enabled. Has anyone got any light to shed on using the cooling function on these ?

 

I remember being advised a while back that installing a system that has cooling accessible from the user controls means the RHI eligibility is problematic. Just before the lockdown I talked to someone who suggested this was no longer the problem it once was - is that correct ?

Share this post


Link to post
Share on other sites
3 hours ago, davidc said:

I'm in contact with not yet answered question as to whether they will install and commission a new system with the cooling function enabled

AIUI this varies a lot based mst of all on the installer, rather than the manufacturer.

Some will do it without batting an eyelid, some will insist "metering for usage" needs installing, some will tell you you're breaking the law and deserve to be put in jail if you enable it.

 

RHI itself is now clear that colling is allowed, but the payments will only be made based on predicted heating use. (Or actual heating use, if they require you to do metering for usage)

 

some manufacturers go to greater lengths than others to permanently  disable cooling, so the above is based on ones where it's broadly possible. No idea where Vaillant sit on that spectrum.

After going around this several times, my end tactic is to install it without cooling enabled, but make sure I'm with a manufacturer with plenty of track record of ppl being able to DIY enable is post-installation (specifically, Mitsubishi in my case) 

 

 

  • Like 1

Share this post


Link to post
Share on other sites

^ all of which is to say, your question is a very good one and I'd also be interested to know if anyone has experience of this with the Vaillant too :-)

 But don't hold your breath waiting to find an installer that will give a straight answer!

 

Share this post


Link to post
Share on other sites
3 hours ago, joth said:

^ all of which is to say, your question is a very good one and I'd also be interested to know if anyone has experience of this with the Vaillant too 🙂

 But don't hold your breath waiting to find an installer that will give a straight answer!

 

 

@davidc In the U.K they come with cooling disabled.  Cooling can be enabled by adding a "coding resistor"

image.png.74fd9e2d2e80913b6de6a1f148edf62a.png

  • Thanks 1

Share this post


Link to post
Share on other sites
1 hour ago, Dan F said:
5 hours ago, joth said:

 But don't hold your breath waiting to find an installer that will give a straight answer!

 

 

@davidc In the U.K they come with cooling disabled.  Cooling can be enabled by adding a "coding resistor"

 

Once again, @Dan F knows the products better than their own sales people.

 

  • Like 1

Share this post


Link to post
Share on other sites
5 minutes ago, joth said:

Once again, @Dan F knows the products better than their own sales people.

 

It was the Vaillant sales guy that told me this, rather than a supplier/partner. You can get him on twitter @  https://twitter.com/cj_Vaillant

Share this post


Link to post
Share on other sites
Posted (edited)

Thanks @joth and @Dan F .

 

I guess if clipping the resistor over a couple of pins on the PCB is sufficient alone to get the cooling working without any other measures on the UK units that is a result. Straying off topic ever so slightly, that would mean the installer would be unaware the system would be used for cooling post-install so are there any subtleties that the wider system i.e. UFH, pipework, manifolds etc need to be designed in mind with if the whole system is to be able to run in cooling mode also ? Instincts tell me not as it is the same thermodynamics just with the energy flowing in the opposite sense to warming mode.

 

Interest in these for me was piqued a few weeks back as supplier local to my build (who was previously going to supply and install a Woodfire CX12 and 500L thermal store) phoned me up saying there were expanding into heat pumps and were now a new Vaillant agent - obviously he started extolling the virtues of the new aroTHERM units. I was slightly concerned about the potential to add to summer overheating problems with a thermal store under the previous plan and also to have both heating and cooling delivered by the one single appliance is a potential bonus.

Edited by davidc
typo

Share this post


Link to post
Share on other sites

The main thing using the same piping for cooling is watch out for condensation.

 

If i ever implement cooling properly for my LG unit, it will be via a fan coil unit or 2 in the upstairs bedrooms, so extra insulated pipework and an extra motorised valve, and alterations to the control wiring.

Share this post


Link to post
Share on other sites
Posted (edited)

I guess that might be a problem @ProDave - especially condensate on the floor !

 

Ah interesting, now I think of it I remember seeing an LG ASHP diagram with showing a fan coil for cooling, I think I tried to find out more from LG and also ask them about an installer and got, well, not very far ! So have I understood correctly in that that solution would cool the air rather the what is connected to the heating flow output ? Do any other ASHPs pair up easily with fan coils ?

Edited by davidc

Share this post


Link to post
Share on other sites
3 hours ago, davidc said:

! So have I understood correctly in that that solution would cool the air rather the what is connected to the heating flow output ? Do any other ASHPs pair up easily with fan coils ?

 

If you cooling demand is low, you have MVHR and you can insulate ducts you could consider one of these: https://veab.com/kategori/duct-heaters-cooler-water.  MVHR isn't a great way to cool though so only good for low cooling demand.

Share this post


Link to post
Share on other sites
4 hours ago, davidc said:

I guess that might be a problem @ProDave - especially condensate on the floor !

 

Ah interesting, now I think of it I remember seeing an LG ASHP diagram with showing a fan coil for cooling, I think I tried to find out more from LG and also ask them about an installer and got, well, not very far ! So have I understood correctly in that that solution would cool the air rather the what is connected to the heating flow output ? Do any other ASHPs pair up easily with fan coils ?

I tried the cooling function on my ASHP last summer.  On the LG you just trigger it by activating the cooling thermostat input and it starts up in cooling mode.  Because I had not provisioned for cooling, I had to set the heating programmer to come on, then go and turn up all the room thermostats to bring the UFH on, and then it circulated cool water through the UFH.  It seemed to work without issue but of course it did nothing to cool upstairs which is where it was too hot.

 

To implement it properly would mean an additional motorised valve to pass the chilled water to a fan coil unit or 2 upstairs and activate  the cooling input from a cooling room thermostat. I stalled when I found fan coil units were hard to source and seemingly expensive for a heat exchanger and a fan in a box.  The best I could do was about £100 from China from alibaba but I never got around to ordering one.  Something I may still do if summer heat becomes more of an issue.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now