Does this ASHP schematic work for cooling?

[jfb]

As the title suggests - would this schematic specified for an Ecodan PUZ-WM 6kw ASHP and pre plumbed cylinder with an FTC6 controller work for cooling?

I seem to remember reading past posts that suggest something different needs to be done (is it to isolate the cylinder when working in reverse?).

 

A further point - I know that some think 3 port valves the work of the devil! Why is that and what is the alternative?

 

Thanks for any advice.

[PeterW]

Is this one from Alto..?? The multiple pumps are a waste, and it works much better when you use pairs of diverter valves to fully isolate the tank. 
 

The difference on valves is the mid-position vs diverter which is normally used with S/Y plan. A mid position holds by use of stalling a motor, a diverter just pushes across and holds in one position. 
 

I also prefer a decent buffer rather than LLH - you can use as a secondary dump load using an immersion in the buffer. 

[LA3222]

I think the key point in this story is that the cylinder mentioned by the OP is pre-plumbed.

 

Doesn't matter what schematic they dig up from the Web. All the parts are there and fitted. Just need to connect ASHP to flow/return on the cylinder. Then connect hot and cold feeds to cylinder and the expansion tank which is supplied loose.

 

Job done.

 

@jfb the only schematic you need is the Ecodan one showing how to connect it all. Cooling mode is just a dip switch on the FTC board.

Edited August 8, 2022 by LA3222

[PeterW]

2 minutes ago, LA3222 said:

All the parts are there and fitted. Just need to connect ASHP to flow/return on the cylinder. Then connect hot and cold feeds to cylinder and the expansion tank which is supplied loose.

Which is the point you’ve missed - hence my comment. 
 

33 minutes ago, PeterW said:

it works much better when you use pairs of diverter valves to fully isolate the tank. 
 

The difference on valves is the mid-position vs diverter which is normally used with S/Y plan.

You need to install a pair of diverter valves, or a full isolation set of 4 zone valves to make this work. It’s not a pre-plumb fit and forget, and it’s not just lob it in and it will all be fine. 
 

Given most pre-plumb cylinders are only really wired for S or Y using a standard 75°C boiler feed, a multi temperature setup such as this and the use of the FTC requires the plumbing and electrical connections to identify to the FTC what to do - that’s not possible with a single micro switch in a cheap mid position valve. 
 

So to answer the OP question, no, this set up using an unknown pre-plumb cylinder won’t work with cooling. 

[LA3222]

25 minutes ago, PeterW said:

Which is the point you’ve missed - hence my comment. 
 

You need to install a pair of diverter valves, or a full isolation set of 4 zone valves to make this work. It’s not a pre-plumb fit and forget, and it’s not just lob it in and it will all be fine. 
 

Given most pre-plumb cylinders are only really wired for S or Y using a standard 75°C boiler feed, a multi temperature setup such as this and the use of the FTC requires the plumbing and electrical connections to identify to the FTC what to do - that’s not possible with a single micro switch in a cheap mid position valve. 
 

So to answer the OP question, no, this set up using an unknown pre-plumb cylinder won’t work with cooling. 

I think you are missing the point here. Your comments on the schematic are valid and I don't dispute that.

 

My point, is that the question is moot.

 

The OP is asking about the use and suitability of the Alto schematic when they have a preplumbed cylinder and matching Ecodan ASHP. The question does not warrant an answer. The OP should instead be informed that the component parts required are all fitted to the cylinder when it arrives and the connecting of said system should be carried out in accordance with the mitsubishi MIs and not the Alto schematic.

 

The question is probably, what is the OPs intention for the OP which may bear relevance. Without digging my MIs out I am sure that two zone connections are covered in their.

 

I would hazard that the best starting point would be the mitsubishi MIs rather than the Alto drawing.

Edited August 8, 2022 by LA3222

[joth]

1 hour ago, jfb said:

As the title suggests - would this schematic specified for an Ecodan PUZ-WM 6kw ASHP and pre plumbed cylinder with an FTC6 controller work for cooling?

As well as the points Peter makes (and I agree with) about using a buffer instead of LLH, and using zone isolation valves, another key question is:

What emitters are you using in the two zones?  Do they expect different flow  temperatures? 

If so you'll also need a. Electronic mixing valve on zone 2 to mix down the correct temperature for heating/cooling. (The FTC6 can drive that mixing valve for you)

 

This also allows the buffer tank to store water at hotter/colder temp that required (e.g. charging it up during cheap rate or from solar PV excess)  and mix the  it down to required temperature when used. 

[jfb]

2 hours ago, PeterW said:

Is this one from Alto..?? The multiple pumps are a waste, and it works much better when you use pairs of diverter valves to fully isolate the tank. 
 

The difference on valves is the mid-position vs diverter which is normally used with S/Y plan. A mid position holds by use of stalling a motor, a diverter just pushes across and holds in one position. 
 

I also prefer a decent buffer rather than LLH - you can use as a secondary dump load using an immersion in the buffer.

Firstly, I really appreciate everyone's input - thanks.

I have to say I am a little lost when it comes to the intricacies of all this - I couldn't tell you without looking it up the difference between an S and Y plan for example so bear with me!

It is from Alto as you all seem to know. It has finally arrived after a long wait and I will have got a recommended plumber ready to install it. I am not fully confident that left to their own devices the plumber and electrician will install it to allow for cooling and so I would like to have a solid understanding of the necessary steps needed to succeed.

 

It is a 150l pre-plumbed standard cylinder EHPT15X-UKHDW that accompanies the 6KW Ecodan and FTC6 controller.

I have 4 UFH loops downstairs that will be one zone and radiators upstairs as a second zone that are sized for low temperature so can run at the same temperature as the UFH (I assume that is the case as it is well insulated, airtight with MVHR and initially I considered not having rads upstairs but have them partly because without them I wouldn't be eligible for the new £5k grant). Currently no PV or plans to do so.

 

I can't quite grasp the mid-position v. diverter issue and how it relates to S or Y plans (is S/Y plan another one!?). From what I can gather the schematic they suggest is a Y plan (the 3 port being the Y) but you are suggesting that S is needed for cooling. By mid-position are you referring to the Y plan and for S plan I need the diverter valves?

 

One thing I don't know - is the low loss header something not likely to be included in the kit (I can't see one) and so the choice of LLH or buffer is still open. Looking at the diagram in the manual for cylinder it seems to specify a LLH (number 22 in the picture below). I am slightly worried once I suggest the buffer alternative that Alto will say that isn't what Mitsubishi specify so they can't recommend it/sign it off. I'll attach a couple of pics of the cylinder down below as well.

 

 

 

Edited August 8, 2022 by jfb

[jfb]

[jfb]

[joth]

20 minutes ago, jfb said:

I have 4 UFH loops downstairs that will be one zone and radiators upstairs as a second zone that are sized for low temperature so can run at the same temperature as the UFH (I assume that is the case as it is well insulated, airtight with MVHR and initially I considered not having rads upstairs but have them partly because without them I wouldn't be eligible for the new £5k grant). Currently no PV or plans to do so.

What floor finishes do you intend to install downstairs? - are they temperature sensitive? 
which zone(s) are you thinking would be used for cooling?

 

Personally I'd install the electronic mixing valve onto Z2 and use that for the UFH, as even if it turns out you can run the rads and UFH at the same temperature, it's nice to have the option of being able to set them to different flow temps or compensation curves.

 

Also note that this design will be fairly limited for cooling. I doubt rads will work. You'll get a bit from via UFH loops, but as they're all downstairs you have stratification working against you, so downstairs will have a puddle of cool air at ground height, but upstairs won't benefit at all. This may not be an issue to you, but for our house this is exactly the opposite to what we'd like. (Generally we want the office and bedrooms cooler than the living area, not warmer than).

Unless you want to get caught up in installing Fan Coil Units upstairs, on a new build, my own recommendation would be to put UFH upstairs too. It won't add much expense compared to rads and is a LOT more flexible.

 

 

Edited August 8, 2022 by joth

[LA3222]

30 minutes ago, jfb said:

I believe (been a while since I was looking at this in depth) that item 22 you refer to is that copper pipe on left of the cylinder with the AAV on.

 

Don't get sucked into making this more complicated than it needs. A pre plumbed cylinder makes all of this far easier as it's all there.

 

IIRC all the items within the dotted line on the schematic come prefitted except the expansion vessel which is supplied.

 

As I said earlier, if you want cooling its just a dip switch. 

 

I stuck a 100l buffer between the ASHP and UFH.

 

If your emitters can take the same temp then no need for multiple zones - run it all at same temp from a buffer tank.

 

You may want to check though as condensation can be an issue for rads, not so much with UFH.

 

As suggested UFH upstairs is better than rads for the condensation issue. 

[LA3222]

There is literally 6 connections.

 

1. ASHP flow to connection on cylinder

2. ASHP return from same.

3. Heating O/P from cylinder to buffer

4. Heating return from buffer

5. Cold fill from mains

6. DHW to house

[LA3222]

I tell a lie, there is also the O/P from the tundish (prefitted to the T&PRV and PRV) and the O/P to the expansion vessel.

 

The 3.5bar PRV is supplied loose and needs fitting to the mains. 

[jfb]

1 hour ago, joth said:

What floor finishes do you intend to install downstairs? - are they temperature sensitive? 
which zone(s) are you thinking would be used for cooling?

150mm polished concrete slab with UFH pipes downstairs. Was presuming it would just be the UFH that I would be cooling though I take your point about upstairs being more desirable to cool in some ways.

Too late for UFH upstairs as I am a fair way towards completion!

[jfb]

1 hour ago, LA3222 said:

Don't get sucked into making this more complicated than it needs

I like the sound of this but I am worried that there is a bit more to it as Peter has alluded to, including electrical connections and valves, etc

 

 

[jfb]

1 hour ago, LA3222 said:

I stuck a 100l buffer between the ASHP and UFH.

Is that the sort of size a buffer should be or can it be a lot smaller?

Not sure I have much room for more cylinders!

[LA3222]

24 minutes ago, jfb said:

I like the sound of this but I am worried that there is a bit more to it as Peter has alluded to, including electrical connections and valves, etc

 

 

All the valves are pre fitted and hard wired in to the controller. If you were doing this from scratch, absolutely, but you're not - this was the same.reason why I chose to go pre-plumbed and match a mitsubishi cylinder to ecodan ASHP. The hard work is already done.

[LA3222]

24 minutes ago, jfb said:

Is that the sort of size a buffer should be or can it be a lot smaller?

Not sure I have much room for more cylinders!

Think it depends in the size.of your house and amount of fluid in the UFH pipes in order to prevent short cycling. There are some on here that didn't bother.

 

The way I run my system at the minute is to heat the buffer tank to 45 degrees. When the UFH kicks in, it draws from that tank and drops the flow temp to 25 degrees at the manifold. There is nothing complicated about all of this.

 

I found it helps to think of the buffer as your 'central heating'. Your ASHP is either heating the hot water cylinder or the central heating system.

 

The UFH I think off as a seperate system which does its own thing according to the room stats. If it needs heat it will.pull water from the buffer tank. If it doesn't, it does nothing. Job done.

[PeterW]

With all due respect to everyone on here, the pre plumbed cylinders are expensive and crap. Very rare they are used as tbh they are a fudge. Sadly this appears to have the LLH plumbed in already (left side with AAV fitted) but none of it is insulated….. 

 

PHE is on no-ones drawings but is fitted to the tank - again, waste of time and is going to cause problems as it looks like it constantly draws water through the PHE to heat the water and the tank is just a dumb tank ..? 

 

Adding cooling to that lot is a non-starter - the diverter and temperature controls are locked in on the FTC which means it won’t allow you to change it. I would guess there is a bill for £3k min for the tank ..? Plus FTC (£800) and the ASHP (£3k)..??

[LA3222]

24 minutes ago, PeterW said:

With all due respect to everyone on here, the pre plumbed cylinders are expensive and crap. Very rare they are used as tbh they are a fudge. Sadly this appears to have the LLH plumbed in already (left side with AAV fitted) but none of it is insulated….. 

 

PHE is on no-ones drawings but is fitted to the tank - again, waste of time and is going to cause problems as it looks like it constantly draws water through the PHE to heat the water and the tank is just a dumb tank ..? 

 

Adding cooling to that lot is a non-starter - the diverter and temperature controls are locked in on the FTC which means it won’t allow you to change it. I would guess there is a bill for £3k min for the tank ..? Plus FTC (£800) and the ASHP (£3k)..??

Once you remove VAT I paid £4900 for 300l cylinder and 8.5kW ASHP. I gwt you can buy a naked cylinder and parts for less, I preferred this option.

 

Adding insulation is not difficult or a problem AFIAC see.

 

Why is cooling a non starter? This comment makes no sense to me. I use cooling when necessary - a dip switch and done. No additional cost.

[PeterW]

3 minutes ago, LA3222 said:

Why is cooling a non starter? This comment makes no sense to me. I use cooling when necessary - a dip switch and done. No additional cost.

to properly implement cooling you need to isolate the hot tank and all it’s circuits from the chilled supply - essentially you need to double isolate as these have twin pumps and you can get pull through on the diverter valves especially spring return ones. That needs additional valves plus the additional control logic to drive the correct pumps and isolators. 
 

on top of that, the FTC is dumb when it comes to variant zone control and essentially you could get the upstairs controls asking for heat fighting the cooling downstairs - you then have further zone issues as the internal pipe stats get very confused as they want hot not cold water …

 

Furthermore, 150 litre tanks mean invariably unless you have a very small (ie 2 bed, 3 occupant max) property, the ASHP will need to run during the day. At significant cost over off peak night time running. These units are designed for spanner monkeys to plug and play into HA properties where they don’t have to think. They definetely aren’t designed for cooling or anything non standard. 
 

 

[joth]

2 hours ago, jfb said:

150mm polished concrete slab with UFH pipes downstairs. Was presuming it would just be the UFH that I would be cooling though I take your point about upstairs being more desirable to cool in some ways.

Too late for UFH upstairs as I am a fair way towards completion!

Fair enough.

 

Have you already got this pre-plumbed cylinder?

If so my thought now is run it with the simplest heating-only design you can, per LA3222, and if come next summer you have issues requiring active cooling do it properly and install a2a unit(s) upstairs. They're very plausible to retrofit 

 

 

[LA3222]

41 minutes ago, PeterW said:

to properly implement cooling you need to isolate the hot tank and all it’s circuits from the chilled supply - essentially you need to double isolate as these have twin pumps and you can get pull through on the diverter valves especially spring return ones. That needs additional valves plus the additional control logic to drive the correct pumps and isolators. 
 

on top of that, the FTC is dumb when it comes to variant zone control and essentially you could get the upstairs controls asking for heat fighting the cooling downstairs - you then have further zone issues as the internal pipe stats get very confused as they want hot not cold water …

 

Furthermore, 150 litre tanks mean invariably unless you have a very small (ie 2 bed, 3 occupant max) property, the ASHP will need to run during the day. At significant cost over off peak night time running. These units are designed for spanner monkeys to plug and play into HA properties where they don’t have to think. They definetely aren’t designed for cooling or anything non standard. 
 

 

I think some of what you say makes sense but you're at risk of over egging this and tainting the good info in there with the bad.

 

The OP has a 150l tank, maybe that is sufficient to meet their needs - have you asked or assumed?

 

I have a 300l tank, family of four, showers baths at random times - I have yet to run out of hot water so not an issue.

 

My hot water runs at 12 at the minute to try and make use of PV rather than grid. Once a day to get tank up to temp - no issues there. I run it during the day - so what....I'm using PV. 

 

Variant zone control. Why. I have not seen a single.person on here doing the like. Everyone on here seems to tread a well worn path - well insulated house with UFH, usually as a single zone. Why are you looking to complicate this? So you can use your argument as to why it's no good?

 

Not designed for cooling. No systems are designed for cooling in this country in the manner we are using them. Everyone on here using the cooling mode in the UFH is treading a path which was paved by those before us who tested whether the ASHP could be run in cooling through the UFH and whether it worked. None of this is in any manual. 

 

Too many people on here are using the ASHP in cooling mode for your comment about not being designed for such to wash. I have a pre plumbed unit and it works. Not sure what else I can say other than I moved a dip switch and it is now an option on the controller. I turn it on and guess what, water cooled to 12 degrees to my buffer.

 

Why would you heat upstairs at the same time as cool downstairs - this is going down a hole now.

 

The cylinder is set to DHW as default iirc. Hot water takes priority and it stops doing the other if DHW comes on. I have seen it happen when running cooling. Gets to 12pm and need some hot water topping up, surprise surprise, the cooling stops and the water starts heating.

 

You have a bee in your bonnet about something and like I say, the valid points you make are being drowned out by the odd ones.

 

As an aside, I don't dispute you are the SME here, you gave a lot of feedback and heavily influenced my own system. I think the higher level issues you raise are not really commensurate with the way that most on here use them. KISS.

Edited August 8, 2022 by LA3222

[PeterW]

1 hour ago, LA3222 said:

Not designed for cooling. No systems are designed for cooling in this country in the manner we are using them. Everyone on here using the cooling mode in the UFH is treading a path which was paved by those before us who tested whether the ASHP could be run in cooling through the UFH and whether it worked. None of this is in any manual. 

I’m a partner in a design and consult business that does around 80-100 ASHP designs a year along with significant numbers of full M&E specs for LA and HA clients. What’s your experience based on ..? 
 

1 hour ago, LA3222 said:

Variant zone control. Why. I have not seen a single.person on here doing the like. Everyone on here seems to tread a well worn path - well insulated house with UFH, usually as a single zone. Why are you looking to complicate this? So you can use your argument as to why it's no good?

The OP doesn’t have this ! Has UFH and Rads ..??? 
 

1 hour ago, LA3222 said:

turn it on and guess what, water cooled to 12 degrees to my buffer.

OP has pre plumbed unit with an LLH already on it - not a buffer… you are also indicating this is manual in your system, 99.9% of the client base we have need automatic and simple controls. 
 

Poor design and not understanding the basics of what is being put into a spec is the core issue when end customers realise they can’t do what they want to do - usually because the incomplete requirements haven’t been passed on. Hypothetically*  if an end customer came to us and said I want heat, cool and DHW, then there are a whole new set of questions to ask before a pen even hits paper….

 

*we don’t deal with end customers / individual clients and have no interest in doing so.  

Edited August 8, 2022 by PeterW
Clarification

[joth]

7 hours ago, PeterW said:

it works much better when you use pairs of diverter valves to fully isolate the tank. 
 

 

Just to confirm my own understanding, for a system with cooling, you'd recommend a pair of 3-port valves one on each end of the UVC coil, so both the supply and return end of it are shut off and diverted into the buffer when the FTC switches over from DHW to  space heating/cooling mode?

Do you have a preferred make/model of diverter valve to use for this?

 

My system is currently plumbed with the schematic attached, more or less, using a single 3 port mid-position valve for the change over (the typical honeywell one), and I've never been overly happy with it. It uses way more primary energy in cooling mode than heating mode each year, for a fair number of reasons, and I'm sure this is one contributor. (So  I appreciate the chasm that can open between getting cooling to work, and getting it to work well.)

 

Standalone with Third Party Cylinder 2ZM - FTC6.WMXXX.STP.2ZM.pdf