Panasonic Air Rads - be warned

[NSS]

Sorry chaps, the pub was calling. Will read all your replies properly in the morning but to answer one query, yes @Nickfromwales it does also supply DHW.

[Nickfromwales]

Enjoy !

Thats why the LLH is there then, so the UFH can circulate when the motorised valve isolates the UFH from the ASHP and directs flow to the cylinder at max temp. 

It'll also allow the two pumps to be running at different speeds so deffo for hydraulic separation and not much else. 

 

The answer to the original post has to be, that setting the UFH temp via the ASHP flow temp setting means there is no option or mechanism to allow the ASHP space heating temp to be increased without increasing the UFH flow temp . 

A very peculiar design, BUT, it works. 

Another qiestion....did the installer know the air rad was being fitted at the design stage or was it a bolt-on?   

[NSS]

8 minutes ago, Nickfromwales said:

Enjoy !

Thats why the LLH is there then, so the UFH can circulate when the motorised valve isolates the UFH from the ASHP and directs flow to the cylinder at max temp. 

It'll also allow the two pumps to be running at different speeds so deffo for hydraulic separation and not much else. 

 

The answer to the original post has to be, that setting the UFH temp via the ASHP flow temp setting means there is no option or mechanism to allow the ASHP space heating temp to be increased without increasing the UFH flow temp . 

A very peculiar design, BUT, it works. 

Another qiestion....did the installer know the air rad was being fitted at the design stage or was it a bolt-on?   

@Nickfromwales , the original design was done by a company who subsequently went bust (after installing the UFH pipes in the floor and the manifold), but before the rest of the kit could be fitted (leaving me about ₤1800 out of pocket in the process). The company who took over just installed as per the original spec so no blame on them (in fact they've been very good considering they'd never installed Panasonic kit before).

[Nickfromwales]

15 minutes ago, NSS said:

@Nickfromwales , the original design was done by a company who subsequently went bust (after installing the UFH pipes in the floor and the manifold), but before the rest of the kit could be fitted (leaving me about ₤1800 out of pocket in the process). The company who took over just installed as per the original spec so no blame on them (in fact they've been very good considering they'd never installed Panasonic kit before).

??

How does everything perform as it is now?

[Jeremy Harris]

I'd still question whether the MINIMUM operating power of that LLH at the ASHP flow temperature is within limits (basically they don't work properly much below the minimum power).  My guess from it's apparent size in the photo is that its minimum rating is around 40 kW at 60 to 65 deg C which means it will have a minimum of well over 60 kW at ASHP flow temperatures.  I doubt your ASHP is rated at a minimum power anywhere near this.

 

 

[NSS]

7 hours ago, Nickfromwales said:

??

How does everything perform as it is now?

Though I've never had UFH before so have nothing to compare to, the ground floor seems to be working fine. At present, the hall circuit tends to stay on for a bit longer than it would if it wasn't in effect trying to heat the upstairs too.

 

Looks now as though bypassing the temp probe on the air rad is not a complete solution as it's made very little difference overnight. It calls for heat but there appears to be very little flow rate to the rad. The feed tees off before both the LLH (at least I now know what that lump is) and the circulating pump/manifold so i suspect they are drawing most of the flow. I'll add a pic showing a more general view of the set up.

[Nickfromwales]

Adding a gate valve to the LLH flow ( before the LLH but AFTER where it tees off for the rad ) will allow you to balance the output from the ASHP and split it equally between the manifold air rad. 

[Jeremy Harris]

As the flow temp from the ASHP is very low, the heat output to the air rad would be well below it's design temperature, and the heat output is highly non-linear with temperature; a few degrees higher flow temperature can give a massive increase in heat output to the room when the initial flow temperature is as low as it is.

 

My point about the low loss header, is that they have a minimum operating power at a rated temperature, and when run a long way below that power there will be a great deal of ASHP flow and return mixing, and this may well be reducing the heat available to the air rad even more, almost by accident.

 

Edited to add:

 

Posted at the same time as @Nickfromwales. Choking the flow to the LLH would effectively reduce the problem, but does the ASHP have a minimum flow shutdown?  Some do, our Carrier does and I know that the Samsung units do too.  The fix for them is not to fit a LLH but to fit a bypass relief valve, to allow sufficient flow through the ASHP if the demand side flow requirement is low.

 

Personally, I'm not convinced a LLH is a good solution for an ASHP, as if you look at how they work they need a significant temperature differential between the heat source flow and return to operate well (hence the minimum power rating, I think).  They were designed for use on boilers, really.

 

 

Edited December 7, 2017 by JSHarris
cross posted with Nick

[NSS]

2 pics

 

 

[Nickfromwales]

A 2-port AFTER the 3-port valve

Curioser and curioser. . 

[Nickfromwales]

@NSS

Can you post the model / part numbers  of each of those ( silver metal boxed ) zone valves please? 

[Jeremy Harris]

7 minutes ago, Nickfromwales said:

A 2-port AFTER the 3-port valve

Curioser and curioser. . 

 

 

And a magnetic filter intended for use in a system with ferrous metal components, something that would be routinely fitted to a boiler and radiator system but not to an ASHP and UFH system, as it serves no useful purpose.  Any debris in such a system won't be magnetic, (no steel radiators), there's no collection of mixed metals to exacerbate corrosion, and all an ASHP system ever needs is a Y strainer.

 

I'm even more convinced that the design was by someone unfamiliar with both ASHPs and UFH, and that the system has been designed as if it were radiators running from a boiler.  This isn't surprising, as has been quoted here a few times, there is a bit of a lack of experience in fitting ASHP systems in the UK, and was the main reason given for the very poor results from the first heat pump performance survey conducted by the Energy Saving Trust some time ago.

Edited December 7, 2017 by JSHarris

[NSS]

12 minutes ago, Nickfromwales said:

A 2-port AFTER the 3-port valve

Curioser and curioser. . 

Yep, that has me confused too, particularly as the 2-port is not actually wired into anything. They are both Honeywells,  V4044C1569 and V4043H1106 

[NSS]

13 minutes ago, JSHarris said:

 

 

And a magnetic filter intended for use in a system with ferrous metal components, something that would be routinely fitted to a boiler and radiator system but not to an ASHP and UFH system, as it serves no useful purpose.  Any debris in such a system won't be magnetic, (no steel radiators), there's no collection of mixed metals to exacerbate corrosion, and all an ASHP system ever needs is a Y strainer.

 

I'm even more convinced that the design was by someone unfamiliar with both ASHPs and UFH, and that the system has been designed as if it were radiators running from a boiler.  This isn't surprising, as has been quoted here a few times, there is a bit of a lack of experience in fitting ASHP systems in the UK, and was the main reason given for the very poor results from the first heat pump performance survey conducted by the Energy Saving Trust some time ago.

Actually there are steel radiators (dual fuel towel rails) in the two ground floor bathrooms. Each is fitted in line to the respective UFH circuits. 

[Jeremy Harris]

6 minutes ago, NSS said:

Actually there are steel radiators (dual fuel towel rails) in the two ground floor bathrooms. Each is fitted in line to the respective UFH circuits. 

 

 

Ah, OK, so the filter makes sense.  It begs another question though, with the ASHP set to such a very low flow temp, these radiators must be running at the same temperature, so they will also barely be getting warm.    That may be fine if they are massively oversized to allow for the large reduction in heat output with flow temperature, though.

 

I'm no heating engineer, but it would seem logical to me to run the higher temperature heating appliances, the radiators and air rads, directly from the ASHP, and set the ASHP to a reasonable temperature, say 40 deg C, so these work OK, then have a thermostatic mixer to reduce the flow temperature to the UFH so that can run at it's optimum temperature, probably no more than about 28 to 30 deg C, if that.

Edited December 7, 2017 by JSHarris

[NSS]

2 minutes ago, JSHarris said:

 

 

Ah, OK, so the filter makes sense.  It begs another question though, with the ASHP set to such a very low flow temp, these radiators must be running at the same temperature, so they will also barely be getting warm.    That may be fine if they are massively oversized to allow for the large reduction in heat output with flow temperature, though.

Sufficient to take the chill off of a towel, and we can boost them with the electric heating element when the UFH is not running.

[NSS]

29 minutes ago, JSHarris said:

I'm even more convinced that the design was by someone unfamiliar with both ASHPs and UFH, and that the system has been designed as if it were radiators running from a boiler.  This isn't surprising, as has been quoted here a few times, there is a bit of a lack of experience in fitting ASHP systems in the UK, and was the main reason given for the very poor results from the first heat pump performance survey conducted by the Energy Saving Trust some time ago.

Both the company who did the original design (since gone bust) and the company that took over were/are specialist heat pump installers.The latter certainly doesn't have a background of traditional boiler/radiator CH systems, and they also undertook our Solar PV install and integrated it (via Power Diverter) to our DHW tank immersion.

[Nickfromwales]

9 minutes ago, NSS said:

Sufficient to take the chill off of a towel, and we can boost them with the electric heating element when the UFH is not running.

Tbh I'd rather them set like that. No need for a hot towel, just not a cold one. I was just about to ask if they were fortified with electric elements aka dual-fuel. ?

 

24 minutes ago, NSS said:

V4044C1569

That's a true diverter so absolutely no need whatsoever for the second valve

They probably just saw that in the box and thought "must do something....let's just fit it and worry later"  Actually, you could take the motorised head off and use it manually as a gate valve to choke the flow to the LLH , ( just an expensive gate valve ! ). 

[Jeremy Harris]

3 minutes ago, NSS said:

Both the company who did the original design (since gone bust) and the company that took over were/are specialist heat pump installers.The latter certainly doesn't have a background of traditional boiler/radiator CH systems, and they also undertook our Solar PV install and integrated it (via Power Diverter) to our DHW tank immersion.

 

Curious that they should choose such an unusual configuration, and one that imposes restrictions on both the air rad performance and the ASHP performance, then.

 

Out of simple curiosity, and as someone fond of odd and unusual set ups, why did you choose to have the system configured in this unusual way, with the ASHP throttled back to a small fraction of its rated output in order to maintain a very low flow temperature to the heating circuits?

 

The efficiency hit must be quite high, as the ASHP will be running way below its minimum modulated output much of the time, especially with no buffer ( I assume there's no buffer because there's the low loss header).  That implies that a lot of the time the ASHP will be doing many more starts and stops than it needs to, and it's starts and stops that hit ASHP life quite hard, particularly the compressor.

 

 

Edited December 7, 2017 by JSHarris

[NSS]

2 minutes ago, Nickfromwales said:

Tbh I'd rather them set like that. No need for a hot towel, just not a cold one. I was just about to ask if they were fortified with electric elements aka dual-fuel. ?

 

That's a true diverter so absolutely no need whatsoever for the second valve

They probably just saw that in the box and thought "must do something....let's just fit it and worry later"  Actually, you could take the motorised head off and use it manually as a gate valve to choke the flow to the LLH , ( ust an expensive gate valve ! ). 

Would that not 'choke' the flow to the manifold too?

[NSS]

8 minutes ago, JSHarris said:

 

 

 

Curious that they should choose such an unusual configuration, and one that imposes restrictions on both the air rad performance and the ASHP performance, then.

 

Out of simple curiosity, and as someone fond of odd and unusual set ups, why did you choose to have the system configured in this unusual way, with the ASHP throttled back to a small fraction of its rated output in order to maintain a very low flow temperature to the heating circuits?

 

The efficiency hit must be quite high, as the ASHP will be running way below its minimum modulated output much of the time, especially with no buffer ( I assume there's no buffer because there's the low loss header).  That implies that a lot of the time the ASHP will be doing many more starts and stops than it needs to, and it's starts and stops that hit ASHP life quite hard, particularly the compressor.

 

 

Not sure how it effects what you're saying, but it does have a buffer. 

 

[Jeremy Harris]

That's the pressure vessel, not a buffer tank.  The low loss header is acting as an extremely low heat capacity buffer, but frankly won't really be working properly, because the temperature differential between the top and the bottom of it will be way below the design rating for that model, which looks to be a 40 kW boiler model.

 

You can get taller low loss headers that are specifically designed to be used with low power output and low flow temperature heat sources like ASHPs.  They are designed to reduce the cross flow top to bottom when the temperature differential is low, when compared to the high temperature boiler-type units, so they work OK at typical ASHP temperatures of around 40 deg C or so.  They aren't that popular, it seems,  perhaps because they are expensive when compared to the simpler fix of just fitting a standard pressure bypass valve across the ASHP flow and return in order to meet the minimum flow requirement without triggering a primary circuit over-pressure event.

Edited December 7, 2017 by JSHarris

[PeterW]

I’m not sure even that LLH is correct as it’s behind the 3 way valve and there are what looks like tee’d returns into the manifold return before that. 

 

If that’s the case then that air rad is probably not going to get anything like the flow it needs as it’s reliant on back pressure elsewhere in the system to force the flow into it which the LLH is designed to eliminate ...

 

Also if the rad is tee’d off before the diverted valve, then it will get heat during the DHW cycle too..!

[NSS]

13 minutes ago, JSHarris said:

That's the pressure vessel, not a buffer tank.  The low loss header is acting as an extremely low heat capacity buffer, but frankly won't really be working properly, because the temperature differential between the top and the bottom of it will be way below the design rating for that model, which looks to be a 40 kW boiler model.

 

You can get taller low loss headers that are specifically designed to be used with low power output and low flow temperature heat sources like ASHPs.  They are designed to reduce the cross flow top to bottom when the temperature differential is low, when compared to the high temperature boiler-type units, so they work OK at typical ASHP temperatures of around 40 deg C or so.  They aren't that popular, it seems,  perhaps because they are expensive when compared to the simpler fix of just fitting a standard pressure bypass valve across the ASHP flow and return in order to meet the minimum flow requirement without triggering a primary circuit over-pressure event.

Okay, as most of you will have guessed, a lot of this is going straight over my head. Here's a close up of the 'plates' on the LLH.

 

[Jeremy Harris]

Yes, that's a standard boiler 40 kW low loss header.