Are pipe stats required for an ASHP with UFH.

[joe90]

Right, I need to get my head around wiring for the UFH, ASHP, etc. PeterW has shared his diagram with me as his system is similar but I have a question, do we need pipe stats?  The DHW tank and buffer tank for the UFH both have tank stats, surely the ASHP delivers water at the temp programmed and the tanks tell the ASHP when it’s up to temperature. There is talk of water at different temps going to different tanks but I don’t see how a pipe stat would control this but only short cycle the ASHP to keep the temp lower. I plan to run the ASHP to only about 45 degrees to ( hopefully) stop a defrost cycle.  On a separate question, is it not possible to programme the ASHP to deliver water at a higher temp but when it detects it’s about to go into defrost mode it simply stops, this way when the weather is good you get hotter water ( up to tank set temps) and on cold winter days lower temps but no defrost cycle.

[PeterW]

Who's ASHP is it..??

 

Mine (and the one @readiescards has) needs the pipe stats to control the ASHP, so it may be that yours has internal controls.

[DeeJunFan]

@PeterW

 

From Memory you went for the same one as me the Ecolane IVT from Ice Energy?

 

Would you be able to share your pluming plan again?

 

Thanks

Damian

[PeterW]

1 minute ago, DeeJunFan said:

@PeterW

 

From Memory you went for the same one as me the Ecolane IVT from Ice Energy?

 

Would you be able to share your pluming plan again?

 

Thanks

Damian

 

Yep see attached...

 

Bear in mind... I run a Telford HP UVC at 47c from the ASHP, and a buffer for the UFH at 38c. Its a modified W Plan which allows me to switch temperatures on the ASHP with the diverter valve microswitch. The relay just isolates the UVC stat so ensures I can run buffer only even when the tank stat is calling for heat.

 

Heating Schematic V2 2504.pdf

[joe90]

Mine is a Kingspan 4kw ( same as Jeremy,s I think). I also got the advanced programmer so I am sure the ASHP can be controlled from this.

[DeeJunFan]

7 minutes ago, PeterW said:

 

Yep see attached...

 

Bear in mind... I run a Telford HP UVC at 47c from the ASHP, and a buffer for the UFH at 38c. Its a modified W Plan which allows me to switch temperatures on the ASHP with the diverter valve microswitch. The relay just isolates the UVC stat so ensures I can run buffer only even when the tank stat is calling for heat.

 

Heating Schematic V2 2504.pdf

Thanks for that

 

So you have given the buffer priority over the UVC,  any particular reason for that?

 

My setup is in a complete mess as i have to date had 4 different plumbers do work on site and there is no real coherent plan between the lot of them.  One made a plan and  the rest are trying to follow on with it in some way. 

 

At the moment I have a setup that basically uses the UFH loops as the buffer.   we will have 3 zones.   UFH (downstairs) UFH (Upstairs) and DHW cylinder.   Only 1 of these zones will be getting heat at any one time and the DHW will have the preference.   And the UFH zone preference i believe is going to be time managed   so Downstairs in the morning/afternoon and upstairs in the evening. 

 

 

[PeterW]

OK - in W Plan you have an anomoly in the wiring which means if you are in heating only mode there is still a back link to the stat for the DHW to trigger the valve to move over. I've isolated this as my expectation (and calculation..) is that my heating load is marginally higher than the DHW. Also, DHW will be taken to 47c by the ASHP overnight before the E7 immersion kicks in to take the tank to 65c.

 

Clear as mud..? 

[joe90]

Duh, I need to digest all this info. My electrician popped in ( for a cup of tea as he has become a good friend) and it was him that asked why we need pipe stats, so, in the ASHP programming I guess you set the temp of water it delivers and when the tank stats reach their desired temp the ASHP is told to shutdown?

[Jeremy Harris]

2 hours ago, joe90 said:

Duh, I need to digest all this info. My electrician popped in ( for a cup of tea as he has become a good friend) and it was him that asked why we need pipe stats, so, in the ASHP programming I guess you set the temp of water it delivers and when the tank stats reach their desired temp the ASHP is told to shutdown?

 

 

No need for pipe stats with the re-badged Carrier units, they have a sensor built in to the flow pipe from the ASHP that is used to set the flow temperature, depending on selected mode.  For example, I have ours set to deliver a flow temperature of 40 deg C in heating mode, 55 deg C in hot water mode (which I don't have connected) and 12 deg C in cooling mode.  You can make the heating mode temperature follow a weather compensation characteristic if you wish, but I found it worked better for us with it set for a constant 40 deg C.  By default the unit will be pre-programmed to a weather compensation characteristic, probably one that doesn't work that well for the UK climate, if my experience is anything to go by.

 

In terms of controls, all I have is two room stats (one for heating, one for cooling), a standard single channel programmer to turn the whole system on and off, and a tank stat on the buffer tank that has priority over the room stats.  Giving the tank stat priority means the buffer is always charged to between 35 and 40 deg C when the programmer is on, irrespective as to whether the heating or cooling is on. 

 

If cooling is on with no call from the tank stat for heat, then the buffer tank valve (in the flow to the buffer from the ASHP) will be closed, the UFH valve (on the return from the UFH manifold) will be open. 

 

If heating is on with no call from the tank stat for heat then the buffer tank valve is left open (so the buffer works as a buffer for the UFH) and the UFH valve is open.

 

If the heating is on and there is no call from the room stat or the tank stat then the buffer tank valve stays open and the UFH valve stays open but the ASHP and UFH pump is turned off.

 

If the cooling is on and there is a call for heat from the tank stat the ASHP is turned off, then set to heating mode, the UFH valve is closed and the buffer valve opens then the ASHP restarts in heating mode.  This way the floor stays cool but warm water can recharge the buffer.

[joe90]

Jeremy, a comprehensive answer to my problems ( as always) many thanks.

[joe90]

Right, after putting it off I finally got round to reading up and understanding what I need to do, but this has led to even more questions. The carrier user interface installation and user manual only talks about heating, cooling, sleeping or away modes (no DHW mode) but the front screen has a “sanitary hot water” symbol?. Also the user interface has timers and thermostats that are programmable so presumable I don’t need the single channel timer but I guess I still need the UFH room stat?. I was interested to see it dealt with cooling as others have said they needed to reverse engineer theirs to do this.  Frankly I am right out of my depth with this so would appreciate some guidance. Here are the two installation pages ?

 

 

Edited September 4, 2018 by joe90

[Jeremy Harris]

If you install the control unit where it can work as a room stat, then you can also use it as the only heating programmer/stat, as it's got normally heating programming capabilities and a room temperature sensor.

 

If you don't want to use the control unit as a programmable room stat, then you can ignore all the time/day programming stuff and just use another method to control the heating (which is what I've done).

 

Sanitary hot water is DHW as far as we are concerned, and the ASHP has relay outputs to drive motorised valves to switch from heating to hot water mode and the heat pump can control the hot water temperature without a tank thermostat because it just limits the flow temperature to either 50 or 55 deg C in sanitary hot water mode, and has enough hysteresis to not need anything else to maintain hot water at that temperature without anything else.

 

It's a bit either/or, in that if you opt to position the control unit as the main programmable thermostat, then you can set everything from there and only need to add a motorised valve to switch the flow from the UFH to the hot water system (if you're using it for hot water).  If you're only using the heat pump for the UFH, then you don't need the motorised valve and you can ignore the sanitary hot water bit.

 

Setting the temperature curves for the flow temperature is a bit of a pain, but worth doing if you want best efficiency from the thing.  Depending on what you want to do I can give you settings for doing that, using the custom curve option.

 

You can leave most of the installer settings at their default values, as there are only a handful that may need changing.

[joe90]

Thanks JH, I think I need to get it fired up using factory settings (as SWMBO keeps telling me it’s Septemberish, I.e. chilly) and see how it goes, I may pick your brains regarding curves once we settle down to using it. I will also consider using E7 or E10 once we know how the house performs.

[Jeremy Harris]

Happy to talk you through changing the settings as needed.  The manual isn't as clear as it could be, IMHO.  There may be a slight delay whilst I get back up to speed on the settings, as it's a while since I've played with ours - I got the settings right and have just left it alone since!