Idiots guide to ASHP

[Russell griffiths]

Morning all. 

I’ve got the shell of the house up and really need to sort out the nitty gritty of how the place is going to work. 

I have had a couple of guys at the house looking at all the different methods of how we will heat the place and supply hot water. 

Now it has been so long since I started looking into all this that I’ve gone around and around until I have tied my brain up in knots. 

 

So I would like a Forums idiot guide to ASHP. 

 

 What I think I know, 

ashp is a metal box that works like an air conditioner in reverse. 

 

So does this box of magic have a cold feed going into it and after the magic has happened hot water comes out of it ??.

 

The hot coming out needs to go somewhere, where’s this go ??

 

the temperature coming out is ok for ufh, but not hot enough for a bath or shower ??.

 

how do you get it hotter ???

 

i have purposely asked some basic questions, some I know the answers to, but I thought by going back to basics I might get a better grip on what I’m trying to do. 

 

I have hundreds more questions but I hope this gets the ball rolling so I can ask some more equally silly ones. 

 

Stay safe out there. 

Russ. 

[ProDave]

The "box of tricks" has a flow and a return pipe.  That is it for the plumbing.  You would normally make it as a pressurised system topped up with a fill loop.  Some ASHP's have a built in expansion vessel, most don't.

 

If you get a decent, inverter driven ASHP then you can set the flow temperature for heating to a different flow temperature for DHW.  The ASHP only does one at a time, unlike a system boiler than can do both together.

 

I have my ASHP set to deliver the low temperature for the UFH.

 

The flow and return circulate water around a closed loop, either the UFH or the heat input coil to the HW tank.

 

Control of whether the water circulates to UFH or HW tank is controlled by a couple of motorised valves.

 

So when it's doing heating the temperature coming out of the ASHP will be low.  When it switched to DHW (and the valves change over) the water coming out of the ASHP will be hotter (and the compressor will work a bit harder to achieve that)

 

Notice all of that relates to an inverter driven ASHP.  The old fashioned direct drive sort just run the compressor at full tilt until it gets to set temperature then turns it off.  I have just wired one like that for a customer and it does both heating and HW at 55 degrees.  In this case it's feeding radiators soo probably okay, but I  really would not recommend that sort.

[joe90]

Wot he said. I have a buffer tank fir the UFH, some don’t. @ProDave and I heat DHW to 48’ which we find very adequate but may mean a larger DHW tank as you won’t blend it down to use. I have a couple of immersions in the buffer tank and DHW tank fir back up or to top up the DHW if necessary.

1 hour ago, Russell griffiths said:

I have hundreds more questions but I hope this gets the ball rolling so I can ask some more equally silly ones. 

no such thing as silly questions, we have all been there so ask away.

[joe90]

33 minutes ago, ProDave said:

So when it's doing heating the temperature coming out of the ASHP will be low.  When it switched to DHW (and the valves change over) the water coming out of the ASHP will be hotter (and the compressor will work a bit harder to achieve that)

mines not like that, the controller requires a degree in techno speak (which I failed) so my ASHP delivers at 48’ whether to UFH (blended down by the manifold) or the DHW tank.. I have never noticed the ASHP defrost (an indication youre COP will be lower).

[Jeremy Harris]

3 minutes ago, joe90 said:

mines not like that, the controller requires a degree in techno speak (which I failed) so my ASHP delivers at 48’ whether to UFH (blended down by the manifold) or the DHW tank.. I have never noticed the ASHP defrost (an indication youre COP will be lower).

 

 

Doesn't it just!  I find I have to relearn how to decode the damned thing every time I try to use it.  If ever there was something that deserved a prize for being the least user friendly bit of kit, it has to be that Carrier/Kingspan/Glowworm command unit.  Whoever the person was that "designed" (too strong a word) the display and interface on that needs to be made to use it every day, with a mandatory overnight loss of memory.

[ProDave]

I am convinced mine is running on pre release beta testing firmware.  My favourite "niggle" is you can only adjust the DHW temperature if the heating is on.  So if I want to adjust the DHW temperature in summer, I have to go downstairs, turn on heating on the time clock,. go and turn one of the room thermostats up to create a heating demand, go back upstairs and adjust the DHW temperature, then go and turn the heating off again.  When heating is off, it will only display the DHW set temperature and not let you adjust it.

 

Mine has separate "water leaving temperature" settings for DHW and Heating.

[zoothorn]

I am an idiot & I'd like to ask a Q too.

 

Does the outside box thing link up to the existing HW tank, if a new C.heating ASHP system is to be installed?

 

Or would it come with a new one, specific to the ASHP system, included in the mix? IE throw old one in the river..?

 

Thx zoot.

 

 

[ProDave]

Because an ASHP generally will not heat water as hot as a gas or oil boiler, it is normal to have a larger capacity HW tank, and one with a high surface area input coil for better heat transfer, so sadly you probably do want a new tank.

[zoothorn]

31 minutes ago, ProDave said:

Because an ASHP generally will not heat water as hot as a gas or oil boiler, it is normal to have a larger capacity HW tank, and one with a high surface area input coil for better heat transfer, so sadly you probably do want a new tank.

 

Its ok for me, I think, as the whole shebang's been done via govt grant.. fingers x'd.

 

But does what you say apply if my existing HWT is 'leccy?

[Russell griffiths]

Ok let’s start with the silly questions. 

 

Ashp heats the water to 48’ and sends it to a tank via motorised valves and other do,dads. 

If this is not hot enough, how do I get it hotter??

 

if I am happy with 48’  what happens with legion aires disease??

 

 

[Jeremy Harris]

10 minutes ago, Russell griffiths said:

Ok let’s start with the silly questions. 

 

Ashp heats the water to 48’ and sends it to a tank via motorised valves and other do,dads. 

If this is not hot enough, how do I get it hotter??

 

if I am happy with 48’  what happens with legion aires disease??

 

 

 

 

48° feels surprisingly hot, it's about what our hot water thermostatic mixing valve is set to.  Our shower is set to 38°C.

 

Legionnaires is not a risk within a closed system, as it's an airborne pathogen that somehow has to get into the water.  An unvented cylinder fed by mains water cannot get infected, as air can't get to it.  I really wish that this bit of common sense logic was sensibly applied, but it seems not.  If you're paranoid about it (and I'd personally not be the slightest bit worried) then fit an immersion heater with a time switch set to boost the tank above 60°C for half an hour once every few weeks.

 

You can always use the immersion to boost the tank if you ever need it, too.

[ProDave]

I chose 48 degrees by trial and error, as the hottest temperature I can just about hold my hands under without it hurting. So take washing up water, I can run that so hot I can barely put my hands in the sink.  I can think of no reason why you would want it any hotter.

 

We discussed legionairs a while back, and with an unvented hot water tank and treated mains water there really was no risk.  But the standard procedure if you want to do an anti legionairs cycle is once a week you heat it hotter with the immersion heater.

[joe90]

2 hours ago, Jeremy Harris said:

 

 

Doesn't it just!  I find I have to relearn how to decode the damned thing every time I try to use it.  If ever there was something that deserved a prize for being the least user friendly bit of kit, it has to be that Carrier/Kingspan/Glowworm command unit.  Whoever the person was that "designed" (too strong a word) the display and interface on that needs to be made to use it every day, with a mandatory overnight loss of memory.

that makes me feel better, not as thick as I feel sometimes.

 

[Russell griffiths]

Excellent answers everyone 

i will be back in the morning with more silly questions. 

 

8 o clock is cowboy film time

adios amigos. ??

[ProDave]

5 hours ago, Jeremy Harris said:

 

 

Doesn't it just!  I find I have to relearn how to decode the damned thing every time I try to use it.  If ever there was something that deserved a prize for being the least user friendly bit of kit, it has to be that Carrier/Kingspan/Glowworm command unit.  Whoever the person was that "designed" (too strong a word) the display and interface on that needs to be made to use it every day, with a mandatory overnight loss of memory.

A bit like the one I finished wiring last week.  There is a normal boiler programmer on the wall and next to it the heat pumps own "user interface"  When it came to the customer "how do I operate it"  I just said you turn it on and off and program the times with the normal programmer, just like you do any other heating system.  The other box is for information only and diagnosing if it goes wrong. Don't touch it.