Willis heater ASHP backup discussion

[Nickfromwales]

55 minutes ago, Gav_P said:

That’s 2 advantages you have with your system; the immersion, and the buffer tank. 

 

However, we’ve not had proper heating for 4 years so another couple of months is nothing!!

 

1 hour ago, joe90 said:

I am fortunate that @Nickfromwales suggested I put an immersion heater in my buffer tank so I am running my UFH from that, and it works very well but more costly than running an ASHP at the moment.

Thats the reason with every heat pump install I’ll spec and fit some form of injecting grid electricity, whether it be Willis or direct immersion or an e-prefix SA. 

@joe90 how warm is the place on just the one 3kW immersion? I take it you have to run it for a good while to get up to temp, eg no on / off-ability to speak of?

[Gav_P]

45 minutes ago, Nickfromwales said:

 

Thats the reason with every heat pump install I’ll spec and fit some form of injecting grid electricity, whether it be Willis or direct immersion or an e-prefix SA. 

@joe90 how warm is the place on just the one 3kW immersion? I take it you have to run it for a good while to get up to temp, eg no on / off-ability to speak of?

@Nickfromwales So what would you recommend for a system without a buffer tank? Except the obvious of adding a buffer tank.

Edited October 28, 2018 by Gav_P

[Nickfromwales]

52 minutes ago, Gav_P said:

@Nickfromwales So what would you recommend for a system without a buffer tank? Except the obvious of adding a buffer tank.

Willis heaters, my good man.   

Inline thermos flask sized water jackets where a standard 3kW immersion heater gets inserted. 

Bingo.

 

 

Stack multiples until you get to your required heating input. 2x usually will suffice. Cheap as chips for a simple backup solution. ?

[Gav_P]

13 minutes ago, Nickfromwales said:

Willis heaters, my good man.   

Inline thermos flask sized water jackets where a standard 3kW immersion heater gets inserted. 

Bingo.

 

 

Stack multiples until you get to your required heating input. 2x usually will suffice. Cheap as chips for a simple backup solution. ?

Oh , never heard of them... *trotting of to look at google now.

[Nickfromwales]

You can go posh and zone valve them, or you can go caveman and just use a pair of 1/4 turn lever valves. One on the flow from the original heat source and the other on the flow from the Willis. Just swap them both to redirect flow from the pump to the chosen device. 

1 may struggle whereas 2 would easily cope with the flow rate normally associated with the 28mm pipe. 

[Gav_P]

Nice... looks like I have a little project for this week whilst ProDave is taking a look at the PCB

 

when you say 2, I assume you mean in series? Out of 1 in to second then back into the main loop?

Edited October 28, 2018 by Gav_P

[Gav_P]

I’ve now ordered a pair of willis heaters. 

Just have to figure out how to fit them in (all my plumbing is tucked away in what is effectively a stud wall) and get some power to them!! 

 

Thanks @Nickfromwales

[Nickfromwales]

9 minutes ago, Gav_P said:

Nice... looks like I have a little project for this week whilst ProDave is taking a look at the PCB

 

when you say 2, I assume you mean in series? Out of 1 in to second then back into the main loop?

Two in parallel to get the flow rate.

Make sure the pipe work from each outlet to the T and from each inlet to the T are equal so they each share the same flow rate ( pipe resistance ). 

[Gav_P]

Ah ok thanks...?

[Gav_P]

I’m just working out how to fit the Willis heaters in and everything I read about them says to install them vertically... I’m assuming that’s because in a tradition installation (for DHW) they use a syphoning effect to circulate the water. However this feels odd to have the electrical side underneath (not ideal if there’s a leak).

 

@Nickfromwales or anybody else’s who knows, do they have to be vertical or can I install horizontally? 

Edited October 29, 2018 by Gav_P

[ProDave]

My LG heat pump has one built in and I can confirm the element enters the tube from the bottom.  It also looks like a right pig to dismantle of you ever want to get at it.

 

The Willis heater just goes in series with the heat pumps heat exchanger so just in the flow from the heat pump.  If you are not using the heater then water just passes through it.

[Gav_P]

That’s interesting. I was planning on inserting them as a kind of bypass, so sort of cutting off the circuit to the ASHP. Or cut the Willis out of the circuit when not required.

 

Do you just have the one? I assume it’s larger bore than the standard 15mm versions. 

[ProDave]

Mine was put there by LG the manufacturer of the heat pump, it's function being to help heat hot water, as an emergency heater if the heat pump has a fault, and to help defrosting.  The pipework looks to be about 22mm.

[Gav_P]

Sounds very sensible. Although in my situation it wouldn’t work as a backup due to breaking the HP. ??‍♂️

[Nickfromwales]

Just fit them horizontally with the side outlet uppermost, and fit bottle vents to automatically release any trapped air. 

 

Prob best to avoid heat rising to the heater base tbh, but can’t really say it would be to any detriment as I’ve removed scores of them ( immersions ) top-loaded and facing down in old copper cylinders. 

Sealed and pressurised is totally different to gravity / convection flow, so imo you can fit these however you like and they’ll work A1. 

[Gav_P]

Perfect. I was hoping that you’d say that as I really only have space for horizontal installation.

[Gav_P]

So I have now installed my willis heaters... TBH it’s a bit of a cobbled together affair, as I wanted to get some sort of heating ASAP for SWMBO, but it does seem to be working... the temp in the UFH manifold is creeping up slowly. ?

 

I can now think about making it prettier over the next few weeks. 

 

Many thanks to @Nickfromwales for your advice and guidance. ???

 

As a side point, I am wondering if there is a way to split the second part of this thread (where it deviated away from the Cool Energy ASHP) into a new thread for any future forum members to find a bit easier? 

 

 

[Nickfromwales]

It’s what we do   

[ProDave]

1 hour ago, Gav_P said:

As a side point, I am wondering if there is a way to split the second part of this thread (where it deviated away from the Cool Energy ASHP) into a new thread for any future forum members to find a bit easier? 

 

 

It wasn't as easy as I thought it would be but we got there.

[TerryE]

I have mine mounted vertically across my UFH manifolds. By the time that we are down to a sustained external temp of 0°C we need about 8hrs a day to keep our largish 4 bedroom house toastie.  (Each deg C drop adds about 40 mins on-time to keep the house in balance).  I will be fitting an ASHP next summer because the numbers work and it will be good for peak summer cooling, but the Willis will remain an essential backup component. Why? Because the ASHP won't be a mission critical component in our heating system, so I can take a far more relaxed attitude to maintenance / spairs, etc. 

 

At the moment, my Node RED system does a daily calc using the weather forecast, slab temperature profile, etc. to work out the heating profile for the next day - typically a solid block overnight during cheap rate and and extra top-up late afternoon if the weather gets cold. No other feedback.  Dear simple.  Good enough to keep the house temp better than ±½°C which is good enough for me.

Edited November 2, 2018 by TerryE

[Gav_P]

On 02/11/2018 at 01:32, TerryE said:

I have mine mounted vertically across my UFH manifolds. By the time that we are down to a sustained external temp of 0°C we need about 8hrs a day to keep our largish 4 bedroom house toastie.  (Each deg C drop adds about 40 mins on-time to keep the house in balance).  I will be fitting an ASHP next summer because the numbers work and it will be good for peak summer cooling, but the Willis will remain an essential backup component. Why? Because the ASHP won't be a mission critical component in our heating system, so I can take a far more relaxed attitude to maintenance / spairs, etc. 

 

At the moment, my Node RED system does a daily calc using the weather forecast, slab temperature profile, etc. to work out the heating profile for the next day - typically a solid block overnight during cheap rate and and extra top-up late afternoon if the weather gets cold. No other feedback.  Dear simple.  Good enough to keep the house temp better than ±½°C which is good enough for me.

That’s pretty impressive temp control.

 

Am I reading this correctly that you are currently only using Willis heater(s) to heat your UFH? 

[joe90]

Mine is Fairly similar in that I am using an immersion in the buffer tank to run my UFH and the house is toastie (no data or probes but SWMBO is happy), will get the ASHP up and running when I can but no rush. There is a case for direct electric heating in a well insulated house, very little to go wrong and minimum outlay.

[Ed Davies]

34 minutes ago, joe90 said:

There is a case for direct electric heating in a well insulated house, very little to go wrong and minimum outlay.

 

Absolutely. If you're just about at Passivhaus levels (15 kWh/m²·a) and use the typically assumed 3 kWh/peep·day for DHW for three people in a 120 m² house then it's just over 5000 kWh/a. Even with full-rate electricity at £0.16/kWh that's “only“ £800/year. Add E7 or E10 or PV (remembering that the bulk of the use is for DHW which happens at least as much in the summer) and the ROI on anything more complicated begins to look a bit weak. Even the standing charge on mains gas will bite into any further savings to be made. I think an ASHP makes sense but it's got to be as cheap and simple as possible.

[ProDave]

Interesting observations.

 

I have just got a full week data on energy use in our house for a "cold" week, outside average temperature for the week 0 inside temperature 20.  The heat pump used 87KWh in the week.

 

If I assume a COP of 3, that would have been 261KWh for the same heat from a willis heater.  That's a big enough difference for me to conclude the heat pump is essential.

 

At that usage, if the temperature was 0 all year, the heating bill would be £678 with the heat pump  it should be a lot less than that for a real year.  The saving over just a willis heater will pay for my (very cheap) heat pump in the first year. 

 

The maths may be a bit different if you are paying a company £10K to install a heat pump for you (I know at least one person who paid more than that)

[joe90]

Like @ProDave my “Ebay special” ASHP will be paid for quickly (if I can get it working properly?) then give us cheap heating/DHW.