help with heat calcs

[SteamyTea]

8 minutes ago, Nickfromwales said:

In terms of when the hybrid kicks in, that will be nothing to do with prices of energy?

I would hope it was used to minimise overall CO_2e emissions, or the whole thing is pointless.

The use of HPs is to minimise CO_2e after all.

[Nickfromwales]

17 minutes ago, SteamyTea said:

I would hope it was used to minimise overall CO_2e emissions, or the whole thing is pointless.

The use of HPs is to minimise CO_2e after all.

The use of hybrid HP's is to get you warm. I'm not talking about regular HP's so the argument / situations would be very different. The idea being you'd only be using the absolute minimum amount of fossil as possible, but have the opportunity to employ a HP for the shoulder months. When it gets baltic and a typical HP would then 'max out' without providing enough heat input, you employ a hybrid to get the best of both worlds; electricity based heating to a point where the SCoP is still sensible, and then fossil for when it is unavoidable. That gets homes off fossil only heating, so the CO_2e will be minimised as much as is practical.

Edited February 7, 2022 by Nickfromwales

[ProDave]

The whole concept of a hybrid has puzzled me.  What is the actual purpose of it and exactly how does it work?

 

We know heat pumps work best at relatively low temperatures and relatively low power output.  I am struggling to see just how adding an oil boiler can help that, without the oil taking over completely.  About the only thing I can think is use the ASHP element for low temperature heating and the oil element for quicker and hotter hot water heating. but if that is the aim they would be better off as completely separate systems.

[SteamyTea]

6 hours ago, Nickfromwales said:

When it gets baltic and a typical HP would then 'max out' without providing enough heat input, you employ a hybrid to get the best of both worlds;

I understand this, and it is probably a cheap option. 

If/When HPs come down in price, and assuming enough room, hybrids, like the vehicle equivalent, will become unnecessary.

6 hours ago, ProDave said:

We know heat pumps work best at relatively low temperatures and relatively low power output

We don't.

I know this is just a translation thing, and I know you have not typed what you actually mean.

So for clarity.

They work at a higher CoP when the output temperature is lower than a thermal boiler.

The output, in kW, regardless of temperature is to do with mass flow, lower temperature, more mass of fluid needs to flow.

Then there is the energy, the kWhs, that is power (kW) times time (h).

Such a shame we don't use joules for energy.

[ProDave]

19 minutes ago, SteamyTea said:

I understand this, and it is probably a cheap option. 

If/When HPs come down in price, and assuming enough room, hybrids, like the vehicle equivalent, will become unnecessary.

We don't.

I know this is just a translation thing, and I know you have not typed what you actually mean.

So for clarity.

They work at a higher CoP when the output temperature is lower than a thermal boiler.

The output, in kW, regardless of temperature is to do with mass flow, lower temperature, more mass of fluid needs to flow.

Then there is the energy, the kWhs, that is power (kW) times time (h).

Such a shame we don't use joules for energy.

What I was trying, very badly, to say, was lets say you are (wrongly) trying to fit a HP in place of an oil boiler that is driving radiators that need to reach 70 degrees to get the house hot enough in the depths of winter.  I have heard it say something along the lines of "the heat pump heats the water so far and the oil boiler bit heats it the rest"  That is the bit I just can't fathom because I just can't see it working.

 

Or in other words, I hope people are not expecting to fit a hybrid where what they should be doing is modifying the heat emitters so they will operate in a temperature range the heat pump is capable of.

[SteamyTea]

6 minutes ago, ProDave said:

have heard it say something along the lines of "the heat pump heats the water so far and the oil boiler bit heats it the rest"  That is the bit I just can't fathom because I just can't see it working

Would run the risk of the return temperature being higher than the HPs flow temperature, do as you say, pointless.

Maybe if the HP side did an hour or two of DHW heating, then disconnected and the oil took over, it could be useful. But easier and cheaper to just use the imerssion heater to top up.

 

I can't see much use for them, but they will be fitted by lazy plumbers that still think that HPs 'are not there yet' AKA uneducated tossers.

[Nickfromwales]

49 minutes ago, SteamyTea said:

I understand this, and it is probably a cheap option. 

If/When HPs come down in price, and assuming enough room, hybrids, like the vehicle equivalent, will become unnecessary.

We don't.

I know this is just a translation thing, and I know you have not typed what you actually mean.

So for clarity.

They work at a higher CoP when the output temperature is lower than a thermal boiler.

The output, in kW, regardless of temperature is to do with mass flow, lower temperature, more mass of fluid needs to flow.

Then there is the energy, the kWhs, that is power (kW) times time (h).

Such a shame we don't use joules for energy.

It's such a relief that we have a father figure on here. Keeps us on the straight and narrow   

[SteamyTea]

41 minutes ago, Nickfromwales said:

It's such a relief that we have a father figure on here. Keeps us on the straight and narrow   

Too right.

You would not fit a system that would not work.

[JohnMo]

This is what I picked from reading a user manual for hybrid HP and gas boiler.

 

Hybrids are normal controlled on a cost to heat, DHW and CH basis.

 

You import to the control software, the cost of electricity, gas/oil or whatever the alternative fuel you are using.

 

The software, looks at expected cop from the heat pump, which is the default heat supplier.  If it is likely to cost you more running the heat pump than the boiler, the boiler will be started.

[Nickfromwales]

12 minutes ago, JohnMo said:

This is what I picked from reading a user manual for hybrid HP and gas boiler.

 

Hybrids are normal controlled on a cost to heat, DHW and CH basis.

 

You import to the control software, the cost of electricity, gas/oil or whatever the alternative fuel you are using.

 

The software, looks at expected cop from the heat pump, which is the default heat supplier.  If it is likely to cost you more running the heat pump than the boiler, the boiler will be started.

Yes, my thoughts exactly. Eg heat demand goes up to the point that CoP diminishes or flatlines, so it uses fossil to compensate. I'm just curious to know how comprehensive or 'clever' the controls are, where it stands with outdoor air temp vs internal demand and what-not. Time for some annoyingly long chats with the good people at Grant. Wish me luck.

[SteamyTea]

5 minutes ago, Nickfromwales said:

I'm just curious to know how comprehensive or 'clever' the controls are, where it stands with outdoor air temp vs internal demand and what-not.

How would you set it up?

3 scenarios:

Lowest running costs

Guaranteed output

Lowest CO_2e

 

See how their answers compare to yours.

[Nickfromwales]

4 minutes ago, SteamyTea said:

Guaranteed output

The only reason I'd fit a hybrid basically, otherwise it would be a correctly sized and appropriately installed HP

[JohnMo]

This what Daikin say.

 

"Our Daikin Altherma hybrid heat pump combines renewable air-to-water heat pump technology with a gas condensing boiler, to ensure the highest efficiency. Its smart programming helps to save up to 35% more energy than a traditional condensing boiler by automatically determining the most economically and energy efficient combination based on energy prices, outdoor temperatures and indoor heat capacity."

 

The other thing is, it can operate with a cylinder or without.  Some an ASHP only cannot do.

 

[Mike_scotland]

Soooo im speaking to my builder and his mcs registered contact and there now suggesting a 10kw grant heat pump, i asked for the hear calcs and was told there going by a basic 45w per m2.... this is making me feel a tad uneasy

 

Any advice?

[Kevm]

1 hour ago, Mike_scotland said:

Soooo im speaking to my builder and his mcs registered contact and there now suggesting a 10kw grant heat pump, i asked for the hear calcs and was told there going by a basic 45w per m2.... this is making me feel a tad uneasy

 

Any advice?

 

I would be uneasy too.  Any ASHP system designer/installer should do a proper heat loss calculation.  It will be routine for them.  And your house is a new build, right?  My 1990 bungalow has a heat loss of about 56 w/m2; I would have thought yours would be much lower.  You need the proper calculations.

[Mike_scotland]

49 minutes ago, Kevm said:

 

I would be uneasy too.  Any ASHP system designer/installer should do a proper heat loss calculation.  It will be routine for them.  And your house is a new build, right?  My 1990 bungalow has a heat loss of about 56 w/m2; I would have thought yours would be much lower.  You need the proper calculations.

Yeah new build mate 

[Mike_scotland]

Can anyone tell me what this means lol? 

 

Im assuming at -7 the heating output is 9lw?

[SteamyTea]

13 hours ago, Mike_scotland said:

going by a basic 45w per m2.... this is making me feel a tad uneasy

So would I be, my heating energy for yesterday, divided by my total floor area, works out at 15W.m^-2.  And my house is over 30 years old.

[Mike_scotland]

6 minutes ago, SteamyTea said:

So would I be, my heating energy for yesterday, divided by my total floor area, works out at 15W.m^-2.  And my house is over 30 years old.

atleast mines wouldnt be under sized haha, 

[SteamyTea]

3 minutes ago, Mike_scotland said:

atleast mines wouldnt be under sized haha, 

True.

 

Have you called a few MCS companies to come and give you a quote?

[Mike_scotland]

7 minutes ago, SteamyTea said:

True.

 

Have you called a few MCS companies to come and give you a quote?

my builder has a chosen MCS guy he uses, but when i asked him for a heat loss calc he was stuttering and muttering then eventually said the guy uses a 45w/m2 basic heat loss calc.... thats fine but if you do my house size at 225m2 and x it by 45w you dont get a 10kw heat pump lol as he said we needed, so im unsure whats going on but its made me question it

any my builder (who i know wont know much about heat pumps hence why we use MCS) he was saying as we had a heat calc done from Vailliant that will do but im trying to explain to him that a vaillant ashp is much different from a grant ashp.... so a vaillant 10kw was described as needed and he thinks a 10kw grant will do then but i dont think it will as already checked a 13kw grant heat output is 10kw i think 

[SteamyTea]

On 02/02/2022 at 15:25, Mike_scotland said:

Thanks,

So the HP has almost doubled in size.

On 02/02/2022 at 16:35, SteamyTea said:

Roughly 100 kWh/m².year.

Or assuming 5 months heating, 25W.m² power needed.

And almost doubles in size as well.

 

Get someone in that knows what they are doing.

Edited February 9, 2022 by SteamyTea

[Mike_scotland]

1 minute ago, SteamyTea said:

So the HP has almost doubled in size.

And almost doubles in size as well.

 

Get someone in that knows what they are doing.

what do you mean? Vaillant said we needed a 10kw HP

[Bramco]

22 minutes ago, SteamyTea said:

Have you called a few MCS companies to come and give you a quote?

 

It's hard to get a sensible answer from them - we've tried.

 

Each of them is tied to a manufacturer in some way, so the answer always comes out as - you need a xxx (fill in the manufacturer name and model.).

 

We've also had MCS companies that won't quote until they've charged us for a heat loss analysis, even though we have a full M+E tender document with that analysis. In fact, we commissioned a comparison between 2G and 3G windows to work out if 3G would be worth the extra investment, so have all the info needed.

 

Quotes vary a lot and if you take out the material costs (it's easy to find prices on the web) then there is a massive markup for the 'MCS' bit against a plumber simply doing the install without the 'MCS' bit.

 

Simon

Edited February 9, 2022 by Bramco

[SteamyTea]

2 minutes ago, Mike_scotland said:

what do you mean? Vaillant said we needed a 10kw HP

Must have misread it, though it was a max heat load of 7.9 kW.

Ah, add water.