Interesting SCOP with an MVHR

waqasahmed

shinytop said:

waqasahmed said:

shinytop said:

waqasahmed said:

DougMLancs said:

The main reason their performance is so high is that they’re running at 31C flow temp with weather compensation, no buffer, no zoning on trv’s (just overheat protection and no glycol. 

Part of the reason that they can run such a low flow temp through their radiators is that it looks like they’ve calculated the MVHR to cover around 1400kWh of the 6345kWh heat loss based on the heat pump size being 5kW. In theory though, they could’ve skipped the MVHR and gone for a larger emitter area to have the same COP so you don’t HAVE to have MVHR to get such figures.

In our case, 8 K2’s and 1 K3 with decentralised MVHR in the kitchen and bathroom was enough for us to design to a flow temperature of 35C. Yes we could’ve gone all out with extra wall insulation and super efficient glazing first but the benefit isn’t proportional to the cost so we’ll save that for when the opportunity naturally presents itself (and there are no toddlers around!).

Could I also ask why you wouldn't use glycol? I thought it's useful as an anti freeze? 

A typical glycol mix for an ASHP increases by c. 5% the amount of liquid that needs to be pumped round the system, because it has a lower heat capacity than pure water.  It's also more viscous than water so the circulation pumps have to work harder.  And, it's expensive; maybe £200 to treat an ASHP system.  It's not the same very toxic stuff you put in your car that is cheap as chips. But as well as freeze protection, it contains additional things like corrosion and bacterial inhibitors. 

You can fit antifreeze valves instead but if they freeze or stick; they will empty all the water out of the system.  

Or you can use nothing and hope you don't have an extended power cut when it's very cold. 

Thanks. Surely it's still better to have glycol than not? Ie: for the protection of the system?

I mean I wouldn't turn my radiators completely off in winter for example, purely because the pipes would potentially crack if they don't have heat going through them 

I think you'd be unwise to have no antifreeze protection at all.  Most people have their heating on in winter or if on holiday they leave it on a holiday setting, which keeps it ticking over.  Problems could occur if there is a power cut for say 24 hours or more and it's very cold. 

I have glycol in mine because it's what the installers use as standard because the manufacturer (Mitsubishi) recommends it.  If it's a little less efficient then so be it.

Thanks. That's sort of what I was alluding to above too ie : the reduced efficiency is surely better than cracks in your system 

waqasahmed

shinytop said:

waqasahmed said:

shinytop said:

waqasahmed said:

DougMLancs said:

The main reason their performance is so high is that they’re running at 31C flow temp with weather compensation, no buffer, no zoning on trv’s (just overheat protection and no glycol. 

Part of the reason that they can run such a low flow temp through their radiators is that it looks like they’ve calculated the MVHR to cover around 1400kWh of the 6345kWh heat loss based on the heat pump size being 5kW. In theory though, they could’ve skipped the MVHR and gone for a larger emitter area to have the same COP so you don’t HAVE to have MVHR to get such figures.

In our case, 8 K2’s and 1 K3 with decentralised MVHR in the kitchen and bathroom was enough for us to design to a flow temperature of 35C. Yes we could’ve gone all out with extra wall insulation and super efficient glazing first but the benefit isn’t proportional to the cost so we’ll save that for when the opportunity naturally presents itself (and there are no toddlers around!).

Could I also ask why you wouldn't use glycol? I thought it's useful as an anti freeze? 

A typical glycol mix for an ASHP increases by c. 5% the amount of liquid that needs to be pumped round the system, because it has a lower heat capacity than pure water.  It's also more viscous than water so the circulation pumps have to work harder.  And, it's expensive; maybe £200 to treat an ASHP system.  It's not the same very toxic stuff you put in your car that is cheap as chips. But as well as freeze protection, it contains additional things like corrosion and bacterial inhibitors. 

You can fit antifreeze valves instead but if they freeze or stick; they will empty all the water out of the system.  

Or you can use nothing and hope you don't have an extended power cut when it's very cold. 

Thanks. Surely it's still better to have glycol than not? Ie: for the protection of the system?

I mean I wouldn't turn my radiators completely off in winter for example, purely because the pipes would potentially crack if they don't have heat going through them 

I think you'd be unwise to have no antifreeze protection at all.  Most people have their heating on in winter or if on holiday they leave it on a holiday setting, which keeps it ticking over.  Problems could occur if there is a power cut for say 24 hours or more and it's very cold. 

I have glycol in mine because it's what the installers use as standard because the manufacturer (Mitsubishi) recommends it.  If it's a little less efficient then so be it.

They've got anti freeze valves in theirs I think? Isn't that "good enough"? 

shinytop

waqasahmed said:

shinytop said:

waqasahmed said:

shinytop said:

waqasahmed said:

DougMLancs said:

The main reason their performance is so high is that they’re running at 31C flow temp with weather compensation, no buffer, no zoning on trv’s (just overheat protection and no glycol. 

Part of the reason that they can run such a low flow temp through their radiators is that it looks like they’ve calculated the MVHR to cover around 1400kWh of the 6345kWh heat loss based on the heat pump size being 5kW. In theory though, they could’ve skipped the MVHR and gone for a larger emitter area to have the same COP so you don’t HAVE to have MVHR to get such figures.

In our case, 8 K2’s and 1 K3 with decentralised MVHR in the kitchen and bathroom was enough for us to design to a flow temperature of 35C. Yes we could’ve gone all out with extra wall insulation and super efficient glazing first but the benefit isn’t proportional to the cost so we’ll save that for when the opportunity naturally presents itself (and there are no toddlers around!).

Could I also ask why you wouldn't use glycol? I thought it's useful as an anti freeze? 

A typical glycol mix for an ASHP increases by c. 5% the amount of liquid that needs to be pumped round the system, because it has a lower heat capacity than pure water.  It's also more viscous than water so the circulation pumps have to work harder.  And, it's expensive; maybe £200 to treat an ASHP system.  It's not the same very toxic stuff you put in your car that is cheap as chips. But as well as freeze protection, it contains additional things like corrosion and bacterial inhibitors. 

You can fit antifreeze valves instead but if they freeze or stick; they will empty all the water out of the system.  

Or you can use nothing and hope you don't have an extended power cut when it's very cold. 

Thanks. Surely it's still better to have glycol than not? Ie: for the protection of the system?

I mean I wouldn't turn my radiators completely off in winter for example, purely because the pipes would potentially crack if they don't have heat going through them 

I think you'd be unwise to have no antifreeze protection at all.  Most people have their heating on in winter or if on holiday they leave it on a holiday setting, which keeps it ticking over.  Problems could occur if there is a power cut for say 24 hours or more and it's very cold. 

I have glycol in mine because it's what the installers use as standard because the manufacturer (Mitsubishi) recommends it.  If it's a little less efficient then so be it.

They've got anti freeze valves in theirs I think? Isn't that "good enough"? 

Yes, one or the other is fine (IMO)

waqasahmed

shinytop said:

waqasahmed said:

shinytop said:

waqasahmed said:

shinytop said:

waqasahmed said:

DougMLancs said:

The main reason their performance is so high is that they’re running at 31C flow temp with weather compensation, no buffer, no zoning on trv’s (just overheat protection and no glycol. 

Part of the reason that they can run such a low flow temp through their radiators is that it looks like they’ve calculated the MVHR to cover around 1400kWh of the 6345kWh heat loss based on the heat pump size being 5kW. In theory though, they could’ve skipped the MVHR and gone for a larger emitter area to have the same COP so you don’t HAVE to have MVHR to get such figures.

In our case, 8 K2’s and 1 K3 with decentralised MVHR in the kitchen and bathroom was enough for us to design to a flow temperature of 35C. Yes we could’ve gone all out with extra wall insulation and super efficient glazing first but the benefit isn’t proportional to the cost so we’ll save that for when the opportunity naturally presents itself (and there are no toddlers around!).

Could I also ask why you wouldn't use glycol? I thought it's useful as an anti freeze? 

A typical glycol mix for an ASHP increases by c. 5% the amount of liquid that needs to be pumped round the system, because it has a lower heat capacity than pure water.  It's also more viscous than water so the circulation pumps have to work harder.  And, it's expensive; maybe £200 to treat an ASHP system.  It's not the same very toxic stuff you put in your car that is cheap as chips. But as well as freeze protection, it contains additional things like corrosion and bacterial inhibitors. 

You can fit antifreeze valves instead but if they freeze or stick; they will empty all the water out of the system.  

Or you can use nothing and hope you don't have an extended power cut when it's very cold. 

Thanks. Surely it's still better to have glycol than not? Ie: for the protection of the system?

I mean I wouldn't turn my radiators completely off in winter for example, purely because the pipes would potentially crack if they don't have heat going through them 

I think you'd be unwise to have no antifreeze protection at all.  Most people have their heating on in winter or if on holiday they leave it on a holiday setting, which keeps it ticking over.  Problems could occur if there is a power cut for say 24 hours or more and it's very cold. 

I have glycol in mine because it's what the installers use as standard because the manufacturer (Mitsubishi) recommends it.  If it's a little less efficient then so be it.

They've got anti freeze valves in theirs I think? Isn't that "good enough"? 

Yes, one or the other is fine (IMO)

Very fair. In that sense, their SCOP is honestly amazing. I'll "track" it over the winter to see what they get then too

Though even without that, my DHW requirements are at least 215 kWh a month, even when it isn't winter. So, for 8 months assuming less than 2000 kWh of hot water, and a SCOP of 6, that's not a lot of money at all for 8 months.

Equally, you could get those waste water recovery thingies, and halve your DHW too

shinytop

waqasahmed said:

shinytop said:

waqasahmed said:

shinytop said:

waqasahmed said:

shinytop said:

waqasahmed said:

DougMLancs said:

The main reason their performance is so high is that they’re running at 31C flow temp with weather compensation, no buffer, no zoning on trv’s (just overheat protection and no glycol. 

Part of the reason that they can run such a low flow temp through their radiators is that it looks like they’ve calculated the MVHR to cover around 1400kWh of the 6345kWh heat loss based on the heat pump size being 5kW. In theory though, they could’ve skipped the MVHR and gone for a larger emitter area to have the same COP so you don’t HAVE to have MVHR to get such figures.

In our case, 8 K2’s and 1 K3 with decentralised MVHR in the kitchen and bathroom was enough for us to design to a flow temperature of 35C. Yes we could’ve gone all out with extra wall insulation and super efficient glazing first but the benefit isn’t proportional to the cost so we’ll save that for when the opportunity naturally presents itself (and there are no toddlers around!).

Could I also ask why you wouldn't use glycol? I thought it's useful as an anti freeze? 

A typical glycol mix for an ASHP increases by c. 5% the amount of liquid that needs to be pumped round the system, because it has a lower heat capacity than pure water.  It's also more viscous than water so the circulation pumps have to work harder.  And, it's expensive; maybe £200 to treat an ASHP system.  It's not the same very toxic stuff you put in your car that is cheap as chips. But as well as freeze protection, it contains additional things like corrosion and bacterial inhibitors. 

You can fit antifreeze valves instead but if they freeze or stick; they will empty all the water out of the system.  

Or you can use nothing and hope you don't have an extended power cut when it's very cold. 

Thanks. Surely it's still better to have glycol than not? Ie: for the protection of the system?

I mean I wouldn't turn my radiators completely off in winter for example, purely because the pipes would potentially crack if they don't have heat going through them 

I think you'd be unwise to have no antifreeze protection at all.  Most people have their heating on in winter or if on holiday they leave it on a holiday setting, which keeps it ticking over.  Problems could occur if there is a power cut for say 24 hours or more and it's very cold. 

I have glycol in mine because it's what the installers use as standard because the manufacturer (Mitsubishi) recommends it.  If it's a little less efficient then so be it.

They've got anti freeze valves in theirs I think? Isn't that "good enough"? 

Yes, one or the other is fine (IMO)

Very fair. In that sense, their SCOP is honestly amazing. I'll "track" it over the winter to see what they get then too

Though even without that, my DHW requirements are at least 215 kWh a month, even when it isn't winter. So, for 8 months assuming less than 2000 kWh of hot water, and a SCOP of 6, that's not a lot of money at all for 8 months.

Equally, you could get those waste water recovery thingies, and halve your DHW too

waqasahmed said:

shinytop said:

waqasahmed said:

shinytop said:

waqasahmed said:

shinytop said:

waqasahmed said:

DougMLancs said:

The main reason their performance is so high is that they’re running at 31C flow temp with weather compensation, no buffer, no zoning on trv’s (just overheat protection and no glycol. 

Part of the reason that they can run such a low flow temp through their radiators is that it looks like they’ve calculated the MVHR to cover around 1400kWh of the 6345kWh heat loss based on the heat pump size being 5kW. In theory though, they could’ve skipped the MVHR and gone for a larger emitter area to have the same COP so you don’t HAVE to have MVHR to get such figures.

In our case, 8 K2’s and 1 K3 with decentralised MVHR in the kitchen and bathroom was enough for us to design to a flow temperature of 35C. Yes we could’ve gone all out with extra wall insulation and super efficient glazing first but the benefit isn’t proportional to the cost so we’ll save that for when the opportunity naturally presents itself (and there are no toddlers around!).

Could I also ask why you wouldn't use glycol? I thought it's useful as an anti freeze? 

A typical glycol mix for an ASHP increases by c. 5% the amount of liquid that needs to be pumped round the system, because it has a lower heat capacity than pure water.  It's also more viscous than water so the circulation pumps have to work harder.  And, it's expensive; maybe £200 to treat an ASHP system.  It's not the same very toxic stuff you put in your car that is cheap as chips. But as well as freeze protection, it contains additional things like corrosion and bacterial inhibitors. 

You can fit antifreeze valves instead but if they freeze or stick; they will empty all the water out of the system.  

Or you can use nothing and hope you don't have an extended power cut when it's very cold. 

Thanks. Surely it's still better to have glycol than not? Ie: for the protection of the system?

I mean I wouldn't turn my radiators completely off in winter for example, purely because the pipes would potentially crack if they don't have heat going through them 

I think you'd be unwise to have no antifreeze protection at all.  Most people have their heating on in winter or if on holiday they leave it on a holiday setting, which keeps it ticking over.  Problems could occur if there is a power cut for say 24 hours or more and it's very cold. 

I have glycol in mine because it's what the installers use as standard because the manufacturer (Mitsubishi) recommends it.  If it's a little less efficient then so be it.

They've got anti freeze valves in theirs I think? Isn't that "good enough"? 

Yes, one or the other is fine (IMO)

Very fair. In that sense, their SCOP is honestly amazing. I'll "track" it over the winter to see what they get then too

Though even without that, my DHW requirements are at least 215 kWh a month, even when it isn't winter. So, for 8 months assuming less than 2000 kWh of hot water, and a SCOP of 6, that's not a lot of money at all for 8 months.

Equally, you could get those waste water recovery thingies, and halve your DHW too

You won't get a SCOP of 6 for DHW if that's what you're saying. 2.5 to 3 at the most.    

waqasahmed

shinytop said:

waqasahmed said:

shinytop said:

waqasahmed said:

shinytop said:

waqasahmed said:

shinytop said:

waqasahmed said:

DougMLancs said:

The main reason their performance is so high is that they’re running at 31C flow temp with weather compensation, no buffer, no zoning on trv’s (just overheat protection and no glycol. 

Part of the reason that they can run such a low flow temp through their radiators is that it looks like they’ve calculated the MVHR to cover around 1400kWh of the 6345kWh heat loss based on the heat pump size being 5kW. In theory though, they could’ve skipped the MVHR and gone for a larger emitter area to have the same COP so you don’t HAVE to have MVHR to get such figures.

In our case, 8 K2’s and 1 K3 with decentralised MVHR in the kitchen and bathroom was enough for us to design to a flow temperature of 35C. Yes we could’ve gone all out with extra wall insulation and super efficient glazing first but the benefit isn’t proportional to the cost so we’ll save that for when the opportunity naturally presents itself (and there are no toddlers around!).

Could I also ask why you wouldn't use glycol? I thought it's useful as an anti freeze? 

A typical glycol mix for an ASHP increases by c. 5% the amount of liquid that needs to be pumped round the system, because it has a lower heat capacity than pure water.  It's also more viscous than water so the circulation pumps have to work harder.  And, it's expensive; maybe £200 to treat an ASHP system.  It's not the same very toxic stuff you put in your car that is cheap as chips. But as well as freeze protection, it contains additional things like corrosion and bacterial inhibitors. 

You can fit antifreeze valves instead but if they freeze or stick; they will empty all the water out of the system.  

Or you can use nothing and hope you don't have an extended power cut when it's very cold. 

Thanks. Surely it's still better to have glycol than not? Ie: for the protection of the system?

I mean I wouldn't turn my radiators completely off in winter for example, purely because the pipes would potentially crack if they don't have heat going through them 

I think you'd be unwise to have no antifreeze protection at all.  Most people have their heating on in winter or if on holiday they leave it on a holiday setting, which keeps it ticking over.  Problems could occur if there is a power cut for say 24 hours or more and it's very cold. 

I have glycol in mine because it's what the installers use as standard because the manufacturer (Mitsubishi) recommends it.  If it's a little less efficient then so be it.

They've got anti freeze valves in theirs I think? Isn't that "good enough"? 

Yes, one or the other is fine (IMO)

Very fair. In that sense, their SCOP is honestly amazing. I'll "track" it over the winter to see what they get then too

Though even without that, my DHW requirements are at least 215 kWh a month, even when it isn't winter. So, for 8 months assuming less than 2000 kWh of hot water, and a SCOP of 6, that's not a lot of money at all for 8 months.

Equally, you could get those waste water recovery thingies, and halve your DHW too

waqasahmed said:

shinytop said:

waqasahmed said:

shinytop said:

waqasahmed said:

shinytop said:

waqasahmed said:

DougMLancs said:

The main reason their performance is so high is that they’re running at 31C flow temp with weather compensation, no buffer, no zoning on trv’s (just overheat protection and no glycol. 

Part of the reason that they can run such a low flow temp through their radiators is that it looks like they’ve calculated the MVHR to cover around 1400kWh of the 6345kWh heat loss based on the heat pump size being 5kW. In theory though, they could’ve skipped the MVHR and gone for a larger emitter area to have the same COP so you don’t HAVE to have MVHR to get such figures.

In our case, 8 K2’s and 1 K3 with decentralised MVHR in the kitchen and bathroom was enough for us to design to a flow temperature of 35C. Yes we could’ve gone all out with extra wall insulation and super efficient glazing first but the benefit isn’t proportional to the cost so we’ll save that for when the opportunity naturally presents itself (and there are no toddlers around!).

Could I also ask why you wouldn't use glycol? I thought it's useful as an anti freeze? 

A typical glycol mix for an ASHP increases by c. 5% the amount of liquid that needs to be pumped round the system, because it has a lower heat capacity than pure water.  It's also more viscous than water so the circulation pumps have to work harder.  And, it's expensive; maybe £200 to treat an ASHP system.  It's not the same very toxic stuff you put in your car that is cheap as chips. But as well as freeze protection, it contains additional things like corrosion and bacterial inhibitors. 

You can fit antifreeze valves instead but if they freeze or stick; they will empty all the water out of the system.  

Or you can use nothing and hope you don't have an extended power cut when it's very cold. 

Thanks. Surely it's still better to have glycol than not? Ie: for the protection of the system?

I mean I wouldn't turn my radiators completely off in winter for example, purely because the pipes would potentially crack if they don't have heat going through them 

I think you'd be unwise to have no antifreeze protection at all.  Most people have their heating on in winter or if on holiday they leave it on a holiday setting, which keeps it ticking over.  Problems could occur if there is a power cut for say 24 hours or more and it's very cold. 

I have glycol in mine because it's what the installers use as standard because the manufacturer (Mitsubishi) recommends it.  If it's a little less efficient then so be it.

They've got anti freeze valves in theirs I think? Isn't that "good enough"? 

Yes, one or the other is fine (IMO)

Very fair. In that sense, their SCOP is honestly amazing. I'll "track" it over the winter to see what they get then too

Though even without that, my DHW requirements are at least 215 kWh a month, even when it isn't winter. So, for 8 months assuming less than 2000 kWh of hot water, and a SCOP of 6, that's not a lot of money at all for 8 months.

Equally, you could get those waste water recovery thingies, and halve your DHW too

You won't get a SCOP of 6 for DHW if that's what you're saying. 2.5 to 3 at the most.    

Ah fair. I guess you could still get the WWHRS and halve your usage, regardless 

Qyburn

waqasahmed said:

Though even without that, my DHW requirements are at least 215 kWh a month, even when it isn't winter. So, for 8 months assuming less than 2000 kWh of hot water, and a SCOP of 6, that's not a lot of money at all for 8 months.

Equally, you could get those waste water recovery thingies, and halve your DHW too

You'll need a flow temp of more than 27 Deg.C for DHW.

As I posted before it's really not clear what that heat pump is achieving at the moment. They shouldn't need heat, and flow temp is too low for DHW.

waqasahmed

Qyburn said:

waqasahmed said:

Though even without that, my DHW requirements are at least 215 kWh a month, even when it isn't winter. So, for 8 months assuming less than 2000 kWh of hot water, and a SCOP of 6, that's not a lot of money at all for 8 months.

Equally, you could get those waste water recovery thingies, and halve your DHW too

You'll need a flow temp of more than 27 Deg.C for DHW.

As I posted before it's really not clear what that heat pump is achieving at the moment. They shouldn't need heat, and flow temp is too low for DHW.

35c perhaps? 

QrizB

waqasahmed said:

Qyburn said:

You'll need a flow temp of more than 27 Deg.C for DHW.

As I posted before it's really not clear what that heat pump is achieving at the moment. They shouldn't need heat, and flow temp is too low for DHW.

35c perhaps? 

A 35C flow temp will give you hot water in the low 30s. Which might be OK if you like cold showers & tepid baths but wouldn't be acceptable to most people.

If you buy or borrow a baby bath thermometer you can feel for yourself how warm water temps in the 30-40c range are.

Most people want their DHW to be 50C or more.

waqasahmed

QrizB said:

waqasahmed said:

Qyburn said:

You'll need a flow temp of more than 27 Deg.C for DHW.

As I posted before it's really not clear what that heat pump is achieving at the moment. They shouldn't need heat, and flow temp is too low for DHW.

35c perhaps? 

A 35C flow temp will give you hot water in the low 30s. Which might be OK if you like cold showers & tepid baths but wouldn't be acceptable to most people.

If you buy or borrow a baby bath thermometer you can feel for yourself how warm water temps in the 30-40c range are.

Most people want their DHW to be 50C or more.

Fair. 35C is probably fine in the summer then