ASHP - Investigations and calculations

[richbee]

Rich, I second Joe’s view that this will be a very informative thread - your ongoing musings and experience plus the input of others.

We are in the position of having a seldom used, 9 year old combi - tend to use WBS as main heat.

My biggest concern is provision of DHW - we don’t have a ‘hot water tank’ and due to using space afforded by not having one/having a combi boiler, would need some disruptive changes to provide one, that, from my
‘Survey’ would be relatively small and struggle to provide enough HW for multiuser showers and/or a bath.

Not having researched the grant T’s&C’s, presuming having a secondary form of heat (WBS) precludes qualifying for the grant ?

I'm hoping not as we have 2x WBS
I know you can't have an eg. combined gas and heatpump combi system.

We also don't have a hot water tank currently - I think we can fit one in where the old one used to be many years ago - fingers crossed- will have to relocate the junk (important stuff)!
I think the standard heatpump specification for the grant includes a certain size of water tank depending on house size, possibly number of bedrooms

looking at the details of the grant, it only mentions replacing gas or oil central heating, nothing about WBS - phew
https://www.gov.uk/apply-boiler-upgrade ... e-eligible

[richbee]

I think the only sensible way of working out how much heat energy is to record what you use (as stated above)

Take a measurement on the 1st of each month or every week during the real winter and then you have YOUR need. Oil is 10kwh/L and burns with at best a 80% efficiency. Without those figs i would not know where to start sizing the HP.

Another problem to consider is that if the HP is only just big enough and on 24/7 then there is no capacity to heat up the building eg after a holiday.

In terms of what we use now - I know roughly for the whole year in terms of oil in litres. I think one of the problems will be that currently we aggressively zone the heating, so only the kitchen / lounge / office / bedroom is being heated as we use them for most of the time.
This keeps the oil consumption down, but I believe it is very much not the recommended way to use a heat pump, especially if you want to achieve a good COP - and also it is not designed to give a quick boost in temp to individual rooms, it doesn't have the power to do that. We may wll just have to get someone in see what they say.

In terms of capacity to reheat after a holiday - if the pump is sized to keep up with the worst case weather, it should only be a problem to heat up if you go away in January/Feb - any other time it should have some spare capacity

[Countrypaul]

I think the only sensible way of working out how much heat energy is to record what you use (as stated above)

Take a measurement on the 1st of each month or every week during the real winter and then you have YOUR need. Oil is 10kwh/L and burns with at best a 80% efficiency. Without those figs i would not know where to start sizing the HP.

Another problem to consider is that if the HP is only just big enough and on 24/7 then there is no capacity to heat up the building eg after a holiday.

In terms of what we use now - I know roughly for the whole year in terms of oil in litres. I think one of the problems will be that currently we aggressively zone the heating, so only the kitchen / lounge / office / bedroom is being heated as we use them for most of the time.
This keeps the oil consumption down, but I believe it is very much not the recommended way to use a heat pump, especially if you want to achieve a good COP - and also it is not designed to give a quick boost in temp to individual rooms, it doesn't have the power to do that. We may wll just have to get someone in see what they say.

In terms of capacity to reheat after a holiday - if the pump is sized to keep up with the worst case weather, it should only be a problem to heat up if you go away in January/Feb - any other time it should have some spare capacity

Depending on how you control things, if you are away on holiday you can set the tempertures down (or even off) for a period and set the temperature back to normal for a day or two before returning, unless the weather is very cold (in which case stay where you are? ) tha should get things back close to mormal by the time you turn. The use of direct electric heating, for example oil filled radiator, might also help, either just when you get back, or on timers if necessary. Again, don't let the perfect get in the way of the good.

[Countrypaul]

I think the only sensible way of working out how much heat energy is to record what you use (as stated above)

Take a measurement on the 1st of each month or every week during the real winter and then you have YOUR need. Oil is 10kwh/L and burns with at best a 80% efficiency. Without those figs i would not know where to start sizing the HP.

Another problem to consider is that if the HP is only just big enough and on 24/7 then there is no capacity to heat up the building eg after a holiday.

In terms of what we use now - I know roughly for the whole year in terms of oil in litres. I think one of the problems will be that currently we aggressively zone the heating, so only the kitchen / lounge / office / bedroom is being heated as we use them for most of the time.
This keeps the oil consumption down, but I believe it is very much not the recommended way to use a heat pump, especially if you want to achieve a good COP - and also it is not designed to give a quick boost in temp to individual rooms, it doesn't have the power to do that. We may wll just have to get someone in see what they say.

In terms of capacity to reheat after a holiday - if the pump is sized to keep up with the worst case weather, it should only be a problem to heat up if you go away in January/Feb - any other time it should have some spare capacity

In terms of zoning, why would you need to heat the zones you don't currently heat just because you have a heat pump?

Depending on how you control things, if you are away on holiday you can set the tempertures down (or even off) for a period and set the temperature back to normal for a day or two before returning, unless the weather is very cold (in which case stay where you are? ) tha should get things back close to mormal by the time you turn. The use of direct electric heating, for example oil filled radiator, might also help, either just when you get back, or on timers if necessary. Again, don't let the perfect get in the way of the good.

[AGT]

Arent you meant to work the heat loss based on say inside 21 deg and -3 outside ( for my location)?

[Ken]

I think the only sensible way of working out how much heat energy is to record what you use (as stated above)

Take a measurement on the 1st of each month or every week during the real winter and then you have YOUR need. Oil is 10kwh/L and burns with at best a 80% efficiency. Without those figs i would not know where to start sizing the HP.

Another problem to consider is that if the HP is only just big enough and on 24/7 then there is no capacity to heat up the building eg after a holiday.

In terms of what we use now - I know roughly for the whole year in terms of oil in litres. I think one of the problems will be that currently we aggressively zone the heating, so only the kitchen / lounge / office / bedroom is being heated as we use them for most of the time.
This keeps the oil consumption down, but I believe it is very much not the recommended way to use a heat pump, especially if you want to achieve a good COP - and also it is not designed to give a quick boost in temp to individual rooms, it doesn't have the power to do that. We may wll just have to get someone in see what they say.

In terms of capacity to reheat after a holiday - if the pump is sized to keep up with the worst case weather, it should only be a problem to heat up if you go away in January/Feb - any other time it should have some spare capacity

Knowing the Avg or total for the yr does not help as what you need to know is how much energy is used at the worst time of the yr and particularly the avg worst day but perhaps not the extreme.

[richbee]

I think the only sensible way of working out how much heat energy is to record what you use (as stated above)

Take a measurement on the 1st of each month or every week during the real winter and then you have YOUR need. Oil is 10kwh/L and burns with at best a 80% efficiency. Without those figs i would not know where to start sizing the HP.

Another problem to consider is that if the HP is only just big enough and on 24/7 then there is no capacity to heat up the building eg after a holiday.

In terms of what we use now - I know roughly for the whole year in terms of oil in litres. I think one of the problems will be that currently we aggressively zone the heating, so only the kitchen / lounge / office / bedroom is being heated as we use them for most of the time.
This keeps the oil consumption down, but I believe it is very much not the recommended way to use a heat pump, especially if you want to achieve a good COP - and also it is not designed to give a quick boost in temp to individual rooms, it doesn't have the power to do that. We may wll just have to get someone in see what they say.

In terms of capacity to reheat after a holiday - if the pump is sized to keep up with the worst case weather, it should only be a problem to heat up if you go away in January/Feb - any other time it should have some spare capacity

Knowing the Avg or total for the yr does not help as what you need to know is how much energy is used at the worst time of the yr and particularly the avg worst day but perhaps not the extreme.

The heat loss calcs in kW are for the average worst day - so -4.6 degrees in my postcode and elevation. That worked out at 12.5kW heat loss, which will presumably lead to a suitable heat pump size - I guess will need a little bit of extra for emergencies

[Joeboy]

Rich,
Do Octopus run a vac test on your house or would you benefit from paying to have that done? I see the idea of low&slow working well on the HP but I think I'd also want to improve where I could after a leak test. Just a thought but maybe not practical?

We noticed huge differences across the home when actively hunting down leaks. There were SO many it would be embarrassing to list (maybe 60 to 80 leaks addressed).

The whole heat up/ cool down timings radically shifted in our favour. I didn't have a leak test performed but did multiple runs through the house clipboard in hand and over time addressed all that I could. Didn't cost much other than time but the returns were (are) insane. 1982 barrett bungalow extended 3 times.

[AGT]

Agree with the leak hunting,

Think I might make a fan to fit into a window opening and do a blower test next year….

[Ken]

I would love to have a leak test and a infrared heat test but would probably frighten myself.!

Well worth it i can imagine.