Heat Pumps: anyone have one/thought about it?

It’s 10C here and my flow temp is 32 currently but of course my rads are sized for it.

I seem to be able hold 20.5C with a 40-41C flow temperature at -2C outside which is handy (I allow 1C of modulation in the controller). So much for octopus 50C design :p
 
b0rn2sk8 said:
It’s 10C here and my flow temp is 32 currently but of course my rads are sized for it.

I seem to be able hold 20.5C with a 40-41C flow temperature at -2C outside which is handy (I allow 1C of modulation in the controller). So much for octopus 50C design :p
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does that reduce your bill that much? and are we talking gas boiler here or heat pump?
 
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On a heat pump, yes of course because of time of use tariffs, solar and batteries to drastically reduce electricity costs. Gas is just expensive all the time and there isn’t any getting away from it.

I got though the whole day yesterday on 7p leccy. 17kwh was used used by the heat pump and it would have produced >60kwh kwh of heat.

£1.19 of electric.
Gas would have cost at least £4 plus 30p standing charge.
 
We run our combi at the moment at 55C for heating and it gets the house up to temperature pretty well, so I'm hopeful not too many changes would be needed for a heat pump at 45-50C, especially as we currently run the combi in bursts rather than constantly so its starting from lower.

Our Octopus survey is booked in for next Thursday. Hopefully the hot water cylinder location isn't the issue I think it might be.
 
reef said:
We run our combi at the moment at 55C for heating and it gets the house up to temperature pretty well, so I'm hopeful not too many changes would be needed for a heat pump at 45-50C, especially as we currently run the combi in bursts rather than constantly so its starting from lower.

Our Octopus survey is booked in for next Thursday. Hopefully the hot water cylinder location isn't the issue I think it might be.
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octopus rang me an hour ago, after filling in their survey online the other day and asked when did i want the to come and do a full survey. but i have put them off for now as other things currently taking priority. but once the additional solar has been added ( soon ) and a battery or two later in the year, then i will get them in to do the full survey.

i might drop the boiler to 55 when i get home and see how it copes with the lower evening temps
 
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reef said:
We run our combi at the moment at 55C for heating and it gets the house up to temperature pretty well, so I'm hopeful not too many changes would be needed for a heat pump at 45-50C, especially as we currently run the combi in bursts rather than constantly so its starting from lower.

Our Octopus survey is booked in for next Thursday. Hopefully the hot water cylinder location isn't the issue I think it might be.
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How many hours a day would you say your boiler is on per day?
 
TNA said:
How many hours a day would you say your boiler is on per day?
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At the moment, about 5 hours. 3 hours in the morning and 2 hours in the evening. Maybe an hour or two extra when it was cold the last couple of weeks. We only use about 7200kWh of gas per year, including the gas hob.
 
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reef said:
We run our combi at the moment at 55C for heating and it gets the house up to temperature pretty well, so I'm hopeful not too many changes would be needed for a heat pump at 45-50C, especially as we currently run the combi in bursts rather than constantly so its starting from lower.

Our Octopus survey is booked in for next Thursday. Hopefully the hot water cylinder location isn't the issue I think it might be.
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Had my Octopus survey done today. Not had the full report back yet, but just from word of mouth as the guy was going around:

  • Heat loss of house is about 3.9kW (I'd done the fag packet maths at 3.6kW so pretty close). I believe this was the 21ºC indoor/-3ºC outdoor heat loss, but hoping this is confirmed on the report. Certainly means we're down in the 1-2kW heat loss range on "normal" days, and completely proves our 35kW boiler is vastly oversized, as it only modulates down to 7kW!!
  • Main heating piping and even the 10mm plastic to the rads would have worked OK
  • Need an additional structural survey at about £500 if I wanted the hot water tank in the only cupboard we have (we don't!), which is "floating" above the stairs.
  • Loft hatch is too small right now to get a tank up in the loft. Needs professionally doing as the current hatch is the full width between two main beams.
  • Additional checks needed but pushed on space even in the loft for where the tank would go vs beams etc. 180L tank looked to be our maximum available if everything aligned.
  • Outside location at the back of the house (north facing) very suitable, and close to where the boiler is now.
  • Water pressure too low (10L/min vs required 14L/min) - I suspect this is due to nearby housing construction as it's felt a little low over the last couple of months.

Forgot to ask if any rads would have needed changing but according to my own workings, only one or two should have needed attention as we almost always run the house at <50ºC flow temperature on the current gas boiler anyway. Hoping to get a little more from the full report, but realistically it's a no-go, and even the Octopus chap said he'd get the refund started for me.
 
Mains water pressure/flow is a tricky one.

Are you are the stop valve on the meter is fully open (likewise the one in the house?).

If so, short of repiping to the main or installing an accumulator and booster pump, you are kind of stuck.
 
b0rn2sk8 said:
Mains water pressure/flow is a tricky one.

Are you are the stop valve on the meter is fully open (likewise the one in the house?).

If so, short of repiping to the main or installing an accumulator and booster pump, you are kind of stuck.
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So I shut off the water early last year when I broke our shower. When I opened the tap under the sink, I gave it a good few turns, but didn't keep going for fear of the tap popping off or something :D would it normally have a stop on it once it's fully opened?

EDIT: Went and checked. Had a good couple more turns until it was fully open, and I've wound it back about half a turn from full. Has made bugger all difference to the feel of the pressure though :D
 
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squerble said:
Had my Octopus survey done today. Not had the full report back yet, but just from word of mouth as the guy was going around:

  • Heat loss of house is about 3.9kW (I'd done the fag packet maths at 3.6kW so pretty close). I believe this was the 21ºC indoor/-3ºC outdoor heat loss, but hoping this is confirmed on the report. Certainly means we're down in the 1-2kW heat loss range on "normal" days, and completely proves our 35kW boiler is vastly oversized, as it only modulates down to 7kW!!
  • Main heating piping and even the 10mm plastic to the rads would have worked OK
  • Need an additional structural survey at about £500 if I wanted the hot water tank in the only cupboard we have (we don't!), which is "floating" above the stairs.
  • Loft hatch is too small right now to get a tank up in the loft. Needs professionally doing as the current hatch is the full width between two main beams.
  • Additional checks needed but pushed on space even in the loft for where the tank would go vs beams etc. 180L tank looked to be our maximum available if everything aligned.
  • Outside location at the back of the house (north facing) very suitable, and close to where the boiler is now.
  • Water pressure too low (10L/min vs required 14L/min) - I suspect this is due to nearby housing construction as it's felt a little low over the last couple of months.

Forgot to ask if any rads would have needed changing but according to my own workings, only one or two should have needed attention as we almost always run the house at <50ºC flow temperature on the current gas boiler anyway. Hoping to get a little more from the full report, but realistically it's a no-go, and even the Octopus chap said he'd get the refund started for me.
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Thats a shame. The hot water tank is my biggest concern too. I want it in the cupboard where the combi boiler is currently located but it is only 850mm x 650mm. Our loft hatch is the same as yours - narrow and between two main beams, plus i already have enough weight up there with my batteries.
 
reef said:
Thats a shame. The hot water tank is my biggest concern too. I want it in the cupboard where the combi boiler is currently located but it is only 850mm x 650mm. Our loft hatch is the same as yours - narrow and between two main beams, plus i already have enough weight up there with my batteries.
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That sounds like an absolute no go. This is what Octopus said in their initial email after booking:

The dimensions for the normal cylinder are 760 (w) x 760 (d) x 2100 (h), we also have slimline cylinders available.

...so you need ~2 metres of height
 
squerble said:
That sounds like an absolute no go. This is what Octopus said in their initial email after booking:

The dimensions for the normal cylinder are 760 (w) x 760 (d) x 2100 (h), we also have slimline cylinders available.

...so you need ~2 metres of height
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We have over 2.2m of height, so hopefully their slimline cylinder will fit.
 
squerble said:
Additional checks needed but pushed on space even in the loft for where the tank would go vs beams etc. 180L tank looked to be our maximum available if everything aligned.
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have they said what tank it is ... seems stelflow is popular for them ... and hadn't appreciated they can be horizontal - which would spread the load in our loft,
also suggest they overstate dimensions of space to allow for working space etc.

 
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