Heat pump - new radiators and pipes

ashe

Just curious as have read a bit about heat pumps needing larger rads and larger pipes 

is this not incredibly disruptive as imagine many houses have pipes under flooring which might be tiled, or in walls which might be papered /plastered or behind tile? 

Is it just larger rads of existing types or are they a set type? My partner hates the look of standard rads and last few years we switched them out to nicer looking ones so just trying to figure through how it works when you get a quote for a heat pump, does or basically turn your house upside down for pipes and radiators?

TELLIT01

I don't think there is a simple answer to that question.  There are so many variables such as standard of insulation.  I've certainly seen the requirement for larger radiators mentioned many times, but not replacing pipework too.  As you say, replacing pipework could be incredibly disruptive and make it very difficult to remain in the property when the work was being done.  If considering moving to a heat pump you would need to have an in depth discussion with potential installers to get answers.

Albermarle

When you get a heat pump installer round for a look, they will look carefully at your whole system/house and then make various calculations as to what will be necessary for a heat pump system to work effectively in your situation.
Until they do that you will not really know what the job will entail.

New_in_the_fens

I’ve had new CH put in this year. I’m currently on an oil tank, but looking to move over to a heat pump in the future. 

We’ve had the larger radiators put in, the pipes to the radiators bedded in the walls are 15mm, the other pipes are 22mm which apparently is where they need to be bigger. 

Once we’ve got the insulation sorted etc, we should be in a position to move over. 

If you need bigger radiators and your current ones are fed by a 15mm pipe, you will probably need some sort of extension piping to cover the larger sized radiators. I suppose It’ll depend where the 22mm pipes need to go as to whether it’ll cause disruption. Your heating engineer will be able to advise. 

Ectophile

You don't necessarily need bigger radiators, if more efficient ones can be fitted.  The old-fashioned radiators (say, 1970's) tended to be a simple panel.  Modern ones have lots of fins on them to encourage heat transfer to the air.  A single radiator could also be replaced with a double.

But it's the disruption and cost that puts me off getting a heat pump, however much I want to go for the greener option.  My whole central heating system would need ripping out and replacing with something better.  It's barely adequate with a modern condensing boiler, let alone a heat pump.

EssexExile

Ectophile said:

You don't necessarily need bigger radiators, if more efficient ones can be fitted.  The old-fashioned radiators (say, 1970's) tended to be a simple panel.  Modern ones have lots of fins on them to encourage heat transfer to the air.  A single radiator could also be replaced with a double.

But it's the disruption and cost that puts me off getting a heat pump, however much I want to go for the greener option.  My whole central heating system would need ripping out and replacing with something better.  It's barely adequate with a modern condensing boiler, let alone a heat pump.

When I last had my boiler repaired the nice man turned down the flow temperature as he said a condensing boiler is more efficient at lower temperatures. It may well be but in the cold weather the house never got up to a warm temperature with the heating on all the time. I think the place will need a lot more work before a heat pump becomes an option.

GrubbyGirl_2

EssexExile said:

Ectophile said:

You don't necessarily need bigger radiators, if more efficient ones can be fitted.  The old-fashioned radiators (say, 1970's) tended to be a simple panel.  Modern ones have lots of fins on them to encourage heat transfer to the air.  A single radiator could also be replaced with a double.

But it's the disruption and cost that puts me off getting a heat pump, however much I want to go for the greener option.  My whole central heating system would need ripping out and replacing with something better.  It's barely adequate with a modern condensing boiler, let alone a heat pump.

When I last had my boiler repaired the nice man turned down the flow temperature as he said a condensing boiler is more efficient at lower temperatures. It may well be but in the cold weather the house never got up to a warm temperature with the heating on all the time. I think the place will need a lot more work before a heat pump becomes an option.

I had the opposite advice from my plumber when he saw I'd turned my flow rate down.  He said that having the flow temp at 70 means the whole system warms up much quicker and as I have modern horizontal radiators they hold the heat longer so the system is running for less time.  Weather hasn't been cold enough to test the theory out, but like you it seemed to take forever to warm up last winter.

ThisIsWeird

EE and GG2, both are correct.

For a condensing boiler, you keep the flow temp as low as possible, whilst still effectively heating your home. If that needs to be 70o, then so be it - no point having a CH system that doesn't warm you up.

Even 70o will give you reasonable condensing, as the return will be cooler.

We had a floor-mounted Mexico when we moved in, and the elderly vendors had it permanently kettling. The single-skinned flue had a heat shimmer coming from it - very scary. But the house was warm, even via the ancient single-panel, no fin, rads.

The new combi only gets up to around 75, and I generally have it much lower. Obviously the previously 'ouch'-hot rads no longer become that, but I did replace the living area ones with larger output versions so the effective output is similar.

So, turn your boiler to an output temp that warms your house effectively, and quickly enough, but as low as possible to still do this. In colder weather, mine can take well over an hour... I will also turn my flow temp up and down a few times over the winter period to match large changes in outdoor temps.

 

Albermarle

So, turn your boiler to an output temp that warms your house effectively, and quickly enough, but as low as possible to still do this. In colder weather, mine can take well over an hour... I will also turn my flow temp up and down a few times over the winter period to match large changes in outdoor temps.

 
I do the same, but you also have to keep in mind that if you do not have a combi the boiler flow temperature should not go below 65 degrees, as this is needed to heat the hot water tank to a high enough temperature to kill any legionnaire bugs. ( although the risk in a domestic setting is relatively low) .
So setting boiler flow temperature is a trade off of competing factors. However it is clear that having it as high as possible is not sensible.

FreeBear

Albermarle said: I do the same, but you also have to keep in mind that if you do not have a combi the boiler flow temperature should not go below 65 degrees, as this is needed to heat the hot water tank to a high enough temperature to kill any legionnaire bugs. ( although the risk in a domestic setting is relatively low) .

No. You can still run with a low flow temperature even with a system/heat-only boiler. If you are genuinely worried about the very small chance of catching legionella, maintain a water temperature of 50-55°C in the tank for a few hours each week - This can be done by adjusting the flow temperature up or switching on the immersion heater.

Albermarle

FreeBear said:

Albermarle said: I do the same, but you also have to keep in mind that if you do not have a combi the boiler flow temperature should not go below 65 degrees, as this is needed to heat the hot water tank to a high enough temperature to kill any legionnaire bugs. ( although the risk in a domestic setting is relatively low) .

No. You can still run with a low flow temperature even with a system/heat-only boiler. If you are genuinely worried about the very small chance of catching legionella, maintain a water temperature of 50-55°C in the tank for a few hours each week - This can be done by adjusting the flow temperature up or switching on the immersion heater.

When I have read about this before, you often see the figures 60 to 65 degrees mentioned to prevent bugs growing, so I am only going off that . In fact the Health and Safety Executive recommend 'at least 60 degrees'
HSE - Legionnaires' disease - Risk systems - Hot and cold water systems
However the risks are small, so probably not worth worrying about too much. In any case most people ( and heating engineers) have the boiler flow temperature turned up quite high anyway, probably too high for the boiler to work at best efficiency.