ASHP / backup generator

[Bozza]

Currently my wee Draper / toolstation back up generator runs some essential basics during power cuts at my house.  I’m looking at upgrading with a proper changeover switch and a bigger generator.  
 

There are plenty of guidance lists online with regards to the consumption of the usual domestic appliances, to allow me to estimate the correct capacity generator I require. 
 

The bit I need help with is - How is the best way to figure out the consumption of my ASHP, to see if it’s viable to have it running off a back up genny.  Appreciate its consumption will relate to variable outdoor temperatures etc.  I’m a bit of a biff when it comes to watts, kWh, and such calculations and can’t seem to get an answer anywhere else online.

 

cheers Bozza

 

 

 

 

[joth]

24 minutes ago, Bozza said:

Currently my wee Draper / toolstation back up generator runs some essential basics during power cuts at my house.  I’m looking at upgrading with a proper changeover switch and a bigger generator.  
 

There are plenty of guidance lists online with regards to the consumption of the usual domestic appliances, to allow me to estimate the correct capacity generator I require. 
 

The bit I need help with is - How is the best way to figure out the consumption of my ASHP, to see if it’s viable to have it running off a back up genny.  Appreciate its consumption will relate to variable outdoor temperatures etc.  I’m a bit of a biff when it comes to watts, kWh, and such calculations and can’t seem to get an answer anywhere else online.

 

cheers Bozza

 

 

 

 

Most ASHP will have a number for max or startup current (in amps). That will be the number you need to look most carefully at, as a small gennie may struggle to respond to the sudden load. 

It'd be interesting if a small couple kWh battery could work well to reinforce a generator to cover odd peaks. Obviously if you have solar PV the battery comes into its own for this use case 

[Bozza]

Thanks @joth  have attached the label for the pump how do I interpret these numbers in relation to what you’re advising, it’s all gobledegook to my brain.

 

 

[markc]

Unfortunately small genies are a nightmare to spec.  We have a lot of machines with 2.2kw single phase motors that will start and run happily on a 13amp plug. We have a old heavy Haverhill 5kva generator that has no problem at all running these machines but a new 10kva won’t because the voltage drop on start up causes our machine to shut down.

[sharpener]

It looks as though the 28A starting current would need as a bare minimum a 6kW genny and as @markc says they are notoriously difficult to size correctly. Modern inverter based gennys are more economical at part-load but have all sorts of protection in them which may trip.

 

Suggest you hire one for the weekend and if successful buy the exact same model.

 

Does your HP have a quiet mode or night mode which might draw less current?

 

Another old trick is to get a biggish induction motor and run that in parallel. Start that first with a star-delta starter, then its rotating mass will help supply the HP on startup. But this would require intervention every time and is not easy to automate.

 

[JohnMo]

I use one of these, induction hob, oven, lights tv at same time no problem. Our 6kW ASHP no issue.  But your heat pump is bigger so idea.

 

https://hyundaipowerequipment.co.uk/p1pe-p10000le-7-9kw-9-8kva-recoil-electric-start-site-petrol-generator-powered-by-hyundai?gclid=CjwKCAjw69moBhBgEiwAUFCx2Fbz7H-U8e087ep8aNj5WsMWeXQBVip-bHh7G5iLfnaQfHVlSxUlphoCSAQQAvD_BwE

[sharpener]

Remote start might be useful but it hardly seems worth paying twice the price https://hyundaipowerequipment.co.uk/hyundai-hy6500sei-petrol-inverter-generator-6500w-pure-sine-wave.

 

However it is also a good bit quieter.

[TonyT]

Use a switchbot for remote switching!!

 

[TonyT]

I’d go with the hiring of the unit first as posted earlier, as starting currents on generators can be a funny thing.

 

as always start the generator, let it get warmed up and then apply load, too many dafties, turn generator on, then apply full load and it dies… they then give negative Amazon reviews due to the lack of brain cells/ not reading manufacturer instructions 

 

[Bozza]

Thanks for comments & input folks.  Managed to get someone to figure out how big a generator I’d need.  

[sharpener]

@Bozza what did they say?

[LeeVanCleef]

Resurrecting this thread as I sit in a house with the power knocked out from a recent storm. Thankfully in August.

 

@Bozza did you manage to get an answer on this? 
 

We are currently contemplating an ASHP  and reliability during power outages was one of the concerns in the back of my mind that has been brought to the front.

[SteamyTea]

17 minutes ago, LeeVanCleef said:

We are currently contemplating an ASHP  and reliability during power outages was one of the concerns in the back of my mind that has been brought to the front.

Not many heating systems will work without mains power.

Generally, because of the relatively high start up current needed to run a heat pump, you will need a full sine wave generator and a small battery/inverter system.

[LeeVanCleef]

@JohnMo seems to have one working, although I understand he has a battery too.

 

A different predicament in Oct-Mar, especially with young kids in the house.

[JohnMo]

Prior to battery house was run direct from Hyundai 9.6kVa generator, including the heat pump.

 

But heat pump is 6kW, starting requirements are not that hard. Our battery inverter is 6kW and that has no issues either.

[SteamyTea]

13 minutes ago, JohnMo said:

9.6kVa generator

That delivers around 40A though.

 

13 minutes ago, JohnMo said:

Our battery inverter is 6kW and that has no issues either.

Generally, inverters can go over current for a few seconds, which is all that is needed to start an inductive load.

[Dillsue]

33 minutes ago, LeeVanCleef said:

@JohnMo 

 

A different predicament in Oct-Mar, especially with young kids in the house.

Got the tee shirt for the winter outage, with young kids at the time, and never been without a genny since.

 

If you've got a working non electric heating system now, don't replace it but add a HP to it and use the existing system as a backup to the HP. Existing system will likely run off a small genny which will keep the heating, lights and telly going.

 

Heat pumps are complex technology and it's you'll do well to get a quick fix if something fails so having a backup for power cuts and HP failure is a nice place to be, for me anyway:)

Edited August 4 by Dillsue

[-rick-]

3 minutes ago, SteamyTea said:

Generally, inverters can go over current for a few seconds, which is all that is needed to start an inductive load.

 

Modern heat pumps are inverter driven. This doesn't present an inductive load (or at least nothing like a traditional motor). They will soft start,

[JohnMo]

34 minutes ago, SteamyTea said:

That delivers around 40A though.

Isn't that the point you use a generator fit for purpose, heat pump on, oven or hob on for cooking you tea, lights as normal and watch the TV, live life as normal - main on or off.

[Kelvin]

Our Sigenergy 8kW energy controller (inverter) can peak to 12kW for 10 seconds in backup mode and then fall back to 8.8kW (with a max of 40A) The backup gateway has quite a flexible feature in what they call a smart port to connect high loads to like an ASHP. The idea is that you can separately control anything connected to it or it will do it automatically such as shutting it down to conserve energy. You can also connect a generator to it. I’ve not bothered connecting the ASHP to it separately though so it’s backed up with the rest of the house.