Will a GSHP work on generator?

steveR

Member
Mixed Farmer
Just been chatting with Herself about the after effects of Arwen and the problems of out total reliance on electricity...

The property's hot water and heating comes from a GSHP, installed in 2011, and got the RHI approval a few years later which runs out (I think) next year. Both the houses I have built will run from a gennie, the first used LPG for heating.

However, this property has a 12kW heat pump output, and needs a good slug of juice for startup*, so the 4KW gennie is not up to running the heatpump, so in power cuts, I switch it off and run the house from the gennie, and heat with a mix of a small woodburner stove in one room, and a Superser gas heater. However, this means no hot water!

When the house refurb was being done, I discussed an LPG combi as backup with the heating engineers, but was advised that an RHI inspection would look unfavourably on one, unless is was fancy hidden system.... So I left it.

Now that the RHI is coming to an end, I am thinking again on what is the best way forward to safeguard our comfort etc

1. Gas combi install about £2K, for a simple manual changeover system, running off a 47kg bottle. House on a cheap existing gennie

2. A simple, £2K, 25KVA gennie. However these seem to require that the tractor PTO runs at a genuine 540 output, as running on economy mode leads to problems... http://www.omafra.gov.on.ca/english/engineer/facts/00-059.htm#choose So probably rather loud near the house

Or go and buy a similiar priced stand-alone powered generator, sized to start and then run the GSHP from it.

* But I cannot find out how much load!!
 
How often have you been in the Poo before though?

The trouble with back ups is, by definition as soon as you get it, it sits there for years Unused, then when you need it she’s not good to go.

Can you rig something temporary for an immersion for the wood burner? Or just have a small Genny for immersion, the start up on the GSHP will mean you need a big genie sat there
 

steveR

Member
Mixed Farmer
How often have you been in the Poo before though?

The trouble with back ups is, by definition as soon as you get it, it sits there for years Unused, then when you need it she’s not good to go.

Can you rig something temporary for an immersion for the wood burner? Or just have a small Genny for immersion, the start up on the GSHP will mean you need a big genie sat there
Not for a few years TBH, the power company rejigged the networks around us which has improved matters when there is an outage now.

We used to be a real Hotspot of problems!! Overhead and undergrounds all over the place! IKWYM about backups needing constant checking and being cared for..

Not sure of the circuits for running the DHW immersion tank... The internal immersion for the GSHP, needs the whole device to be on!
 

Exfarmer

Member
Location
Bury St Edmunds
My GSHP engineer (VERY good at the job) said the following:


It’s all about the clean supply I have always be told genie can never be clean enough for a heat pump
I find this difficult to believe. Their is little reason why a proper gennie should not be able to do the job. Many Gennies are running equipment around the country with no issue. The problems usually arise when the Gennie is not up to the job and voltage drops which can destroy motors and other equipment.
Looking ay my friends site with large chicken sheds and a huge range of equipment, fans, feeders, heat exchangers and a range of computer equipment controlling everything including the feeding, watering, temperature and monitoring of the sheds themselves, including warning of power outage, means he is totally reliant on his generator to ensure a constant supply of electricity. Even then he has to manually start it, to ensure the load is balanced as he brings the different sheds back on to power, in the infrequent failure
 

steveR

Member
Mixed Farmer
I find this difficult to believe. Their is little reason why a proper gennie should not be able to do the job. Many Gennies are running equipment around the country with no issue. The problems usually arise when the Gennie is not up to the job and voltage drops which can destroy motors and other equipment.
Looking ay my friends site with large chicken sheds and a huge range of equipment, fans, feeders, heat exchangers and a range of computer equipment controlling everything including the feeding, watering, temperature and monitoring of the sheds themselves, including warning of power outage, means he is totally reliant on his generator to ensure a constant supply of electricity. Even then he has to manually start it, to ensure the load is balanced as he brings the different sheds back on to power, in the infrequent failure
I don't, having seen numerous Starters being replaced on my GSHP, largely due to a fluctuations in the mains! NIBE are now providing much uprated starter kit for rural areas, although I do not see what we should be any different to an urban site.

However I agree that a decent gennie would do the job, and that is not a PTO powered unit where the engine to load, is rarely balanced, with voltage fluctuations all over the place! When I was doing some work for MEB, back I the dark ages, the 50KW mobile units on a skid or trailer, were impressive little beasts, quiet and ever so stable when I had to monitor the outputs...
 

steveR

Member
Mixed Farmer
I can believe that. If it was a full time problem spending the money is easier but as it’s periodic it makes for a harder call.

Hence my looking at a number of options... :)

I will be asking if it is possible to isolate the GSHP itself, but use the HP control gear and then use the internal 3kW immersion heater for emergency heating, which is what I do if the starter or similiar, fails. That way, a gennie could work. Possible an option using the software controls.
 

gmgmgm

Member
Mixed Farmer
We have an 11kw GSHP, which pulls about 2.8kw when running. On start-up, it will pull much more, a guideline for compressor motors is often 3x?

If there are problems, we use the log burner for heating the house. If we still have electric (through generator etc) we can run hot water using the immersion heater.

If you don't have a specific immersion heater, check your GSHP manual carefully. Most have electric supplemental heat (like our Worcester/IVT/Bosch), and can be configured to use these exclusively. Ours for example, I can set to run as a 3, 6 or 9kw electric heater, which is much less vulnerable to damage from fluctuating voltage. It's in the installation settings. Your 4kw generator should run it happily.

I've had to replace a few starting electrics (potential relays, caps and soft-starters) over the years, and being able to run as a purely electric heater for DHW when the compressor has been offline has been very handy.
 
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steveR

Member
Mixed Farmer
If you don't have a specific immersion heater, check your GSHP manual carefully. Most have electric supplemental heat (like our Worcester/IVT/Bosch), and can be configured to use these exclusively. Ours for example, I can set to run as a 3, 6 or 9kw electric heater, which is much less vulnerable to damage from fluctuating voltage. It's in the installation settings. Your 4kw generator should run it happily.

I've had to replace a few starting electrics (potential relays, caps and soft-starters) over the years, and being able to run as a purely electric heater for DHW when the compressor has been offline has been very handy.
Same here. I no longer need to dig the manual out to get the immersion running... Done it too many times!!

Our immersion system will actually heat the house as well as DHW, although in theory it doesn't... :rolleyes: Not sure what rating it is though... Needs a bit more investigation on isolating the heat pump to allow the gennie to run the system...
 

Mur Huwcun

Member
Livestock Farmer
Location
North West Wales
Same here. I no longer need to dig the manual out to get the immersion running... Done it too many times!!

Our immersion system will actually heat the house as well as DHW, although in theory it doesn't... :rolleyes: Not sure what rating it is though... Needs a bit more investigation on isolating the heat pump to allow the gennie to run the system...

Ours has a 7kw immersion. You can easily switch the HP element off on ours on the control panel. Only time I used the immersion is when we were without power during beast from the east and the house lost all the heat so when power came back on I used the add heat function using the in board immersion, switched DHW off to concentrate on heating and used the tank immersion for hot water for about 12 hrs to get some warmth back. Think I set it at about 4kw add heat at the time
 

steveR

Member
Mixed Farmer
Ours has a 7kw immersion. You can easily switch the HP element off on ours on the control panel. Only time I used the immersion is when we were without power during beast from the east and the house lost all the heat so when power came back on I used the add heat function using the in board immersion, switched DHW off to concentrate on heating and used the tank immersion for hot water for about 12 hrs to get some warmth back. Think I set it at about 4kw add heat at the time
Thanks.

As I said, I know I can produce heat from the immersions for DHW and the CH, but I need to suss out switching off the HP, on demand. Looks like I need to RTFM!! ;)
 
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