Heat meter - Fun & games

michaels

FreeBear said:

michaels said:

FreeBear said:

First graph in - A couple of radiators down as I'm plastering upstairs.

Just the instantaneous power at a flow temperature of ~52°C. Need a spell of cold weather to do some more tuning and get some representative plots.

Brilliant - and are you able to measure the power into the heat pump at the same time?!

As per earlier post, this is with a gas boiler. I fitted the heat meter so that I could instrument the heat demand of the building and get a better idea of heat pump size needed when the time comes. Now that spring is here, I won't be needing the heating for at least six months.

If you have a smart meter (and no other gas appliances) then I guess in theory you do have the gas input for the period - so whilst not your main purpose you could get some indication of the actual as opposed to theoretical efficiency of the boiler.

FreeBear

michaels said:

FreeBear said:

michaels said:

FreeBear said:

First graph in - A couple of radiators down as I'm plastering upstairs.

Just the instantaneous power at a flow temperature of ~52°C. Need a spell of cold weather to do some more tuning and get some representative plots.

Brilliant - and are you able to measure the power into the heat pump at the same time?!

As per earlier post, this is with a gas boiler. I fitted the heat meter so that I could instrument the heat demand of the building and get a better idea of heat pump size needed when the time comes. Now that spring is here, I won't be needing the heating for at least six months.

If you have a smart meter (and no other gas appliances) then I guess in theory you do have the gas input for the period - so whilst not your main purpose you could get some indication of the actual as opposed to theoretical efficiency of the boiler.

No other gas appliances. Just got hold of an Octopus mini, and if I could get the darned thing set up, I'd be able to import gas consumption to Home Assistant. May well end up getting a Hildebrand Glow (means I don't have to rely on Octopus servers for the data).

michaels

FreeBear said:

michaels said:

FreeBear said:

michaels said:

FreeBear said:

First graph in - A couple of radiators down as I'm plastering upstairs.

Just the instantaneous power at a flow temperature of ~52°C. Need a spell of cold weather to do some more tuning and get some representative plots.

Brilliant - and are you able to measure the power into the heat pump at the same time?!

As per earlier post, this is with a gas boiler. I fitted the heat meter so that I could instrument the heat demand of the building and get a better idea of heat pump size needed when the time comes. Now that spring is here, I won't be needing the heating for at least six months.

If you have a smart meter (and no other gas appliances) then I guess in theory you do have the gas input for the period - so whilst not your main purpose you could get some indication of the actual as opposed to theoretical efficiency of the boiler.

No other gas appliances. Just got hold of an Octopus mini, and if I could get the darned thing set up, I'd be able to import gas consumption to Home Assistant. May well end up getting a Hildebrand Glow (means I don't have to rely on Octopus servers for the data).

Have you tried https://www.n3rgy.com/consumer/ ?

FreeBear

michaels said:

FreeBear said:

michaels said:

FreeBear said:

michaels said:

FreeBear said:

First graph in - A couple of radiators down as I'm plastering upstairs.

Just the instantaneous power at a flow temperature of ~52°C. Need a spell of cold weather to do some more tuning and get some representative plots.

Brilliant - and are you able to measure the power into the heat pump at the same time?!

As per earlier post, this is with a gas boiler. I fitted the heat meter so that I could instrument the heat demand of the building and get a better idea of heat pump size needed when the time comes. Now that spring is here, I won't be needing the heating for at least six months.

If you have a smart meter (and no other gas appliances) then I guess in theory you do have the gas input for the period - so whilst not your main purpose you could get some indication of the actual as opposed to theoretical efficiency of the boiler.

No other gas appliances. Just got hold of an Octopus mini, and if I could get the darned thing set up, I'd be able to import gas consumption to Home Assistant. May well end up getting a Hildebrand Glow (means I don't have to rely on Octopus servers for the data).

Have you tried https://www.n3rgy.com/consumer/ ?

No, but I've now had a look and even found a Home Assistant integration. Bad news is it only pulls data for the previous day. Looks like a shortcoming of the n3rgy API. To be of any real use, the data needs to be "real time" or no more than 30 minutes out of date.

michaels

FreeBear said:

michaels said:

FreeBear said:

michaels said:

FreeBear said:

michaels said:

FreeBear said:

First graph in - A couple of radiators down as I'm plastering upstairs.

Just the instantaneous power at a flow temperature of ~52°C. Need a spell of cold weather to do some more tuning and get some representative plots.

Brilliant - and are you able to measure the power into the heat pump at the same time?!

As per earlier post, this is with a gas boiler. I fitted the heat meter so that I could instrument the heat demand of the building and get a better idea of heat pump size needed when the time comes. Now that spring is here, I won't be needing the heating for at least six months.

If you have a smart meter (and no other gas appliances) then I guess in theory you do have the gas input for the period - so whilst not your main purpose you could get some indication of the actual as opposed to theoretical efficiency of the boiler.

No other gas appliances. Just got hold of an Octopus mini, and if I could get the darned thing set up, I'd be able to import gas consumption to Home Assistant. May well end up getting a Hildebrand Glow (means I don't have to rely on Octopus servers for the data).

Have you tried https://www.n3rgy.com/consumer/ ?

No, but I've now had a look and even found a Home Assistant integration. Bad news is it only pulls data for the previous day. Looks like a shortcoming of the n3rgy API. To be of any real use, the data needs to be "real time" or no more than 30 minutes out of date.

Depends what you need it for - I use it to monitor my monthly offpeak electricity usage.  I thought all the app based services (except perhaps for the supplier ones) only polled the data every 3 hours or less?

Reed_Richards

FreeBear said:

No, but I've now had a look and even found a Home Assistant integration. Bad news is it only pulls data for the previous day. Looks like a shortcoming of the n3rgy API. To be of any real use, the data needs to be "real time" or no more than 30 minutes out of date.

I have been discussing this on another thread.  The reason that the n3rgy data you get is delayed is probably so that they can charge other information providers like Loop or Hugo for data that is more up to date.  None of these third party usage information suppliers give you real time data.  

FreeBear

A couple of graphs from this morning after adjusting the PID gains of the thermostat.

Power being generated by the boiler..

Temperature increase...

Despite having an Octopus Home Mini, still can't get 30min gas consumption data imported in to Home Assistant. Can get the data via the Octopus app (which is of limited use). Still, good enough to get an idea of efficiency. Generated 6kW of heat with 6.5kW of gas for 92% efficiency.

FreeBear

Final burn of the day, and used just 16.44kWh for 16kWh of heat out for an efficiency of 97%. Just need  few days of subzero temperatures to see what the heat demand is like, and then I can ponder heat pump sizes.

NedS

FreeBear said:

Meatballs said:

The other approach is to get these values from the HP itself. Daikin has open source projects with espaltherma and p1p2serial that can collect these from the serial busses on the device. I think there's similar with the Mitsubishi Ecodans etc

Would be OK if I had a heat pump. The goal of the current project is to determine how much heat I'm getting from my current gas boiler. Once I have that data, I'll be in a much better position to size a heat pump when the time comes.

In the meantime, the information I post here may be of interest to others heading down the same path.

Sizing a heat pump is really difficult. Having actual heat loss data will really help you, but there are other factors to also consider.

Say for example you determine you have a heat loss of 6kW - i.e, you need 6kWh of heat to maintain a desired room temp of 20C on the coldest days. So you install a 6kW heat pump.

Most heat pumps are rated at a flow temp of 35C at an ambient temp of 7C. So your 6kW heat pump will generate 6kW with 35C flow temp at 7C ambient. But on the coldest days, you may need 50C flow temps, so it will be lower, maybe 5.5kW. And it's not 7C outside, but -2C so it may be more like 5kW under those conditions (heat pump manufacturers normally supply tabulated data for this).

Additionally, your heat pump will not be available 24/7 to heat the house as it will need to spend maybe 1-1.5 hour per day heating the hot water cylinder, depending upon size, required water temperature and usage. Also, when it's working hardest, on the coldest of days, it will also need to run defrost cycles which will again reduce it's effective output significantly.

I didn't really understand a lot of this until recently when the weather turned colder. We had a heat loss calc of 7.4kW and our installers installed a 12kW heat pump which I considered to be very oversized. The next model down in the range was the 8kW model which superficially seemed far more suitable to me. However, inspecting the datasheet showed it was only capable of 6.18kW peak output for a flow temp of 50C at 2C ambient once defrost cycles were taken into account, and that's before we factor in the time required for heating hot water. Assuming the heat loss calc were accurate, we would have been struggling to maintain house temp on the coldest days as could have got into defrost spirals whereby the heat pump is constantly working at maximum, frosting up and then defrosting, and is unable to effectively heat the house. Our 12kW model can output 10.4kW under the coldest conditions we are likely to see, so 7.4kW required for heating leaves us some capacity for hot water and means we are not running flat out on the coldest days (heat pumps are more efficient when operating in the 30-80% range).

So pay close attention to those datasheets when choosing your heat pump size, and maybe allow an additional 20% for good measure. In hindsight, our installers were probably correct to insist on the 12kW model and not go with my requests for the 8kW model (albeit I think their 7.4kW heat loss figure is on the high side, and we don't keep the house at the 21C design temp)

michaels

On the flip side the 12kw will be much too powerful for the majority of the time when temps are 5c and higher and is unlikely to be able to modulate to a point where it isn't cycling on and off which is less efficient....