Radiator Fans rather than upgraded Radiators with ASHP

Exiled_Tyke

FreeBear said:

matelodave said: You could measure the flow temps of the rad (in and out) using a differential thermometer to find the DeltaT across the rad either without the fan and then with the fan to see by how much the Dt changes.

Throw in a flow sensor (on the return side is usually best), and coupled with an Arduino or ESP, you could calculate how much energy is being dissipated.

shinytop said:I can confirm this is true; we have a fancoil radiator in the kitchen (think car radiator with a fancy cover) that gives off next no heat unless the fan is switched on, when it emits a nice stream of warm air that warms the kitchen.  And of course a car radiator has a fan for the same reason, to increase the amount of heat dissipated for the same water flow. 

Got a plinth heater in my kitchen. Depending on water temperature, it will kick out 2kW at low speed, and 2.4kW at high(flow temp of 75°C). But as my flow temperatures are between 40°C and 60°C, actual output is more like 1-1.5kW..

Now that's interesting.  octopus disconnected my plinth heater claiming not only would it not be effective but would interfere with the rest of the system.  I can accept it only kicking in on the coldest days when the ASHP is programmed to use hotter water but can you please confirm that it is ok to have it connected even though it won't work most of the time and when it does it won't be doing a great deal? 

matelodave

There's no reason a plinth heater would not work with a heatpump, its the same as a fan-coil radiator. Depending on how its controlled, adjustable thermostat or fixed temperature switch then it's not difficult to make the fan run when there is warm/hot water in the system.

An adjustable thermostat should cause the fan to run when the room temp drops below its set point but some plinth heaters or fancoils also have a thermostatic switch which inhibits the fan if the hot water is below a certain temperature - its not difficult to change it to one with a lower switching temp if you are running a low temperature system.

FreeBear

Exiled_Tyke said:

shinytop said:I can confirm this is true; we have a fancoil radiator in the kitchen (think car radiator with a fancy cover) that gives off next no heat unless the fan is switched on, when it emits a nice stream of warm air that warms the kitchen.  And of course a car radiator has a fan for the same reason, to increase the amount of heat dissipated for the same water flow. 

Got a plinth heater in my kitchen. Depending on water temperature, it will kick out 2kW at low speed, and 2.4kW at high(flow temp of 75°C). But as my flow temperatures are between 40°C and 60°C, actual output is more like 1-1.5kW..

Now that's interesting.  octopus disconnected my plinth heater claiming not only would it not be effective but would interfere with the rest of the system.  I can accept it only kicking in on the coldest days when the ASHP is programmed to use hotter water but can you please confirm that it is ok to have it connected even though it won't work most of the time and when it does it won't be doing a great deal? 

Make and model of your plinth heater ?

When I fitted my new one (a Thermix KPH-2400), needed a lockshield on one side to allow for the system to be balanced - Most installation instructions say a lockshield is not needed... Once the flow had been adjusted to give a 5°C drop,  it performed adequately. BUT... There is a thermal switch inside to switch the fan on once hot water starts to flow. Some may not switch on until the water gets to 45°C, others might turn on at 35°C - Fortunately, not too difficult to replace as long as you use a Normally Open type. I bypassed mine with a smart switch so the fan runs only when the boiler is heating.

As long as you can adjust the flow and the thermal switch operates at a low enough temperature, I see no reason why a plinth heater could not work with a heat pump.

Side note - Thermix do a couple of heat pump specific plinth heaters. But looking at the specs, the 1.5kW model appears to be the standard KPH-2400 version with a lower temp thermal switch and added WiFi control, adding an extra £105 to the price.

30°C thermal switch - £3.85 (+P&P) -> https://cpc.farnell.com/microtherm/03en35t044-20-30/thermal-switch-n-o-30c/dp/SN35838

Smart switch - Sonoff Mini (from £5) or Shelly Mini (from £12). Other smart switches available.

michaels

FreeBear said:

Exiled_Tyke said:

shinytop said:I can confirm this is true; we have a fancoil radiator in the kitchen (think car radiator with a fancy cover) that gives off next no heat unless the fan is switched on, when it emits a nice stream of warm air that warms the kitchen.  And of course a car radiator has a fan for the same reason, to increase the amount of heat dissipated for the same water flow. 

Got a plinth heater in my kitchen. Depending on water temperature, it will kick out 2kW at low speed, and 2.4kW at high(flow temp of 75°C). But as my flow temperatures are between 40°C and 60°C, actual output is more like 1-1.5kW..

Now that's interesting.  octopus disconnected my plinth heater claiming not only would it not be effective but would interfere with the rest of the system.  I can accept it only kicking in on the coldest days when the ASHP is programmed to use hotter water but can you please confirm that it is ok to have it connected even though it won't work most of the time and when it does it won't be doing a great deal? 

Make and model of your plinth heater ?

When I fitted my new one (a Thermix KPH-2400), needed a lockshield on one side to allow for the system to be balanced - Most installation instructions say a lockshield is not needed... Once the flow had been adjusted to give a 5°C drop,  it performed adequately. BUT... There is a thermal switch inside to switch the fan on once hot water starts to flow. Some may not switch on until the water gets to 45°C, others might turn on at 35°C - Fortunately, not too difficult to replace as long as you use a Normally Open type. I bypassed mine with a smart switch so the fan runs only when the boiler is heating.

As long as you can adjust the flow and the thermal switch operates at a low enough temperature, I see no reason why a plinth heater could not work with a heat pump.

Side note - Thermix do a couple of heat pump specific plinth heaters. But looking at the specs, the 1.5kW model appears to be the standard KPH-2400 version with a lower temp thermal switch and added WiFi control, adding an extra £105 to the price.

30°C thermal switch - £3.85 (+P&P) -> https://cpc.farnell.com/microtherm/03en35t044-20-30/thermal-switch-n-o-30c/dp/SN35838

Smart switch - Sonoff Mini (from £5) or Shelly Mini (from £12). Other smart switches available.

And that level of price differential (mark up) between a do it yourself solution and a supplier add on part surprises you?

Exiled_Tyke

FreeBear said:

Exiled_Tyke said:

shinytop said:I can confirm this is true; we have a fancoil radiator in the kitchen (think car radiator with a fancy cover) that gives off next no heat unless the fan is switched on, when it emits a nice stream of warm air that warms the kitchen.  And of course a car radiator has a fan for the same reason, to increase the amount of heat dissipated for the same water flow. 

Got a plinth heater in my kitchen. Depending on water temperature, it will kick out 2kW at low speed, and 2.4kW at high(flow temp of 75°C). But as my flow temperatures are between 40°C and 60°C, actual output is more like 1-1.5kW..

Now that's interesting.  octopus disconnected my plinth heater claiming not only would it not be effective but would interfere with the rest of the system.  I can accept it only kicking in on the coldest days when the ASHP is programmed to use hotter water but can you please confirm that it is ok to have it connected even though it won't work most of the time and when it does it won't be doing a great deal? 

Make and model of your plinth heater ?

When I fitted my new one (a Thermix KPH-2400), needed a lockshield on one side to allow for the system to be balanced - Most installation instructions say a lockshield is not needed... Once the flow had been adjusted to give a 5°C drop,  it performed adequately. BUT... There is a thermal switch inside to switch the fan on once hot water starts to flow. Some may not switch on until the water gets to 45°C, others might turn on at 35°C - Fortunately, not too difficult to replace as long as you use a Normally Open type. I bypassed mine with a smart switch so the fan runs only when the boiler is heating.

As long as you can adjust the flow and the thermal switch operates at a low enough temperature, I see no reason why a plinth heater could not work with a heat pump.

Side note - Thermix do a couple of heat pump specific plinth heaters. But looking at the specs, the 1.5kW model appears to be the standard KPH-2400 version with a lower temp thermal switch and added WiFi control, adding an extra £105 to the price.

30°C thermal switch - £3.85 (+P&P) -> https://cpc.farnell.com/microtherm/03en35t044-20-30/thermal-switch-n-o-30c/dp/SN35838

Smart switch - Sonoff Mini (from £5) or Shelly Mini (from £12). Other smart switches available.

Wow.  thanks very much.  I fear the alterations are probably beyond me.  I have a KPH-1800 Classic. This suggests that running from the heat pump could in theory give me an equivalent of about 1kW which would be just fine.  I don't want to create work for you, so is there somewhere I can learn to make these changes?  

On the other hand I've now read that the specs on this suggest it will cut in at 38 degrees which I can live with as it would only then come on, on the coldest days.  Am I ok to simply have it plumbed back in? 

Many thanks. 

FreeBear

michaels said:

FreeBear said:

Side note - Thermix do a couple of heat pump specific plinth heaters. But looking at the specs, the 1.5kW model appears to be the standard KPH-2400 version with a lower temp thermal switch and added WiFi control, adding an extra £105 to the price.

30°C thermal switch - £3.85 (+P&P) -> https://cpc.farnell.com/microtherm/03en35t044-20-30/thermal-switch-n-o-30c/dp/SN35838

Smart switch - Sonoff Mini (from £5) or Shelly Mini (from £12). Other smart switches available.

And that level of price differential (mark up) between a do it yourself solution and a supplier add on part surprises you?

Or a £35+ uplift between standard WiFi model and the heat pump version - The only difference being a thermal switch operating at a lower temperature.

Exiled_Tyke said:  I fear the alterations are probably beyond me.  I have a KPH-1800 Classic. This suggests that running from the heat pump could in theory give me an equivalent of about 1kW which would be just fine.  I don't want to create work for you, so is there somewhere I can learn to make these changes?  

On the other hand I've now read that the specs on this suggest it will cut in at 38 degrees which I can live with as it would only then come on, on the coldest days.  Am I ok to simply have it plumbed back in?

The thermal switch is just held in place by a cable tie (if I remember correctly) and uses standard 1/4" spade terminals. If you can wield a screwdriver, very easy to change - I found several suppliers on ebay (mostly Chinese) advertising N.O. thermal switches rated from 20°C and up for around £2.

If you are happy with the fan kicking in at around 40°C, that little bit of extra heat in the kitchen would help to keep the space warm. You'll probably want a lockshield and might need an adaptor or two so that the flow can be limited to a ~5°C temperature drop. Also make sure the flow is at the top or you might find the fan kicks in erratically.

At a flow temperature of 45°C, output will be about 513W on low, or 625W on high. To get 1kW out of the KPH-1800, you'd close to 55°C flow.

Exiled_Tyke

FreeBear said:

michaels said:

FreeBear said:

Side note - Thermix do a couple of heat pump specific plinth heaters. But looking at the specs, the 1.5kW model appears to be the standard KPH-2400 version with a lower temp thermal switch and added WiFi control, adding an extra £105 to the price.

30°C thermal switch - £3.85 (+P&P) -> https://cpc.farnell.com/microtherm/03en35t044-20-30/thermal-switch-n-o-30c/dp/SN35838

Smart switch - Sonoff Mini (from £5) or Shelly Mini (from £12). Other smart switches available.

And that level of price differential (mark up) between a do it yourself solution and a supplier add on part surprises you?

Or a £35+ uplift between standard WiFi model and the heat pump version - The only difference being a thermal switch operating at a lower temperature.

Exiled_Tyke said:  I fear the alterations are probably beyond me.  I have a KPH-1800 Classic. This suggests that running from the heat pump could in theory give me an equivalent of about 1kW which would be just fine.  I don't want to create work for you, so is there somewhere I can learn to make these changes?  

On the other hand I've now read that the specs on this suggest it will cut in at 38 degrees which I can live with as it would only then come on, on the coldest days.  Am I ok to simply have it plumbed back in?

The thermal switch is just held in place by a cable tie (if I remember correctly) and uses standard 1/4" spade terminals. If you can wield a screwdriver, very easy to change - I found several suppliers on ebay (mostly Chinese) advertising N.O. thermal switches rated from 20°C and up for around £2.

If you are happy with the fan kicking in at around 40°C, that little bit of extra heat in the kitchen would help to keep the space warm. You'll probably want a lockshield and might need an adaptor or two so that the flow can be limited to a ~5°C temperature drop. Also make sure the flow is at the top or you might find the fan kicks in erratically.

At a flow temperature of 45°C, output will be about 513W on low, or 625W on high. To get 1kW out of the KPH-1800, you'd close to 55°C flow.

fantastic . thanks again.  Farnells are down the road from me so I'll try to pop in when they have stock of the switches.  I found the stats for heat output too this afternoon so those aren't a surprise .  We've had an extra radiator fitted with the ASHP and so just a little bit extra het at the other end of the room will be fine.    

benson1980

FreeBear said:

Exiled_Tyke said:

shinytop said:I can confirm this is true; we have a fancoil radiator in the kitchen (think car radiator with a fancy cover) that gives off next no heat unless the fan is switched on, when it emits a nice stream of warm air that warms the kitchen.  And of course a car radiator has a fan for the same reason, to increase the amount of heat dissipated for the same water flow. 

Got a plinth heater in my kitchen. Depending on water temperature, it will kick out 2kW at low speed, and 2.4kW at high(flow temp of 75°C). But as my flow temperatures are between 40°C and 60°C, actual output is more like 1-1.5kW..

Now that's interesting.  octopus disconnected my plinth heater claiming not only would it not be effective but would interfere with the rest of the system.  I can accept it only kicking in on the coldest days when the ASHP is programmed to use hotter water but can you please confirm that it is ok to have it connected even though it won't work most of the time and when it does it won't be doing a great deal? 

Make and model of your plinth heater ?

When I fitted my new one (a Thermix KPH-2400), needed a lockshield on one side to allow for the system to be balanced - Most installation instructions say a lockshield is not needed... Once the flow had been adjusted to give a 5°C drop,  it performed adequately. BUT... There is a thermal switch inside to switch the fan on once hot water starts to flow. Some may not switch on until the water gets to 45°C, others might turn on at 35°C - Fortunately, not too difficult to replace as long as you use a Normally Open type. I bypassed mine with a smart switch so the fan runs only when the boiler is heating.

As long as you can adjust the flow and the thermal switch operates at a low enough temperature, I see no reason why a plinth heater could not work with a heat pump.

Side note - Thermix do a couple of heat pump specific plinth heaters. But looking at the specs, the 1.5kW model appears to be the standard KPH-2400 version with a lower temp thermal switch and added WiFi control, adding an extra £105 to the price.

30°C thermal switch - £3.85 (+P&P) -> https://cpc.farnell.com/microtherm/03en35t044-20-30/thermal-switch-n-o-30c/dp/SN35838

Smart switch - Sonoff Mini (from £5) or Shelly Mini (from £12). Other smart switches available.

I was looking at the heat pump model for our kitchen renovation to replace a radiator (it's right where I want to put some tall units) but then I'd pretty much written it off as I thought it might feel a bit drafty with the fans at the lower flow temps (our min flow temp is set at 35). I did ask Thermix directly and they said that it might indeed feel drafty so place it where no-one is going to stand for prolonged periods. I was tempted on this basis just to relocate the radiator to another wall. I'd be interested for your take on that when yours drops down to 40?

matelodave

Not being an expert on hot-water plinth heaters (although I've rebuilt several hot water Myson Fan convectors which I suggest are pretty similar) you dont really need a fan that runs like a gas turbine but one with a fan that keeps the air moving.

I would think that a plinth heater running at around 30=35 degrees with a gentle speed fan would circulate air rather than that generating a hurricane across your toes.

A lot depends on whether you are hoping to get the kitchen up to temperature in a short time or just keep it warm all of the time as that would determine the instantaneous heat output and thus the size of the heat exchanger and fan speed.

We have underfloor heating that runs at about 30 degrees and it keeps the place cozy as it's on most of the time but if we let the place get really cold it can take 24-36 hours to reheat unless I increase the flow temp significantly.

FreeBear

benson1980 said:

FreeBear said:

Exiled_Tyke said:

shinytop said:I can confirm this is true; we have a fancoil radiator in the kitchen (think car radiator with a fancy cover) that gives off next no heat unless the fan is switched on, when it emits a nice stream of warm air that warms the kitchen.  And of course a car radiator has a fan for the same reason, to increase the amount of heat dissipated for the same water flow. 

Got a plinth heater in my kitchen. Depending on water temperature, it will kick out 2kW at low speed, and 2.4kW at high(flow temp of 75°C). But as my flow temperatures are between 40°C and 60°C, actual output is more like 1-1.5kW..

Now that's interesting.  octopus disconnected my plinth heater claiming not only would it not be effective but would interfere with the rest of the system.  I can accept it only kicking in on the coldest days when the ASHP is programmed to use hotter water but can you please confirm that it is ok to have it connected even though it won't work most of the time and when it does it won't be doing a great deal? 

Make and model of your plinth heater ?

When I fitted my new one (a Thermix KPH-2400), needed a lockshield on one side to allow for the system to be balanced - Most installation instructions say a lockshield is not needed... Once the flow had been adjusted to give a 5°C drop,  it performed adequately. BUT... There is a thermal switch inside to switch the fan on once hot water starts to flow. Some may not switch on until the water gets to 45°C, others might turn on at 35°C - Fortunately, not too difficult to replace as long as you use a Normally Open type. I bypassed mine with a smart switch so the fan runs only when the boiler is heating.

As long as you can adjust the flow and the thermal switch operates at a low enough temperature, I see no reason why a plinth heater could not work with a heat pump.

Side note - Thermix do a couple of heat pump specific plinth heaters. But looking at the specs, the 1.5kW model appears to be the standard KPH-2400 version with a lower temp thermal switch and added WiFi control, adding an extra £105 to the price.

30°C thermal switch - £3.85 (+P&P) -> https://cpc.farnell.com/microtherm/03en35t044-20-30/thermal-switch-n-o-30c/dp/SN35838

Smart switch - Sonoff Mini (from £5) or Shelly Mini (from £12). Other smart switches available.

I was looking at the heat pump model for our kitchen renovation to replace a radiator (it's right where I want to put some tall units) but then I'd pretty much written it off as I thought it might feel a bit drafty with the fans at the lower flow temps (our min flow temp is set at 35). I did ask Thermix directly and they said that it might indeed feel drafty so place it where no-one is going to stand for prolonged periods. I was tempted on this basis just to relocate the radiator to another wall. I'd be interested for your take on that when yours drops down to 40?

I run my plinth heater on the low setting pretty much all the time. When running, I don't notice any draughts. Even at low flow temperatures, it is just a gentle warm(ish) breeze.

Quite happy with the heat output once I realised output increased as ΔT decreased with ~5°C being the sweet spot. Thermix makes no mention of flow rates or ΔT in their installation documents...

If you don't want or need the WiFi stuff that comes with the heat pump version, just get the basic KPH-2400 and fit a lower rated thermal switch. For the sake of £2-4 and five minutes with a screwdriver, you save yourself £85.