UFH Upgrade

[Mr Binks]

I have a 4 zone UFH system fired by a Trianco 6KW electric boiler. I’ve always thought it would be nice to add weather compensation by varying the boiler flow temperature, but the Trianco does not have a way to break in to the flow temperature control circuit, and I didn’t fancy getting in there with a soldering iron. I’ve discovered on here the existence of the Willis heater which to me seems like it may be the way forward.

I’ve seen some people have used SSRs to control them, but what about thyristor control? Then you could add weather compensation…thoughts anyone?

[ProDave]

Weather compensation on a resistance heating boiler is not going to make any differnce.

 

As it is only a 6kW boiler and it presumably has enough output to heat the house, I would be looking at replacing that with a similar sized air source heat pump.  That will roughly cut your heating bill to 1/3 and in principle should be an easy swap.  Then with an ASHP weather compensation might make sense which most of them offer as standard.

[Mr Binks]

44 minutes ago, ProDave said:

Weather compensation on a resistance heating boiler is not going to make any differnce.

 

As it is only a 6kW boiler and it presumably has enough output to heat the house, I would be looking at replacing that with a similar sized air source heat pump.  That will roughly cut your heating bill to 1/3 and in principle should be an easy swap.  Then with an ASHP weather compensation might make sense which most of them offer as standard.

So far I’ve been quoted £8-13K for an ASHP system, but the more I learn about how they work, protect themselves with auxiliary heaters, yearly maintenance costs and eventual replacement if it breaks down, the savings on running costs starts to diminish, especially as I have a small well insulated home. With the Trianco I’ve been adjusting the flow temperature manually using the blending valve according to the weather forecast, this works but relies on me remembering to adjust it hence the desire to introduce weather compensation 

[JohnMo]

1 hour ago, Mr Binks said:

Willis heater which to me seems like it may be the way forward.

Basically an immersion, which is a fixed output similar to your existing heater.  So not seeing any advantage.

[Mr Binks]

23 minutes ago, JohnMo said:

Basically an immersion, which is a fixed output similar to your existing heater.  So not seeing any advantage.

Thyristor control would turn the Willis in to a variable output heater and allow modulation, which you need for weather compensation

[ProDave]

1 hour ago, Mr Binks said:

So far I’ve been quoted £8-13K for an ASHP system, but the more I learn about how they work, protect themselves with auxiliary heaters, yearly maintenance costs and eventual replacement if it breaks down, the savings on running costs starts to diminish, especially as I have a small well insulated home. With the Trianco I’ve been adjusting the flow temperature manually using the blending valve according to the weather forecast, this works but relies on me remembering to adjust it hence the desire to introduce weather compensation 

Try approaching plumbers and electricians not "heat pump specialists"  you will comfortably buy a heat pump for £4K so say £6K installed. I am in the Highlands. You don't get much colder winters in the UK than here and mine just works.  Maintenance is a check over that you can do yourself and they only actually need "work" if they break down.

 

What is your actual problem?  You have to keep adjusting the temperature so is the problem the house overheats?  i.e. lack of basic controls like room thermostats?  Turning down the boiler temperature won't make it more efficient with a resistance heater like it will with an ASHP.

[Mr Binks]

OK I have a 100mm UFH slab that heats up a couple of times a day on off peak electricity. By the time the heat comes through in to the room it’s too late to regulate with a room stat so yes - overheating occurs in milder conditions if the flow temperature is not turned down. I’m just looking for a way to automatically match the heat input to the UFH to the heat loss of the house. I’ve already proved the theory manually as mentioned. I am aware that this type of control won’t make the element more efficient, but it will save energy.

 

Heat pumps I’ve looked at require a check by an approved installer to comply with the warranty, down in the south that’s £100+

 

Which model of heat pump do you have btw?

[ProDave]

The alternative as at least one regular member does with a willis heater, is calculate the required heat input based on weather forecast, and adjust the turn on time to give the required amount of heat (turn off time remains when the off peak rate finishes) 

[SteamyTea]

12 hours ago, ProDave said:

What is your actual problem?

 

11 hours ago, Mr Binks said:

OK I have a 100mm UFH slab that heats up a couple of times a day on off peak electricity. By the time the heat comes through in to the room it’s too late to regulate with a room stat so yes - overheating occurs in milder conditions

How much insulation is under the slab?

As a R or U value would be useful.

[Mr Binks]

It’s about 170mm of PIR board so it holds the heat will

[SteamyTea]

2 hours ago, Mr Binks said:

It’s about 170mm of PIR board so it holds the heat will

Well that should limit disproportionate heat losses.

 

What you could do, is fit a secondary timer and let it run full power until the last hour, then pulse the input, say 12 minutes on, 6 minutes off. See if that helps the overshooting.

Can always play about with those timings.

[JohnMo]

What I did when I experimented with batch charging the floor.

 

I knew the temp would overshoot if I switched off the heating at the ideal room temp.  So set a a lower switch off temp of 18.5 and a 3 hour window.  As soon as the thermostat got to 18.5 deg, it switched off and over the next couple of hours the temp rose to about 19.5.  The heating would run from about 0.30am until about 7 to 9am depending on the heat losses.  It worked ok, but did change to WC this year, which is better.

[SteamyTea]

21 minutes ago, JohnMo said:

I knew the temp would overshoot if I switched off the heating at the ideal room temp

I shifted my heating window by an hour yesterday. It had usually finished heating up the storage heaters by 6 AM.

Noticed this morning that the room was a little cooler than normal, but so was the external air temperature.

May try shifting the time by 20 minutes.

[Mr Binks]

On 05/02/2023 at 20:44, ProDave said:

The alternative as at least one regular member does with a willis heater, is calculate the required heat input based on weather forecast, and adjust the turn on time to give the required amount of heat (turn off time remains when the off peak rate finishes) 

 

[Mr Binks]

Yes this is in effect what I’m doing now by changing the flow temperate. Weather compensation would automatically adjust the flow temperature. What I need is a way to modulate the flow temperature, ideally at source (the boiler) but failing that, a blending valve with an external adjustment would do the same job

[Mr Binks]

On 06/02/2023 at 11:46, SteamyTea said:

Well that should limit disproportionate heat losses.

 

What you could do, is fit a secondary timer and let it run full power until the last hour, then pulse the input, say 12 minutes on, 6 minutes off. See if that helps the overshooting.

Can always play about with those timings.

I’ve going to give that ago as it will be easier to get at to adjust than the the blending valve, and once I’ve proved it works I can look to automate it. Thanks for the idea 😀

[SteamyTea]

1 minute ago, Mr Binks said:

I’ve going to give that ago as it will be easier to get at to adjust than the the blending valve, and once I’ve proved it works I can look to automate it. Thanks for the idea 😀

Let us know if it works, and is a practical solution.

[Mr Binks]

Here’s what I’m getting https://www.amazon.co.uk/gp/product/B07R5S3Q2Z?ref=ppx_pt2_tab_b_prod_image I’ll update the post in due course one way or another