Honeywell tanks stat calibration

[knighty]

They do look good, but the price is a bit low. It says the sensor is NTC which I think implies that the device is a thermistor, so that's good. Downrating the 10amp spec might well be good idea. Tempted to buy one just have on the shelf. I see that the voltage rating is 110-220V. I'm usually up around 246V here.

With all cheap stuff from the far east, there is little quality control, so one item comes down the product line and is perfectly good but the next one following it could be perfectly rubbish - a bit of a lucky dip sometimes. the cheapo battery charger I bought last summer lasted 3 months and then boiled a battery when it failed to shut off .

I thought the same... but I've got a whole bunch of them running, had them running ages and so far so good

 

[daleyd]

you can get strap on temperature gauges that go on pipes easy enough and cheap bruv has one on his rayburn cooker https://www.ebay.co.uk/itm/20354528...=5338365712&toolid=20006&customid=EB88319644&

Just got to be careful with the google search for those …

 

[brightspark]

Just got to be careful with the google search for those …

like snapon

 

[Gareth J]

My understanding is that the stat on the Rayburn is more of an underheat stat? I.e. it should cut the power to the CH pump if the temps fall below 50C? Not sure if it can be wired in an alternative way though?

What we have done is put a stat on the tank just under the CH flow pipe and set that at 55C, when the stat reaches 55, it triggers the CH pump. So this is independent of the boiler central heating controls to an extent - realistically the Rayburn is never going to get the house too hot (its 50,000 BTU at full chat and the boiler for the house is specced at double that). So this way, heat from the Rayburn is always circulated and keeps the house a nice ambient temp (around 19C it seems from having had it on about a month now). This way the tank will never overheat as the heat is dumped when the lower third of the tank reaches 55C.

The boiler is controlled by the timer/room/tank stat more conventionally except that the CH circulation is still as above - so the CH will circulate when the stat controlling that pump reaches 55C. If the room stat isnt satisfied, the boiler will keep firing and the CH will keep circulating. We have hardly had the boiler on since the Rayburn was lit a month ago (maybe for about four hours in total)

Hopefully that makes sense.

In a power cut we would need to reign the Rayburn back, switch it so the heat goes to the oven and kitchen and less to the boiler and then have a bath if things get too hot . We contemplated a leak rad on the system and can add one later if needed but decided not to and to get the heat into the store and around the house instead. Its not much of a risk when we are out as its always left topped up and damped down on tickover as no point having it racing if we are out so nothing will get too hot then. Eventually i want a generator setup to run the boiler and pumps in a powercut. I know where the supply for the lot is so this would be fairly easy to rig up.

All makes sense, yes. Except, what happens if room stat is satisfied and Rayburn is on? Likely not an issue now it's so cold but is there a way the store can loose heat if the house is hot enough, or even if the stat got accidentally altered?

The Rayburn's thermostat as you describe it there is acting more like a loading valve (ladomatt or similar) to reduce overcooling the boiler. If it's effective as you have it no point altering. Particularly as, while a proper loading valve will let the Rayburn get up to speed quicker and promote good stratification in the store, I don't know if they'll work via gravity?

I agree that your risks of boiling the store aren't too high as your Rayburn is batch loaded. I had considered plumbing my oil fired Rayburn into the thermal store but decided against it. One of the concerns was and extended power cut. Took the boiler out of the Rayburn instead. Happy with the decision.

 

[reb78]

The CH pump is largely independent of the room stat. So that simply operates on the store temp. So if the room stat is satisfied, the CH pump will still circulate. The oil boiler wont fire though. I know keeping that pump seperate to the room stat seems a bit odd but realistically the rayburn is never going to overheat the house.

The oil boiler has its own pump on the flow to the tank - thats triggered when the boiler is called to come on.

We have plumbed the rayburn so it works almost fully on gravity. I say almost as there is a third pump set to come on and push the rayburn flow into the bottom of the store IF the top of the store is getting too hot - currently set to 65C but we had planned to have it at 80C but we havent run the rayburn flat out and havent hit those temps at the top yet.

The way out plumber has designed this makes perfect sense to me and I think stops anything overheating and makes beat use of the store. My only niggle currently is having a bath in the big bath. The store needs an oil heat top up for that just to boost the heat. We didnt go for a bigger store as we werent sure of putting more weight in and we dont use the bath all that often. I think this just needs fiddling to get the temps set right though.

But you can see why we need all these stats to work!

 

[reb78]

I thought the same... but I've got a whole bunch of them running, had them running ages and so far so good

They look worth a shot. I will get three. Thanks for pointing them out.

 

[Gareth J]

The CH pump is largely independent of the room stat. So that simply operates on the store temp. So if the room stat is satisfied, the CH pump will still circulate. The oil boiler wont fire though. I know keeping that pump seperate to the room stat seems a bit odd but realistically the rayburn is never going to overheat the house.

The oil boiler has its own pump on the flow to the tank - thats triggered when the boiler is called to come on.

We have plumbed the rayburn so it works almost fully on gravity. I say almost as there is a third pump set to come on and push the rayburn flow into the bottom of the store IF the top of the store is getting too hot - currently set to 65C but we had planned to have it at 80C but we havent run the rayburn flat out and havent hit those temps at the top yet.

The way out plumber has designed this makes perfect sense to me and I think stops anything overheating and makes beat use of the store. My only niggle currently is having a bath in the big bath. The store needs an oil heat top up for that just to boost the heat. We didnt go for a bigger store as we werent sure of putting more weight in and we dont use the bath all that often. I think this just needs fiddling to get the temps set right though.

But you can see why we need all these stats to work!

Don't I know it. I designed our TS/heating system, and, compared to a normal heating system is very complicated and very bespoke. Even with all that, it's not management free either. But it has reduced our bought in fuel consumption a lot.

As far as I understand, your setup sounds great.

A couple things to consider with the boiler, an overrun relay on its pump can help squeeze a few more kwhs from the boiler into the TS. Not such an issue now but if used to heat DHW in summer, might be worth it. Can be done with a timer, or a stat on the water jacket of the boiler that keeps the pump running until the hot water is flushed out of it. And a blending valve, if you get situations where you're asking the boiler to heat the TS up from scratch, return temperatures to boiler can be too low for too long (as specced in boiler manual). Both are marginal gains really and neither are relevant if the boiler isn't working on the TS fluid but is running via a coil.

 

[reb78]

Don't I know it. I designed our TS/heating system, and, compared to a normal heating system is very complicated and very bespoke. Even with all that, it's not management free either. But it has reduced our bought in fuel consumption a lot.

As far as I understand, your setup sounds great.

A couple things to consider with the boiler, an overrun relay on its pump can help squeeze a few more kwhs from the boiler into the TS. Not such an issue now but if used to heat DHW in summer, might be worth it. Can be done with a timer, or a stat on the water jacket of the boiler that keeps the pump running until the hot water is flushed out of it. And a blending valve, if you get situations where you're asking the boiler to heat the TS up from scratch, return temperatures to boiler can be too low for too long (as specced in boiler manual). Both are marginal gains really and neither are relevant if the boiler isn't working on the TS fluid but is running via a coil.

Very good suggestions, thanks. The oil boiler is working directly on the TS, not via a coil (as is the rayburn and in the future, potentially a log burner back boiler). I have noticed how long the pump can pull heat from the boiler flow after the boiler has stopped firing but is waiting to cool to fire up again.

 

[DickyDoDah]

I've used one of these as I needed a high hysteresis stat and this allows you to set what you want. Only downside is its not a no volt contact but a small modification changed that for me as I'm just experimenting.

XH-W3002/XH-W3001 Digital LED Temperature Controller Thermostat Control Switch | eBay

Reverse connection protection. automatic mode. Press the up button once, the startup temperature will be displayed, long press the up button for about 3 seconds, the startup temperature number will flash, and the desired temperature value can be set by the up and down buttons.

www.ebay.co.uk

 

[Gareth J]

Very good suggestions, thanks. The oil boiler is working directly on the TS, not via a coil (as is the rayburn and in the future, potentially a log burner back boiler). I have noticed how long the pump can pull heat from the boiler flow after the boiler has stopped firing but is waiting to cool to fire up again.

Hmm, you mean that, sometimes, when the boiler is going, it fires up for a bit, then reaches its internal temperature target, but its pump carries on running until the circulated temp drops a bit, when it goes again? Think that's short cycling and with a TS, should be avoidable. Again, marginal gains, but it is, as I understand it, more efficient to do longer burns, than lots of on/off cycling.

If it's doing it, suggests the return temperature to the boiler is too high, or circulation pump too slow, or boiler target temperature too low (or some combination). Or maybe the flow temperature to your rads is too high, or flowrate too fast, so the water coming back to the bottom of the store is too warm. Everything is interconnected!

If your rads are returning too hot a water, you could get a blending valve put in to allow some control over their flow (and therefore return) temperature to aid maintaining stratification of the tank and keeping the bottom cool. Hope that makes sense!

 

[reb78]

Hmm, you mean that, sometimes, when the boiler is going, it fires up for a bit, then reaches its internal temperature target, but its pump carries on running until the circulated temp drops a bit, when it goes again? Think that's short cycling and with a TS, should be avoidable. Again, marginal gains, but it is, as I understand it, more efficient to do longer burns, than lots of on/off cycling.

If it's doing it, suggests the return temperature to the boiler is too high, or circulation pump too slow, or boiler target temperature too low (or some combination). Or maybe the flow temperature to your rads is too high, or flowrate too fast, so the water coming back to the bottom of the store is too warm. Everything is interconnected!

If your rads are returning too hot a water, you could get a blending valve put in to allow some control over their flow (and therefore return) temperature to aid maintaining stratification of the tank and keeping the bottom cool. Hope that makes sense!

Interesting. I wouldnt say its doing it loads/frequently but it will turn off for a time after a burn - i guess as one of the stats stops it burning and the pump will still pull heat through.

The boiler return is fairly cool to the touch. Flow is too hot to touch. CH return is cool too so I think that bits working properly.

The boiler does two houses but I dont think that affects things too much but it does mean we have 28mm pipes in that tee off into 22s to go to each house (our house now has the store and Rayburn and the annexe is just conventional). We have to fix two rads that are not heating and fit an additional relay on the pump in the other house after christmas and will also flush the system then so I will chat to the plumber about the boiler then and see what we can do.

All good advice though. Thanks.

 

[Gareth J]

Interesting. I wouldnt say its doing it loads/frequently but it will turn off for a time after a burn - i guess as one of the stats stops it burning and the pump will still pull heat through.

The boiler return is fairly cool to the touch. Flow is too hot to touch. CH return is cool too so I think that bits working properly.

The boiler does two houses but I dont think that affects things too much but it does mean we have 28mm pipes in that tee off into 22s to go to each house (our house now has the store and Rayburn and the annexe is just conventional). We have to fix two rads that are not heating and fit an additional relay on the pump in the other house after christmas and will also flush the system then so I will chat to the plumber about the boiler then and see what we can do.

All good advice though. Thanks.

If the boiler circulation pump continues to run but the boiler doesn't fire, it should be because the boiler water jacket has reached the maximum temperature allowed, controlled by the adjustable temperature knob on the boiler (usually). May be that it only happens when the annex is being heated alone. You could try turning the boiler temp knob up/down when it happens to test. But turning it up hotter, while it might stop short cycling, is probably not a good solution as the cooler you can get away with the boiler (within spec), the more efficient it'll run.

 

[Gareth J]

Our TS was feeding the boiler too cold a water to start with often ~30C. This is not only an issue for the boiler, which, according to the manual would like to see a 45C return, but also for the flow temp and charging the store - instead of a nice stratification hot at the top and cool at the bottom, it mixed it all up and heated the whole, gradually. So we put a mixing valve on the boiler return, set to recirculate water around the boiler, until it reaches 45C. Once it does, with the pump set to achieve a ∆T of ~20C, that achieves a consistent flow of ~65C, which is useful for DHW.

This might not be an issue for you at all, but might rear it's head in summer, when trying to only heat the top portion - for DHW.

 

[reb78]

So the boiler is set to 75C and tank stat (the one on the TS connected to the controls in our house) to 65C. I am not sure altering the bouler stat would help here? Dont want it any hotter but I guess it should be above the tank stat?

 

[Gareth J]

So the boiler is set to 75C and tank stat (the one on the TS connected to the controls in our house) to 65C. I am not sure altering the bouler stat would help here? Dont want it any hotter but I guess it should be above the tank stat?

75 will probably be at, or near the boiler's max anyway? I agree, no point in going hotter. Yes, the "call" for the boiler stat needs to be lower. Otherwise the boiler will keep circulating water needlessly.

If your boiler is set to 75, AND you're occasionally getting times where the boiler water jacket temp is causing the boiler to stop firing but continue circulating, when that happens, is the return to the boiler very hot? ∆T through the boiler should be about 20C so, that would mean the return temp to boiler would be approaching 55C for it to cut out. If it's not ~55C, maybe the boiler circulation pump flowrate can be increased in order to lower the ∆T.

 

[reb78]

Thanks. I think 85 is the hottest on the boiler stat but don't want to go higher as you say.

The boiler return is tepid. I havent measured it but i would say not 55 as i can comfortably touch it and its cooler than the CH flow which is set around 55.

I will see if we can turn the pump up. Its only set to 1 IIRC. The pumps on the boiler flow and close to the TS so the plumber was worried it may push water into the header tank (it doesnt) but that may be why he set it on 1.

 

[Gareth J]

Thanks. I think 85 is the hottest on the boiler stat but don't want to go higher as you say.

The boiler return is tepid. I havent measured it but i would say not 55 as i can comfortably touch it and its cooler than the CH flow which is set around 55.

I will see if we can turn the pump up. Its only set to 1 IIRC. The pumps on the boiler flow and close to the TS so the plumber was worried it may push water into the header tank (it doesnt) but that may be why he set it on 1.

I'm very much a novice when it comes to all this. While I know my own system and boiler, yours may be lots different. Definitely check the recommended boiler return temps and the expected delta T in a manual for your model rather than taking my word for it. Mine's a grant vortex btw