Willis heater not heating! Scaled up?

[oranjeboom]

Right, so following on from my blog entry here where I discuss using Willis heaters to heat up my UFH (https://forum.buildhub.org.uk/blogs/entry/680-temporary-heat-source-for-ufh-willis-heaters/ ) I'd initially tested them earlier in the year when I'd set them up and then only in the past 4wks really started to use them for some evening heat in the house and they did their job pretty well (not turned on all the loops yet as there are some rooms that aren't completed yet (north colder part of house). So only switched them on manually for say 2-3 hours each day.

 

 

 

Yesterday one of the heaters started 'making noises' that he was not happy, so I switched that one off and left the other one to run. Then today the other one also decided it was not happy. Video below, with aforementioned Willis...'making noises'.

 

 

To me it sounds like a kettle that's trying to boil/simmer with not enough water. I'm suspecting it's scaled up already in this short time. There's no heat coming from the outlet pipes at all and the heaters themselves don't feel warm either. I still have pressure (1.5 bar) so I don't think I have a leak anywhere and no water in pipes. The manual bleed valves indicate there's water in the manifold at least. 

 

Any other ideas before I start dismantling the buggers as there's at least 4 compressions I have to bugger about with which were a pain to seal initially? Resident willis heater experts @Nickfromwales, @TerryE ? :-) 

 

TIA!

 

 

 

[Nickfromwales]

Are you running the Willis heaters through a constantly recirculating loop with its own pump? Then the UFH should be Teed into that loop for flow and return to the manifold pump? A bit like a figure of 8 with the two pumps remaining hydraulically separate from each other. If so, the pump speed of the Willis circuit is too low.

Have you turned the 2 Willis heaters down on the internal stats? They should be set to no more than 45oC.

[oranjeboom]

9 minutes ago, Nickfromwales said:

Are you running the Willis heaters through a constantly recirculating loop with its own pump

 

No, I'm using the manifold pump for both heaters:

 

 

Pump appears to work fine with this arrangement on slow speed and had no issues up until now. It's a distance of approx 1.6m between heaters and manifold.

 

16 minutes ago, Nickfromwales said:

They should be set to no more than 45oC.

 

They are both set to about 50oC. The thermometer on mixing valve never went much over 30oC

[Nickfromwales]

10 minutes ago, oranjeboom said:

No, I'm using the manifold pump for both heaters:

You cannot do that. You'll have to alter it to have a pump and a recirculating loop. The heaters are kettling and overheating.

[Nickfromwales]

[Nickfromwales]

Please tell me you have 2 x 20a switches not one 20a switch and the feeds to both heaters doubled up off the one supply? 

[Gav_P]

15 minutes ago, Nickfromwales said:

Please tell me you have 2 x 20a switches not one 20a switch and the feeds to both heaters doubled up off the one supply? 

Looks like 2 in the photo above 

[oranjeboom]

1 hour ago, Nickfromwales said:

Please tell me you have 2 x 20a switches not one 20a switch and the feeds to both heaters doubled up off the one supply? 

2x20a switches back to CU both on separate breakers.

 

1 hour ago, Nickfromwales said:

You cannot do that. You'll have to alter it to have a pump and a recirculating loop. The heaters are kettling and overheating.

 

So why has this setup been okay up until now (well 4wks). Build up of scale on elements restricting water flow and causing it to kettle?

 

Pic of 'naked' setup without all the insulation:

 

[Onoff]

I've got some pucker descaler here, 48% phosphoric acid. You're welcome to a gallon.

[oranjeboom]

20 minutes ago, Onoff said:

I've got some pucker descaler here, 48% phosphoric acid. You're welcome to a gallon.

 

Just pop the bottle in the post please...

 

I;ll try not to store it next to the wife's wine collection.

[Onoff]

1 minute ago, oranjeboom said:

 

Just pop the bottle in the post please...

 

I;ll try not to store it next to the wife's wine collection.

 

Seriously, if you want 5L of it, no problem. The clever people on here will say whether it's OK. Cleans up elements a treat.

[PeterW]

Seal the UFH off, drain the Willis heaters and drop the elements and see what they are like. Also try dropping a thermostat and just check the resistance and make sure it’s tripping in and out. 

[Nickfromwales]

10 minutes ago, PeterW said:

Seal the UFH off, drain the Willis heaters and drop the elements and see what they are like. Also try dropping a thermostat and just check the resistance and make sure it’s tripping in and out. 

These things are brazed shut, sealed units. The only access for viewing is through the pipe entries.

These are just kettling as the water flow rate through them is way too low / slow when the TMV nears the target / set flow temp. Needs a second pump as per my Rolf Harris drawing, and then you'll be fine.

[trialuser]

2 hours ago, Nickfromwales said:

@Nickfromwales, for my sanity, could you indicate on here where the flow and return from the boiler or ashp would join into this please. And also where the ufh loops pump sits. Thanks

[CC45]

when I was a kid we didn't have an automatic pump switch on the coal boiler - when the water boiled in the pipes you'd think the house was about to fall down.  I think Nick is right.  I'm guessing a pump wired into the elec feed to one / both of the Willis heaters would be OK?

[oranjeboom]

1 hour ago, Nickfromwales said:

These are just kettling as the water flow rate through them is way too low / slow when the TMV nears the target / set flow temp.

 

But still don't get why it was fine to start off with. Scaled up in 4-5wks? It's kettling as soon as I switch the unit on so TMV is nowhere near target temp.

 

If I go get a pump locally tomorrow (SF/TS), any flavour I should be getting? I like the green colour on this one: https://www.toolstation.com/wilo-yonos-pico-circulating-pump/p75983 A bit of contrast to the other colours I have in there. but best of all I get some kind of free bag with this one!

 

Current one I have on the manifold is a Grundfos GFTHB (UPS2 25-40/60 130)

[Nickfromwales]

10 hours ago, oranjeboom said:

But still don't get why it was fine to start off with. Scaled up in 4-5wks? It's kettling as soon as I switch the unit on so TMV is nowhere near target temp.

‘Twas a ticking time bomb my friend. 
This was just a crash that hadn’t yet happened, now it’s happened. “Simples” ( insert picture of smug looking rodent here ).

 

The above arrangement does not lend itself to having any additional external heat source of any kind. This is a temporary rig only. 
 

Edited November 13, 2020 by Nickfromwales

[oranjeboom]

Dear Nick, this is the best I could find. Ratlike.

 

 

I've taken one heater out and yes, some scale on that. I'll try and insert a camera in there to have a good inspection and then get some vinegar in there to soak for a while.

 

So which pump would you recommend?

 

https://www.screwfix.com/c/heating-plumbing/central-heating-pumps/cat831036?action=compare

 

4 minutes ago, Nickfromwales said:

The above arrangement does not lend itself to having any additional external heat source of any kind. This is a temporary rig only. 

 

huh?  I'm not planning to adding any further heat source. I may go for ASHP next year depending how the heaters work out this winter.

 

 

 

 

 

 

[trialuser]

3 hours ago, oranjeboom said:

huh?  I'm not planning to adding any further heat source. I may go for ASHP next year depending how the heaters work out this winter.

 

 

 

 

 

 

I think that was in response to my post, thanks.

I was hoping to initially fit a willis heater, prior to an ashp, then leave it in situ as a backup or possibly as a dump for a little bit of excess solar.

Would that be possible?

Presumably if I just connected it in series with the flow to the ufh from the ashp it might throttle the flow rate a bit much?

Cheers.

[Nickfromwales]

5 hours ago, oranjeboom said:

huh?  I'm not planning to adding any further heat source. I may go for ASHP next year depending how the heaters work out this winter.

 

17 hours ago, trialuser said:

for my sanity, could you indicate on here where the flow and return from the boiler or ashp would join into this please.

Hence my comment on you asking where you can add another external heat source. It was general advice, sorry. Just texting between disasters atm so take with a pinch of salt ?

Edited November 13, 2020 by Nickfromwales

[oranjeboom]

57 minutes ago, Nickfromwales said:

Just texting between disasters atm so take with a pinch of salt

 

What have you done now???????????!!!

[Nickfromwales]

1 hour ago, oranjeboom said:

 

What have you done now???????????!!!

Not put Willis heaters in upside down that’s for sure   

If I didn’t get bad luck, I wouldn’t have any. Yay. 

[joth]

4 hours ago, trialuser said:

I was hoping to initially fit a willis heater, prior to an ashp, then leave it in situ as a backup or possibly as a dump for a little bit of excess solar.

 

I think the consensus would be to use a (oversized) buffer tank with an immersion pocket in it for this combined use case

?

[Ferdinand]

1 hour ago, joth said:

I think the consensus would be to use a (oversized) buffer tank with an immersion pocket in it for this combined use case

?

 

Is that some sort of diving suit?

[Gav_P]

1 hour ago, joth said:

I think the consensus would be to use a (oversized) buffer tank with an immersion pocket in it for this combined use case

?

How do you size a buffer tank? When does it become oversized?