UVC install

[JohnMo]

Several months ago I purchased a 210L slimline Ideal Heat Pump UVC. Then completed the UVC training, so I could self install and certify.

 

There will be secondary circulation also. An interesting thread, a while ago, brought up an issue of secondary returns temp being high if you have a mixing valve on the cylinder hot water outlet, as cold water cannot enter what is a sealed system. So what you need is a split in the piping after the returns pump to allow water two different flow paths either to the mixing valve or back to the tank.

 

So although this is a heat pump system and cylinder temps should be now higher in theory than 46 degs, solar excess is being diverted also.

 

So have replicated the above with a little mechanical automation using a Reliance valve and a gate valve. The reliance valve is adjustable to close at an adjustable temperature. So the theory is

 

1. Secondary returns pump starts

2. gate valve (B) is set to reduce flow going to mixing valve, so all or most flow goes via reliance valve (A) to cylinder,

3. once return temp gets to set point, the Reliance valve closes and all flow goes via the mixing valve

 

 

 

 

 

The Tee below the mixing valve incorporates a check valve, pipe entering the side port of the Tee is the gate valve (B).

 

Will give an update as things progress 

 

[JohnMo]

Quick run down on what's on the cylinder.

 

A - flow and return from ASHP

B - secondary turns pump, has integrated timer

C - wiring centre, timer timer, thermostat, 3 port valve and secondary returns pump.

D - timer for DHW heating

E - check valve on hot water outlet. Expansion vessel is the white bit above cylinder.

Tundish is visible to right of C and D.

Between D and E is the water outlet mixing valve.

G - is a 3 port valve

F - air release valve

 

So basically water from ASHP comes in via the top pipe at A, if the 3 way valve allows it passes water upwards to the top of the coil, water passes through the coil and out the bottom of the cylinder towards the 3 way valve out the lower pipe at A. Any air in the coil can be bled out of the air release valve at F.

 

As this is a retrofit, the cold system is not directly balanced to 3 bar, so a check valve is installed on the cylinder outlet at point E. This prevents any reverse flow through the system.

 

I decided to put all the electrical bits on the cylinder so I have just one power cable and the immersion cable coming off the cylinder.

 

Call for heat from the heat pump is via a radio signal.

 

[JohnMo]

Comparison photo, showing 210L slimline UVC next to a combi boiler with an Alpha Flowsmart 50L preheat cylinder below it.

 

So if you have a wall hung combi boiler, you can install a decent sized heat pump cylinder in the same space.

 

 

The white box to the right is the MVHR unit.

 

[JohnMo]

Started filling with water, and realised why I hate compression fittings. They never seem to seal first time. One of the joints has been made about 5 times. Lucky it was on the heating coil part so not so much to drain down.

 

Think they must just be piss poor quality. Eventually got them to seal with a liberal application of liquid PTFE over the olive.

[JohnMo]

All sorted, cylinder installed and commissioned, and charged with hot water.

 

Heated cylinder to 50 degs, ASHP was at about 56 deg. Need to get final set point of the mixing valve set, think it's a little low as the shower is running cooler than I would like. Will mess with that over the next couple of days.

 

Have secondary circulation, with built in timer and thermostat. Currently set to run a couple of hours morning and evening, temp thermostat set to 30, the pump stops and starts to manage this temp within the time window.

 

Combi boiler now isolated.

 

Will look to get the gas disconnected in next week's, once I am comfortable there are no issues

 

[S2D2]

Is the 50 degrees due to the mixing valve always allowing some cold through or for hot water capacity/legionella?

 

Thanks for the write up, interesting as I'll be putting one in soon. 

[JohnMo]

1 hour ago, S2D2 said:

Is the 50 degrees due to the mixing valve always allowing some cold through or for hot water capacity/legionella?

 

Thanks for the write up, interesting as I'll be putting one in soon. 

I did 50 just to see how the heat pump performed doing it really.  But just read the instructions for the mixing valve (was in my stock of bits), it drops the temperature a minimum of 10 degs, not really much of an issue except the shower seems to do the same.  So may remove it tomorrow, then run the cylinder at a lower temp and have a hitter shower.

[JohnMo]

Wife was watching strictly, so just removed the mixer valve, and installed a pipe instead - the cylinder will be reheated tomorrow morning, so will check out the shower temp after that.

[S2D2]

1 hour ago, JohnMo said:

I did 50 just to see how the heat pump performed doing it really.  But just read the instructions for the mixing valve (was in my stock of bits), it drops the temperature a minimum of 10 degs, not really much of an issue except the shower seems to do the same.  So may remove it tomorrow, then run the cylinder at a lower temp and have a hitter shower.

Not an issue if you want the increased capacity, but if you didn't need it running the heat pump 10 degrees higher is a big hit in efficiency no? This is an outstanding question for me, to fit one or not, so thanks for the experimentation!

[JohnMo]

8 minutes ago, S2D2 said:

This is an outstanding question for me, to fit one or not, so thanks for the experimentation!

 

I was more worried about summer when the cylinder should be mostly PV heated and at higher temps. Plus the fact that secondary circulation would put high temps direct to taps. But tried the thermostat mode on the pump and it works well. So mixer is possibly an add-on not needed.

[JohnMo]

So TRV removed from UVC outlet, temperature of stored water reduced to 45. Wife complained the shower was too hot this morning, with TRV I couldn't get it much above warm. So reset the mixer adjuster and all good.

 

Currently letting the cylinder heat when it wants between 6am and 6pm. And will see how it goes. Aim is keep water at lowest temperature without complaints.

[JohnMo]

So a few changes.

 

Mixer valve has been removed.

Set heating windows at 6am to 7am (cheap rate), and 12pm to 1 pm (make most of any solar).

 

Heat to 47 degs, and the cylinder heating time is around 45 mins.

 

Had to tweek the shower mixer, flow temp settings down (inside the mixer), but all good. Was too hot for the wife 

 

Will monitor usage and possibly reduce set point slightly, over a few days

[JohnMo]

Have tried to reduce cylinder set point, but resulted in max temperature at shower slightly lower than I want, so upped to 47/48. Currently still have two heating periods, the one in cheap rate takes 45 mins, the one in the day 35 mins.

 

So next will try to have a single heating period instead of two. Even if I have to up the temperature slightly it will be cheaper than two heat sessions. Will report back in a few days.

[JohnMo]

Slight update.

 

Cancelled the cylinder charge scheduled for this afternoon, so last charge finished at 7am this morning. Set point was 48, it took 45 mins to charge the 210L slimline cylinder from a 6kW ASHP.

 

Wife showered this morning and general house usage, I also showered, shower temp ok, but not as hot as it was yesterday. So have upped the temperature to 50.

 

Added some additional temperature gauges on the cylinder this evening.

 

Prior the shower the normal temperature probe was reading 21 degs, but it's close to the bottom of the cylinder. So pretty meaningless to the content temperature and how much hot water is remaining.

 

4 cheap temperature probes, a 6mm to drill through the outer casing and I had a very basic level gauge. Interestingly the gauges at 21 degs read within 0.1 of each other. Not bad for £24 for 8 off including delivery.

 

 

Tappings are 250, 500, 750 and 1000mm from top of the cylinder. So down to 50% of the cylinder height.

 

Will check the temperature reading in the morning to see how accurate they are. To me it looks like the top 500mm of the cylinder is still quite usable.

 

Next job is to tidy the gauges up and look a little prettier.

 

 

[Jenki]

I'm waiting delivery of my ASHP, so reading your posts thinking I might be removing the TMV I installed. Also looking at your temp gauges see another Arduino project added to the list. ( I've got a mock up to show flow and return at the cylinder, flow and return outside at the ASHP, and DHW and Buffer temps, might add some more probes for the DHW.) Just need the ASHP delivered and to get it  working.

[JohnMo]

8 hours ago, Jenki said:

Just need the ASHP delivered

So they took the other one back? What make did you get.

[Jenki]

27 minutes ago, JohnMo said:

So they took the other one back? What make did you get.

It's on its way back, should be there today, no refund yet, assume they want to see it, as it was sat outside for 6 weeks while they tried to help

 

I've gone for the Samsung 5KW. managed to get the control kit new off eBay for half price so helped ease the extra cost, plus they do a coastal version.

 

[JohnMo]

Set the thermostat for 50 overnight, the gauge on the thermostat was reading 51 this morning. The heating cycle took 1 hour and 15 mins.

 

Looking at legionella protection, a couple of images from heat geek. First is the recommended storage temperature, solid black line, when looking at store water turnover. The dotted black is with a legionella immersion cycle. 50 degs is well within our range for not needing the legionella cycle.

 

The second image is the death cycle, at 51 degs at close to base of the cylinder a couple of hours after the heating cycle at least 90% have already died - if they were there in the first place. Another much discussed topic. But looking at worse case, thought better be on the safe side.

 

 

 

Gauging the cylinder

The additional gauges I added, were all reading slightly lower - around 5 degs. So would suspect as they are only within the insulation and just touching the cylinder wall, I am getting an under reading compared to a proper thermal pocket.

 

 

Interesting the third gauge down reads slightly low, this gauge coincides (is just below) with the secondary returns port and although the pump has been off for a hour, there is still an influence on cylinder temperature. Tried the gauges in different positions and that position was always cooler, irrespective of gauge installed.

 

So now have a cost effective contents gauge. So should help me optimise our water heating.

 

So cylinder install complete, all pipes are insulated as far as practical, using mostly either 19mm or 25mm wall thickness insulation. Where I have a Hep2O or Tectite fitting or valve I used 35mm X 12mm insulation.

 

No legionella cycle required

Just a matter of a little optimisation of heating cycles.