Delay timer for heating pump

[plumb_know]

HI everyone,

installed new ideal heat only boiler in replacement for dead potterton suprima, flushed system when boiler fitted, s plan system with bypass in working order, all works ok until circuits shut off then boiler over heats. pump overrun not provided on ideal logic and pump in airing cupboard 2 floors below.

Ideal suggested fitting a relay timer to enable pump to over run a couple of minutes, has anyone done this and could recommend a good product for this?? i guess this just gets wired in on pump cable with permanent live also wired to the timer which will provide a timed amount of power to pump when switch live has stopped?/

hope this makes sense.

Appreciate advise.

Many thanks

 

[ShaunCorbs]

Analogue multifunction timer relays Selec 600XU-A-1-CU

Multifunction timer relays, analog, 13 time functions, 10 time ranges, 20-240 V AC/12-240 V DC, 1 x changeover contact, DIN rail mounting, IP20 protection, Screw-type terminals, Functions: On-delay/interval/flashing with off…

www.automation24.co.uk

GEYA On Off Time Delay Relay ACDC12-240V 1xSPDT Multifunction Timer Relay 1SPDT | eBay

Output: 16A 1SPDT. 1 function of latching relay ( I ).

www.ebay.co.uk

Something like this is what you need

 

[plumb_know]

thanks shaun, have you ever used one for this application??

on reading the bottom link you sent would it be E. off delay s break i would be using??? how would i wire this up?? also would i need to put this within a chock box/wiring centre??

Appreciate the help,
many thanks

 

[ShaunCorbs]

Yes delay off
Permanent powe to the supply side
Pump to the load side
Your switch eg pump to turn on eg oranges on a splan etc to your coil eg a1 then a neural to a2

 

[plumb_know]

thanks shaun, much appreciated

 

[plumb_know]

Hi Shaun,

I have ordered the Geya relay as suggested, but sorry think i am being a bit dense but cant make sense of wiring diagram.

The way i imagined wiring something like this would be to cut the cable leading to heating pump in half.

Have L,E,N from wiring centre go into the inlet side of relay on one side of relay (live being essentially switch live) then connecting the L,E,N to the lead leading to the pump coming out other side of relay. then running another permanent Live from wiring centre into the inlet side of relay for providing power when overrun needed. Is this in principle right??

If so where would i put L,E,N coming from wiring centre? then L,E,N to heating pump? what terminals would i use to Connect Permanent L,E,N to??

or does the this work with capacitors inside in which case do i just cut pump cable in half and wire L,E,N from wiring centre into one side and then cable going to pump out other side?? if so what cables go what terminals on the unit??


Thanks for your time helping me with this

 

[ShaunCorbs]

Not a problem

replace the pump cable with a 4 core flex keeping the 3 connections the same as the old one

and the 4 th core into a permanent live

The old pump live into a1
Neutral into a2
Permanent live into 15
Pump feed into 18

then set up via instructions eg run time and function

would test it on the bench to make sure your happy with the wiring etc

 

[plumb_know]

Thanks shaun, appreciate the help

 

[plumb_know]

Hi Shaun, tried installing the timer today but didnt go to plan. i believe i wired it in correctly and other functions on the device worked but could not get setting E to work.

when 2 port made contact green light came on but no power to pump, i have attached some pics can you see anything if i have done anything wrong?? Or is it a faulty device??

switch live from wiring centre going to A1
Neutrals from wiring centre & to pump went in A2
no cables in S

permanent live from wiring centre in 15
nothing on 16
Live to pump in 18

Earths in connector block

I had setting on E, timer on 10M and percentage on 20% - but did try other settings - also tried messing around with wiring but could not get setting E to work

Thanks

 

[ShaunCorbs]

Are you getting live on 15 eg 240v

when there’s call is there live to a1 eg 240v

you should have live on either 16 or 18 the drawings I saw said 18 would become live but stranger things have happened so could be something simple as it’s been miss labelled

 

[ShaunCorbs]

leave the wiring as is and link a1 and s try that

 

[plumb_know]

HI Shaun,

Yes electrician on a site i was working today had a look at it and said wire it the same way you suggested in earlier thread.

yes was getting 240V on A1, didnt check permanent live but fairly sure there would have been. also would have thought it would still work during normal operation even if not 240V on permanent live??

I could get it to work on function A delaying start function also seemed to work on other setting just not on setting E. I also disconnected 15,16 & 18 leaving A1 & A2 connected but got no power to 15,16 or 18 when on setting E.

 

[plumb_know]

tried linking A1 & S still nothing

 

[plumb_know]

also tried swapping A1 & 18, and putting pump feed into 16

 

[ShaunCorbs]

Correct aslong as you had power coming in on the bottom side eg 15 it should be a closed circuit eg power on 18 when a1 is calling

15 should have power all the time even when it was off would be checking that first

 

[plumb_know]

found this and seems to be wired correctly - think it might just be faulty unit

 

[plumb_know]

Thanks shaun, i will wire it up to plug or something tomorrow and see if i can get power on 16 or 18 in setting E.

if not think it must be faulty and will try another one.

Thanks for your time helping me out

 

[ShaunCorbs]

Not a problem

it’s a strange one would test to see if you have perm 240v at 15 before you strip if

wouldn’t be the first time there’s no power there

 

[plumb_know]

i removed it and wired cables into block to get customer heating & hot water back but will make sure 240v on 15 when i test it. hopefully it was just that hate the fuss of returning stuff

 

[GrahamPye]

Rather than start a new thread, I thought I'd piggy back on this one as I have a similar problem...

I have a Grant Vortex Utility 15-26 Oil Boiler and a Range Tribune Cylinder and controls. For reasons best only known to the person (no names!) both the boiler and the cylinder were specified and installed as system units meaning I initially had two pumps and two pressure vessels. After some time I finally managed to get Grant Technical Support to agree that this wasn't a terribly good idea, so I removed the pump and pressure vessel from inside the boiler casing.

All worked well for a number of years (the system was installed in 2007) and the boiler is serviced every year by a qualified Engineer. We've never been really happy about the heating output in this house so 18 months ago I got the Engineer to replace the burner nozzle with the a bigger size to bring the boiler up to its maximum output, making any other adjustments to the burner to suit.

The system has always had a very intermittent problem with the 110C overheat thermostat tripping out, but until recently this could be kept to a very occasional event by turning the boiler thermostat down slightly. This isn't helping with the shortage of heat, of course! So recently the overheat thermostat started tripping out more often, especially when I had the boiler thermostat full on. I replaced the overheat thermostat (Grant VBS147) with a new one, but somewhat to my annoyance the new one tripped out too! Thinking I had a faulty unit I removed it for further testing and wired the old one back in temporarily, but I also took the precaution of tucking a thermocouple down the side of the boiler pocket where the thermostat bulb went.

This is the point where my story begins to merge with the OP's - somewhat to my surprise I found that after the room stat had turned off, thus stopping the boiler and circulating pump, the residual heat in the boiler caused it to gradually creep up to 110C over the course of several minutes - so the overheat stat was doing the right thing after all.

So, what to do - having found this thread, I decided that I needed to arrange a pump overrun to cool the boiler down somewhat after the burner had been switched off.

Firstly is there a view about whether it's better to control the overrun with a timer or a pipe stat?

Secondly, it seems unlikely that pumping the water round a fairly short length of piping, via the automatic bypass, isn't going to achieve much cooling, so what I really need to do (I thought) was get one of the motorised valves (S- Plan) open as well to give the heat somewhere to go. On further thought it seems like using the cylinder coil would be the sensible choice as this problem might also happen in the summer when the heating is not on. Now this makes the wiring quite a lot more complicated, and at the moment I haven't worked out how to do it without at least one relay being involved as I have to stop the closed valve bringing the boiler back on again.

Has anyone worked out how to do this in as simple a way as possible? Using the time switch described above would give two sets of SPDT contacts, but I've not found a pipe stat with two contact sets, and I'm not yet sure if two is enough anyway!

Finally, I'm a retired Computer Programmer with an electronic Engineering degree, and as you can see I know a bit about how heating systems work, but I don't pretend to be a Heating Engineer! I mention this so you can use "dirty" words in any replies. Sorry this is so long...

 

[GrahamPye]

Results of some experiments... My preference would be to use some sort of thermostat rather than a timer as I thought that would be "self adjusting". First discovery was that the pump didn't seem to object to circulating through the by-pass with both the motorised valves shut.

So I tried measuring the pipe temperature on the output of the boiler while running the pump, and also looking at the boiler body temperature as before. What happened was that after a couple of minutes, the circulating water reached a fairly stable temperature (about 55C) and didn't get any cooler. This had obviously taken the boiler body down as well, but once I turned the pump off, it gradually started rising again.

Which gives me a problem that there isn't a pipe temperature that I could monitor to turn the pump off again. Perhaps I need a thermostat with a remote sensor that I can put in one of the boiler pockets alongside the other stats and use that to power the pump?

Maybe a time switch is a better idea! But what signal do you use to trigger the time starting - is the boiler being switched off enough?

Or is there some way that I can get one of the motorised valves to open without it bringing the boiler back on again - I can't easily think of how to do this without relays or a stat with at least two pairs of contacts.

Sorry - I'm thinking "aloud" here, or maybe I'm rambling aloud

Graham

 

[SJB060685]

Results of some experiments... My preference would be to use some sort of thermostat rather than a timer as I thought that would be "self adjusting". First discovery was that the pump didn't seem to object to circulating through the by-pass with both the motorised valves shut.

So I tried measuring the pipe temperature on the output of the boiler while running the pump, and also looking at the boiler body temperature as before. What happened was that after a couple of minutes, the circulating water reached a fairly stable temperature (about 55C) and didn't get any cooler. This had obviously taken the boiler body down as well, but once I turned the pump off, it gradually started rising again.

Which gives me a problem that there isn't a pipe temperature that I could monitor to turn the pump off again. Perhaps I need a thermostat with a remote sensor that I can put in one of the boiler pockets alongside the other stats and use that to power the pump?

Maybe a time switch is a better idea! But what signal do you use to trigger the time starting - is the boiler being switched off enough?

Or is there some way that I can get one of the motorised valves to open without it bringing the boiler back on again - I can't easily think of how to do this without relays or a stat with at least two pairs of contacts.

Sorry - I'm thinking "aloud" here, or maybe I'm rambling aloud

Graham

You probably would be best to copy and paste your post and start a new thread.

The problem you're experiencing is something I've come across on oil boilers a lot. You're not going mad, the overheat stat is doing its job. There's a lot of residual heat left in oil boilers when burner and pump shut down and as you say creeps quite rapidly on shutdown. There's several ways you could go about this, each would be a somewhat custom design.
A time delay relay on pump and possible heat sink circuit is one way. There are other possible approaches though.

 

[John.g]

Why not consider installing a normally open type motorized valve like the Honeywell V4043B1257 installed between the flow & return as far away as possible from the boiler and wired so that when there is no demand from all zones it will (spring) open and will close with demand from any zone, this may not even need pump overrun due to gravity circulation around the boiler and pipework but if overrun is required a simple pipe stat set to say 85C will start/stop the pump as/if required with its normal 5C to 8C hysteresis.

 

[GrahamPye]

Why not consider installing a normally open type motorized valve like the Honeywell V4043B1257 installed between the flow & return as far away as possible from the boiler and wired so that when there is no demand from all zones it will (spring) open and will close with demand from any zone, this may not even need pump overrun due to gravity circulation around the boiler and pipework but if overrun is required a simple pipe stat set to say 85C will start/stop the pump as/if required with its normal 5C to 8C hysteresis.

John,

Thanks, that's quite a neat idea. I presume I'd wire that into the boiler feed so it closes whenever the boiler is firing. The downside is that it's (for me!) quite an expensive part, and in my house there isn't going to be an easy place a long way from the boiler that I can get at the pipework and run a wire to!

Having rejected the idea of a pipe stat as that doesn't change enough, I've now ordered a stat with a capillary tube, and I'm going to put the capsule in one of the boiler pockets and use that to bring the pump on - I really only need it to trigger at about 90C (or more) so that it will take enough heat from the boiler to stop the 110C overheat stat triggering.

If it turns out that there isn't enough pipework to dissipate the heat, I'll come back to your idea and see if I can work out somewhere to put the valve.

OR.... What if I replaced the existing MoMo DHW valve with the one you suggest and wired it so it would close when the Heating zone was calling for heat, but at all other times it would be open so the pump overrun would circulate through the cylinder. I'd have to work out how the DHW stat/timer would bring the boiler and pump on though. This might also mean that I couldn't have Heat and DHW at the same time - I think I need to draw a diagram!

Graham

 

[SJB060685]

As John said above is another approach. How about a time delay relay to pump, set at say 5 minutes for pump overrun and an additional motorised valve feeding a heat sink radiator or towel rail for example. Wire it in so when there is a demand on boiler live from other motorised valves the new valve closes shut and the boiler and pump energise. When the room stat or cylinder is satisfied power to the boiler live will be cut, the new valve springs open and the pump overruns for the set time around the heat sink circuit. I really do think you're going to need some mass to help prevent overheating, im not convinced a dead short from flow to return is going to be enough, although I could be wrong.