Strange Radiator Problem

[WarHammer]

Let me try & explain my problem.....

I've moved into a house that has an unvented heating system - uses a gloworm fuelsaver complheat 55 boiler & a IMI Tribune Premier 180 ltr unvented cylinder + Lifestyle 3 port mid-position valve. All rads (about 16 of them) have TRV's except for two towel rails & donwstairs loo rad.

All of this is run via a Drayton LP 722 programer (seperate HW + CH channels) - also there is a wireless room programable thermostat Honeywell CM927 - the Drayton LP722 programmer Heating side wiring has been isolated & the actions replaced by the programable CM927 thermostat.

Anyways - the problem I have is when the heating is on - all rads get nice & toasty (hot) in all rooms....& seems fine - however when only the (HW) hot water is on & CH is turned off - two radiators in a recently fitted upstairs extension get hot.

In other words there are two rads in the upstairs extension that get hot when HW is on as well as getting hot when the CH is on. No other rads get hot in the house when only the HW is on - why are these two doing so - my suspicions are they have been wrongly plumbed in by the builders of the extension - but without lifting laminate & flooring I am unable to verify.

I woudl welcome your collective thoughts & ideas on this problem please & also what easy/cheap remedies are there to fix it?

Cheers all

 

[Gasguru]

If the new rads are sited close to the mid position valve then perhaps the mid position valve is letting by on the heating side when only the hot water is selected. Feel the pipework from port A

or you may now have mulitple return pipes from the new radiator circuit plumbing.

Hence when the HW is on there is a reverse flow of heated water through these new radiators (the water is pumped through the cylinder coil and then backwards through these radiators to the boiler).

If there is no way of correctly re-piping the return pipework a bodge (that I don't recommend unless absolutely necessary) may be to install non-return valves on the radiator tails of each new radiator. You will need to find non-return valves to cope with the higher water temperatue though.

 

[fitz1]

could be to do with a wrongly piped bypass.

 

[WarHammer]

Thanks for the quick reply gasguru.

The new rads are at the opposite end of the house to the mid position valve - the valve is connected into the pipework next to the cylinder at one end of the house & the two new upstairs rads are at the other end of the house in the bedroom above the boiler.

 

[WarHammer]

could be to do with a wrongly piped bypass.

Where would this be fiited please? & is it is for a professional to fix?

 

[fitz1]

pipe joing flow and return. joins after pump but before three port valve, with an online possibly gate valve leading to boiler return , but not before any heating tees.

 

[WarHammer]

The boiler has an in-built bypass - would this be it?

Worse case scenario though - what would be the consequences of just simply leaving it as it is & just turning down the trv's to these two rads so as not to overheat the room in summer?

Will it cause any issues being left alone or am I slowly poisening the family with radiator hot water in the tap hot water system?

Also is it costing me more in gas usage terms to leave it as it is?

 

[gas4you]

I would tend to agree with Gasguru on this one. From the description you give of the new rads being above the boiler I would suspect that the installer has taken the shortest route to the return (just above the boiler) and this is where the reverse flow is occuring.

I to do not like non-return valves being fitted. Last time I used these as a last resort they created loads of noise in the system so I had to bite the bullet and pull up upstairs boards and re-pipe

 

[WarHammer]

I would tend to agree with Gasguru on this one. From the description you give of the new rads being above the boiler I would suspect that the installer has taken the shortest route to the return (just above the boiler) and this is where the reverse flow is occuring.

I to do not like non-return valves being fitted. Last time I used these as a last resort they created loads of noise in the system so I had to bite the bullet and pull up upstairs boards and re-pipe

Thanks for the reply gas4you....

Would I be best just leaving it as it is? - as per above?

Also from what you know of my system/boiler & me not having been used to this type of system, what would be a typical average amount of time to reheat the cylinder of HW - at the moment I seem to have to run the HW for about an hour & half in the mornings, an hour at lunchtime & two or so hours in the evening in order to have sufficient HW for a 3 person family with two showers per day (in mornings) & normal evening washing up of pots etc - in other words HW is on for about 4 & half or so hours per day - anything less then we seem to run out quickly & also the HW doesn't seem to stay how from morning through to evening without an hours run at lunchtime....is this all usual & typical would you say?

All opinions welcomed

 

[gas4you]

I personally dont like thes cylinders and therefore have not got invloved with them. As a guide the un-vented cylinders that I fit would take around 17 - 25 mins to reheat from cold for 180litre size. The time you are indicating seems excessive to me.

If you have all had showers in morning then yes it probably would not have any hit water left to keep hot all day!

I generally would expect a customer with a family your size to have water on for aroung 2 hours in the morning and 2 hours in the evening (as set on the programmer) whether or not the boiler heats the hot water in this time frame will depend upon usage with demand from the cylinder stat.

Try timing the hot water to come on on its own for 30mins before heating kicks in so you get full power from the boiler just heating the cylinder up on its own

 

[sambotc]

Hi,

Your radiator's being left piped in this way will not poison your family, as the water is heated indirectly through a coil in the cylinder. Basically the water going around these 2 radiator's will not be the same as what come's out your hot water tap's, so no need to worry.

Sound's like what other's have said, the builder's have tee'd the 2 new rad's into the primary flow from before the 3 port valve, therefore you will have no control over them other than the boiler being ON/OFF. If there in your bathroom's maybe it was done on purpose for heating towel's but more than likely not.

If this is the case, you have 2 option's:
A) live with it as is, it will do no harm.

B) Trace the flow and return back to where they join in to the existing pipework, and re-run them back to after the 3 port valve on the heating side, as it should have been done originally.

Obviously without seeing the job, i could not tell you how involved it would be, but will mean lifting floor boards etc

HTH Sam

 

[Balenza]

Tribune are quality cylinders.The re-heat time for the Tl 180/L model is 21 minutes with a coil rating of 18.9 KW.
The re-heat performance is measured from 15C to 60C after drawing off 70 percent of the capacity.