Separate pump in addition to one in condensing boiler?

[hughs]

My main question is whether I need a separate pump in addition to the pump within the condensing boiler.

I am replacing a boiler. The previous boiler was the old open flue type and had two external pumps. The new boiler is a Vaillant EcoTec 630 plus system boiler. The boiler together with the hot water tank are situated in the garage. The boiler also feeds the hot water system to heat up three towel rails (i.e. they are heated whenever the hot water is switched on). There is an independent pump for the showers, which has a separate run to the house and back. The condensate from the boiler will be put into a soakaway adjacent to the garage wall. The pipe run from the beginning of the house and the boiler in the garage is approx 9 metres. The house has 4 bedrooms.

Almost all the engineers suggested that we needed a pump in addition to the pump included in the boiler and the shower pump. My chosen supplier does not believe that a separate pump is required. He states that the boiler pump will be sufficient to pump both the hot water and the central heating system to the house (quite apart from the shower pump which is independent). I am confused. What is the purpose of the additional pump? Is it required for the above system? What part of the system would it pump (i.e. central heating radiators, hot water etc). What difference would I notice if I do not have the additional pump installed?

Urgent advice would be much appreciated. Many thanks.

 

[gas4you]

Certainly sounds like you are, or have been confused by different advice!

The pump in the 630 should be plenty powerful enough to cope with the heating and primary water delivery to your indirect cylinder without the need for an additional one.

My only concern is that those quoting haven't told you it is against Part L energy efficiency regs to have the towel rails come on with the hot water.

These should be plumbed to come on with the rest of the radiators.

Apart from the shower pump, are you certain that this extra pump was not a booster pump for your hot water taps?

 

[hughs]

Certainly sounds like you are, or have been confused by different advice!

The pump in the 630 should be plenty powerful enough to cope with the heating and primary water delivery to your indirect cylinder without the need for an additional one.

My only concern is that those quoting haven't told you it is against Part L energy efficiency regs to have the towel rails come on with the hot water.

These should be plumbed to come on with the rest of the radiators.

Apart from the shower pump, are you certain that this extra pump was not a booster pump for your hot water taps?

Thank you Gas4You for your advice.

The extra pump could have been for the hot water taps. The water from the taps did not previously feel as though it was pumped under pressure - i.e. water gushing out as soon as the hot water taps were opened. If it was for the hot water taps (unfortunately, the old system has now been dismantled), would the flow of water now with only the condensing boiler pump be far less than I had previously? The flow rate previously was satisfactory or rather adequate - even when the hot water taps were fully open, the flow rate was reasonable (almost akin to a manual system). Note that the previous pump was not very powerful.

Under the Part L regs, does it mean that my system will not be certified as compliant for Local Authority purposes if the towel rails come on with the hot water?

Your help is really appreciated.

 

[hughs]

One further point. In the previous system, one pump was for the central heating system and the other for the hot water. I could only switch on the central heating if the hot water came on at the same time.

In the new system there will be a motorised valve to separate the hot water and the central heating. Therefore I am told that we do need a separate additional pump.

Does this help? Is the above statement by the engineer (the reason we do not need an additional pump) accurate?

Thanks again.

 

[Agile]

The boiler pump is the only one needed for the heating water from the boiler.

Other pumps could be used to improve the pressure at the taps or to provide a circulation of hot water if the house is large.

Depending on how the towel rads are connected they would normally only come on while the hot water is actually being reheated which might only be for 30 minutes a day! That needs reconfiguring!

Tony

 

[gas4you]

Under Part L and CHeSS, heating and hot water should be independently controlled. Whether your installer notifies to BC and then whether they actually ever check up on an installation is another story.

Most BC officers haven't the time, or inclination to go out and check any installations. It would only be you, as the customer, that would suffer with higher heating bills.

 

[hughs]

The boiler pump is the only one needed for the heating water from the boiler.

Other pumps could be used to improve the pressure at the taps or to provide a circulation of hot water if the house is large.

Depending on how the towel rads are connected they would normally only come on while the hot water is actually being reheated which might only be for 30 minutes a day! That needs reconfiguring!

Tony

Thanks Tony.

How would one configure to improve the towel rads being heated more often?

 

[hughs]

Under Part L and CHeSS, heating and hot water should be independently controlled. Whether your installer notifies to BC and then whether they actually ever check up on an installation is another story.

Most BC officers haven't the time, or inclination to go out and check any installations. It would only be you, as the customer, that would suffer with higher heating bills.

Thanks Gas4You.

Good point. Under the new system, heating and hot water will be independently controlled (and will switch on and off independent of the other). I presume that is what you meant. I very much hope so, as I would not wish to increase heating bills unnecessarily!

Please let me know if I have misunderstood you.

Thanks again for your help.

 

[gas4you]

No you are correct in your assumption. Therefore to me the towel rails have not been fitted/piped up correctly, unless you specifically insisted on this arrangement.

 

[hughs]

No you are correct in your assumption. Therefore to me the towel rails have not been fitted/piped up correctly, unless you specifically insisted on this arrangement.

Thanks again Gas4You.

I did not specify this arrangement. Essentially the engineer is leaving the new set-up the same as the old one. How can I improve it (as far as the towel rads are concerned)?

 

[gas4you]

The pipe work to the towel rails needs to be disconnected from the primary circuit to the HW cylinder and then teed into the standard heating pipe work at an appropriate position.

Depending on the outputs of the towel rails you may get away with connecting to 15mm pipe circuit, but there is an outside chance it may need to be onto 22mm if they are all large towel rails.

 

[hughs]

The pipe work to the towel rails needs to be disconnected from the primary circuit to the HW cylinder and then teed into the standard heating pipe work at an appropriate position.

Depending on the outputs of the towel rails you may get away with connecting to 15mm pipe circuit, but there is an outside chance it may need to be onto 22mm if they are all large towel rails.

Thank you Dave.

In your suggestion, would the towel rails come on when either the central heating or the water is being heated up?

The engineer initially thought that I needed one new motorised valve to switch off the flow from the cylinder to the towel rails, when the central heating comes on. However he has had after thoughts and does not believe it will work (as he thinks the thermostat for the cylinder will not be able to switch off the water supply to the cylinder and will be ineffective). He feels he needs to think about it. Any advice?

 

[gas4you]

The towel rails would be on the radiator circuit only, so therefore would come on only when the heating is activated, but be controlled by their own TRV's.

If you had another zone valve off the HW cyl circuit, then I would suspect that the towel rails would still only come on if the HW was selected.

Would depend on the piping arrangements though.

 

[Agile]

It would be quite easy to add a zone valve to the towel rail circuit which was timed from the hot water clock.

Currently it will be controlled by the cylinder stat which will turn off within 30 minutes of using hot water which is not much use!

It seems that your installer is having some difficulty in working things out in his mind!

Tony

 

[hughs]

Thank you very much Dave and Tony for your advice.