New System Suggestions

[Homeland]

Hello all,

I live in a 5 bed, 5 bath 1930's solid wall house. I currently have two Potterton 100e boilers and two cylinders with tanks in the loft. The boilers usually fire at the same time. Each of the 5 showers has its own shower pump. These are the issues I have:

1. The two upstairs bathrooms have really low water pressure
2. The downstairs kitchen hot water pressure is really low
3. The boilers are inefficient and I would like to upgrade them
4. The radiators in the downstairs bedroom do not heat up (there may be gunge in the system and a power flush may resolve this as well as maybe installing a more powerful pump). This problem, therefore, may not be related to the above 3 points.

As my sons have moved to university there are only two of us in the house most of the time. Some weekends we have friends/family staying over and at Xmas we may have full house. So, most days only one bath is being used at any one time and occasionally 2 or more are used at the same time.

I've spoken to a few heating engineers and they have differing opinions on how to go forward.

1. One recommended going the combi boiler route.
2. Others have suggested going down the unvented cylinder route, removing the shower pumps and upgrading to condensing boilers.
3. Another suggested upgrading to condensing boilers and putting electric hot water heaters in the two upstairs bathrooms but the issue is that the consumer board is at the front of the house and an electrician will have to run new cabling to the bathrooms - its a long and messy run.

What are the views of the people on this forum?

P.S When Thames Water tested the pressure they said that the tap in the front garden has 20 litres per minute flow. The stopcock flow was 44 litres per minute. The pressure was 36 litres/per head.

 

[ianmcd]

you are mixed up somewhere, pressure is not measured in litres/per head but not that important anyway, are you sure they said you have 44 L/min it is possible but not very common

 

[Homeland]

Hi, I've attached both pages of the the Thames Water report

 

[Gasguru]

If at all possible I would go down the unvented cylinder route.

On the face of it 3.6 bar pressure (static we assume ie. the street main pressure with no water flow) is sufficient for an unvented cylinder. The 44 litres/min flow at the boundary is probably also sufficient. You would need to do further tests within the house to ascertain whether the you can achieve sufficient flowrates at a typical pressure required for showering eg. with multiple outlets open is there still good pressure and flowrate for showering etc. You may require the service pipe from boundary to house upgrading if it's too restrictive. It would also be sensible to fit flow limiters to certain outlets.

If all ok then then howabout something like a 210 litre ACV Smart tank in tank cylinder combined with a 30 or 40 kW Worcester CDi Classic heat only boiler. Wired as hot water priority the cylinder will be re-charged relatively quickly due to the high heat transfer of these unique cylinders (although can sometimes be an issue (if the whole cylinder is drained) as the radiator circuit is temporarily off whilst re-charging takes place).

I can't see why you'd need 2x 100,000 btu boilers in a 5 bed house...surely the boilers are massively oversized.

 

[dilalio]

Do you really need 5 baths?

 

[Homeland]

I can't see why you'd need 2x 100,000 btu boilers in a 5 bed house...surely the boilers are massively oversized.

This system was put in by the previous owners. What they told me was that initially they only installed one boiler but it was apparent immediately that this wasn't sufficient and so they had the second boiler installed. Since then, every heating engineer who has looked at the system has said that for the size of the house I would need two boilers (due to all the rooms being large, the house is on the large side). Apparently if I was to replace them with a large boiler it would be classified as a commercial boiler and it wouldn't be supported by the likes of Homeserve and I would have to pay commercial call out rates.

 

[Homeland]

Do you really need 5 baths?

Thats a fair point and its something we thought when we viewed the house. But it ticked most of the other boxes in terms of school access, train access etc that we bought the place.

 

[StephenStephen]

We live in a 5 bed, 4 bathroom house and none of the recent heating engineers have suggested that we need more than 1 domestic boiler

 

[dilalio]

The pressure was 36 litres/per head

That's about 3.5bar

 

[fezster]

Since then, every heating engineer who has looked at the system has said that for the size of the house I would need two boilers (due to all the rooms being large, the house is on the large side).

But has anyone done a whole house heat loss calc to determine if that is actually the case. Unless your house is very, very poorly insulated, it's highly unlikely you'd require over 40kw.

There are other advantages to having 2 smaller boilers, over a single large one, but that doesn't sound like why you have them fitted.

 

[dilalio]

Get an Intergas and joule 300 UV on D plan.

 

[Gasguru]

A bathroom per bedroom is becoming more common with multi-generational living, we've got renovations going on round our way that are doing that.

Either your house is very mismatched in terms of bedrooms to downstairs rooms or those heating installers that have suggested 2 boiler are misguided. Get a proper heatloss calculation done and go from there...the amount of times I've come across massively oversized boilers feeding rads that are too small or poorly positioned or unbalanced.

 

[D_Hailsham]

We live in a 5 bed, 4 bathroom house and none of the recent heating engineers have suggested that we need more than 1 domestic boiler

How old is your house? The OP says his is a 1930's solid wall, which will make a considerable difference to the heat loss compared to a modern well-insulated house.

 

[fixitflav]

The two upstairs bathrooms have really low water pressure

Is that just the taps or the shower as well? How about the other showers?

My suggestion would be an unvented cylinder to supply 2 of the showers direct, and a conventional HW cylinder fed from a cold water storage tank for the other 3, retaining the shower pumps. One boiler to feed both cylinders via auto valves. Boiler could have a F/E tank in the loft, or an expansion vessel, whichever you prefer. 40kW sounds plenty, but depends on heat calculations. The various HW taps fed from either cylinder, depending on the house layout.
I think that gives you a fair chance of it working if all the showers are used at the same time. That might be unlikely, but if you think you need 5 showers might be worth considering.

 

[Homeland]

But has anyone done a whole house heat loss calc to determine if that is actually the case. Unless your house is very, very poorly insulated, it's highly unlikely you'd require over 40kw.

There are other advantages to having 2 smaller boilers, over a single large one, but that doesn't sound like why you have them fitted.

I don't know if the previous owners did a heat loss calculation but I haven't done one - sounds like I need to get one done.

What doesn't make sense to me is the design of the system. More than one heating engineer has said that this looks like a semi commercial system (I've included some pictures of the cupboard with the boilers and the surrounding pipes so that you can make your own mind up). If it was designed well, then if two boilers were needed 2 would have been installed together initially but in this case one was added afterwards.