He needs way more sleep than that as I'm sure you realise. Once he is up in the morning start looking for signs that he is getting sleepy after an hour and half. At the first yawn take him into a dark quiet bedroom. Then take as long as it takes to get him to sleep. When he wakes up repeat looking for when he starts to get tired. You will find the interval he can happily stay awake for this way. Once you know it never let him stay awake for more than that time and before you know it assume 2 hours as a maximum. If he yawns when you are feeding him get him straight back to bed to continue sleeping. Come evening once he is asleep after 6pm treat any more awakenings as if it was night time and feed him in the dark then put him back to bed. Don't worry about lots of day time sleep impacting on night time sleep - they need it. They also tell us how much they need but they can be bloody subtle about it. If you keep him awake beyond his window he will go wide eyed and look like he's "taking it all in". He isn't he is overwhelmed and will have trouble falling asleep.
At the moment he's sleeping in the pram downstairs in the dining room - not really dark -
I definitely know when he's tired, and he drops off relatively easily (only in the pram, though), but it's proving impossible to get him to sleep for longer than 20 minutes. I think he becomes overtired and gets really grumpy.
He has a strong bedtime 'routine', starting at about 6pm with bath, feed and then bed - he sleeps until 11.30pm usually, sometimes longer, so I know he can sleep for longer periods.
I guess I need to grit my teeth and keeping trying to get him to sleep upstairs.
i agree with becky. the only time my dd (15 wks) sleeps longer than 35 min at home -- as opposed to in her pram -- is when it is quite dark. i also put on white noise to mask the sirens and honking from the A1.